<%BANNER%>

Zoysiagrass Evaluation for DNA Content, Sting Nematode Response, Nitrogen Management, and Estimates of Heritability for ...

Permanent Link: http://ufdc.ufl.edu/UFE0022755/00001

Material Information

Title: Zoysiagrass Evaluation for DNA Content, Sting Nematode Response, Nitrogen Management, and Estimates of Heritability for Turfgrass Performance Traits
Physical Description: 1 online resource (127 p.)
Language: english
Creator: Schwartz, Brian
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2008

Subjects

Subjects / Keywords: cytometry, flow, heritability, management, nematode, turfgrass, zoysia, zoysiagrass
Agronomy -- Dissertations, Academic -- UF
Genre: Agronomy thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Zoysiagrass (Zoysia spp.) use in landscapes and on golf courses has primarily occurred in the transition zone of the United States. Variation associated with several abiotic, biotic, and turfgrass performance characteristics is well documented. Laboratory, glasshouse, and field studies utilizing zoysiagrass germplasm were conducted from 2005 through 2008 to quantify 2C nuclear DNA content, sting nematode (Belonolaimus longicaudatus) response, effects of nitrogen fertilization rate and mowing height management, and broad-sense heritability estimates of turfgrass performance and stress related characteristics. All experiments were managed with supplemental irrigation. Genotypes from Z. minima and Z. matrella had the largest (0.96 pg) and smallest (0.77 pg) 2C nuclear DNA contents, respectively. The observed 0.19 pg spread between zoysiagrass species was less than variation reported in other tetraploid warm-season grasses within the same species. Total root lengths of 'TifEagle' bermudagrass (Cynodon dactylon L. Pers. var. dactylon ? C. transvaalensis Burtt-Davy) were 57%, 55%, and 31% greater for uninoculated treatments when compared to an average of the two sting nematode inoculated treatments in the 45-d conetainers, 90-d conetainers, and 90-d clay pots, respectively. Quantifying root damage using 45-d conetainers inoculated with 50 sting nematodes provided reproducible results characteristic of those reported in other greenhouse and field evaluations. Sting nematode populations multiplied on the evaluated zoysiagrass and St. Augustinegrass (Stenotaphrum secundatum Walt. Kuntze) cultivars with reproduction factors ranging from 2.2 to 11.0. The experimental Zoysia germplasm line UFTZ exhibited greater tolerance to sting nematode injury than other turfgrass cultivars and exhibited no total root length reduction under sting nematode pressure. Significant total root length percent reductions were observed between uninoculated and inoculated treatments for 'Empire' (-24%), 'Cavalier' (-29%), 'Emerald' (-29%), TifEagle (-32%), and 'Floratam' (-37%) in 45-d conetainers. In the management study, nitrogen rate had the greatest influence on turfgrass performance, but mowing height was important during colder periods or in the presence of Bipolaris disease pressure. Turfgrass density was not maintained in Empire or 'Palisades' at the lowest N rate. Bipolaris incidence was noted on 'Cavalier' and 'Zeon', and had the most detrimental effect on turf quality at the lower mowing height and highest N rate. 'JaMur', 'Ultimate', 'Diamond', and 'Pristine' all had acceptable density at the low nitrogen rate, but often did not have adequate color to sustain turf quality. Genotypic variance largely contributed to the wide range in expressed phenotypic response in a set of 324 zoysiagrass germplasm lines for establishment, turf density, turf quality, genetic color, and seedhead density which resulted in higher broad-sense heritability estimates (0.62 < H^2 < 0.94). Fall dormancy and spring greenup were influenced more by the environment and had lower heritabilities (0.32 < H^2 < 0.58). Turf quality was also rated considering the effects of glufosinate herbicide application, Bipolaris incidence, and mole cricket damage. Large error variances and low broad-sense heritabilities were typical for these stress related traits. Overall, the potential exists for combining desirable traits in superior clonally propagated F1 zoysiagrass hybrids.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Brian Schwartz.
Thesis: Thesis (Ph.D.)--University of Florida, 2008.
Local: Adviser: Kenworthy, Kevin E.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2009-12-31

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2008
System ID: UFE0022755:00001

Permanent Link: http://ufdc.ufl.edu/UFE0022755/00001

Material Information

Title: Zoysiagrass Evaluation for DNA Content, Sting Nematode Response, Nitrogen Management, and Estimates of Heritability for Turfgrass Performance Traits
Physical Description: 1 online resource (127 p.)
Language: english
Creator: Schwartz, Brian
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2008

Subjects

Subjects / Keywords: cytometry, flow, heritability, management, nematode, turfgrass, zoysia, zoysiagrass
Agronomy -- Dissertations, Academic -- UF
Genre: Agronomy thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Zoysiagrass (Zoysia spp.) use in landscapes and on golf courses has primarily occurred in the transition zone of the United States. Variation associated with several abiotic, biotic, and turfgrass performance characteristics is well documented. Laboratory, glasshouse, and field studies utilizing zoysiagrass germplasm were conducted from 2005 through 2008 to quantify 2C nuclear DNA content, sting nematode (Belonolaimus longicaudatus) response, effects of nitrogen fertilization rate and mowing height management, and broad-sense heritability estimates of turfgrass performance and stress related characteristics. All experiments were managed with supplemental irrigation. Genotypes from Z. minima and Z. matrella had the largest (0.96 pg) and smallest (0.77 pg) 2C nuclear DNA contents, respectively. The observed 0.19 pg spread between zoysiagrass species was less than variation reported in other tetraploid warm-season grasses within the same species. Total root lengths of 'TifEagle' bermudagrass (Cynodon dactylon L. Pers. var. dactylon ? C. transvaalensis Burtt-Davy) were 57%, 55%, and 31% greater for uninoculated treatments when compared to an average of the two sting nematode inoculated treatments in the 45-d conetainers, 90-d conetainers, and 90-d clay pots, respectively. Quantifying root damage using 45-d conetainers inoculated with 50 sting nematodes provided reproducible results characteristic of those reported in other greenhouse and field evaluations. Sting nematode populations multiplied on the evaluated zoysiagrass and St. Augustinegrass (Stenotaphrum secundatum Walt. Kuntze) cultivars with reproduction factors ranging from 2.2 to 11.0. The experimental Zoysia germplasm line UFTZ exhibited greater tolerance to sting nematode injury than other turfgrass cultivars and exhibited no total root length reduction under sting nematode pressure. Significant total root length percent reductions were observed between uninoculated and inoculated treatments for 'Empire' (-24%), 'Cavalier' (-29%), 'Emerald' (-29%), TifEagle (-32%), and 'Floratam' (-37%) in 45-d conetainers. In the management study, nitrogen rate had the greatest influence on turfgrass performance, but mowing height was important during colder periods or in the presence of Bipolaris disease pressure. Turfgrass density was not maintained in Empire or 'Palisades' at the lowest N rate. Bipolaris incidence was noted on 'Cavalier' and 'Zeon', and had the most detrimental effect on turf quality at the lower mowing height and highest N rate. 'JaMur', 'Ultimate', 'Diamond', and 'Pristine' all had acceptable density at the low nitrogen rate, but often did not have adequate color to sustain turf quality. Genotypic variance largely contributed to the wide range in expressed phenotypic response in a set of 324 zoysiagrass germplasm lines for establishment, turf density, turf quality, genetic color, and seedhead density which resulted in higher broad-sense heritability estimates (0.62 < H^2 < 0.94). Fall dormancy and spring greenup were influenced more by the environment and had lower heritabilities (0.32 < H^2 < 0.58). Turf quality was also rated considering the effects of glufosinate herbicide application, Bipolaris incidence, and mole cricket damage. Large error variances and low broad-sense heritabilities were typical for these stress related traits. Overall, the potential exists for combining desirable traits in superior clonally propagated F1 zoysiagrass hybrids.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Brian Schwartz.
Thesis: Thesis (Ph.D.)--University of Florida, 2008.
Local: Adviser: Kenworthy, Kevin E.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2009-12-31

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2008
System ID: UFE0022755:00001


This item has the following downloads:


Full Text

PAGE 1

ZOYSIAGRASS EVALUATION FOR DNA CONT ENT, STING NEMATODE RESPONSE, NITROGEN MANAGEMENT, AN D ESTIMATES OF HERITA BILITY FOR TURFGRASS PERFORMANCE TRAITS By BRIAN M. SCHWARTZ A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2008 1

PAGE 2

2008 Brian M. Schwartz 2

PAGE 3

To Sz 3

PAGE 4

ACKNOWLEDGMENTS I would like to express my si ncere appreciation to Dr. Kevin Kenworthy, the members of my advisory committee, the Agronomy Department and the staff at the Plant Science Research and Education Unit for all of the guidance, support, and help. Th anks are also in order for the generous donation of laboratory equipment from Mark Kann and the Seven Rivers Golf Course Superintendents Association. This research would not have been possible without these efforts. 4

PAGE 5

TABLE OF CONTENTS page ACKNOWLEDGMENTS...............................................................................................................4 LIST OF TABLES................................................................................................................. ..........7 LIST OF FIGURES.........................................................................................................................9 ABSTRACT...................................................................................................................................12 CHAPTER 1 INTRODUCTION................................................................................................................. .14 2 VARIATION IN 2C NUCLEAR DNA CONTENT OF Zoysia spp. AS DETERMINED BY FLOW CYTOMETRY.....................................................................................................17 Introduction................................................................................................................... ..........17 Materials and Methods...........................................................................................................20 Plant Materials.................................................................................................................20 Flow Cytometry...............................................................................................................20 Morphological Measurements.........................................................................................21 Statistical Analysis..........................................................................................................2 1 Results and Discussion......................................................................................................... ..22 Conclusions.............................................................................................................................24 3 EFFICIENT METHODOLOGY FOR SCR EENING STING NEMATODE RESPONSE IN A TURFGRASS BREEDING PROGRAM......................................................................28 Introduction................................................................................................................... ..........28 Materials and Methods...........................................................................................................30 Results.....................................................................................................................................34 Discussion...............................................................................................................................36 4 VARIABLE RESPONSES OF ZOYSIAGR ASS, ST. AUGUSTINEGRASS, AND BERMUDAGRASS GENOTYPES TO THE STING NEMATODE....................................46 Introduction................................................................................................................... ..........46 Materials and Methods...........................................................................................................48 Results and Discussion......................................................................................................... ..51 Conclusions.............................................................................................................................55 5

PAGE 6

5 MOWING HEIGHT AND NITROGEN FERTILITY MANAGEMENT OF ZOYSIAGRASS IN FLORIDA.............................................................................................59 Introduction................................................................................................................... ..........59 Materials and Methods...........................................................................................................61 Results and Discussion......................................................................................................... ..63 Zoysia japonica ...............................................................................................................63 Zoysia matrella ................................................................................................................66 Conclusions.............................................................................................................................69 6 HERITABILITY ESTIMATES FOR TURFGRASS PERFORMANCE AND STRESS RESPONSE IN Zoysia spp.....................................................................................................97 Introduction................................................................................................................... ..........97 Materials and Methods.........................................................................................................100 Results and Discussion......................................................................................................... 103 Conclusions...........................................................................................................................106 REFERENCES............................................................................................................................113 BIOGRAPHICAL SKETCH.......................................................................................................127 6

PAGE 7

LIST OF TABLES Table page 2-1 Means for 2C nuclear DNA content and leaf blade width of zoysiagrass genotypes for five species and five interspecific hybridizations........................................................26 3-1 Mean squares for Belonolaimus longicaudatus reproduction fact or (Rf), final population density (Pf), population density on a total root length basis (Pf/TRL), population density on a total dry root basi s (Pf/TDRW), total dry root weight (TDRW), total dry root wei ght percent reduction (TDRW % red.), total root length (TRL), total root length per cent reduction (TRL % red.), fine root length (FRL), and fine root length percent reduction (FRL % red.) of TifEagle bermudagrass evaluated in three establishment (Est.) methods with different inoculation treatments (Inoc. TRT) in two experimental trials.........................................................................................41 3-2 Mean reproduction factor (Rf), final population density (Pf), population density on a total root length basis (Pf/TRL), populat ion density on a total dry root basis (Pf/TDRW), of Belonolaimus longicaudatus on TifEagle bermudagrass 90 days after inoculation evaluated in three establishmen t methods with two inoculation treatments in two experimental trials...................................................................................................42 3-3 45-d and 90-d conetainer (above diagonal) and 90-d clay pot (below diagonal) correlation coefficients of Belonolaimus longicaudatus reproduction factor (Rf), final population density (Pf), population density on a total root length basis (Pf/TRL), population density on a total dry root weight basis (Pf/TDRW), total dry root weight (TDRW), total dry root wei ght percent reduction (TDRW % red.), total root length (TRL), total root length per cent reduction (TRL % red.), fine root length (FRL), and fine root length percent reduction (FRL % red.) of TifEagle bermudagrass.....................43 3-4 Mean total dry root weight (TDRW), to tal dry root weight percent reduction (TDRW % red.), and total root length (TRL) of TifEagle bermudagrass 90 days after inoculation evaluated in three establis hment methods with uninoculated and inoculated treatments in tw o experimental trials...............................................................44 3-5 Mean total root length pe rcent reduction (TRL % red.), fi ne root length (FRL), and fine root length percent reduction (FRL % red.) of TifEagle bermudagrass 90 days after inoculation evaluated in three esta blishment methods with uninoculated and inoculated treatments in tw o experimental trials...............................................................45 4-1 Mean squares for Belonolaimus longicaudatus reproduction factor (Rf), total root length (TRL), and total dry root weight (T DRW) of six turfgra sses evaluated in two establishment (Est.) methods with uninoc ulated and inoculated treatments (Inoc. TRT) in two experimental trials.........................................................................................57 4-2 Mean reproduction factor (Rf) of Belonolaimus longicaudatus on six turfgrasses 90 days after inoculation with 50 B. longicaudatus, evaluated in 45-d conetainers and 90-d conetainers in two experimental trials.......................................................................57 7

PAGE 8

4-3 Mean total root length (TRL) and total dry root weight (TDRW) of six turfgrasses 90 days after inoculati on evaluated in 45-d conetain ers and 90-d conetainers with uninoculated (U) and inoculated (I) trea tments in two experimental trials.......................58 5-1 Mean squares for turfgrass performance characteristics and that ch depth of four Zoysia japonica cultivars and four Zoysia matrella cultivars evaluated at two mowing heights and three nitrogen fertili ty rates near Gainesville, FL............................71 5-2 Mean thatch depth of four Zoysia japonica cultivars when eval uated at two mowing heights and three nitrogen fertility rates in November of 2007 near Gainesville, FL.......84 5-3 Mean thatch depth of four Zoysia matrella cultivars when eval uated at two mowing heights and three nitrogen fertility rates in November of 2007 near Gainesville, FL.......84 6-1 Evaluation dates for turfgrass performan ce characteristics of zoysiagrass genotypes with very fine, fine, or coarse leaf texture visually rated during 2006, 2007, and 2008..................................................................................................................................108 6-2 Expected mean squares for turfgrass pe rformance traits of zoysiagrass genotypes evaluated on one date.......................................................................................................109 6-3 Expected mean squares for turfgrass pe rformance traits of zoysiagrass genotypes evaluated on multiple dates..............................................................................................109 6-4 Variance component estimate s, descriptive statistics, a nd broad-sense heritabilities (H2) for turfgrass performance characteristi cs of zoysiagrass genotypes with very fine, fine, or coarse leaf text ure evaluated during 2006, 2007, and 2008........................110 6-5 Variance component estimate s, descriptive statistics, a nd broad-sense heritabilities (H2) for turfgrass color characteristics of z oysiagrass genotypes with very fine, fine, or coarse leaf texture ev aluated during 2006 and 2007...................................................111 6-6 Variance component estimate s, descriptive statistics, a nd broad-sense heritabilities (H2) for turfgrass performance characteristi cs of zoysiagrass genotypes with very fine, fine, or coarse leaf te xture evaluated during 2006 and 2007...................................112 8

PAGE 9

LIST OF FIGURES Figure page 5-1 Genetic color responses and significance of treatment effects in Empire zoysiagrass at two mowing heights (M) and three nitrogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, August, and October of each year. Visual rating of five was considered to be the minimum acceptable value.......................72 5-2 Genetic color responses and significance of treatment effects in JaMur zoysiagrass at two mowing heights (M) and three ni trogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, August, and October of each year. Visual rating of five was considered to be the minimum acceptable value.......................73 5-3 Genetic color responses and significa nce of treatment effects in Palisades zoysiagrass at two mowing heights (M) and three nitrogen le vels (N) during 2007 and 2008. Fertilizer treatments were applie d in March, May, August, and October of each year. Visual rating of five was cons idered to be the minimum acceptable value.....74 5-4 Genetic color responses and significance of treatment effects in Ultimate zoysiagrass at two mowing heights (M) and three nitrogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, August, and October of each year. Visual rating of five was considered to be the minimum acceptable value.......................75 5-5 Turf density responses and significance of treatment effect s in Empire zoysiagrass at two mowing heights (M) and three ni trogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, August, and October of each year. Visual rating of five was considered to be the minimum acceptable value.......................76 5-6 Turf density responses and significance of treatment eff ects in JaMur zoysiagrass at two mowing heights (M) and three ni trogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, August, and October of each year. Visual rating of five was considered to be the minimum acceptable value.......................77 5-7 Turf density responses and significance of treatment eff ects in Palisades zoysiagrass at two mowing heights (M) and three nitrogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, August, and October of each year. Visual rating of five was considered to be the minimum acceptable value.......................78 5-8 Turf density responses and significance of treatment effects in Ultimate zoysiagrass at two mowing heights (M) and three nitrogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, August, and October of each year. Visual rating of five was considered to be the minimum acceptable value.......................79 5-9 Turf quality responses and significance of treatment effects in Empire zoysiagrass at two mowing heights (M) and three ni trogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, August, and October of each year. Visual rating of five was considered to be the minimum acceptable value.......................80 9

PAGE 10

5-10 Turf quality responses and significance of treatment effects in JaMur zoysiagrass at two mowing heights (M) and three ni trogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, August, and October of each year. Visual rating of five was considered to be the minimum acceptable value.......................81 5-11 Turf quality responses and significance of treatment effects in Palisades zoysiagrass at two mowing heights (M) and three nitrogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, August, and October of each year. Visual rating of five was considered to be the minimum acceptable value.......................82 5-12 Turf quality responses and significance of treatment effects in Ultimate zoysiagrass at two mowing heights (M) and three nitrogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, August, and October of each year. Visual rating of five was considered to be the minimum acceptable value.......................83 5-13 Genetic color responses and significance of treatment effects in Cavalier zoysiagrass at two mowing heights (M) and three nitrogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, July, September, and November of each year. Visual rating of five was cons idered to be the minimum acceptable value.....85 5-14 Genetic color responses and significa nce of treatment effects in Diamond zoysiagrass at two mowing heights (M) and three nitrogen le vels (N) during 2007 and 2008. Fertilizer treatments were applied in March, May, July, September, and November of each year. Visual rating of five was considered to be the minimum acceptable value............................................................................................................... ..86 5-15 Genetic color responses and significance of treatment effects in Pristine zoysiagrass at two mowing heights (M) and three nitrogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, July, September, and November of each year. Visual rating of five was cons idered to be the minimum acceptable value.....87 5-16 Genetic color responses and significance of treatment effects in Zeon zoysiagrass at two mowing heights (M) and three ni trogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, July, September, and November of each year. Visual rating of five was cons idered to be the minimum acceptable value.....88 5-17 Turf density responses and significance of treatment eff ects in Cavalier zoysiagrass at two mowing heights (M) and three nitrogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, July, September, and November of each year. Visual rating of five was cons idered to be the minimum acceptable value.....89 5-18 Turf density responses a nd significance of treatment effects in Diamond zoysiagrass at two mowing heights (M) and three nitrogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, July, September, and November of each year. Visual rating of five was consid ered to be the minimum acceptable value.....90 10

PAGE 11

11 5-19 Turf density responses and significance of treatment effect s in Pristine zoysiagrass at two mowing heights (M) and three ni trogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, July, September, and November of each year. Visual rating of five was cons idered to be the minimum acceptable value.....91 5-20 Turf density responses a nd significance of treatment ef fects in Zeon zoysiagrass at two mowing heights (M) and three ni trogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, July, September, and November of each year. Visual rating of five was cons idered to be the minimum acceptable value.....92 5-21 Turf quality responses and significance of treatment effects in Cavalier zoysiagrass at two mowing heights (M) and three nitrogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, July, September, and November of each year. Visual rating of five was cons idered to be the minimum acceptable value.....93 5-22 Turf quality responses and significance of treatment effects in Zeon zoysiagrass at two mowing heights (M) and three ni trogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, July, September, and November of each year. Visual rating of five was cons idered to be the minimum acceptable value.....94 5-23 Turf quality responses and significance of treatment effects in Diamond zoysiagrass at two mowing heights (M) and three nitrogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, July, September, and November of each year. Visual rating of five was cons idered to be the minimum acceptable value.....95 5-24 Turf quality responses and significance of tr eatment effects in Pristine zoysiagrass at two mowing heights (M) and three ni trogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, July, September, and November of each year. Visual rating of five was cons idered to be the minimum acceptable value.....96

PAGE 12

Abstract of Dissertation Pres ented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy ZOYSIAGRASS EVALUATION FOR DNA CONT ENT, STING NEMATODE RESPONSE, NITROGEN MANAGEMENT, AN D ESTIMATES OF HERITA BILITY FOR TURFGRASS PERFORMANCE TRAITS By Brian M. Schwartz December 2008 Chair: Kevin E. Kenworthy Major: Agronomy Zoysiagrass ( Zoysia spp.) use in landscapes and on gol f courses has primarily occurred in the transition zone of the United States. Varia tion associated with several abiotic, biotic, and turfgrass performance characteri stics is well documented. La boratory, glasshouse, and field studies utilizing zoysiagrass germplasm were conducted from 2005 through 2008 to quantify 2C nuclear DNA content, sting nematode ( Belonolaimus longicaudatus ) response, effects of nitrogen fertilization rate and mowing height management, and broad-sense herita bility estimates of turfgrass performance and stre ss related characteristics. All experiments were managed with supplemental irrigation. Genotypes from Z. minima and Z. matrella had the largest (0.96 pg) and smallest (0.77 pg) 2C nuclear DNA contents, re spectively. The observed 0.19 pg spread between zoysiagrass species was less than variation reported in other tetraploid warm-season grasses within the same species. Total root lengths of TifEagle bermudagrass ( Cynodon dactylon [L.] Pers. var. dactylon C. transvaalensis Burtt-Davy) were 57 %, 55 %, and 31 % greater for uninoculated treatments when compared to an average of the two sting nematode inoculated treatments in the 45-d conetainers, 90-d cone tainers, and 90-d clay pots, respectively. Quantifying root damage using 45-d conetainers inoculated with 50 sting nematodes provided 12

PAGE 13

13 reproducible results characteristic of those reported in other greenhouse and field evaluations. Sting nematode populations multiplied on the evaluated zoysiagrass and St. Augustinegrass ( Stenotaphrum secundatum [Walt.] Kuntze) cultivars with reproduction factors ranging from 2.2 to 11.0. The experimental Zoysia germplasm line UFTZ exhibited greater tolerance to sting nematode injury than other turf grass cultivars and exhibited no total root lengt h reduction under sting nematode pressure. Significant total root length percent reductions were observed between uninoculated and inoculated treatments for E mpire (-24%), Cavalier (-29%), Emerald (29%), TifEagle (-32%), and Floratam (-37%) in 45-d conetainers. In the management study, nitrogen rate had the greatest influence on turfgrass perfor mance, but mowing height was important during colder periods or in the presence of Bipolaris disease pressure. Turfgrass density was not maintained in Empire or Palisades at the lowest N rate. Bipolaris incidence was noted on Cavalier and Zeon, and had the most detrimental effect on turf quality at the lower mowing height and highest N rate. JaMur, Ultimate, Dia mond, and Pristine all had acceptable density at the low nitrogen rate, but ofte n did not have adequate color to sustain turf quality. Genotypic variance largely contributed to the wide range in expressed phenotypic response in a set of 324 zoysiagrass germplasm lines for establishment, turf density, turf quality, genetic color, and seedhead density which resu lted in higher broad-sense heritability estimates (0.62 H2 0.94). Fall dormancy and spring greenup were influenced more by the environment and had lower heritabilities (0.32 H2 0.58). Turf quality was also rated considering the effects of glufosinate herbicide application, Bipolaris incidence, and mole cricket damage. Large error variances and low br oad-sense heritabilities were t ypical for these stress related traits. Overall, the potential exists for combini ng desirable traits in su perior clonally propagated F1 zoysiagrass hybrids.

PAGE 14

CHAPTER 1 INTRODUCTION Zoysia Willdenow are perennial grasses assigned to the family Gramineae (Poaceae), subfamily Chloridoideae, and tribe Zoysieae. Th ey are native to the Pacific Rim countries and the center of origin is specula ted to be near southeastern Asia and Indonesia (Engelke and Anderson, 2003). Anderson (2000) classified available specimens into 11 species based on morphological variation and nucle ar DNA restriction fragment length polymorphism (RFLP) fingerprints. Many of these species can be managed as turfgrasses, producing stolons and rhizomes, having pointed leaves of various widt hs with rolled vernat ion, and characterized by individual, raceme inflorescences which appear spike-like. Seed and plant samples of Zoysia japonica and Z. matrella were first introduced into the United States in the early 20th century by United States Depart ment of Agriculture (USDA) researchers Frank N. Meyer and C.V. Piper (Childers and White, 1947; Grau and Radko, 1951). Other notable United States Depa rtment of Agriculture-Agricu ltural Research Service (USDAARS) scientists who have made collection trip s on the Eurasia continent include G.W. Burton, D.R. Dewey, W.W. Hanna, D.A. Johnson, and J.J. Murray (M.C. Engelke, personal communication, 2006). Plant breeders in the private sector have collected in collaboration with overseas scientists in efforts to expand the germplasm base necessary for improved seed yields (Samudio, 1996). The two most extensive zoys iagrass collection trips were made by M.C. Engelke and J.J. Murray in 1982 and by M.C. E ngelke, M.P. Kenna, C.M. Taliaferro, and R.J. Tyrl in 1993. In total, over 1000 unique Zoysia accessions have been brought back to the United States, many of which are still maintained at Texas A&M University. Genotypes were collected from as far north as 43N latitude to as far s outh as 9N latitude, indica ting the adaptability of zoysiagrass to many climates. Considerable variation was noted among accessions for color, 14

PAGE 15

winter dormancy, shade tolerance, growth habits, s eed set, leaf texture, disease resistance, and growing conditions. Samples were collected fr om areas under intensiv e grazing, prolonged snow cover, and from the edge of the ocean where plants were growing unde r constant salt spray (Engelke, 2000; Engelke and Anderson, 2003; Mu rray and Engelke, 1983). Further discovery and collection of germplasm will broaden genetic diversity, thereby contributing to reduced vulnerability of future cultivars (Brede and Sun, 1995; Busey, 1977; Loch et al., 2005). In 1951, the USDA-ARS and the United States Golf Association (USGA) Green Section released a finer textured Zoysia japonica named Meyer (Grau and Radko, 1951). This cultivar is often credited as the first zoysiagrass, although an improved Z. matrella was released as FC13521 in 1930 by the Alabama Agricultural E xperiment Station in Auburn (Ruemmele and Engelke, 1990). Ian Forbes studied the cy tological and morphological variation among many zoysiagrasses and recommended that Z. japonica Z. matrella and Z. tenuifolia be considered varieties of one species based on their cross compatibility. Eme rald was released in 1955 as a result of these efforts and was described as a Z. japonica Z. tenuifolia hybrid (Forbes et al., 1955; Forbes, 1952), although the results of RFLP fi ngerprint analysis la ter suggested that it arose from a hybridization of Z. matrella Z. pacifica (Anderson, 2000). Very few improved cultivars were develope d in the 30 years following the release of Emerald, likely because of a lack in variab le germplasm resources needed for plant improvement. Midwest was released from the Indiana Agricultural Experiment Station in 1963 by W.H. Daniel. The breeding efforts J.J. Murray of the USDA-ARS in Beltsville, Maryland and V.B. Youngner at the University of California, Riverside even tually led to the release of Belair (1985) and El Toro (1986), respectively (Diesburg, 2000; Ruemmele and Engelke, 1990). Approximately 27 vegetatively propagated cult ivars have since been released or patented, 15

PAGE 16

16 although many are no longer, or never have been, readily available. Many challenges have impeded the successful development of seeded zoysiagrass cultivars. These include small seed yields, seed dormancy, poor seedli ng vigor, and loss of stand unifo rmity and quality over time. More recent synthetic releases Compadre and Zenith do show improvement. Roughly another 17 seeded zoysiagrasses have been devel oped and tested in the United States, but have had little market success (E ngelke and Anderson, 2003; Morris 2000; Morris, 2006; Morris and Shearman, 1995; Samudio, 1996; Unruh et al., 2007) Haydu et al. (2005) reported that 1% of Floridas sod production h ectareage was planted with Zoysia spp. Variation for many abiotic, biotic, and turfgrass performance characteristics has been quantified in zoysiagrass. Ge notypic differences in drought and rooting characteristics (Marcum et al., 1995), response to low te mperatures (Patton and Reiche r, 2007), salinity (Qian et al., 2000), shade (White and Engelke, 1990), and wear tolerance (Youngne r, 1961) have been observed. Levels of insect (Rei nert et al., 1997) and plant-para sitic nematode (Busey et al., 1982) resistance have been iden tified. Some disadvantages of these turfgrasses are slow establishment rate (Busey and Myers, 1979) and divot recovery (Karcher et al., 2006), delayed spring greenup (Gibeault et al., 1997), thatch accumulation (Soper et al., 1988), and disease susceptibility (Green et al., 1993). Documentation of such extensive varia tion indicates the potential for continued improvement of these species. Therefore, the objectives of the following chapters are to (i) investigate the range between Zoysia spp. for 2C nuclear DNA content, (ii) develop procedures for efficient screening of sting nematode respons e, (iii) identify base management guidelines for nitrogen fertilization and mowing of zoysiagrass in Florida, a nd (iv) evaluate germplasm for variation and herita bility of turfgrass performance traits.

PAGE 17

CHAPTER 2 VARIATION IN 2C NUCLEAR DNA CONTENT OF Zoysia spp. AS DETERMINED BY FLOW CYTOMETRY Introduction Anderson (2000) suggests that the genus Zoysia is comprised of 11 species that vary with respect to morphology and nuclear DNA constituti on. Speciation appears to have occurred through geographic isolation (Kim 1983; Weng et al., 2007) rath er than by genetic changes associated with an increase or de crease in ploidy level (Forbes, 1952). All cytological studies of Zoysia spp. have determined that 2n = 40 (Arum uganathan et al., 1999; Chen and Hsu, 1962; Christopher and Abraham, 1974; Forbes, 1952; Murray et al., 2005; Tateoka, 1955), except for an unexplained report of a diploid plant, 2n = 20, collected from Sri Lanka (Gould and Soderstrom, 1974). Forbes (1952) theorized that Zoysia spp. were diploid in nature, but did not disregard the possibility that the basic chromosome number could be 5 or 10. Chen and Hsu (1962) suspected that the basic chromosome number was 10 based on cytological studies in other eragrostoid grasses. This wa s later confirmed by Gould (1968) Zoysiagrasses are currently described as allotetraploids ba sed on restriction fragment lengt h polymorphism (RFLP) linkage mapping and analysis (Yaneshita et al., 1999). The absence of an aphase bridges, fragments, lagging chromosomes, univalents or multivalen ts during meiosis I in conjunction with the formation of 95% viable pollen (Forbes, 1952) supports the allotetr aploid classification. Taxonomic assignment in Zoysia has been predominately weighted towards morphological and molecular marker variation rather than by repr oductive isolation as suggested by Forbes et al. (1955) in accordance with the bi ological species concept (Mayr, 1948). Genetic variability has been characterized through ra ndom amplification of polymorphic DNA (RAPD) (Choi et al., 1997; Weng et al., 2007), RFLP (Anderson, 2000; Ya neshita et al., 1999; Yaneshita et al., 1997), amplified fragment length polymor phism (AFLP) (Cai et al., 2004), and simple 17

PAGE 18

sequence repeat (SSR) (Cai et al., 2005; Tsur uta et al., 2005) marker analyses to discern relatedness among zoysiagrass speci es. Cross-compatibility does exist between a number of the Zoysia species (Forbes, 1952; Hong and Yeam, 1985), although Engelke and Anderson (2003) observed low germination percentages betw een a few interspecific combinations. Flow cytometry (FCM) was first developed for analyzing animal cells. The techniques and instrumentation were modified for lysis of the plant cell wall and se paration of the nucleus from plastid and mitochondrial DNA (Galbrait h, 1990). This methodol ogy provides rapid and accurate ploidy determination and DNA content analysis for plant breeding programs (Arumuganathan and Earle, 1991a; Dolezel et al., 1989; Laat et al., 1987). A major application of FCM has been the general characterization of plant sp ecies for their DNA contents (Arumuganathan and Earle, 1991b; Bennett and Leitc h, 1995), but other uses include analysis of plant cell cycles (Galbraith et al., 1983), sex identification in dioecious plants (Costich et al., 1991), the estimation of C-banded constitutive heterochromatin (Rayburn et al., 1992), and use as a taxonomic marker when the gain or lo ss of DNA is correlated with evolutionary relationships between species (Ohri, 1998). Reports of variation in DNA content from Zoysia spp. are limited. In an analysis of native New Zealand grasses, Murray et al. (2005) concluded that in general, tropical grasses have lower DNA contents than those of temperate origin. Zoysia pauciflora ranked the lowest of all grasses surveyed with a 2C-value of 0.97 pg. Zoysia minima was recorded to have a genome size of 0.99 pg. Arumuganathan et al. (1999) repo rted the 2C nuclear DNA content of Zenith, a seeded Z. japonica Steud. cultivar, to be 0.86 0.00 pg. Flow cytometry has become a useful tool for plant breeders to ch aracterize the nuclear DNA content and ploidy level in other warm-season turfgrass species. Tali aferro et al. (1997) 18

PAGE 19

developed an accurate method to determine pl oidy level and genome size in bermudagrass ( Cynodon spp.). This methodology was used by Wu et al. (2006) to study the genetic diversity of Chinese bermudagrass germplasm. Triploid, tetraploid, pentaploid, and hexaploid genotypes were identified and further characterized with AFLPs. Johnson et al. (1998) used FCM to distinguish diploid, tetraploi d, and hexaploid buffalograss ( Buchloe dactyloides [Nutt.] Engelm.) germplasm for breeding purposes. In doing so th ey discovered three previously un-described pentaploid clones. Jarret et al. (1995) surveyed the nuclear DNA contents of 35 Paspalum species and determined that there was insuffici ent variation to discriminate between genotypes within a species, but that ploidy evaluation was accurate and repeatable Vaio et al. (2007) observed genome sizes in natural dallisgrass ( Paspalum dilatatum Poir.) tetraploids that were less than twice the size of their diploid progeni tors. This reduction in DNA content was not present in synthetically created allotetraploid dall isgrasses. This phenomenon, documented in other polyploid species, was credited to genome downsizin g (Leitch and Bennett, 2004). Genome analysis by FCM has been classified as a rapid and reliable method to identify cytotypes with varying ploidy le vels in Kentucky bluegrass (Poa pratensis L.) (Barcaccia et al., 1997; Huff and Bara, 1993). Eaton et al. (2004) were able to di stinguish true hybrids derived from both intraand interspeci fic hybridizations, and Wieners et al. (2006) differentiated genotypes with the four major reproductive path ways in Kentucky bluegrass according to the presence and position of peaks. Other cool-season grasses in which ploidy level variation has been researched utilizing FCM include fine fescue ( Festuca spp.) (Huff and Palazzo, 1998), ryegrass ( Lolium spp.) (Barker et al., 2001), and bentgrass ( Agrostis spp.) (Bonos et al., 2002). Flow cytometry has been shown to reliably characterize nuclear DNA content and ploidy level in plants. Consideri ng that these data are largely absent for members of the Zoysia genus, 19

PAGE 20

research was initiated to (i) ch aracterize the variation in 2C nuclear DNA content of available cultivars and experimental lines represen ting true, or intersp ecific hybrids between, Zoysia japonica Z. macrantha Z. matrella Z. minima Z. pacifica and Z. pauciflora species through flow cytometry, and (ii) determine if sufficient variation exists between 2C nuclear DNA content within and among Zoysia species to statistically identify intermediate, mid-parent nuclear DNA contents from F1 hybrids. Materials and Methods Plant Materials Zoysiagrass materials consiste d of 20 cultivars and 16 expe rimental lines from five species and five interspecific hybridizations (Table 2-1). Ge notypes were assigned to their respective species based on mor phology and not genotypic characte rization. Each genotype was vegetatively propagated into three, five cm pots containing a 50% sand, 50% Metro-Mix 250 (Scotts-Sierra Horticu ltural Products Co., Mary sville, OH) growing medium in January, 2008. Plants were organized in a completely randomized design with three replications and grown in a glasshouse in Gainesville, FL with supplemental overhead irrigation. Fertilizer was applied monthly with Peters Professional 20-20-20 General Purpose Water Soluble Fertilizer (ScottsSierra Horticultural Products Co., Ma rysville, OH) at a rate of 2.4 g m-2. Leaf canopies were trimmed twice monthly except fo r overhanging, aerial stolons. Flow Cytometry Flow cytometry analysis was initiated when at least one aerial stol on was present in each pot. The terminal node and tip from one stol on was removed from each experimental unit and stored on ice prior to FCM analysis. A Cy Stain PI Absolute P (05-5002, Partec North America, Inc., Mt. Laurel, NJ) nuclei extract ion and DNA staining kit was used to prepare samples using a technique modified from Arumug anathan and Earle (1991a). The terminal end 20

PAGE 21

of each stolon was chopped with a razor blade and scalpel in a glass petri dish with 500 L of extraction buffer for approximately 60 s. The resulting solution, containing isolated nuclei, was pipetted into a five mL test tube through a 50 m nylon mesh filter cap. One drop of chicken red blood cell (CRBC) standard (BioSu re Inc., Grass Valley, CA) was then added to the test tube followed by two mL of the propidium iodide (P I) based DNA staining solution. Samples were incubated at 4C for 60 min in the dark. Fl ow cytometry analysis was conducted at the University of Floridas Interdisciplinary Center for Biotechnology Research on a LSR-II cytometer (BD Biosciences, San Jose, CA) using a 100 milliwatt solid-state laser emitting at 488 nm to excite the PI. DNA peak data, based on 10,000 scanned particles, were quantified using FACS DiVa v5.2 software (BD Bios ciences, San Jose, CA). The mean 2C nuclear DNA content of each sample, measured in picograms, was ad justed based on the peak of the CRBC internal standard by taking the ratio of the plant sample peak mean and the CRBC peak mean, then multiplying by the 2C nuclear DNA content of the internal standard, i.e., 2.5 pg (Rasch, 1985; Tiersch et al., 1989). Genotypic 2C nuclear DNA contents are means of three replicates. Morphological Measurements Zoysiagrasses are commonly classified by their leaf width. A digital caliper was used to measure the widest section of three fully expanded and mature leaf blades in each experimental unit. The average value of the sub-samples in each experimental unit was used for further analysis. Statistical Analysis The distribution of data for both 2C nuclear DNA content and leaf blade width was assessed with a histogram and nor mal probability plot for normality. An analysis of variance was performed on each of the measured traits to test whether genotypes, species determined by morphology, and where appropriate, genotypes with in species varied. Genotype and species 21

PAGE 22

means were separated using a Waller-Duncan k -ratio LSD when the main effect was found to be significant. Pearson correlation coefficients were computed to test whether 2C nuclear DNA contents were associated with leaf blade widths. Results and Discussion Consistent extraction and staining of nuclei was not achieved using young, freshly harvested leaves according to standard protocol (Arumuganathan and Earle, 1991a). This is likely due to the high silica cont ent in the leaves (Ruemmele a nd Engelke, 1990) which renders physical chopping very difficult. Tissue from root and rhizome tips also resulted in inconsistent FCM analysis. Only analysis of plant material from the terminal node and tip of a stolon yielded consistent and repeatable results, producing peak CVs < 6.0% for all genotypes. Genotypes varied ( P = 0.001) for 2C nuclear DNA cont ent. Zenith (0.83 pg/2C) and 5194-5 (0.96 pg/2C), a representative of Z. minima were both ~3% lower than found by Arumuganathan et al. (1999) and Murray et al. (2005), respectively (Table 2-1). These small differences could be attributed to sample preparation or betw een-lab instrumental variation (Dolezel et al., 1998). Zoysia matrella was the only species in which genotypes were significantly different ( P = 0.01) for 2C nuclear DNA content. The low measured values for Diamond and Zorro were largely re sponsible for these differences. The observed spread between Diamond, Z. matrella with 0.77 pg/2C nucleus, and 51945, Z. minima with 0.96 pg/2C nucleus, was 0.19 pg. Similar ranges in 2C nuclear DNA content have been reported in other grasses within the same species and ploidy level. Taliaferro et al. (1997) and Wu et al. (2006) reported a range of 0.33 and 0.34 pg/2C nucleus, respectively in tetraploid bermudagrasses. A 0.20 pg variation was reported for common dallisgrass (Jarret et al., 1995), where a larger spread of 0.53 pg was obs erved in tetraploid bu ffalograss (Johnson et al., 1998). 2C nuclear DNA contents are typicall y higher in temperate than tropical grasses 22

PAGE 23

(Arumuganathan et al., 1999; Mu rray et al., 2005) resulting in proportionally larger ranges for this trait in cool season grasses of the same sp ecies and ploidy level (B arker et al., 2001; Bonos et al., 2002; Eaton et al., 2004; Huff and Palazzo, 1998). Differences were found ( P = 0.001) for 2C nuclear DNA content between Zoysia species and interspecific hybrids (Table 1). Only those between Z. minima and the rest of the group as a whole may be meaningful, although ot hers were statistically signifi cant. The ability to detect true interspecific hybrids between Z. minima and other Zoysia spp. is supported by the differences between Z. minima Z. matrella and the interspecific hybrids of the two. A representative Z. pauciflora genotype was unfortunately not avai lable for FCM analysis. Murray et al. (2005) reported Z. pauciflora to have 0.97 pg/2C nucleus. It may be inferred that differences between Z. pauciflora, Z. matrella and interspecific hybrid s of the two could be detected based on their respective 2C nuclear DNA contents. Variation in leaf blade widt h was present between genotypes ( P = 0.001) and species ( P = 0.001). Large leaf widths were typically associated with Z. macrantha and Z. japonica genotypes, where those within Z. minima and Z. pacifica had the smallest leaves. This trait has been well characterized within, and between Zoysia species (Anderson, 2000; Choi et al., 1997; Hong and Yeam, 1985; Kim, 1983; Yaneshita et al ., 1997). Leaf blade wi dth and 2C nuclear DNA content were not correlated ( r = -0.18, P > 0.05). Knight et al. (2005) suggested that leaf anatomical trait (i.e., length, width, area, and ma ss) correlation with 2C nuclear DNA content is dependent on the species sampled. Leaf width was not correlated with 2C nuclear DNA content in buffalograss (Johnson et al., 1998), bentgrass (Bonos et al., 2002), napiergrass ( Pennisetum purpureum Schum.) (Taylor and Vas il, 1987), and switchgrass (Panicum virgatum L.) (Hultquist et al., 1997). 23

PAGE 24

The speciation of zoysiagrass is partially linked to its dissemination over time throughout geographically isolated Pacific Rim countries (Weng et al., 2007). Greilhuber (1998) theorized that genome size variation between reproductively isolated populations will occur over time due to common chromosomal polymorphism s and spontaneous aberrations. Zoysia spp. have one of the smallest genome sizes in the Poaceae family (Murray et al., 2005) A tentative association has been made between species of increasing genome size and a decreased ability to adapt to extreme environments where conditions quickly change (Grime and Mowforth, 1982; Knight et al., 2005). Conceivably, the vast variation in morphological char acteristics and establishment rates (Patton et al., 2007) in Zoysia spp. can be partially explaine d by its small genome size and the corresponding lack of evolutionary constrai nts associated with la rge amounts of repetitive DNA such as longer cell cycles a nd non-coding regions that can bu ffer the effects of mutation. This could also have a factor in the differentia l responses of zoysiagra sses to drought (Marcum et al., 1995; White et al., 2001), shad e (Morton et al., 1991), salinity (Marcum et al., 1998; Qian et al., 2000), temperature (Patton and Reicher, 2007), disease (Green et al., 1994), insect (Braman et al., 2000; Reinert and Engelk e, 2001), and nematode (Busey et al., 1982) pressures. Conclusions Continuous variation for 2C nucl ear DNA content across most of the Zoysia spp. studied herein was present, but over a smaller range th an in other warm-season grasses within the same species and ploidy level. Fu rther quantification of 2C nuclear DNA content variation in additional Zoysia spp. and interspecific hybrids as they be come available is needed before an association between genome size and species is deemed relevant. The rapid and accurate method for screening zoysiagrass germplas m using the terminal end of a st olon as described within will allow for repeatable FCM analysis in the future. 24

PAGE 25

25 An alternative viewpoint that merits re-introduction is the assignment of species based on reproductive compatibility (Mayr, 1948) rather than by genotypic and phe notypic variation that transverse multiple species within the genus. Mu rray (2005) emphasized the need to test for a reduction of fertility in hybrids between individuals that differed in C-value before the two are recognized as different species. This premise coul d apply to any plant char acteristic, whether it is genome size or morphology. Leaf width was not correlated with 2C nuclear DNA content in the genotypes evaluated herein. Under the cu rrent taxonomic system, zoysiagrasses are often incorrectly distinguished as a sp ecies based on leaf texture alon e. This confusion would be eliminated if the biological species concept was in use.

PAGE 26

Table 2-1. Means for 2C nuclear DNA cont ent and leaf blade width of zoysiagra ss genotypes for five species and five interspecific hybridizations 2C DNA content Leaf morphology 2C DNA content Leaf morphology Developing Institution Genotype Genotypic mean SE Blade width Leaf texture Zoysia species Species mean Blade width pg pg mm class pg mm Texas A&M University 5194-5 0.96 a 0.01 0.44 u Very fine Z. minima 0.96 a 0.44 e Texas A&M University 5504-6 0.94 ab 0.02 0.96 r Very fine Texas A&M University 5458-39 0.90 bc 0.00 0.90 rs Very fine Z. matrella Z. minima 0.92 b 0.93 d Texas A&M University 5335-3 0.89 cd 0.02 3.90 e Coarse Z. macrantha Z. matrella 0.89 bc 3.90 a Texas A&M University 5193-19 0.88 c-f 0.01 2.23 kl Medium Texas A&M University 5186-16 0.88 c-g 0.01 3.06 h Coarse Z. macrantha# 0.88 c 2.65 b Texas A&M University 5463-9 0.88 c-g 0.01 0.83 s Very fine Texas A&M University 5459-10 0.87 c-g 0.00 0.67 t Very fine Z. matrella Z. pauciflora# 0.87 cd 0.75 d University of Florida BA433 0.85 d-i 0.03 0.46 u Very fine Z. pacifica 0.85 cde 0.46 e Sod Solutions Empire 0.88 cd 0.02 4.48 b Coarse USDA and USGA Meyer 0.87 c-i 0.01 3.52 g Coarse University of Florida UFTZ 0.86 c-i 0.01 3.11 h Coarse University of Florida Ultimate 0.86 c-i 0.02 2.51 j Medium Texas A&M University Palisades 0.86 c-i 0.01 3.73 f Coarse Seed Research of Oregon Compadre 0.86 c-i 0.02 4.97 a Coarse University of California El Toro 0.85 d-k 0.02 3.61 fg Coarse Bladerunner Farms, Inc. JaMur 0.84 e-l 0.01 4.17 c Coarse University of California Victoria 0.84 f-l 0.01 2.57 j Medium Sod Solutions Empress 0.84 g-l 0.02 2.15 l Medium Texas A&M University Crowne 0.84 g-l 0.00 4.07 cd Coarse Patten Seed Company Zenith 0.83 h-m 0.01 3.59 fg Coarse Z. japonica# 0.85 cde 3.54 a 26

PAGE 27

27Table 2-1 Continued 2C DNA content Leaf morphology 2C DNA content Leaf morphology Developing Institution Genotype Genotypic mean SE Blade width Leaf texture Zoysia species Species mean Blade width Texas A&M University Cavalier 0.87 c-h 0.01 1.80 m Fine Texas Tech University Shadow Turf 0.87 c-i 0.01 1.35 q Fine Texas A&M University Royal 0.86 d-i 0.01 1.60 no Fine Pursley Turf Farms Cashmere 0.85 d-i 0.02 1.66 n Fine Bladerunner Farms, Inc. Zeon 0.85 d-j 0.02 1.38 q Fine USDA and USGA Emerald 0.84 f-l 0.02 1.49 p Fine University of Florida Pristine 0.83 g-m 0.02 1.62 no Fine Texas A&M University Zorro 0.79 mn 0.00 1.54 op Fine Texas A&M University Diamond 0.77 n 0.01 0.97 r Very fine Z. matrella# 0.84 de 1.49 c Texas A&M University 5337-46 0.83 i-m 0.02 3.97 de Coarse Z. japonica Z. macrantha 0.83 e 3.97 a Texas A&M University 5343-52 0.86 c-i 0.00 2.18 l Medium Texas A&M University 5334-6 0.85 d-j 0.00 2.78 i Medium Texas A&M University 5332-52 0.81 j-n 0.02 2.22 kl Medium Texas A&M University 5283-5 0.81 k-n 0.03 2.14 l Medium Texas A&M University 5282-20 0.80 lmn 0.02 2.34 k Medium Z. japonica Z. matrella# 0.83 e 2.33 b % CV 3.11 1.87 3.71 10.19 United States Department of Agriculture and United States Golf Association. Means within a column followed by the same letter are not different at K = 100 (approximates P = 0.05) according to Waller-Duncan LSD. Leaf texture classifications assi gned based on leaf width measurements (Very fine < 1.0mm; 1.0mm < Fine < 2.0mm; 2.0mm < Medium < 3.0mm; 3.0mm < Coarse). #Leaf blade widths were different for genotypes within species at the 0.01 level of probability. 2C nuclear DNA contents were different for genotypes within species at the 0.01 level of probability.

PAGE 28

CHAPTER 3 EFFICIENT METHODOLOGY FOR SCREENI NG STING NEMATODE RESPONSE IN A TURFGRASS BREEDING PROGRAM Introduction Sting nematode ( Belonolaimus longicaudatus ) is a parasite of many warm-season turfgrasses. This nematode feeds primarily on th e actively growing root tips of their hosts which over time results in shallow, necrotic roots. Visual symptoms associated with this root deterioration include chlorosis, wilting, reduced growth rates, a nd thin turf (Perry, 1974). Turf quality and drought tolerance can be reduced as a result of stunted root systems when sting nematode populations are not managed (Trenholm et al., 2005). Damaged turf may not respond to nitrogen fertility or irrigati on over time when plant parasitic nematodes are present in the soil (Luc et al., 2007). Nitrate leaching, as a result of decreased uptake ca pability in areas with weakened rootzones, has the potential to reduce water quality and increase management costs as water resources become limited (Luc et al., 2006). Hybrid bermudagrasses ( Cynodon dactylon [L.] Pers. var. dactylon C. transvaalensis Burtt-Davy) have been widely utilized for turf purposes throughout the warmer environments of the world due to their broad adaptability and superior quality (Hanna, 2008). A limitation of these grasses has been their host suitability and susceptibility to the sting nematode in the sandy soils of the Southeastern United States (Good, 1959; Good et al., 1956; Holdeman and Graham, 1953; Robbins and Barker, 1973) and on artificially constructed, sand-based putting greens (Crow, 2005a; Crow, 2005c). Damage to St. Augustinegrass ( Stenotaphrum secundatum [Walt.] Kuntze) roots, and subsequent top growth chlorosis, have been attributed to this nematode in the field (Kelsheimer and Overman, 1953) and observe d in controlled greenhouse studies (Rhoades, 1962). Dynamics of the host-parasite relationship have been further studie d (Giblin-Davis et al., 1992a). Generally, diploid St. Augustinegrasses have been characterized as susceptible (Busey 28

PAGE 29

et al., 1991), but resistance has b een identified in some polyploid cultivars (Busey et al., 1993). Good et al. (1956) described the sting nematode as one of the most antagonistic pests of zoysiagrass ( Zoysia spp.). Busey et al. ( 1982) identified germplasm with partial resistance, but concluded that many breeding chal lenges regarding better adaptation and pest resistance needed to be overcome before this species could be utilized in the sub-tropics. Seashore paspalum ( Paspalum vaginatum Swartz) is a reproductive host that is damaged by the sting nematode (Hixson et al., 2004). Centipedegrass ( Eremochloa ophiuroides [Munro] Hack) has been reported to be a host of the sting nematode (C hristie et al., 1954; G ood, 1959), but parasitism on this species has not been well documented. A variety of management techniques have been evaluated in an attempt to eliminate or suppress plant parasite nematodes where they are damaging. The most common, and often only, method of nematode management in susceptible cu ltivars has been the use of nematicides (Crow et al., 2003; Giblin-Davis et al., 1991; Johnson, 1970a; Perry et al., 1970). Heald and Burton (1968) found that sting and root-knot nematode populations were reduced when organic sources of nitrogen were used instead of ammonium nitrate. White and Dickens (1984) observed the same trends, but reported that other management practices (i.e., topdr essing, vertical mowing, and core aerification) had no effect on plant parasitic nematode populations. Both endoand ectoparasitic nematodes can be eliminated from bermudagrass sprigs with a 15 min, 55C hot water bath without significantl y increasing sprig mortality (H eald and Wells, 1967), but this procedure has limited practicality. Botanica l nematicides, root biostimulants, and entomopathogenic nematodes have not shown consis tent suppression of plan t parasitic nematode populations as required from turfgrass managers (Crow, 2005b; Crow et al., 2006). Recent loss of fenamiphos, the most commonly used nematicid e on turf in the United States, has heightened 29

PAGE 30

the need for new nematode management strate gies. This has renewed interest in the development of turfgrass cultivars with improved resistance and tolerance to the sting nematode. The search for useful resistance or toleran ce to the sting nematode has been limited to readily available cultivars and a limited number of germplasm accessions (Bekal and Becker, 2000; Giblin-Davis et al., 1992b; Johnson, 1970b; Tarjan and Busey, 1985). In bermudagrass, more effort has been dedicated to breeding a nd selecting for root-kno t nematode resistance (Burton et al., 1946; Riggs et al ., 1962; Sledge, 1962). Burton (1974) stated that several radiation induced mutants of Tif green, Tifway and Tifdwarf were more resistant to rootknot nematodes than their respective parent al clones. Root-knot nematode resistant bermudagrasses often lower the pop ulation of root-knot nematodes, but may serve as a host for other ectoparasitic nematode species (Good et al ., 1965). The forage be rmudagrass Coastcross1 exhibited sting nematode resistance (Burton, 1972). A greater effort to screen broader germplasm of susceptible turfgra ss species would likely result in th e discovery of more resistant or tolerant individuals. Improvement through breeding should be possible because genetic variability for these characteris tics has been demonstrated (Giblin-Davis et al., 1992b). As regulations regarding the use of soil fumigants and nematicides become stricter, it would be valuable to identify a genetic source for effective control of this pest. This research was initiated to investigate evaluation methods to identify a high throughput, accurate and repeatable greenhouse screen useful to turfgrass breeding programs in comparing response to an ectoparasitic nematode, B. longicaudatus. Materials and Methods Two experimental trials were conducted sequentially during the 2007 growing season in a glasshouse at the University of Florida Turfgr ass Envirotron in Gainesville, FL. Planting materials were nematode-free, aerial stolons of TifEagle hybrid bermudagrass (Hanna and 30

PAGE 31

Elsner, 1999). Three establishment protocols we re evaluated using (3.8 cm diameter 21 cm deep) UV stabilized Ray Leach Cone-tainers (SC10, Stuewe & Sons, Inc., Tangent, OR) and (10 cm diameter nine cm deep) tapered clay po ts. Establishment methods were classified as conetainers grown in for 45 days (45-d conetain ers), conetainers grown in for 90 days (90-d conetainers), and clay pots grown in for 90 days (90-d clay pots) before inoculation with sting nematodes, respectively. Two inoculati on rates, 50 and 100 mi xed life-stages of B. longicaudatus /100 cm3 of soil, were compared to an uninoculated control within each establishment method. The experimental design was a split-plot with establishment methods arranged as whole-plots and i noculation treatments as sub-plot s with six replications. Upon inoculation, conetainers were placed in ( 60 35 15 cm) Beaver Plastics Styroblock containers (77/170, Stuewe & S ons, Inc., Tangent, OR) to simulate the insulation provided by the clay pot treatment. The daily average high and low air temperatures in the glasshouse were 33.6 2.9C and 23.9 1.3C, respectively over the course of both trials. Both conetainers and clay pots were f illed with autoclaved United States Golf Association (USGA) root-zone specification sand (Anonymous, 1993) with Poly-fil (Fairfield Processing Corporation, Danbury, CT) placed in the bottom of each to prevent sand from escaping from the drainage holes. Conetainers were planted with one terminal aerial stolon approximately five cm long and clay pots were planted with seven equi valent stolons. One minute of overhead mist was app lied eight times daily for one week to allow the rootless sprigs to establish. The frequency was reduced to four times daily during the second week of growth. Beyond the second week, a single a pplication of two minutes/day of irrigation was scheduled. Peters Professional 20-20-20 General Purpose Water Soluble Fertilizer (Scotts-Sierra Horticultural Products Co., Marysville, OH) was applied weekly at a rate of 2.4 g/m2 for the first 31

PAGE 32

month after planting. Subsequent applications were made at the time of inoculation, and again 45 days later. Leaf canopies were trimmed w eekly for the duration of the experiments. Nematode inoculum was extracted using a modified Baermann funnel method (McSorley and Frederick, 1991) from a pure population of B. longicaudatus which was maintained on FX313 St. Augustinegrass. The population density of nematodes in the extract was estimated by quantifying the number of sting nematodes in one mL aliquots on a counting slide (Hawksley and Sons Limited, Lancing, Sussex, UK). Nematode counts were replicated five times with 83 6 and 85 4 sting nematodes/mL present in th e extracted solutions for the first and second experiments, respectively. The solutions were diluted to deliver aliquots of 50 sting nematodes/three mL of solution. Experimental un its within establishment methods were sorted by canopy density, and groups of three with simi lar densities were assigned to the same replication. Inoculation proceeded sequentially acco rding to replication. An aliquot of inoculum for conetainers receiving the 50 sting nematode/100 cm3 soil treatment was pipetted into a single hole (one cm diameter three cm deep), which was then pressed closed. Those receiving the 100 sting nematode/100 cm3 soil treatment were inoculated with two aliquots in separate holes. Aliquot size was adjusted for the larger soil vol ume in the clay pots. Inoculum was delivered into two and four holes in the 50 and 100 sting nematodes/100 cm3 soil treatments, respectively. Experiments were terminated after 90 days and brought to the labor atory for destructive analysis. The plant and corresponding soil volume were isolated from each conetainer and clay pot. Shoots were trimmed off at the soil leve l and the Poly-fil was removed. Roots and nematodes were extracted from the entire experimental unit in the conetainer treatments, and from a 100 cm3 soil core serving as a representa tive sample from each clay pot. 32

PAGE 33

Nematodes were extracted from inoculated treatments using a centrifugal-sugar flotation technique (Jenkins, 1964), modified by adding five cm3 of clay to keep the sediment plug intact as the supernatant liquid was removed after the fi rst centrifugation. Nemat ode counts were made to determine final sting nematode population densiti es (Pf) on an inverted light microscope at magnification and to verify ne matode pressure was present. Roots were collected from uninoculated and inoculated treatments, submersed underwater in 50 mL plastic centrif uge tubes, and stored at -23C for later analysis. The root samples were thawed after sting nematode counts had been completed. Individual root systems were placed into a clear acrylic glass tray where a digital im age was created using an Epson Perfection V700 Photo scanner (Epson America, In c., Long Beach, CA). Lengths of five root diameter classifications (< 0.125 mm, 0.125 to 0.250 mm, 0.250 to 0.500 mm, 0.500 to 1.000 mm and > 1.000 mm) were indi vidually quantified using WinRHIZO Pro v2007d software (Regent Instruments, Inc., Quebec, QC) and then summed to determine total root length (TRL) of each sample. Roots were later dried at 75C fo r 48 h to obtain total dry root weights (TDRW). Reproduction factor (Rf), sting nematode numbers on a total root length basis (Pf/TRL), sting nematode numbers on a total dry root weight ba sis (Pf/TDRW), total root dry weight percent reduction (TDRW % red.), total root length perc ent reduction (TRL % red.), and fine root (diameter < 0.125 mm) length percent reduction (FRL % red.) were calculated with the measured observations. # Pf Rf ofstingnematodesinoculated (3-1) %. 100 TDRWofinoculatedTDRWofuninoculated TDRWred TDRWofuninoculated (3-2) 33

PAGE 34

%. 100 TRLofinoculatedTRLofuninoculated TRLred TRLofuninoculated (3-3) %. 100 FRLofinoculatedFRLofuninoculated FRLred FRLofuninoculated (3-4) The distribution of data for each characteristi c was assessed with a histogram and normal probability plot for normality. Transformed datase ts were utilized where conditions of normality were not met. An analysis of variance was performed on each trait to te st whether establishment methods and inoculation treatments varied. To further study the precision of each method, data were analyzed separately even where establishm ent method interactions were not significant. Where appropriate, differences between the inoculated treatments and uninoculated controls were tested with orthogonal coefficients. Pearso n correlation coefficients were computed using the CORR procedure in SAS software (SAS, 2008) for 90-d clay pots indi vidually, and both 45-d and 90-d conetainer establishmen t methods collectively, to te st whether any traits were associated with, or could be pr edictors of, other characteristics in the two dissimilar pots. Results Variation between establishm ent methods was detected (P 0.05) in all four sting nematode population characteristic s (Pf, Rf, Pf/TRL, and Pf/TDRW), but inoculation treatment establishment method interac tions were significant ( P 0.05) for final nematode populations and sting nematode numbers on a total dry root weig ht basis (Table 3-1). Nematode populations increased in every treatment except for clay pots inoculated with 100 sting nematodes/100 cm3 soil. Reproduction factors were approximately two times larger ( P 0.01) in the low inoculation treatment than in the higher treatment for both conetainer establishment methods. Final nematode populations and sting nematode number s on a total root length and total dry root weight basis were not different fo r inoculation treatments within establishment methods. Results 34

PAGE 35

for population characteristics were less variable with conetainer treatments than when evaluated in clay pots (Table 3-2). Sting nematode reproduction and final population density were correlated ( P 0.05) with all root char acteristics, excluding total dry root weights, in both conetainer establishment methods. Alternatively, there were no associations detected between nematode count data and root measurem ents in the clay pots (Table 3-3). Total dry root weights were different ( P 0.01) for establishment methods and inoculation treatments (Table 3-1), but no treatme nt differences were found for total dry root weight percent reduction due to variable observa tions in the clay pot establishment method. Total dry root weights we re 38 % and 28 % larger (P 0.01) for uninoculated treatments when compared to an average of the two inoculated treatments in the 45-d and 90-d conetainers, respectively. Root weights were not significantly reduced by sting nematode pressure in the clay pots (Table 3-4). Total dry root weights were good predictors of total ( r = 0.92, P 0.01) and fine ( r = 0.85, P 0.01) root lengths in the conetainer establishment methods. Correlation between total dry root weight percent reduction a nd total root length percent reduction ( r = 0.85, P 0.01) was also observed. Associations between these traits were present ( P 0.01) in the clay pots, but the relationships were not as strong (Table 3-3). Total root lengths and fine root lengths were highly correlated ( r 0.98, P 0.01), as were the corresponding pe rcent reductions ( r 0.97, P 0.01), in all establishment methods (Table 3-3). Analysis of variance indicated a significant interaction ( P 0.01) between inoculation treatments and establis hment methods for total and fine root lengths. Total and fine root length percent reductions did not vary with establishment method, but inoculation treatments differed (P 0.05) for both characteristics in th e combined analysis (Table 3-1). Total root lengths of uninoculated treatme nts were 57 %, 55 %, and 31 % greater ( P 0.01) than 35

PAGE 36

an average of the two inoculated treatments in the 45-d conetainers, 90-d conetainers, and 90-d clay pots, respectively (Table 3-4) Similar results were found for fine root lengths, except in trial two where these lengths were not reduced as greatly in the highe r inoculation treatment within the 90-d conetainer method. Related inoc ulation treatment trial interactions for total and fine root length percent re ductions were also evident (P 0.05) within 90-d conetainers. Differences in root length reduction between inoculation treatments were only significant ( P 0.05) in the 90-d conetainer method at the conclu sion of trial one, but resu lts were inconsistent between trials. Greater nume rical differences in root le ngth percent reduction were found between the higher and lower inocul ation treatments in the clay pot s than with either conetainer method, but within treatment variability preven ted significant detection of these differences (Table 3-5). Discussion Identifying turfgrasses that are resistant to, or tolerant of, plant-parasitic nematodes will become necessary as currently used chemical control agents are restricted or removed entirely from use. Methods used to manage these pests in annual cropping systems, including crop rotation and fallowing fields, are not economically or logistically f easible for most perennials. Sources of genetic resistance may be the onl y way perennial grasse s can persist through nematode pressure for a longer duration in the absence of altern ative control methods. Only a small percentage of available turfgra ss genetic resources have been evaluated for response to ectoparasitic nematode s. For breeding programs, current methods have limited the efficient screening of broader germplasm pools due to the space constraints associated with larger clay pots (Crow and Welch, 2004; Hixson et al., 2004; Winchester and Burt, 1964) or the extended cycle times needed to observe root reductions (Giblin-Davis et al., 1992b; Tarjan and Busey, 1985). Damage induced by plant-parasitic nematodes becomes more apparent on golf 36

PAGE 37

courses when secondary abiotic stresses are pr esent (Crow, 2005a). Simulating field conditions by reducing the frequency of fertilizer applicat ion and limiting irrigation may result in more effective screening. Schwartz et al. (2006) found that weekly fertilization and twice daily irrigation hindered the detection of genetic pot ential for resistance or tolerance to sting nematodes when zoysiagrasses were grown in shorter, uninsulated conetainers. Many turfgrass species are suitable hosts for sting nematode reproduction (Bekal and Becker, 2000; Robbins and Barker, 1973). Identifying an appropriate plant standard for use as a control when evaluating sting nematode response may increase the accuracy of screening large numbers of germplasm lines. Plant standards will need to respond to sting nematode populations in the greenhouse in a manner charac teristic of the host-pathogen re lationship seen in the field. Damaging numbers of sting nematodes have been associated with subjectively measured declines in turf quality and root lengths on ultradwarf bermudagra sses in Florida (Crow, 2005c). Reductions in total and fine r oot lengths of the ultradwarf bermudagrass, TifEagle, also corresponded to increasing sting nematode population densities when evaluated in the greenhouse (Crow and Welch, 2004). Nematode and root characteristics reported for turfgrasses in the literature were evaluated to select the most informativ e and repeatable combinations of establishment method and inoculation treatment used in this study. Dry root weights were the most widely used measure of plant-parasitic inflicted root da mage before the advent of digi tal scanners and root length analysis software. Plant breeders should fi rst focus on the primary symptom of nematode damage, reduction of root lengths, and not the co rrelated decrease in root weight. Root weight can only be used to indirectly measure the proble m if associations between root weight and root length are strong. Qualitative turfgrass quality ratings and clipping weights have not been 37

PAGE 38

consistently associated with root damage in bermudagrass (Giblin-Davis et al., 1992b; Hixson et al., 2004; Tarjan and Busey, 1985) and would probabl y not make effective se lection criteria for estimating plant-parasitic nematode damage. There were sufficient sting nematodes in both inoculation treatments to establish reproducing populations. Lautz (1959) found that inoculum treatments of only 10 sting nematodes/pot resulted in no population increases even though good reproduction was observed when 40 sting nematodes/pot were artificially inoculated onto the same host. Final population densities within the 45-d and 90-d conetainers were equal fo r both low and high inoculation treatments even though the reproduction factors were approximately two times larger in the lower treatment. This indicates that sting ne matode carrying capacities may have been met for the respective size of the root systems in each es tablishment method. Total root lengths in the clay pots were reduced by the high inoculation treatment when compared to the uninoculated control despite a reproduc tion factor below one, suggesting that the carrying capaci ty of the root systems were exceeded and a resulting nemat ode maximum population density occurred. Therefore, if identifying differences in ne matode reproduction (resist ance) is the primary objective of the research, an inoculation rate of 50 B. longicaudatus/100 cm3 of soil and an evaluation period of 90 days appear adequate. Differences in the number of nematodes on a to tal root length and to tal dry root weight basis between establishment methods may not be meaningful when the only treatments are within the same cultivar. Standardized population de scriptors such as these could be more useful when making comparisons between different gr asses within, or among species. Correlation between root length percent redu ctions and sting nematode populat ion density would be expected on a putting green under stress. Th ese traits were si gnificantly correlated in both conetainer 38

PAGE 39

establishment methods with no detectable associa tion found in the clay pots. This may indicate that conditions in the co netainers were more repres entative of field conditions. Differences were not found between total dry root weights of uninocul ated and inoculated treatments in the clay pot establishment method even though total root lengths were reduced by the sting nematode pressure. Johnson (1970b) noted that root systems of uninoculated bermudagrass controls were more dense and fibr ous than those of inoc ulated plants. He concluded that visual symptoms were much more apparent th an indicated by root weight differences. Results found in the conetainer es tablishment methods contrasted those from the clay pots. Identification and selection of supe rior genotypes in conetain ers using only total dry root weight reductions coul d be possible due to signifi cant differences found between uninoculated and inoculated treatments and the high correlation of root weights and lengths in these establishment methods. Total and fine root lengths of TifEagle bermudagrass were reported to be 57 % and 69% greater, respectively, in uninoculated treatments th an inoculated when evaluated in large (15 cm) clay pots (Crow and Welch, 2004). These measurements and the corresponding root length percent reductions were very si milar to the results found in the 45-d conetainer method evaluated herein. When fine root length is highly associated with total root length it may not need to be reported. However, no additional effort is required for its measurement and it may be informative when explaining root damage caused by plant-parasitic nematodes in other turfgrass species with variable root architecture. Results across trials were not consistent for fine root length or total and fine root length percent reductions in the 90-d conetainers suggesting a potential lack of stability fo r this establishment method. 39

PAGE 40

40 Plant breeding methodologies are purposefully designed to only be as comprehensive as required to gather enough information to make genetic gains from selection. The balance between greater investments in time and complexity must be maintained with screening larger population sizes in the search fo r genes of interest. Plant-pa rasitic nematode populations and root systems are inherently variable. Therefore it is particularly necessary to reduce outside variation when experimenting with nematodes in the greenhouse so that the genetic potential of each turfgrass being evaluated can be reached and quantified. Conetainer treatments were not root-bound at the completion of the experime nts. Sting nematode and bermudagrass measurements were characterized from the entire experimental unit rather than from a sample core as necessary in the root -bound clay pots. Sampling error may have attributed to the variability observed in charac teristics measured within the clay pot establishment method. Based on this research, TifEagle bermudagrass can be effectively used as a susceptible plant standard to verify pathogenicity of sting nematode incoculum and quantify root injury of untested genotypes during intial screening of la rge sets of turfgrass germplasm. Use of conetainers will increase the number of germplasm lines that can be evaluated in a single trial because they require less bench space in the greenhouse and the extraction of roots and nematodes does not require sampling as with larger clay pots. Inocula tion levels should be no higher than required to establish reproducing popu lations of nematodes because availability of inoculum can be a limiting factor to the number of genotypes that can be scr eened in a particular trial. Our results support esta blishing turfgrasses for 45 days in deep, insulated conetainers before inoculation with 50 B. longicaudatus/100 cm3 soil to determine initial plant response. Further testing of plant response/tolerance ma y require higher inoculum levels or longer evaluation intervals.

PAGE 41

Table 3-1. Mean squares for Belonolaimus longicaudatus reproduction factor (Rf) final population density (Pf), population density on a total root length basis (Pf/TRL), population density on a total dry root basi s (Pf/TDRW), total dry root weight (TDRW), total dry root weight percent reduction (TDRW % red.), total root length (TRL), total root length percent reduction (TRL % red.), fine root leng th (FRL), and fine root length percen t reduction (FRL % re d.) of TifEagle bermudagrass evaluated in three establishment (Est.) methods with different inoculation treatments (Inoc. TRT) in two experimental trials. Mean squares Source df Rf Pf Pf/TRL Pf/TDRW TDRW TDRW % red. TRL TRL % red. FRL FRL % red. Trial (T) 1 1.488** 95.4** 0.4960** 11789** 0.08664** 7.91 5729209** 1.03 711290** 4.77 Error A: Rep (T) 10 0.034 7.4 0.0135 163 0.00285 2.99 349298 1.44 53090 2.02 Est. Method (E) 2 1.874** 137.1** 0.1377* 1292* 0.03145** 13.08 6132352** 6.03 1358829** 7.67 E T 2 0.499 31.5 0.0449 1144 0.01405** 5.93 1623045** 0.29 250491** 0.85 Error B: Rep E (T) 20 0.177 23.3 0.0276 333 0.00112 3.86 86198 2.15 15915 2.34 Inoc. TRT (I) 1 6.778** 66.2 0.0094 237 0.00584** 2.58 3946964** 7.29* 874549** 9.30** I T 1 0.101 0.0 0.0000 1 0.00007 0.92 265678* 0.00 89535** 0.10 I E 2 0.290 91.1* 0.0563 946* 0.00154 0.18 283354** 0.74 63174** 0.84 I T E 2 0.178 12.5 0.0201 77 0.00098 1.44 63695 2.02 22437 2.22 Error C: MSE 30 0.141 23.5 0.0230 265 0.00079 2.07 58618 1.19 12990 1.05 % CV 26.3 35.0 34.8 32.9 26.0 16.0 17.9 13.2 18.4 12.4 *, **Significant at the 0.05 and 0.01 probability levels, respectively. Analysis included comparison to un-inoculated controls, therefore df for I, I T, I E, I T E, and Error C were 2, 2, 4, 4, and 60, respectively. 41

PAGE 42

Table 3-2. Mean reproduction factor (Rf), final population density (Pf), population density on a total root length basis (Pf/TRL), population density on a total dry root basis (Pf/TDRW), of Belonolaimus longicaudatus on TifEagle bermudagrass 90 days after inoculation evaluated in three establishment methods with two inoculation treatments in two experimental trials. Treatment Rf (nematodes) Pf (nematodes) Pf/TRL (nematodes/cm) Pf/TDRW (nematodes/g) 45-d conetainers I (50) 2.7 1.5** 134 75 0.17 0.10 2790 1976 I (100) 1.4 0.6 138 58 0.22 0.14 3569 3203 90-d conetainers I (50) 4.2 1.6** 210 80 0.14 0.07 1750 863 I (100) 2.2 1.0 223 101 0.15 0.07 1850 789 90-d clay pots I (50) 2.8 1.5** 391 213 0.36 0.17 4518 2597 I (100) 0.8 0.7 221 193 0.29 0.39 3154 4088 **Inoculated treatments significantly different at the 0.01 probability level, according to orthogonal coefficient analysis. Inoculated (I) with 50 or 100 B. longicaudatus/ 100 cm3 soil. Data are means of two trials with six replications each standard deviations. 42

PAGE 43

Table 3-3. 45-d and 90-d conetainer (a bove diagonal) and 90-d clay pot (bel ow diagonal) correlation coefficients of Belonolaimus longicaudatus reproduction factor (Rf), fina l population density (Pf), population density on a total root length ba sis (Pf/TRL), population density on a total dry root weight basis (Pf/TDRW), total dry root weight (TDRW), total dry root weight percent reduction (TDRW % red.), total root length (TRL), total root length percent reduction (TRL % red.), fine root length (FRL), and fine root length percent reduction (FRL % red.) of TifEagle bermudagrass. Nematode and root data Rf Pf Pf/TRL Pf/TDRW TDRW TDRW % red. TRL TRL % red. FRL FRL % red. count count co unt/cm count/g g % cm % cm % Rf 0.89** 0.66** 0.52** -0.17 ns -0.28* -0.27* -0.48** -0.25* -0.41** Pf 0.94** 0.76** 0.59** -0.20 ns -0.34** -0.32** -0.58** -0.32** -0.53** Pf/TRL 0.64** 0.78** 0.95** -0.57** -0.59** -0.64** -0.66** -0.63** -0.59** Pf/TDRW 0.67** 0.77** 0.97** -0.60** -0.58** -0.63** -0.56** -0.60** -0.48** TDRW 0.03 ns 0.02 ns -0.29 ns -0.38* 0.58** 0.92** 0.43** 0.85** 0.37** TDRW % red. 0.13 ns 0.07 ns -0.22 ns -0.25 ns 0.51** 0.59** 0.85** 0.56** 0.74** TRL 0.01 ns -0.05 ns -0.36* -0.39* 0.79** 0.30 ns 0.60** 0.98** 0.57** TRL % red. 0.10 ns -0.01 ns -0.28 ns -0.19 ns 0.08 ns 0.55** 0.32 ns 0.62** 0.97** FRL 0.05 ns -0.01 ns -0.32 ns -0.33* 0.69** 0.25 ns 0.97** 0.37* 0.61** FRL % red. 0.16 ns 0.06 ns -0.23 ns -0.13 ns 0.06 ns 0.45** 0.34* 0.96** 0.41* *, **Significant at the 0.05 and 0.01 probability levels, respectively. Not significant at the 0.05 probability level. Fine root (diameter < 0.125 mm) length. 43

PAGE 44

Table 3-4. Mean total dry root weig ht (TDRW), total dry root weight percent reduction (TDRW % re d.), and total root length (TRL) of TifEagle bermudagrass 90 days after inoculation evaluated in three establishmen t methods with uninoculated and inoculated treatments in two experimental trials. Treatment TDRW (g) TDRW % red. (g) TRL (cm) 45-d conetainers U 0.09 0.04** 1394 523** I (50) 0.07 0.06 -24 23 950 455 I (100) 0.06 0.04 -33 24 828 338 90-d conetainers U 0.16 0.03** 2393 260** I (50) 0.13 0.03 -19 27 1608 352 I (100) 0.12 0.02 -23 19 1478 260 90-d clay pots U 0.11 0.05 1401 609** I (50) 0.10 0.05 4 46 1153 472 I (100) 0.11 0.07 -3 45 994 483 **Uninoculated controls significantly different from both inoculated treatments at the 0.01 probability level, according to orthogonal coefficient analysis. Uninoculated (U); Inoculated (I) with 50 or 100 B. longicaudatus/ 100 cm3 soil. Data are means of two trials with six replications each standard deviations. 44

PAGE 45

Table 3-5. Mean total root length percent reduction (T RL % red.), fine root length (FRL), and fine root le ngth percent reduction (FRL % red.) of TifEagle bermudagra ss 90 days after inoculation evaluated in three establishment methods with uninoculated and inoculated treatments in two experimental trials. Treatment TRL % red. (cm) FRL (cm) FRL % red. (cm) 45-d conetainers U 670 224** I (50) -31 16 438 170 -32 19 I (100) -41 13 383 122 -42 13 90-d conetainers (Trial 1) U 1130 162** I (50) -31 11 787 118 -30 11 I (100) -46 10 573 90 -49 9 90-d conetainers (Trial 2) U 1074 107** I (50) -34 19 721 142 -32 16 I (100) -30 10 776 103 -28 6 90-d clay pots U 610 250* I (50) -9 39 518 193 -6 39 I (100) -28 25 425 184 -28 27 *, **Uninoculated controls significantly different from both inoculated treatments at the 0.05 and 0.01 probability levels, respectiv ely, according to orthogonal coefficient analysis. Uninoculated (U); Inoculated (I) with 50 or 100 B. longicaudatus/ 100 cm3 soil. Data are means of two trials with six replications each standard deviations for 45-d conetainers and 90-d clay pots, and means of one trial with six replications standard deviations for 90-d conetainers. Inoculated treatments significantly different at the 0.05 and 0.01 probability levels, respectively, according to or thogonal coefficient analysis. 45

PAGE 46

CHAPTER 4 VARIABLE RESPONSES OF ZOYSIAGR ASS, ST. AUGUSTINEGRASS, AND BERMUDAGRASS GENOTYPES TO THE STING NEMATODE Introduction Zoysiagrass ( Zoyisa spp.) can be utilized successfully as an alternative turf in warmer environments (Patton and Reiche r, 2007) with various insect pressures (Braman et al., 2000; Reinert and Engelke, 2001). A limitati on preventing more widespread use of Zoysia is their susceptibility to damage by the plant parasitic sting nematode ( Belonolaimus longicaudatus ) on sandy, well drained soils (Christie et al., 1954; Good, 1959; G ood et al., 1956). Rapid sting nematode population increases are possible in favorable environm ents where available food is not limiting. Huang and Becker (1999) reported that reproductive females can lay approximately three eggs every two days and that their life cycl e can be completed in as few as 24 days. Sting nematodes are ectoparasites that f eed on host root tips through an oral stylet. Damage to root tip meristematic tissue ceases growth and serves as an infection point for secondary pathogens. Visual symptoms associated with this root de terioration include chlorosis, wilting, reduced growth rates, and thin turf (Perry, 1974). Stunted root systems of sting nematode damaged turf likely contribute to greater nitroge n leaching (Luc et al., 2006) wh en applications of irrigation and fertilizer are increased to sustain growth. Zoysiagrass was the least effective in limiting nitrate leaching of six warm-season turfgrasses (Bowman et al., 2002). Therefore, there are several factors that may contribute to reduced groundwater quality and increased fertilization costs when growing zoysiagrass in areas su itable for sting nematode population growth. Sting nematodes can parasitize many warm-seas on turfgrasses. Turf quality and drought survival of hybrid bermudagrass ( Cynodon dactylon [L.] Pers. var. dactylon C. transvaalensis Burtt-Davy) can be reduced as a result of stunted root systems when sting nematode populations are not controlled (Trenholm et al ., 2005). The search for useful resistance or to lerance to the 46

PAGE 47

sting nematode in Cynodon spp. has been limited to readily available cultivars and a limited number of germplasm accessions (Giblin-Davis et al., 1992b). Damage to St. Augustinegrass ( Stenotaphrum secundatum [Walt.] Kuntze) roots, and subse quent top growth chlorosis, have been attributed to this nematode in the field (Kelsheimer and Overman, 1953) and observed in controlled greenhouse studies (Rhoades, 1962). Ge nerally, diploid St. Augustinegrasses have been characterized as susceptible (Busey et al., 1991), but resistance was identified in some polyploid cultivars (Busey et al., 1993). Seashore paspalum ( Paspalum vaginatum Swartz) is a reproductive host of the sting nematode and it may not be as tolerant as bermudagrass in some situations (Hixson et al., 2004). Centipedegrass ( Eremochloa ophiuroides [Munro] Hack) is reportedly a host of the sting ne matode (Christie et al., 1954; G ood, 1959), but parasitism on this species has not been well documented. Several management techniques have been eval uated in attempts to eliminate or suppress damaging plant parasitic nematodes. The most common, and often only, method of control has been the use of nematicides (Crow, 2005b; Perry et al., 1970). Heald and Burton (1968) found that sting and root-knot nemat ode populations were reduced when organic sources of nitrogen were used instead of ammonium nitrate on bermudagrass. White and Dickens (1984) observed the same trends, but reported that additional ma nagement practices (i.e., topdressing, vertical mowing, and core aerification) had no effect. Ho wever, Dunn et al. (1981) reported that mowing height and thatch removal did affect nematode populations in Meyer zoysiagrass. Greater numbers of spiral ( Helicotylenchus spp.) and dagger nematodes ( Xiphinema spp.) were associated with higher mowing heights. Thatch removal contributed to higher populations of dagger nematodes, but neither the spiral or stunt nemat ode numbers were significantly affected. Botanical nematicides, root biostimulants, a nd entomopathogenic nematodes have not shown 47

PAGE 48

consistent suppression of plant parasitic nema tode populations as required from turfgrass managers (Crow, 2005a; Crow et al., 2006). The search for useful resistance or tolerance to the sting nematode in Zoysia spp. has been limited to a small number of cultivars and germplasm accessions. Busey et al. (1982) identified germplasm with partia l resistance, but determined th at breeding challenges regarding better adaptation and pest resistance needed addressi ng prior to its utilization in the sub-tropics. Greater efforts to screen divers e germplasm will likely result in the discovery of additional sources of resistance or tolerance. Because zoysiagrass is slow to recover from injury, any source of sting nematode resistance will be valuable because remedial nematicide applications are less effective in species that can not rapidly re-establish root and shoot densities while plant parasitic nematode populations in the soil are low (Busey et al., 1982; Juska, 1972; Perry, 1974). This research was initiated to evaluate the host status and relative tolerance of six turfgrass genotypes to the sting nematode as estimated by two different screening methodologies. Materials and Methods Two experimental trials were conducted sequ entially during the 2007 growing season in a glasshouse at the University of Florida Turfgr ass Envirotron in Gainesville, FL. Planting materials were nematode-free, ae rial stolons of four zoysiagrasses, Cavalier (Engelke et al., 2002), Emerald (Forbes et al., 1955), Empire, and an experimental germplasm line designated UFTZ. Floratam St. Augustinegrass (Horn et al., 1973) was also evaluated and TifEagle bermudagrass (Hanna and Elsner, 1999) was included as a susceptible control. Two establishment protocols were evaluated using (3 .8 cm diameter 21 cm deep) UV stabilized Ray Leach Cone-tainers (SC10, Stuewe & Sons, Inc., Tangent, OR). Establishment methods were classified as conetainers grown in for 45 days (45-d conetainers) and 90 days (90-d conetainers) respectively, before inoculation with sting nematodes. An inoculation treatment of 48

PAGE 49

50 sting nematodes in mixed life-stages per 100 cm3 of soil was compared to an uninoculated control within each establishment method. The e xperimental design was a split-split-plot with establishment methods arranged as whole-plot s, genotypes as sub-pl ots, and inoculation treatments as split-sub-plots with six replications. Upon inoculat ion, conetainers were placed in (60 35 15 cm) Beaver Plastics Styroblock containers (77/170, Stuewe & Sons, Inc., Tangent, OR) to provide insulation from extreme temperature changes. Conetainers were filled with autoclaved Un ited States Golf Association (USGA) rootzone specification sand (Anonymous, 1993) with Poly-fil (Fairfield Pr ocessing Corporation, Danbury, CT) placed in the botto m of each to prevent sand from escaping. Conetainers were planted with one terminal aerial stolon approxima tely five cm long. One minute of overhead mist was applied eight times daily for one week to allow the rootless sprigs to establish. The frequency was reduced to four times daily during the second week of growth. Beyond the second week, a single application of two minutes day-1 was scheduled. Peters Professional 2020-20 General Purpose Water Soluble Fertilizer (Scotts-Sierra Hortic ultural Products Co., Marysville, OH) was applied weekly at a rate of 2.4 g/m2 for the first month after planting. Subsequent applications were made at the time of inoculation, and again 45 days later. Leaf canopies were trimmed weekly for the duration of the experiments. Sting nematode inoculum was extracted using a modified B aermann funnel method (McSorley and Frederick, 1991) from a pure population of B. longicaudatus which was maintained on FX-313 St. Augustinegrass. The population density of nematodes in the extract was estimated by quantifying the number of stin g nematodes in one mL aliquots on a counting slide (Hawksley and Sons Limited, Lancing, Su ssex, UK). Nematode counts were replicated five times with 83 6 and 85 4 sting nematodes mL-1 present in the extracted solutions for the 49

PAGE 50

first and second experiments, respectively. The so lutions were diluted to deliver aliquots of 50 sting nematodes per three mL of solution. E xperimental units within establishment methods were sorted by canopy density, and groups of two with similar densities were assigned to the same replication. Inoculation proceeded sequentia lly according to replica tion. An aliquot of inoculum for conetainers receiv ing the 50 sting nematodes was pipetted into a single hole (one cm diameter three cm deep), which was then pressed closed. Experiments were terminated after 90 days and brought to the laboratory for destructive analysis. The plant and corresponding soil volume were isolated from each conetainer. Shoots were trimmed off at the soil level and the Poly-fil was removed. Nematodes were extracted from inoculated treatments using a centrifugal-sugar flotation technique (Je nkins, 1964), modified by adding five cm3 of clay to keep the sediment plug inta ct as the supernatant liquid was removed after the first centrifugation. Nematode counts we re made on an inverted light microscope at magnification to verify nematode pressure and to determine final sting nematode population densities (Pf). Roots were collected from uninoculated and inoculated treatments, submersed underwater in 50 mL plastic centrifuge tubes, and stored at -23C for later analysis. The root samples were thawed after sting nematode counts had been completed. Individual root systems were placed into a clear acrylic glass tray where a digital im age was created using an Epson Perfection V700 Photo scanner (Epson America, In c., Long Beach, CA). Lengths of five root diameter classifications (< 0.125 mm, 0.125 to 0.250 mm, 0.250 to 0.500 mm, 0.500 to 1.000 mm and > 1.000 mm) were indi vidually quantified using WinRHIZO Pro v2007d software (Regent Instruments, Inc., Quebec, QC) and then summed to determine total root length (TRL) of each sample. Roots were later dried at 75C for 48 h to obtain total dry root weights (TDRW). 50

PAGE 51

Reproduction factor (Rf), mean total root length percent reduction (TRL % red.), and mean total root dry weight percent reduction (T DRW % red.) were then calculated: # Pf Rf ofstingnematodesinoculated (4-1) %. 100 TDRWofinoculatedTDRWofuninoculated TDRWred TDRWofuninoculated (4-2) %. 100 TRLofinoculatedTRLofuninoculated TRLred TRLofuninoculated (4-3) The distribution of data for reproduction factors, total root lengths, and total dry root weights were assessed with a histogram and normal probability plot for normality. Transformed datasets were utilized where conditions of normali ty were not met. An analysis of variance was performed on these traits to test whether es tablishment methods, genotypes, and inoculation treatments varied. Data were analyzed separate ly within each establishment method to further study the effects of these treatm ents. Genotype means were separated using a Waller-Duncan k ratio LSD. Differences between the inoculated treatments and uninoculated controls within each genotype were tested with orthogonal coefficients. Results and Discussion Sting nematode Rfs were not consistent between trials, establishment methods, and genotypes as noted by the significant interactions in the overall analysis of variance (Table 4-1). All turfgrasses were suitable hosts for nematode reproduction, but definitive trends within establishment methods or on individual grasses were not apparent. UFTZ generally supported more sting nematodes with final populations five to 11 times greater than initial inoculation levels. Less reproduction usually occurred in Floratam and TifEagle (Table 4-2). Zoysiagrasses with resistance to, or tolerance of the sting nema tode have not yet been identified in controlled 51

PAGE 52

greenhouse evaluations, although Emerald and other Zoysia cultivars are known reproductive hosts of this plant parasite (Bekal and Becker 2000). Busey et al. (1993) detected partial antibiosis to the sting nematode in Floratam and other pol yploidy St. Augustinegrasses, but complete resistance to nematode reproduction was not observed. Sting nematode reproduction factors reached 25 on TifEagle bermudagrass wh en evaluated in large clay pots (Crow and Welch, 2004). Our results suggest that TifEagle is a good host, but smalle r soil and root volumes from the conetainers may limit total nema tode populations that can be supported. Differences were detected ( P 0.01) between the two coneta iner establishment methods, among the six genotypes, and between uninoculated and inoculated treatments for TRL and TDRW. Genotype establishment method in teractions were also significant ( P 0.01) for these two characteristics (Table 4-1). Data were analyzed separately within each establishment method and genotype to evaluate root damage and the effect of establishment time on detecting tolerance or susceptibility to the sting nematode in each turfgrass. Tota l root length and TDRW of genotypes in the inoculated treatment were evaluated to determine which turfgrasses maintained larger root systems in the presence of sting nematode pressure (Table 4-3). Identifying tolerance in perennial grasses could enhance long term survival by facilitating water and nutrient uptake, especially in the presen ce of other abiotic and biotic stresses. Total root lengths were correlated ( r = 0.91, P 0.01) with fine (diameter < 0.125 mm) root lengths. Data for fine r oot lengths did not offer additiona l explanation of the variation observed between establishment methods and among genotypes, and therefore was not reported. UFTZ was the only genotype in which nematode i noculated plants did no t exhibit a significant decline in TRLs relative to the uninoculated controls indicating a level of tolerance when evaluated in 45-d conetainers. Reductions ( P 0.05) were observed for the remaining inoculated 52

PAGE 53

cultivars and ranged from 24% for Empire to 37% in Floratam (Table 4-3). Percent reductions are useful to determine the relative susceptibility of a genotype, but reveal little concerning the root systems overall ability to remain functional ev en when injured. Total root lengths of UFTZ were greater ( P 0.05) than those of the other turfgra sses under sting nematode pressure, but Empire did demonstrate moderate TRLs when inoculated. TifEagle and Floratam had the smallest TRLs and greatest TRL % reductions of the genotypes evaluated in 45-d conetainers (Table 4-3). Conetainers established for 90 days before i noculation generally had longer TRLs for all genotypes. Sting nematode response in UFTZ, Empire, and TifEagle was similar in both establishment methods, but significant reductions in TRLs were not foun d between inoculated and uninoculated treatments for both Emerald and Cavalier in the 90-d conetainers (Table 4-3). This suggests tolerance to sting nematode feeding may be attributed to r oot maturation prior to the onset of pest pressure for some genotypes. Thicker primary roots were credited for resistance observed in polyploid St. Augustinegrasses (Busey et al., 1993), but our resu lts indicate (data not shown) that coarse (diameter > 1 mm) root length was reduced by the sting nematodes. Maintenance of fine root length primarily contri buted to the differences in estimated tolerance between establishment methods for Emerald an d Cavalier. In the 90-d conetainers UFTZ, Empire, and Emerald had longer ( P 0.05) TRLs than Cavalier, Floratam, and TifEagle when inoculated with sting nematodes (Table 4-3). Estimating plant parasitic nematode damage with dry root weight reductions was the most practical approach before digital scanners and root length an alysis software became readily available. Root injury can only be accurately diagnosed with TDRWs when they are correlated to the primary symptom of sting nematode dama ge, reduction of TRL. Associations between 53

PAGE 54

these two characteristics in this study were significant ( P 0.01), but not strong in either the 45d conetainers ( r = 0.60) or the 90-d conetainers ( r = 0.38). Alternatively, TDRWs were good predictors ( r = 0.91, P 0.01) of coarse root length. Total dry root weights of all genotypes were reduced ( P 0.05) when inoculated in the 45-d c onetainers. The 30% decrease in TDRW of UFTZ in the inoculated treatments indicates for this genotype that heavier, coarse roots may have been stunted, though TRL was maintained. Po ssibly, this genotype increases its lateral fine root production when primary roots are limited due to biotic stress. This would be a highly desirable characteristic and would allow for great er soil volume exploration. Total dry root weight % reductions categorized Empire, Cavalier, and Emerald similarly to TRL % reductions with regards to sting nematode susceptibility when given 45 days to establish. Injury to fine roots and immature coarse roots in Floratam when inoculated in 45-d conetainers was likely responsible for both the TDRW a nd TRL % reductions in these trials. TifEagle TDRWs were reduced the least and had the sm allest weights compared to other genotypes under nematode pressure, suggesting the root arch itecture of this bermudagrass is composed of more fine than coarse roots (Table 4-3). Fewer differences in TDRWs were seen be tween uninoculated controls and inoculated treatments at the conclusion of the study in the 90-d conetainers. Only Emerald and TifEagle behaved similarly for this tr ait in both establishment me thods, exhibiting significant ( P 0.05) TDRW reductions (Table 4-3). Longer establis hment times should allow uninterrupted growth of larger, heavier roots that may be less availabl e for sting nematode feed ing after inoculation. In this case, longer experimental duration w ould be necessary to see TDRW reductions in susceptible genotypes. Giblin-Dav is et al. (1992a) did not see r oot weight reductions in sting nematode inoculated treatments of a suscepti ble St. Augustinegrass cult ivar until 84 days after 54

PAGE 55

inoculation. Floratam, known for producing thicker diameter r oots, had the heaviest TDRWs, where the zoysiagrasses UFTZ, Empire, and Emeral d had root systems of similar weights when grown in the presence of sting nemat odes in 90-d conetainers (Table 4-3). Conclusions Trends of increasing regulation and restricti on of nematicides highlight the importance of identifying turfgrasses with improved genetic resist ance to plant parasitic nematodes. Variability was detected for sting nematode response in the zoysiagrasses studied in dicating that potential exists for improving resistance or tolerance to the sting nematode. Inherent nematode resistance is especially important in Zoysia because the genus lacks the r ecuperative potential of other faster growing grasses (Busey and Myers, 1979). The long term responses of perennial crops must often be estimated by abbreviated selection procedures in order to make progress in a timely manner. Simulating field conditions in greenhouse experiments can help increase real ized genetic gains. The two methods evaluated reproduce conditions where grasses are sprigged in to fumigated soil and can establish root systems before soil nematode populations return. Unfortunately, it is difficu lt to simulate growth into plant parasitic nematode infested soils be cause absence of an initi al food source limits the pathogen in vitro Pathogenicity of the sting nematode inoculum was verified by the response of the susceptible TifEagle bermudagr ass. Total root length measur ements suggest that the degree of tolerance exhibited by genotype s to the sting nematode in 90-d conetainers can be quantified further when less time is allowed for root system development. UFTZ showed tolerance to root length reductions in these trials but was not resi stant to the sting nematode as indicated by its high Rfs. Cavalier and Emerald demonstrated tolerance when their root systems were more mature, but not when inoculated while still es tablishing. In this study, the use of 45-d conetainers produced the most conservative results by identifying only one tolerant genotype. 55

PAGE 56

56 UFTZ maintained its root system under sting nemat ode pressure prior to co mplete establishment, which is perhaps the most desired form of to lerance. Remaining questions are how long can UFTZ continue to sustain root and shoot develo pment and what impacts could secondary biotic and abiotic stress have in the presence of incr eased sting nematode populations. These answers require further research. Empire zoysiagrass had significant TRL damage when compared to its uninoculated control but maintain ed longer TRLs than most of the other turfgrasses in the presence of sting nematode feeding. Selecti on based on percent reduction data and persistent root growth will reduce the risk of overlooking viable sources of tolerance to plant parasitic nematodes in a plant breeding program. Total dr y root weights were associated with larger, more coarse roots and not necessarily the fi ne roots capable of uptaking more water and nutrients. This research supports the need for continued efforts to screen turfgrass germplasm for greater resistance and tolerance to the sting nematode.

PAGE 57

Table 4-1. Mean squares for Belonolaimus longicaudatus reproduction factor (Rf), total root length (T RL), and total dry root weight (TDRW) of six turfgrasses evaluated in two establishment (Est.) methods with uninocula ted and inoculated treatments (Inoc. TRT) in two experimental trials. Mean squares Source df Rf TRL TDRW Trial (T) 1 3.259* 7842180** 0.37681** Error A: Rep (T) 10 0.331 776626 0.03657 Est. Method (E) 1 0.053 27610011** 0.73430** E T 1 4.037* 434739 0.08067** Error B: Rep E (T) 10 0.361 186288 0.00576 Genotype (G) 5 2.642** 7158096** 0.38374** G T 5 1.186** 298312 0.00253 G E 5 0.936* 500769** 0.01588** G T E 5 0.897* 388716* 0.01021* Error C: Rep G (T E) 100 0.303 133142 0.00364 Inoc. TRT (I) 1 13807287** 0.31893** I T 1 31168 0.00026 I E 1 8600 0.02563** I G 5 228443 0.00609 I T E 1 376504 0.00272 I T G 5 97970 0.00690 I E G 5 164457 0.00400 I T E G 5 117750 0.00749 Error D: MSE 120 133109 0.00346 % CV 27.5 19.4 12.8 *, **Significant at the 0.05 and 0.01 probability levels, respectively. Reproduction factor mean squares apply only to inoculated treatments. Table 4-2. Mean repro duction factor (Rf) of Belonolaimus longicaudatus on six turfgrasses 90 days after inoculation with 50 B. longicaudatus evaluated in 45-d conetainers and 90-d conetainers in two experimental trials. Rf 45-d conetainers 90-d conetainers Genotype Trial 1 Trial 2 Trial 1 Trial 2 nematodes UFTZ 5.3 a 11.0 a 5.0 ab 7.4 a Empire 2.4 bc 7.9 a 4.2 ab 3.3 a Cavalier 3.0 bc 8.4 a 5.9 a 3.9 a Emerald 3.4 ab 3.4 b 6.1 a 3.4 a Floratam 2.3 bc 2.2 b 2.7 b 3.2 a TifEagle 1.7 c 3.7 b 3.0 b 5.4 a % CV 23.9 28.2 24.0 31.4 Means within a column followed by th e same letter are not different at K = 100 (approximates P = 0.05) according to Waller-Duncan LSD. 57

PAGE 58

Table 4-3. Mean total root le ngth (TRL) and total dry root weight (TDRW) of six turfgrasses 90 days after inoculation evaluated in 45-d conetainers and 90-d conetainers with uninoculated (U) and inocul ated (I) treatments in two experimental trials. TRL TDRW 45-d conetainers 90-d conetainers 45-d conetainers 90-d conetainers Both trials Both trials Both trials Both trials Genotype U I % red. U I % red. U I % red. U I % red. cm g UFTZ 2343 2142 a -8 2755 2445 a -11 0.30** 0.22 a -30 0.34 0.28 b -16 Empire 2275* 1729 b -24 2837** 2231 a -21 0.22* 0.17 b -25 0.28 0.26 b -7 Cavalier 1631** 1161 cd -29 1944 1752 b -10 0.17** 0.11 c -34 0.23 0.19 c -18 Emerald 1715* 1210 c -29 2491 2142 a -14 0.17** 0.11 c -38 0.31** 0.24 b -23 Floratam 1412** 883 d -37 2000** 1679 b -16 0.36** 0.21 ab -43 0.46 0.40 a -14 TifEagle 1394** 950 cd -32 2393** 1608 b -33 0.09* 0.07 d -21 0.16* 0.13 d -22 *, **Uninoculated controls significantly different from inoculated treatments within establishment method at the 0.05 and 0.01 probability levels, respectively, according to or thogonal coefficient analysis. Inoculated with 50 Belonolaimus longicaudatus Means within a column followed by th e same letter are not different at K = 100 (approximates P = 0.05) according to Waller-Duncan LSD. 58

PAGE 59

CHAPTER 5 MOWING HEIGHT AND NITROGEN FERTILIT Y MANAGEMENT OF ZOYSIAGRASS IN FLORIDA Introduction Zoysiagrasses ( Zoysia spp.) are warm-season perennial gr asses adapted to a wide range of environments. Most cultivars are vegetatively propagated to preserve the hybrid vigor created in the initial cross pollination (Forbes et al., 1955; Grau and Radko, 1951; Hanson, 1966). Maintaining conditions for optimal growth is very important in these species because their slow spread can limit production (Juska, 1959). Topdr essing and the use of preand postemergence herbicides have been shown to quicken zoys iagrass grow-in by improving sprig survival and reducing weed competition. The effects of nitr ogen have generally been found to be minimal during the establishment phase of both plugs and sprigs (Carroll et al., 19 96; Fry and Dernoeden, 1987; Richardson and Boyd, 2001). Fall applicat ions of nitrogen often promote weed infestations in dormant zoysiagrass which can result in decreased spring turf quality due to competition for light interception, water, and nu trients (Busey, 2003; Dunn et al., 1993; Henry et al., 1989). Dunn et al. (1995) recommended only fertilizing Meyer enough to maintain acceptable turf quality and density so that shoot gr owth is not encouraged over root development as excess nitrogen is transported to the canopy. Differential responses of Z. japonica to varying mowing heights have been documented. Joo et al. (1999) reported size and silica content of leaf s were reduced in lower mowed turf, and recommend a mowing height of 3.8 cm or greater to maintain turf quality, shoot density, and root mass under low maintenance conditions. Meyer z oysiagrass maintained acceptable summer turf quality under 71% continuous shade when mowed at 1.6 and 2.5 cm (Bunnell et al., 2005). Engelke et al. (1992) described the effects of three nitrogen fe rtilization rates (49, 98, and 293 kg ha-1) and two mowing heights (1.6 and 2.5 cm ) on 10 zoysiagrass genotypes near Dallas, 59

PAGE 60

TX. Plots fertilized with N at 49 kg ha-1 retained green color during winter months and greenedup quicker in the spring compared to those treate d with higher nitrogen ra tes. Turfgrass quality during summer was improved with higher N rates, especially at the lower mowing height, but there were no discernable effects of N and mowi ng height on winter a nd spring turf quality. Greater incidence of large patch ( Rhizoctonia solani ) was observed on 12 Zoysia cultivars when mowed at 1.2 and 2.5 cm rather than at 4.5 or 5.1 cm, and was not affect ed by nitrogen source or rate (Green et al., 1994 ). Centipedegrass (Eremochloa ophiuroides [Munro] Hack) (Toler et al., 2007), buffalograss ( Buchloe dactyloides [Nutt.] Engelm.) (Frank et al., 2004), and carpetgrass ( Axonopus affinis Chase) (Bush et al., 2000) have been evaluated for response to mowing height and N fertility combinations to find regimes that sustain acceptable quality for lower maintenance locations. Influence of mowing height and nitrogen on characteristics important for intensely managed areas of hybrid bermudagrasses ( Cynodon dactylon [L.] Pers. var. dactylon C. transvaalensis Burtt-Davy) (Guertal and Evans, 2006; Johnson et al., 1987; Tucker et al., 2006) and seashore paspalum (Paspalum vaginatum Swartz) (Kopec et al., 2007) has also been researched. Additional cultural practices ha ve been studied to prevent or reduce the accumulation of thatch in zoysiagrasses. Lower mowing height s, verticutting, and aer ification have been associated with decreased thatch layers, but mechanical injury from increased maintenance (verticutting + aerifying) often caused reduced turf quality and weed invasion (Cockerham et al., 1997; Weston and Dunn, 1985). Hollingsworth et al. (2005) observed similar reductions in quality of ultradwarf bermudagrasses when cultu ral management was too intense. Kenworthy and Engelke (1999) reported that two aer ifications per year and 97 to 195 kg ha-1 N during the growing season produced the highest quality turf when Cavalier, Crown e, Palisades, and El 60

PAGE 61

Toro were maintained at 1.2 cm. Reducing N fe rtilization has been show n to lower thatch and tiller density in zoysiagrass, but clipping removal and growth regulator ap plication had no effects on its accumulation (Soper et al., 1988). Little research has b een performed regarding the management of Zoysia spp. in Florida to date. Several newer cultivars of zoysiagrass are now available for use in the Southeastern United States. This research was init iated to (i) characterize a genera l response (color density, turf quality, thatch accumulation, and disease incidence) to nitrogen fertilization, mowing, and their interactions among zoysiagrass cu ltivars, and (ii) establish appropriate mowing height and fertility recommendations for each of the cultivars studied. Materials and Methods Separate fields of three Zoysia japonica cultivars (Empire, Pa lisades (Engelke et al., 2002c), and Ultimate) and three Z. matrella cultivars (Cavalier (Engelke et al., 2002b), Diamond (Engelke et al., 2002a), and Pristine) were planted from sprigs during the summer and fall of 2005. All plots were establis hed by late summer of 2006. JaMur ( Z. japonica ) and Zeon ( Z. matrella ) were planted from sod in the fall of 2006 and had successfully rooted and begun spreading by the spring of 2007. Applications of irrigation, topdre ssing, fertilizer, preand postemergence herbicides, and fungicides we re uniform between all cultivars before experiments were initiated. Mowing heights we re gradually lowered to designated treatment levels beginning in January of 2007 to avoid scal ping. Plots were verticut annually in March prior to fertilizer applications. All research was conducted on irri gated plots at the University of Florida G.C. Horn Turfgrass Research Facility near Citra, FL in Candler sand (hyperthermic, uncoated Lamellic Quartzipsamments) during 2007 and 2008. Coarse textured Z. japonica cultivars were evaluated independently of the fine textured Z. matrella cultivars because of differences in their required mowing heights and potential uses. 61

PAGE 62

The experiments were split-plot designs nested within cultivars, with mowing heights as whole plots (4.5 1.5 m), and N fertilization levels as the subplots (1.5 1.5 m). Treatments were replicated three times. Empire, JaMur, Palisad es, and Ultimate were mowed weekly at 2.5 and 5.0 cm with a mulching rotory mower. Cavali er, Diamond, Pristine, and Zeon were walk mowed twice weekly at 0.6 and 1.2 cm with a reel mowe r. Clippings were not collected. Total annual nitrogen treatments were 73, 171, and 268 kg ha-1 yr-1 for all cultivars, but split between four or five application dates in the Z. japonica and Z. matrella experiments, respectively. A rotary fertilizer spreader was used to deliver each initi al yearly application uniformly across all plots from a balanced fertilizer (15N-5P-15 K) on 1 March at the N rate of 24 kg ha-1. Subsequent applications were made by hand using Uflexx (J. R. Simplot Company, Boise, ID) fertilizer (46N-0P-0K), with the remaini ng yearly rates split equally on May 1, August 1, and October 1 for the Z. japonica study, and on May 1, July 1, September 1, and November 1 for the Z. matrella experiment. Plots were ir rigated with approximately 1. 3 cm of water immediately following fertilizer applications. All treatments on Pristine were inadvertently fertilized with an additional 48 kg N ha-1 from a balanced fertilizer ( 15N-5P-15K) in June of 2007. Turfgrass quality, density, and genetic colo r were rated visually on a monthly basis. Quality was rated on a scale of 1 to 9 with 1 = poor, 5 = acceptable, and 9 = excellent. The rating scale for density was 1 = least and 9 = most For genetic color 1 = yellow, 5 = acceptable, and 9 = dark green. Bipolaris disease incidence was noted as symptoms occurred. Turfgrass quality ratings were adjusted as warranted by se verity of the disease symptoms. Thatch depth was estimated fall 2007 on each plot by measuring the organic layer that accumulated between the soil surface and the turf canopy with a ru ler from two 10.8 cm diameter cores. 62

PAGE 63

Analysis of variance was performed to test whether cultivars, mowing heights, and N fertilization levels varied by date. Data were analyzed separately by date, and within each cultivar to further study the eff ects of the treatments. Mowing height and N fertilization level means were separated using a Fishers prot ected LSD where statistically significant. Results and Discussion Zoysia japonica Cultivars responded differently ( P 0.01) for turf density, turf quality, and thatch depth in the overall analysis of variance. Mowing height contributed to the observed variation ( P 0.01) in genetic color, turf quality, and thatch dept h. Nitrogen fertilization rates were significant ( P 0.01) in all four measured tr aits and interactions between mowing height and N rate were found for turf density and quality. Turfgrass performance characteristics did not respond consistently over dates as indicated by the significant ( P 0.01) interactions when analyzed as a split-plot in time (Table 5-1). Therefore, responses on each date within individual cultivars were evaluated to determine trends associated with mowing height and N rate treatments. Generalities regarding genetic color were apparent in all four cultivars. N rate accounted for most of the observed variation across all date s, but mowing height was important in the late winter and early spring. Many of the mowing height N rate interactions were due to the response of mowing height at the lowest fertility level when comp ared to either the medium or high rate. Acceptable ge netic color ratings ( 5) were rarely found at the lowest N rate. The highest N fertility typically result ed in the greenest turf, but a cceptable color was maintained at the medium N rate for most of the year outside of the winter months. Only the low mowed plots with the highest annua l N fertility rated 5 during the winter. October fertilizer applications consistently improved genetic color in all tr eatments, and a negative response to the May 63

PAGE 64

fertilizer application at the low N rate was obser ved in both years (Figure 5-1, Figure 5-2, Figure 5-3, Figure 5-4). Empire zoysiagrass lost its color dramatically in the winter when mowed and fertilized at the highest levels (Figure 5-1). Palisades responded similarly with Empire, although mowing heights had a greater impact on genetic color throughout th e year (Figure 5-3). Acceptable color ratings were observed at times on Ultimate at th e lowest N rate. Beginning in July of 2008, scalping resulted in reduced genetic color and over all plot health at the higher mowing height (Figure 5-4). Density was primarily influenced by nitrogen fertility rate in all Z. japonica cultivars. Interactions between mowing height and N rate for this characteristic were more common in the fall and winter months as illustrated in Empire, Palisades, and Ultimate where the relative differences in winter density between low and hi gh mowing heights were greater at low nitrogen fertility compared to those at the medium a nd high N rates. JaMur (2007 and early 2008) and Ultimate (2007 and 2008) maintained acceptable ( 5) density at low N fertility, and were generally denser than Empire and Palisades under the same treatments. A trend of decreasing density during the summer months at the low N rate was present in all cultivars. The late fertilizer application in October resulted in a fa vorable response in all treatments and cultivars, and may help these grasses compete with winter weeds in environments where the turf never completely goes dormant (Figure 5-5, Figure 5-6, Figure 5-7, Figure 5-8). Nitrogen fertility was largely responsible for the differences in turf quality in all cultivars. Mowing height had a significant eff ect in the fall before the October fertilization date and in later winter months. At the low N rate, turfgrass quality was generally greater when mowed low than high, and at times during the year resulted in acceptable ( 5) ratings for JaMur and Ultimate. 64

PAGE 65

Turf quality was not adequately maintained at ei ther mowing height under low fertility in Empire and Palisades. Fall and winter quality declin es were more pronounced at the high than low mowing height when grown under high fertility, except in Palisades. Re sults indicate that acceptable quality in these cultivars may be sustai ned throughout the winter at either the medium or high fertilizer treatment when mowed lower. Negative responses were observed in both years to the May fertilizer application at the low N ra te (Figure 5-9, Figure 5-10, Figure 5-11, Figure 512). Dunn et al. (1995) stressed that zoysiagrass should only be fe rtilized with enough nitrogen to maintain acceptable density and turf quality, but that higher N rates may be necessary on sandier soils with low organic matter content. The initial decline in fall turfgrass quality observed for most cultivars as the season began to change was less prominent in the high mowing he ight of Empire, sugges ting that its prostrate growth habit may facilitate longe r duration of quality until the fi rst hard freeze (Figure 5-9). Ultimate showed a dramatic response to the firs t fall (October 2007) fert ilization application, although scalping at the higher mo wing height in the late summe r months of 2008 indicate that its density and thatch accumulati on may influence long term turf quality (Figure 5-12). Fall and winter fertilizer applications in zoysiagrass have typically resulte d in higher weed infestation, especially when the turf is dormant (Busey 2003; Dunn et al., 1993; Henry et al., 1989). There were no differences in thatch depth between N rates within individual cultivars when measured at the end of 2007. Thatch de pth was numerically grea ter at the high mowing height in all cultivars, but significant differences ( P 0.05) were only found at the low and medium fertility levels in Empire, and at the high nitrogen rate for Palisades and Ultimate. Cockerham et al. (1997) observe d less thatch at lower mowi ng heights in DeAnza and Victoria zoysiagrass. Generall y, thatch depths were comparable for all cultivars at the low 65

PAGE 66

mowing height, but at the high mowing height Em pire and Ultimate performed similarly as did JaMur and Palisades (Table 5-2). Zoysia matrella Much of the observed variation ( P 0.01) for each turfgrass pe rformance characteristic was due to cultivar and N rate in the overall anal ysis of variance, although various significant (P 0.05) interactions between cultivar and other main effects suggested that important seasonal information unique to each cultivar could be gather ed if they were analyzed separately by date. Thatch depths varied ( P 0.05) with mowing heights. Differen ces in thatch were not attributed to the effects of cultivar and N rate (Table 5-1), but were further explained in an analysis of their interaction (Table 5-3). Nitrogen fertility was primarily responsible for the observed respons es in genetic color for all Z. matrella cultivars on most dates. Maintaining acceptable color at the low N rate may not be possible over time, but ratings 5 were sustained at the medi um and high fertility rates in both mowing heights over the enti re year. November fertilizer applications provided drastic improvement to winter color in all treatments, and except for Pristine in 2008, there was generally no response from the May fe rtilizer application at the low N rate in either year (Figure 5-13, Figure 5-14, Figure 5-15, Figure 5-16). Mowing Cavalier at the higher height during the summer months typically resulted in greener genetic color at both th e medium and high nitrogen treatments, although similar color ratings were observed at both mowi ng heights at low N fertility. P eaks and valleys in the genetic color of Cavalier demonstrated instability th rough time (Figure 5-13). Diamond (Figure 5-14) and Pristine (Figure 5-15) had more consistent genetic color and responded similarly to comparable treatments beginning in January of 2008. Mowing height N rate interactions for genetic color in Zeon were of ten observed in the month imme diately following fertilizer 66

PAGE 67

application, and were mostly due to large cha nges in color at low N fertility in the higher mowing height when compared to more consiste nt responses for the medium and high nitrogen rates at both mowing heights (Figure 5-16). Diamond and Pristine have greate r turf density and finer leaf-t exture than either Cavalier or Zeon. Scalping was observed at the high nitrog en rate for both of these cultivars as noted by reductions in density during October of 2007. Ha le (2006) described the same trend in three Z. matrella cultivars when fertilized with annual rates of 146 and 195 kg N ha-1. Results indicate that it may be possible to maintain acceptable dens ity at the lowest nitrogen fertilization level in Diamond and Pristine while avoiding the scalping associated with higher fertility. Leaf spot ( Bipolaris spp.) damage severely reduced turf density in Cavalier during the late summer and fall of 2007. Although the injury was relatively unifo rm across all treatments, plots at the low mowing height and highest N ra te were the least dense. Bipolaris disease incidence was also noted on Zeon at this time, but the damage was not as prominent. When Bipolaris was active on Cavalier and Zeon their density was influenced by mowing height and nitrogen fertility, but when Bipolaris was not limiting, nitrogen fertilization rates were more important (Figure 5-17, Figure 5-18, Figure 5-19, Figure 5-20). Gr een et al. (1994) found that large patch ( Rhizoctonia solani ) more severely blighted 12 zoysiagrass cultivars at lower mowing heights, and that neither nitrogen rate or source in fluenced disease severity. Trends in turfgrass quality were not evident for th e entire set of Z. matrella cultivars because of genetic differences, confounding results from disease incidence, and fertilizer application error. Cavalier zoysiagrass genera lly remained unacceptable due to lasting effects from the initial July 2007 Bipolaris damage, but symptom severity appeared to decrease over time at the higher mowing height possibly as a result of reduced stress (Figure 5-21). 67

PAGE 68

Establishment of mowing treatments and early disease incidence in Ze on impeded the detection of clear treatment differences on turf quality until the winter of 2007. Nitrogen fertility significantly influenced the expression of quality when the turf was not under diseases pressure, with the highest N rates resulting in the best turf. Bipolaris symptoms in August and September of 2008 had less impact on turfgrass quality at the high mowing height under medium or low N fertility (Figure 5-22). Diamond typically performed better at th e low mowing height, especially in the late fall and early spring when the majority of seedheads were not removed at the high mowing height. It may be possible to maintain tu rf quality during the fall and winter months at the low mowing height and nitrogen rate, but not when the turf is actively growing or has been recently injured by mechanical cultivation. N ra te had a greater influence on turf quality during the growing season, but severe scalping was obs erved in the high fertil ity treatment at both mowing heights in September and October of 2007 (Figure 5-23). Effects of fertility and mowing height became more apparent on Pristine in 2008 when the response from an incorrect fertilization in June of 2007 had subsided. Va rious degrees of scalpi ng occurred at the high mowing height periodically through out the study. Slow recovery from mechanical injury following verticutting was noted at the low N ra te. Weston and Dunn (1985) described similar injury and increased weed encroachment in Meyer zoysiagrass when vertical mowing and core aerification were used to manage thatch. Overall tu rfgrass quality was consistent during 2008 at the low mowing height and medium N rate, which may be the appropriate management combination to avoid the above men tioned scalp damage (Figure 5-24). Trends were not clear regardi ng the effect of mowing height a nd N rate on thatch depth in the Z. matrella cultivars. Significant ( P 0.05) differences were observed, but none were meaningful. Thatch depth at the lower mowing height was similar among all cultivars, although 68

PAGE 69

Pristine appeared to have more thatch at the high mowing height (Table 5-3). This occurrence could have directly resulted from the inadvertent fertilizer application. Soper et al. (1988) found a direct relationship between increasing N fert ilization and thatch accumulation in Meyer zoysiagrass. They also conclude d that stolons are less easily degr aded than leaf tissue, and were therefore more influential on thatch depth than returned mower clippings. Conclusions Understanding how cultivars re spond to basic mowing and fer tility treatments is critical in developing more comprehensive management practices. Genetic differences and varying levels of adaptation to the environment in Fl orida were evident among this set of genotypes, although a few trends were common among both Zoysia species. Nitrogen rate had a greater impact on most of the observed characteristics when the turf was activ ely growing, but mowing height was important during the winter and in times of stress. Our results and observations suggest that increasing nitrogen fertility to temporarily maximize genetic potential for color and density may have lasting detrimental effects on tu rfgrass quality. Problems concerning scalping, thatch accumulation, disease incidence, and drought injury may be lessened if consideration is given to maintaining acceptable, rather than exceptional, conditions. Preventing damage to zoysiagrasses is especially important because they lack the recuperative po tential of other faster growing grasses (Busey and Myers, 1979). Each cultivar responded uniquely to the envi ronment and imposed treatments. Turfgrass density was not maintained in Empire or Palisade s at the lowest N rate, but for different reasons than observed in Cavalier and Zeon. Simply in creasing nitrogen fertility could improve turf density to acceptable levels in the Z. japonica cultivars, but higher N fertility may require a preventative fungicide program for the two Z. matrella genotypes. JaMur, Ultimate, Diamond, and Pristine all had acceptable de nsity at the low nitrogen rate, but often did not have adequate 69

PAGE 70

70 color to sustain turf qua lity. In this case additional iron supplementation could augment genetic color without the risk of incurring detrimental eff ects from excess N fertilization. More than one season of growth may be required to detect the effects of mowi ng height and N rate treatments on thatch accumulation. This research should serve as the framework on which additional practices are tested for each cultivar. The results herein suggest th at lowering mowing heights during the winter months, and raising them during times of stress will improve overall turf quality. Likewise, nitrogen fertility should be adjusted accordingly w ith incidence of disease or mechanical injury. Only through further testing of N source and rate additional nutrients, timing of application, thatch management (grooming, verticutting, aer ifying, and topdressing), and fungicide programs in the presence or absence of biotic and abiotic stresses will the best management practices be formulated.

PAGE 71

Table 5-1. Mean squares for turfgrass performa nce characteristics and thatch depth of four Zoysia japonica cultivars and four Zoysia matrella cultivars evaluated at two mowing heights and three nitrogen fertility rates near Gainesville, FL. Mean squares Zoysia japonica Zoysia matrella Source df Genetic color Turf density Turf quality Thatch depth Genetic color Turf density Turf quality Thatch depth Cultivar (C) 3 24.98 277.40** 60.35** 54.68** 86.48** 685.74** 351.72** 38.85 Rep (C) 8 3.82 3.25 5.21 0.63 8.76 8.86 13.04 15.44 Mowing height (M) 1 77.05** 7.87 40.67** 308.88** 21.54* 5.06 7.72 47.69* M C 3 1.24 3.53 3.88 7.88 4.59 39.19* 46.61* 8.22 Rep M (C) 8 1.09 1.14 0.71 3.04 1.04 6.32 7.04 7.18 N rate (N) 2 693.03** 443.48** 520.56** 13.60* 754.13** 124.31** 260.40** 0.42 N C 6 2.97 2.66 3.41 2.24 12.85** 12.34* 21.40** 4.38* N M 2 3.15 9.82** 10.79** 6.17 12.57** 3.69 16.50 0.34 N C M 6 0.53 1.88 1.62 3.20 0.75 10.44* 8.72 1.72 Rep N (C M) 32 0.83 0.90 1.44 3.78 1.61 4.00 4.48 1.54 Date (D) 17 44.45** 10.84 25.78** 32.66 15.22 19.15 D C 51 5.16** 5.72** 3.82** 10.11** 10.59** 13.29** D M 17 3.88** 1.14 2.94** 2.30 3.16 3.40 D N 34 10.40** 4.50** 5.53** 9.61** 6.32** 11.70** D C M 51 1.04** 0.70** 1.11** 0.81** 3.52** 3.63** D C N 102 0.79** 0.68** 0.88** 1.19** 1.39* 2.46** D M N 34 0.73** 0.36 0.49 0.95** 1.38 2.73** D C M N 102 0.35 0.25 0.41 0.41 0.98* 1.41** MSE 816 0.28 0.32 0.46 0.38 0.77 1.00 % CV 10.0 9.3 12.0 11.0 10.3 14.9 18.8 9.6 *, **Significant at the 0.05 and 0.01 probability levels, respectively. Thatch depth only evaluated on one date. 71

PAGE 72

2007 May 2007 Jun 2007 Jul 2007 Aug 2007 Sep 2007 Oct 2007 Nov 2007 Dec 2008 Jan 2008 Feb 2008 Mar 2008 Apr 2008 May 2008 Jun 2008 Jul 2008 Aug 2008 Sep Genetic Color 1 2 3 4 5 6 7 8 9 2.5 cm / 73 kg N 2.5 cm / 171 kg N 2.5 cm / 268 kg N 5.0 cm / 73 kg N 5.0 cm / 171 kg N 5.0 cm / 268 kg N ns ns ns ns ns ns ns ns **ns ns ns ns ns ns ns ** ** ** ** ****** ******ns **** ** ** ns ns ns ns **ns ns **ns ns ns ns ns ns ns ns M N M N Figure 5-1. Genetic color responses and significance of treatment effects in Empire zoysiagrass at two mowing heights (M) and three ni trogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, August, and October of each year. Visual rating of five was considered to be the minimum acceptable value. 72

PAGE 73

2007 May 2007 Jun 2007 Jul 2007 Aug 2007 Sep 2007 Oct 2007 Nov 2007 Dec 2008 Jan 2008 Feb 2008 Mar 2008 Apr 2008 May 2008 Jun 2008 Jul 2008 Aug 2008 Sep Genetic Color 1 2 3 4 5 6 7 8 9 2.5 cm / 73 kg N 2.5 cm / 171 kg N 2.5 cm / 268 kg N 5.0 cm / 73 kg N 5.0 cm / 171 kg N 5.0 cm / 268 kg N ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ** ** ** ** ****** ******ns ** ** ** ** ns ns ns ** ns ns ns ns ns ns ns ns ns ns ** ns ns M N M N Figure 5-2. Genetic color responses and significance of treatment ef fects in JaMur zoysiagrass at two mowing heights (M) and three ni trogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, August, and October of each year. Visual rating of five was considered to be the minimum acceptable value. 73

PAGE 74

2007 May 2007 Jun 2007 Jul 2007 Aug 2007 Sep 2007 Oct 2007 Nov 2007 Dec 2008 Jan 2008 Feb 2008 Mar 2008 Apr 2008 May 2008 Jun 2008 Jul 2008 Aug 2008 Sep Genetic Color 1 2 3 4 5 6 7 8 9 2.5 cm / 73 kg N 2.5 cm / 171 kg N 2.5 cm / 268 kg N 5.0 cm / 73 kg N 5.0 cm / 171 kg N 5.0 cm / 268 kg N ns ns ns ** **ns ns ns ns ns ** ** ns ns ns ** ** ** ** ****** ******** **** ** ** ** ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns M N M N Figure 5-3. Genetic color responses and significance of treatment ef fects in Palisades zoysiagrass at two mowing heights (M) and three ni trogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, August, and October of each year. Visual rating of five was considered to be the minimum acceptable value. 74

PAGE 75

2007 May 2007 Jun 2007 Jul 2007 Aug 2007 Sep 2007 Oct 2007 Nov 2007 Dec 2008 Jan 2008 Feb 2008 Mar 2008 Apr 2008 May 2008 Jun 2008 Jul 2008 Aug 2008 Sep Genetic Color 1 2 3 4 5 6 7 8 9 2.5 cm / 73 kg N 2.5 cm / 171 kg N 2.5 cm / 268 kg N 5.0 cm / 73 kg N 5.0 cm / 171 kg N 5.0 cm / 268 kg N ns ns ns ns ns ns ns ns ns ns ns ns ns ** ** ns ** ** ** ** ****** ******ns ns ** ** ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns M N M N Figure 5-4. Genetic color responses and significan ce of treatment effects in Ultimate zoysiagrass at two mowing heights (M) and three ni trogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, August, and October of each year. Visual rating of five was considered to be the minimum acceptable value. 75

PAGE 76

2007 May 2007 Jun 2007 Jul 2007 Aug 2007 Sep 2007 Oct 2007 Nov 2007 Dec 2008 Jan 2008 Feb 2008 Mar 2008 Apr 2008 May 2008 Jun 2008 Jul 2008 Aug 2008 Sep Density 1 2 3 4 5 6 7 8 9 2.5 cm / 73 kg N 2.5 cm / 171 kg N 2.5 cm / 268 kg N 5.0 cm / 73 kg N 5.0 cm / 171 kg N 5.0 cm / 268 kg N ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ** ** ** ** ****** ******** **** ** ** ns ns ns ns ns ns ns ns ns ns ns ns ns ns M N M N Figure 5-5. Turf density responses and significance of treatment ef fects in Empire zoysiagrass at two mowing heights (M) and three ni trogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, August, and October of each year. Visual rating of five was considered to be the minimum acceptable value. 76

PAGE 77

2007 May 2007 Jun 2007 Jul 2007 Aug 2007 Sep 2007 Oct 2007 Nov 2007 Dec 2008 Jan 2008 Feb 2008 Mar 2008 Apr 2008 May 2008 Jun 2008 Jul 2008 Aug 2008 Sep Density 1 2 3 4 5 6 7 8 9 2.5 cm / 73 kg N 2.5 cm / 171 kg N 2.5 cm / 268 kg N 5.0 cm / 73 kg N 5.0 cm / 171 kg N 5.0 cm / 268 kg N ns ns ns ns ns **ns ns ns ns ns ns ns ns ns ns ** ** ** ** ****** ******** ** ** ** ** ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns M N M N Figure 5-6. Turf density responses and significance of treatment ef fects in JaMur zoysiagrass at two mowing heights (M) and three ni trogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, August, and October of each year. Visual rating of five was considered to be the minimum acceptable value. 77

PAGE 78

2007 May 2007 Jun 2007 Jul 2007 Aug 2007 Sep 2007 Oct 2007 Nov 2007 Dec 2008 Jan 2008 Feb 2008 Mar 2008 Apr 2008 May 2008 Jun 2008 Jul 2008 Aug 2008 Sep Density 1 2 3 4 5 6 7 8 9 2.5 cm / 73 kg N 2.5 cm / 171 kg N 2.5 cm / 268 kg N 5.0 cm / 73 kg N 5.0 cm / 171 kg N 5.0 cm / 268 kg N ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ** ** ** ****** ******** **** ** ** ** ns ns ns ns ns ns ** ns ns ns ns ns ns ns ns M N M N Figure 5-7. Turf density responses and significance of treatment ef fects in Palisades zoysiagrass at two mowing heights (M) and three ni trogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, August, and October of each year. Visual rating of five was considered to be the minimum acceptable value. 78

PAGE 79

2007 May 2007 Jun 2007 Jul 2007 Aug 2007 Sep 2007 Oct 2007 Nov 2007 Dec 2008 Jan 2008 Feb 2008 Mar 2008 Apr 2008 May 2008 Jun 2008 Jul 2008 Aug 2008 Sep Density 1 2 3 4 5 6 7 8 9 2.5 cm / 73 kg N 2.5 cm / 171 kg N 2.5 cm / 268 kg N 5.0 cm / 73 kg N 5.0 cm / 171 kg N 5.0 cm / 268 kg N ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ** ** ** ** ****** ******** **** ns ns ns ns ns ns ns ns ns ns ns ns ** ns ns ns M N M N Figure 5-8. Turf density responses and significan ce of treatment effects in Ultimate zoysiagrass at two mowing heights (M) and three ni trogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, August, and October of each year. Visual rating of five was considered to be the minimum acceptable value. 79

PAGE 80

2007 May 2007 Jun 2007 Jul 2007 Aug 2007 Sep 2007 Oct 2007 Nov 2007 Dec 2008 Jan 2008 Feb 2008 Mar 2008 Apr 2008 May 2008 Jun 2008 Jul 2008 Aug 2008 Sep Turf Quality 1 2 3 4 5 6 7 8 9 2.5 cm / 73 kg N 2.5 cm / 171 kg N 2.5 cm / 268 kg N 5.0 cm / 73 kg N 5.0 cm / 171 kg N 5.0 cm / 268 kg N ns ns ns ns ns ns ns ns ns ns ns ns ns ** ns ns ** ns ** ** ****** ******** **** ** ** ns ns ns ns ** ns ns ns ns ns ns ns ns M N M N Figure 5-9. Turf quality responses and significance of treatment effects in Empire zoysiagrass at two mowing heights (M) and three ni trogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, August, and October of each year. Visual rating of five was considered to be the minimum acceptable value. 80

PAGE 81

2007 May 2007 Jun 2007 Jul 2007 Aug 2007 Sep 2007 Oct 2007 Nov 2007 Dec 2008 Jan 2008 Feb 2008 Mar 2008 Apr 2008 May 2008 Jun 2008 Jul 2008 Aug 2008 Sep Turf Quality 1 2 3 4 5 6 7 8 9 2.5 cm / 73 kg N 2.5 cm / 171 kg N 2.5 cm / 268 kg N 5.0 cm / 73 kg N 5.0 cm / 171 kg N 5.0 cm / 268 kg N ns ns ns ns **ns ns ns ns ns ns ns ns ns ns ** ** ** ** ** ****** ******** ** ** ** ** ns ns ns ns ns ns ns ns ns ns ns ns ns ns M N M N Figure 5-10. Turf quality responses and significance of treatment effects in JaMur zoysiagrass at two mowing heights (M) and three ni trogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, August, and October of each year. Visual rating of five was considered to be the minimum acceptable value. 81

PAGE 82

2007 May 2007 Jun 2007 Jul 2007 Aug 2007 Sep 2007 Oct 2007 Nov 2007 Dec 2008 Jan 2008 Feb 2008 Mar 2008 Apr 2008 May 2008 Jun 2008 Jul 2008 Aug 2008 Sep Turf Quality 1 2 3 4 5 6 7 8 9 2.5 cm / 73 kg N 2.5 cm / 171 kg N 2.5 cm / 268 kg N 5.0 cm / 73 kg N 5.0 cm / 171 kg N 5.0 cm / 268 kg N ns ** ns ns ns ns ns **ns ns ns ns ns ns ns ns ns ns ns ** ** ****** *** **** **** ** ** ** ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns M N M N Figure 5-11. Turf quality responses and significance of treatment effects in Palisades zoysiagrass at two mowing heights (M) and three ni trogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, August, and October of each year. Visual rating of five was considered to be the minimum acceptable value. 82

PAGE 83

2007 May 2007 Jun 2007 Jul 2007 Aug 2007 Sep 2007 Oct 2007 Nov 2007 Dec 2008 Jan 2008 Feb 2008 Mar 2008 Apr 2008 May 2008 Jun 2008 Jul 2008 Aug 2008 Sep Turf Quality 1 2 3 4 5 6 7 8 9 2.5 cm / 73 kg N 2.5 cm / 171 kg N 2.5 cm / 268 kg N 5.0 cm / 73 kg N 5.0 cm / 171 kg N 5.0 cm / 268 kg N ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ** ** ** ** ****** ******ns ns ** ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns M N M N Figure 5-12. Turf quality responses and significan ce of treatment effects in Ultimate zoysiagrass at two mowing heights (M) and three ni trogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, August, and October of each year. Visual rating of five was considered to be the minimum acceptable value. 83

PAGE 84

Table 5-2. Mean that ch depth of four Zoysia japonica cultivars when evaluated at two mowing heights and three nitrogen fertili ty rates in November of 2007 near Gainesville, FL. Thatch depth Empire JaMur Palisades Ultimate N rate 2.5 cm 5.0 cm 2.5 cm 5.0 cm 2.5 cm 5.0 cm 2.5 cm 5.0 cm kg ha-1 yr-1 mm 73 17 aB 19 aA 15 aA 17 aA 14 aA 18 aA 16 aA 20 aA 171 16 aB 22 aA 15 aA 18 aA 14 aA 16 aA 16 aA 22 aA 268 16 aA 22 aA 15 aA 19 aA 15 aB 19 aA 17 aB 24 aA Means within a column followed by the same lo wercase letter are not significantly different a P 0.05 according to Fishers protected LSD. Means w ithin a row and specific cultivar followed by the same uppercase letter are not significantly different a P 0.05 according to Fish ers protected LSD. Table 5-3. Mean that ch depth of four Zoysia matrella cultivars when evaluated at two mowing heights and three nitrogen fertili ty rates in November of 2007 near Gainesville, FL. Thatch depth Cavalier Diamond Pristine Zeon N rate 0.6 cm 1.2 cm 0.6 cm 1.2 cm 0.6 cm 1.2 cm 0.6 cm 1.2 cm kg ha-1 yr-1 mm 73 11 aA 11 aA 12 aA 14 aA 13 aA 16 aA 12 aA 14 aA 171 11 aB 12 aA 14 aA 14 aA 13 aA 16 aA 11 aA 11 bA 268 10 aA 13 aA 13 aA 12 aA 13 aA 16 aA 13 aA 14 aA Means within a column followed by the same lo wercase letter are not significantly different a P 0.05 according to Fishers protected LSD. Means w ithin a row and specific cultivar followed by the same uppercase letter are not significantly different a P 0.05 according to Fish ers protected LSD. 84

PAGE 85

2007 May 2007 Jun 2007 Jul 2007 Aug 2007 Sep 2007 Oct 2007 Nov 2007 Dec 2008 Jan 2008 Feb 2008 Mar 2008 Apr 2008 May 2008 Jun 2008 Jul 2008 Aug 2008 Sep Genetic Color 1 2 3 4 5 6 7 8 9 2.5 cm / 73 kg N 2.5 cm / 171 kg N 2.5 cm / 268 kg N 5.0 cm / 73 kg N 5.0 cm / 171 kg N 5.0 cm / 268 kg N ns ns ** ns ns ns ns ns ns ns ns ns ns ns ns ** ** ** ns **** ******** ** ** ** ** ns ns ns ns ns ns ns ns ns ns ns ns ** M N M N Figure 5-13. Genetic color responses and signi ficance of treatment effects in Cavalier zoysiagrass at two mowing heights (M) a nd three nitrogen leve ls (N) during 2007 and 2008. Fertilizer treatments were applied in March, May, July, September, and November of each year. Visual rating of five was considered to be the minimum acceptable value. 85

PAGE 86

2007 May 2007 Jun 2007 Jul 2007 Aug 2007 Sep 2007 Oct 2007 Nov 2007 Dec 2008 Jan 2008 Feb 2008 Mar 2008 Apr 2008 May 2008 Jun 2008 Jul 2008 Aug 2008 Sep Genetic Color 1 2 3 4 5 6 7 8 9 2.5 cm / 73 kg N 2.5 cm / 171 kg N 2.5 cm / 268 kg N 5.0 cm / 73 kg N 5.0 cm / 171 kg N 5.0 cm / 268 kg N ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ** *** ** ******** **** ** ** ** ns ns ns ns ns ns ns ns ns ns ns ns ns ns ** ns M N M N Figure 5-14. Genetic color responses and signi ficance of treatment effects in Diamond zoysiagrass at two mowing heights (M) a nd three nitrogen leve ls (N) during 2007 and 2008. Fertilizer treatments were applied in March, May, July, September, and November of each year. Visual rating of five was considered to be the minimum acceptable value. 86

PAGE 87

2007 May 2007 Jun 2007 Jul 2007 Aug 2007 Sep 2007 Oct 2007 Nov 2007 Dec 2008 Jan 2008 Feb 2008 Mar 2008 Apr 2008 May 2008 Jun 2008 Jul 2008 Aug 2008 Sep Genetic Color 1 2 3 4 5 6 7 8 9 2.5 cm / 73 kg N 2.5 cm / 171 kg N 2.5 cm / 268 kg N 5.0 cm / 73 kg N 5.0 cm / 171 kg N 5.0 cm / 268 kg N ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ****** ******** **** ** ** ** ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns M N M N Figure 5-15. Genetic color responses and significan ce of treatment effects in Pristine zoysiagrass at two mowing heights (M) and three ni trogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, July, September, and November of each year. Visual rating of five was cons idered to be the minimum acceptable value. 87

PAGE 88

2007 May 2007 Jun 2007 Jul 2007 Aug 2007 Sep 2007 Oct 2007 Nov 2007 Dec 2008 Jan 2008 Feb 2008 Mar 2008 Apr 2008 May 2008 Jun 2008 Jul 2008 Aug 2008 Sep Genetic Color 1 2 3 4 5 6 7 8 9 2.5 cm / 73 kg N 2.5 cm / 171 kg N 2.5 cm / 268 kg N 5.0 cm / 73 kg N 5.0 cm / 171 kg N 5.0 cm / 268 kg N ns ns ns ns ns ns ns ns ns **ns ns ns ns ns ns ns ** ** ** ** ****** ******** **** ** ** ** ns ** ns ns ns ns ** ns ns ns ** ns ** ns M N M N Figure 5-16. Genetic color responses and significan ce of treatment effects in Zeon zoysiagrass at two mowing heights (M) and three ni trogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, July, September, and November of each year. Visual rating of five was cons idered to be the minimum acceptable value. 88

PAGE 89

2007 May 2007 Jun 2007 Jul 2007 Aug 2007 Sep 2007 Oct 2007 Nov 2007 Dec 2008 Jan 2008 Feb 2008 Mar 2008 Apr 2008 May 2008 Jun 2008 Jul 2008 Aug 2008 Sep Density 1 2 3 4 5 6 7 8 9 2.5 cm / 73 kg N 2.5 cm / 171 kg N 2.5 cm / 268 kg N 5.0 cm / 73 kg N 5.0 cm / 171 kg N 5.0 cm / 268 kg N ns ** ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns *** ** ** ** ** ns ns ns ns ns ns ns ns **ns ns ns ns ns ns ns ns M N M N Figure 5-17. Turf density responses and significance of treatment ef fects in Cavalier zoysiagrass at two mowing heights (M) and three ni trogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, July, September, and November of each year. Visual rating of five was cons idered to be the minimum acceptable value. 89

PAGE 90

2007 May 2007 Jun 2007 Jul 2007 Aug 2007 Sep 2007 Oct 2007 Nov 2007 Dec 2008 Jan 2008 Feb 2008 Mar 2008 Apr 2008 May 2008 Jun 2008 Jul 2008 Aug 2008 Sep Density 1 2 3 4 5 6 7 8 9 2.5 cm / 73 kg N 2.5 cm / 171 kg N 2.5 cm / 268 kg N 5.0 cm / 73 kg N 5.0 cm / 171 kg N 5.0 cm / 268 kg N ** ns ns ns ns ns **ns ns ns **ns ns ns ns ns ns ** ns ns ns ns ns ns ns *** ** ** ** ns ns ns ns ns ns ns ns ns ns ns ns ns ns ** ns M N M N Figure 5-18. Turf density responses and significance of treatment effects in Diamond zoysiagrass at two mowing heights (M) and three nitrogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, July, September, and November of each year. Visual rating of five was cons idered to be the minimum acceptable value. 90

PAGE 91

2007 May 2007 Jun 2007 Jul 2007 Aug 2007 Sep 2007 Oct 2007 Nov 2007 Dec 2008 Jan 2008 Feb 2008 Mar 2008 Apr 2008 May 2008 Jun 2008 Jul 2008 Aug 2008 Sep Density 1 2 3 4 5 6 7 8 9 2.5 cm / 73 kg N 2.5 cm / 171 kg N 2.5 cm / 268 kg N 5.0 cm / 73 kg N 5.0 cm / 171 kg N 5.0 cm / 268 kg N ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ** ns ** ** ** ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns M N M N Figure 5-19. Turf density responses and significance of treatment effects in Pris tine zoysiagrass at two mowing heights (M) and three ni trogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, July, September, and November of each year. Visual rating of five was cons idered to be the minimum acceptable value. 91

PAGE 92

2007 May 2007 Jun 2007 Jul 2007 Aug 2007 Sep 2007 Oct 2007 Nov 2007 Dec 2008 Jan 2008 Feb 2008 Mar 2008 Apr 2008 May 2008 Jun 2008 Jul 2008 Aug 2008 Sep Density 1 2 3 4 5 6 7 8 9 2.5 cm / 73 kg N 2.5 cm / 171 kg N 2.5 cm / 268 kg N 5.0 cm / 73 kg N 5.0 cm / 171 kg N 5.0 cm / 268 kg N ns ns ns ns ns **ns ns ns ns ns ns ns ** ns ns ns ns ns ** ns ****** ******** **** ** ** ns ns ns ns ns ns ns ** ns ns ns ns ns ns ns M N M N Figure 5-20. Turf density responses and significance of treatment effects in Zeon zoysiagrass at two mowing heights (M) and three ni trogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, July, September, and November of each year. Visual rating of five was cons idered to be the minimum acceptable value. 92

PAGE 93

2007 May 2007 Jun 2007 Jul 2007 Aug 2007 Sep 2007 Oct 2007 Nov 2007 Dec 2008 Jan 2008 Feb 2008 Mar 2008 Apr 2008 May 2008 Jun 2008 Jul 2008 Aug 2008 Sep Turf Quality 1 2 3 4 5 6 7 8 9 2.5 cm / 73 kg N 2.5 cm / 171 kg N 2.5 cm / 268 kg N 5.0 cm / 73 kg N 5.0 cm / 171 kg N 5.0 cm / 268 kg N ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ** ns ns ** **ns ns ns ns ** ** ** ** ns ns ns ns ns ns ** **ns ns ns ns ns ns ns ns M N M N Figure 5-21. Turf quality responses and significance of treatment effects in Cavalier zoysiagrass at two mowing heights (M) and three ni trogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, July, September, and November of each year. Visual rating of five was cons idered to be the minimum acceptable value. 93

PAGE 94

2007 May 2007 Jun 2007 Jul 2007 Aug 2007 Sep 2007 Oct 2007 Nov 2007 Dec 2008 Jan 2008 Feb 2008 Mar 2008 Apr 2008 May 2008 Jun 2008 Jul 2008 Aug 2008 Sep Turf Quality 1 2 3 4 5 6 7 8 9 2.5 cm / 73 kg N 2.5 cm / 171 kg N 2.5 cm / 268 kg N 5.0 cm / 73 kg N 5.0 cm / 171 kg N 5.0 cm / 268 kg N ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ** ns ****** ******** **** ** ** ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns M N M N Figure 5-22. Turf quality responses and significan ce of treatment effects in Zeon zoysiagrass at two mowing heights (M) and three ni trogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, July, September, and November of each year. Visual rating of five was cons idered to be the minimum acceptable value. 94

PAGE 95

2007 May 2007 Jun 2007 Jul 2007 Aug 2007 Sep 2007 Oct 2007 Nov 2007 Dec 2008 Jan 2008 Feb 2008 Mar 2008 Apr 2008 May 2008 Jun 2008 Jul 2008 Aug 2008 Sep Turf Quality 1 2 3 4 5 6 7 8 9 2.5 cm / 73 kg N 2.5 cm / 171 kg N 2.5 cm / 268 kg N 5.0 cm / 73 kg N 5.0 cm / 171 kg N 5.0 cm / 268 kg N ns ns ns ns ns ns ns ns ns ns ** ns ns ns ns ** ns ns ns ns ns ns ns ** **** ** ** ** ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns M N M N Figure 5-23. Turf quality responses and significan ce of treatment effects in Diamond zoysiagrass at two mowing heights (M) and three ni trogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, July, September, and November of each year. Visual rating of five was cons idered to be the minimum acceptable value. 95

PAGE 96

2007 May 2007 Jun 2007 Jul 2007 Aug 2007 Sep 2007 Oct 2007 Nov 2007 Dec 2008 Jan 2008 Feb 2008 Mar 2008 Apr 2008 May 2008 Jun 2008 Jul 2008 Aug 2008 Sep Turf Quality 1 2 3 4 5 6 7 8 9 2.5 cm / 73 kg N 2.5 cm / 171 kg N 2.5 cm / 268 kg N 5.0 cm / 73 kg N 5.0 cm / 171 kg N 5.0 cm / 268 kg N ** ** ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ** **ns ** ** ** ns ns ns ns ns ns ns ns ns ns ns ns ns ** M N M N Figure 5-24. Turf quality responses and significan ce of treatment effects in Pristine zoysiagrass at two mowing heights (M) and three ni trogen levels (N) during 2007 and 2008. Fertilizer treatments were applied in Marc h, May, July, September, and November of each year. Visual rating of five was cons idered to be the minimum acceptable value. 96

PAGE 97

CHAPTER 6 HERITABILITY ESTIMATES FOR TURFGRASS PERFORMANCE AND STRESS RESPONSE IN Zoysia spp. Introduction Zoysiagrasses ( Zoysia spp.) are sod forming perennials, with both rhizomes and stolons (Watson and Dallwitz, 1992) that have been identified for their potential use as a low maintenance turf (Brede and Sun, 1995). They ar e native to the Pacific Rim and widely adapted to many soils and environments (Engelke, 2000). The Z. japonica and Z. matrella species are of importance to the turfgrass industry (Hawes, 1979) Both species are tetraploids, 2n=4x=40 (Forbes, 1952), but differ morphologically with respect to leaf texture. Zoysia japonica can range from medium to coarse leaf texture, while Z. matrella plants have a fine leaf texture. There are currently (October 2008) 111 accession s of zoysiagrass li sted in the GRIN (Germplasm Resources Information Network) database available from the National Plant Germplasm System (USDA-ARS, 2007). The Texa s A&M University colle ction consists of 1,000 unique and variable Zoysia accessions (Engelke, 2000) that have been characterized with respect to morphological and mol ecular variation (Anderson, 2000). Differences in rooting were reported to be significant for 25 zoysiagrass genotypes maintained under greenhouse conditions (Marcum et al., 1995). White et al. (2001) related physiological adaptation to drought tolerance in zoysiagrass, and demonstrated that improvements in morphological traits could serve to lower its wate r use requirements. Green et al. (1991) reported no differences among 11 zoysiagrass genotypes evaluated for evapotranspiration rate. Genetic diversity for drought responses includi ng canopy wilting, plot color, turf quality, and percent living gr ound cover has been demonstrated for many Zoysia cultivars and germplasm lines (B eard and Sifers, 1997; Chalmers et al., 2008; Kim et al., 1988). 97

PAGE 98

Marcum et al. (1998) evaluated 57 accessions and cultivars of zoys iagrass representing five species for their salt gland density. Salinity tolerance in Zoysia was found to be associated with variation in salt gland density. Qian et al. (2000) showed differences existed among experimental lines and cultivars of zoysiagrass with respect to salt tolerance. Estimated broadsense heritabilities indicated that conventiona l breeding could be uti lized to enhance salt tolerance. The adaptation of 25 zoysiagrass genotypes to shade was evaluated in plots grown under a dense tree canopy under 85 percent sh ade. Entries were ranked as having high, intermediate, or low shade tolerance based on mean performa nce over two years (White and Engelke, 1990). Additionally, Qian and Engelke ( 1997) examined growth parameters for 19 zoysiagrasses under shade levels of 40%, 75% and 88%. Those with enhanced shade tolerance produced more buds, had shorter internode lengths, less decrease in shoot or root mass, le ss increase in shoot:root ratio, or persistent green co lor than non-adapted genotypes. Zoysia spp. exhibited excellent cold tolerance in comparis on to bermudagrass genotypes as indicated by greater percent rhizome survival at low temperatures (Rogers et al., 1977). Patton and Reicher (2007) repor ted variable winter hardiness among 35 zoysiagrasses. Genotypes were identified with very low winter injury (< 7% of plot damaged), intermediate (14 to 79 %), and those exhibiting significant winterkill (> 88%). On average, Z. japonica was more winter hardy than Z. matrella Variable responses of zoysiagr ass to biotic pest stresses have been described. Levels of insect resistance to the tropical sod webworm ( Herpetogramma phaeopteralis ) (Reinert and Engelke, 2001), zoysiagrass mite ( Eriophyes zoysiae) (Reinert et al., 1993), and fall armyworm 98

PAGE 99

( Spodoptera frugiperda) (Reinert et al., 1997; Reinert et al., 1994) ha ve been identified in Zoysia germplasm and cultivars. Metz et al. (1994) reported vari ation for foliar blighting from Rhizoctonia solani and noted that some zoysiagrass genotypes exhib ited resistance, while ot hers were extremely susceptible. Several zoysiagrasses we re identified with good resistance to Pythium blight in contrast to four highly suscepti ble entries inflicted with greater than 50% foliar blight (Colbaugh et al., 1994). Variation for turfgrass performance and growth rate has been well documented. Zoysiagrass NTEP trials have illustrated the differences amon g genotypes for turfgrass quality, genetic color, leaf texture, density, fall dor mancy, spring greenup, es tablishment rate, mowing quality, and seedhead ratings (Morris, 2000; Mo rris, 2006; Morris and Shearman, 1995). Patton et al. (2007) thoroughly quantified the variability of 35 Zoysia genotypes for establishment by evaluating growth rate and dry matter partitioning between stems and leaves. Establishment rates differed for genotypes between and within Z. japonica and Z. matrella and increased for those that produced more stems than leaves. Knowledge of the genetic a nd environmental effects on pheno typic expression is useful regarding the implementation of appropriate breeding methods to improve a species (Hallauer and Miranda, 1981). Broad-sense heritability (H2) is the proportion of genetic variance contributing to total observed phenotypic variation and can be calculated with variance components derived from appropriately designed experiments. Heritability estimates for characteristics only apply to an entire sp ecies if a truly random set of genotypes and environments are tested, otherwise inferences sh ould only be made for the specific individuals and conditions that were evaluate d. Variance and heri tability estimates are valuable in a plant 99

PAGE 100

breeding program for predicting th e selection responses of traits (Dudley and Moll, 1969). Despite the extensive reports on differences am ong zoysiagrass, little research has been completed to describe the potential for improving desirable characteristics within the genus. The objectives of the following study were to es timate variance components and broad-sense heritability of turfgrass perfor mance traits in zoysiagrass. Materials and Methods A collection of zoysiagrass germplasm was separated into three groups based on leaf morphology. Ninety very fine (leaf blade width < 1 mm), 108 fine (1 mm < leaf blade width < 2 mm), and 126 coarse (leaf blade width > 2 mm ) genotypes were evaluated independently because of differences in their optimum mowi ng heights and potential uses. Individual experiments were each arranged in a randomized co mplete block design with three replications to determine the range of variation and broad-sense heritabili ty for characteristics of each respective class. Plots of the fine and coarse zoysiagrasses were plan ted from single, 10 cm plugs on 1.5 m centers in the late summer of 2005 and were maintained separately with a 0.3 m alleyway. Twelve 2.5 cm plugs were planted eq uidistantly apart to establish individual 0.8 m2 plots of each very fine zoysiagrass without alleyw ays in the early fall of 2005. All research was conducted with supplemental irriga tion to prevent drought stress at the University of Florida G.C. Horn Turfgrass Research Facility in Citr a, FL on a Candler sand (hyperthermic, uncoated Lamellic Quartzipsamments). Preemergence herbicide applicatio ns of pendimethalin at 1.8 kg ha-1 were made to all three experiments in November and March of each year to reduce cool and warm-season weed pressure. Fungicides and insecticides were not used in order to rate genotypes for genetic resistance or tolerance to biot ic stresses. The very fine Zoysia experiment was fertilized at 195 kg N ha-1 during the growing season between March and October, split into 16 equal applications 100

PAGE 101

of a greens-grade granular fertilizer (13N-4P-13K), and at 49 kg N ha-1 split into eight equal applications of Uflexx (J. R. Simplot Company, Boise, ID) fertilizer (46N-0P-0K) over the winter months between November and February These plots were topdressed with sand in March and July of each year and were mowed at 4.2 mm three times weekly with a triplex greens mower. Management of the fine and coarse zoysiagrass genotypes was minimal to allow for selection of superior individuals under low i nput conditions. Annual N fertility was 73 kg ha-1 split into three equal applications in March, July and October from a complete fertilizer (15N5P-15K). Fine zoysiagrasses were mowed twice weekly at 1.3 cm with a fairway reel mower and the coarse genotypes were mowed weekly at 6.4 cm with a rotary deck mower. Percent plot coverage, turf density, overal l turf quality, genetic color, fall dormancy, spring greenup, turf quality after glufosinate herbic ide application, turf quality as affected by Bipolaris incidence, turf quality as affected by mole cricket ( Scapteriscus spp.) damage, and seedhead density were visually rated at vari ous times during 2006, 2007, and 2008 (Table 6-1). Percent plot coverage was estimated on the fine and coarse zoysiagrass ex periments using a 5 5 grid. Each of the 25 grid sections represented 4% of the total plot and was given a score of 1 to 4 based on coverage. This data was summed to provide % plot coverage. The rating scale for density was 1 = least and 9 = most. Turf quality wa s rated on a scale of 1 to 9 with 1 = poor, 5 = acceptable, and 9 = excellent. For genetic color 1 = yellow, 5 = acceptable, and 9 = dark green. The scale for fall dormancy and spring greenup was 1 = straw, 5 = moderate necrosis, and 9 = no necrosis. Glufosinate was applied at 0.8 kg ha-1 to the fine and coarse zoysiagrass genotypes in a 10 cm band using a pressurized line painter. Turf quality within the 10 cm band was rated using the above scale two weeks after application. Severity of Bipolaris incidence and mole cricket damage were rated with respect to infl uence on turf quality with 1 representing nine diseased 101

PAGE 102

leaf spots or tunnels, 5 represen ting five diseased leaf spots or tunnels, and 9 = no damage. The rating scale for seedhead density was 1 = many and 5 = none or very few. Turfgrass performance traits evaluated once, or on multiple dates, were analyzed as a randomized complete block (Table 6-2) or split-pl ot in time (Table 6-3), respectively, using the SAS PROC MIXED procedure (SAS 2008) with all sources of va riation considered as random effects. Variance component estimates were dete rmined and their standard errors (SE) were calculated with the followi ng formula (Hallauer, 1970): 2 2 )(2 2 2 i i idf M c SE (6-1) where c equals the coefficient of the mean square, and Mi and dfi are the appropriate mean squares and degrees of freedom, respectively, used in the calculation of the variance components, 2 i. (Table 6-2, Table 6-3). Broad-sense heritabilities were calculated using variance component estimates with the following formulas where genotypic variability was significant, i.e., at least twice the magnitude of its SE: R He g g p g 2 2 2 2 2 2 (6-2) or RDRD He gr dg g g p g 2 22 2 2 2 2 2 (6-3) where 2 g equals the variance of genotypes and 2 p was the phenotypic variance based on the experimental designs for traits evaluated on one date (Equation 6-2) and on multiple dates 102

PAGE 103

(Equation 6-3). Standard errors of heritability estimates were calculated with the following formulas: R SE HSEe g g 2 2 2 2)( )( (6-4) or RDRD SE HSEe gr dg g g 2 22 2 2 2)( )( (6-5) using Equation 6-4 for characteristics evaluated on one date and Equation 6-5 for those evaluated on multiple dates. Results and Discussion Genotypes, dates, and date genotype in teractions were sign ificantly different ( P 0.01) according to the analyses of variance in the very fine, fine, and coarse zoysiagrass experiments for most studied traits (data not show n). Differences were not observed ( P 0.05) for the effects of glufosinate and Bipolaris on turf quality among coarse geno types. Variation did not exist ( P 0.05) for turf quality affected by mole cricket damage in the very fine and fine germplasm sets. This may indicate a lack of genetic variation or large environmental influence for the stress related turf qualities. Generally, the best and worst performing ge notypes were consisten tly ranked across dates for most of the characteristics that were evalua ted more than once. Although significant date genotype interactions were observe d, most were either biologi cally unimportant or unavoidable because of the large number ( 90) of unique treatments (genotype s) that were tested in each of the three experiments. Estimating variance co mponents that are evalua ted over several dates likely gives more appropriate broad-sense heritability estimates for perennial species because 103

PAGE 104

consideration is given to envi ronmental influences (Fehr, 1987). Therefore, the combined analysis over dates was used to examin e long-term responses where possible. Mean, minimum, and maximum responses for % plot coverage, turf density, turf quality (Table 6-4), genetic color, fall dormancy, sp ring greenup (Table 6-5), and seedhead density (Table 6-6) suggest that the assembled z oysiagrass germplasm is highly variable and representative of Zoysia spp. The difference between mini mum and maximum values for % plot coverage in both the fine and co arse zoysiagrass experiments wa s 48%. There were very fine and coarse genotypes that averaged the minimum (1) and maximum (5) values for seedhead density, but interestingly no seedheads were pres ent on the fine genotypes in late January of 2007 even though mowing had been stopped. The observed spread between minimum and maximum ratings for the remaining characterist ics above ranged from 3.8 (spring greenup coarse) to 6.3 (turf density coarse) on a one to nine scale over all three experiments. Germplasm set variances for genetic color, fall dormancy, and spring greenup were generally greater for the very fine, than fine or coarse Zoysia genotypes. Most trait means were near or greater than the minimum acceptable rating, indi cating the suitability of some genotypes for these characteristics during multiple dates. Variance component estimates indicate the extent of which expressed phenotype is influenced by genotypic and environmental effects. Broad-sense heritability estimates can be used in clonally propagated crops to give insi ght into the likelihood that an individual will express a selected trait if grown in a different environment. The contribution of genetic effects to % plot coverage, turf density and turf quality were generally several to many times greater than that of the environment (date genotype) and resulted in high br oad-sense heritability estimates for these three characteristics (0.70 H2 0.83). Much of the observed variability for 104

PAGE 105

% plot coverage was attributed to dates becau se of differences in establishment between evaluation dates as the grasses approached full cover (Table 6-4). Br oad-sense heritabilities described herein for turf density and quality of Zoysia spp. were lower than those found in tetraploid common bermudagra ss (Cynodon dactylon [L.] Pers.) (Wofford and Baltensperger, 1985), similar to estimates in diploid African bermudagrass ( Cynodon transvaalensis BurttDavy) (Kenworthy et al., 2006), and higher than those reported for common carpetgrass ( Axonopus fissifolius Raddi) (Greene et al., 2008). Broad-sense heritability and variance compone nt estimates for genetic color were similar to those of turf density and quality, but larger environmental and error effects resulted in heritability estimates ranging from low (0.32) to moderate (0.58) for fall dormancy and spring greenup (Table 6-5). Kenworthy et al. (2006) were able to slightly improve color heritability using a handheld NDVI sensor versus visual ratings. It ma y be possible to better estimate genetic color, fall dormancy, and spring greenup with digital image an alysis (Karcher and Richardson, 2003; Richardson et al ., 2001) and thereby increase rea lized heritability by reducing error variation. Environmental effects were not accounted for in the calculation of broad-sense heritability for either fall dormancy in the very fine experiment (Table 6-5) or seedhead density (Table 6-6), possibly resulting in inflated es timates. Heritabilities derived from multiple observations over environments offer more conser vative expectations of long-term response. Effects of glufosinate, Bipolaris incidence, and mole cricket damage on the turf quality of a large number of zoysiagrasses have not been previously described. High environmental and error variances coupled with re latively low genetic variance co mponents decreased heritabilities of turf quality affected by glufosinate (0.33) and Bipolaris (0.40) among fine germplasm, and for mole cricket damage (0.38) in the coarse genotypes. Acceptable responses were observed for 105

PAGE 106

these traits, indicating that some levels of tolera nce may exist. However, further examination of these traits is warranted prior to selection as th ey may be largely influenc ed by the environment. Utilizing artificial inoculation rather than rely ing on natural pest infestations could result in better information for making selections (Table 6-6) Artificial inoculati on was successful in the screening of creep ing bentgrass ( Agrostis stolonifera L.) and perennial ryegrass (Lolium perenne L.) for dollar spot ( Sclerotinia homoeocarpa F.T. Bennet.) and gray leaf spot ( Pyricularia oryzae Cavara) resistance, respectively (Bon os et al., 2003; Han et al., 2006). Conclusions Wide ranges between minimum and maximum values of most turfgrass performance characteristics were observed even though enviro nmental and error variances were relatively low, indicating that these traits are quantitative in nature. Significant genotypic variances were detected for most traits, but th ese experiments gave no insight in to the proportion of additive or dominance effects on the total genetic variability. Broad-sense heritabili ties were high for % plot coverage, turf density, turf quality, genetic color, and seedhead density, which suggest that the expression of these characteristics should be repeatable in clonally propagated genotypes selected for further evaluation at other locations. Environmenta l and error vari ation decreased the heritability estimates of stress related turfgr ass qualities, but this information should not be completely overlooked in the proces s of plant selection. Research concerning agronomic traits in several crops indicates that he ritability and breeding progress may be higher in optimal rather than stress environments (Banzi ger and Cooper, 2001; Daday et al., 1973; Rose et al., 2007), but Betran et al. (2003) theorized th at selection in optimal environm ents would not be effective in identifying superior genotypes for stress enviro nments. Work should therefore continue to evaluate zoysiagrass germplasm for response to biotic and abiotic stre sses, although artificial inoculation and some management may be needed to control error variation in order to improve 106

PAGE 107

107 gains from selection. Also, appropriate expe riments should be completed to determine the additive and dominance effects of the most important turfgrass characteristics in Zoysia spp. so that the potential benefits of recurrent selection can be further examined.

PAGE 108

Table 6-1. Evaluation dates for turf grass performance characteristics of zoysiagrass genotypes with very fine fine, or coarse leaf texture visually rated during 2006, 2007, and 2008. Dates of evaluation Characteristic Very Fine Fine Coarse % plot coverage Not measured 26 Jan. 2006; 2 Jun. 2006 26 Jan. 2006; 2 Jun. 2006 Turf density 28 Mar. 2007; 15 May 2007; 24 Jul. 2007; 10 Dec. 2007 28 Mar. 2007; 15 May 2007; 24 Jul. 2007; 10 Dec. 2007 28 Mar. 2007; 15 May 2007; 24 Jul. 2007; 10 Dec. 2007 Turf quality 28 Mar. 2007; 15 May 2007; 24 Jul. 2007; 1 Apr. 2008 22 Aug. 2006; 28 Mar. 2007; 24 Jul. 2007; 1 Apr. 2008 22 Aug. 2006; 28 Mar. 2007; 24 Jul. 2007; 1 Apr. 2008 Genetic color 11 Sep. 2006; 27 Mar. 2007; 15 May 2007; 24 Jul. 2007 11 Sep. 2006; 27 Mar. 2007; 15 May 2007; 24 Jul. 2007 11 Sep. 2006; 27 Mar. 2007; 15 May 2007; 24 Jul. 2007 Fall dormancy 10 Dec. 2007 4 Dec. 2006; 10 Dec. 2007 4 Dec. 2006; 10 Dec. 2007 Spring greenup 26 Jan. 2007; 27 Mar. 2007 16 Mar. 2006; 27 Mar. 2007 16 Mar. 2006; 27 Mar. 2007 Turf quality (glufosinate) Not tested 8 Nov. 2006; 19 Jul. 2007; 5 Oct. 2007 8 Nov. 2006; 19 Jul. 2007; 5 Oct. 2007 Turf quality ( Bipolaris spp.) No damage 31 Aug. 2006; 9 Jul. 2007 31 Aug. 2006; 9 Jul. 2007 Turf quality ( Scapteriscus spp.) 31 Aug. 2006; 5 Dec. 2006 31 Aug. 2006; 5 Dec. 2006 31 Aug. 2006; 5 Dec. 2006 Seedhead density 24 Jan. 2007 Not rated 24 Jan. 2007 108

PAGE 109

Table 6-2. Expected mean squares fo r turfgrass performance traits of zoysiagrass genotypes evaluated on one date. Source of variation df Mean squares Expected mean squares Replication (R) r 1 M1 2 e + G 2 r Genotype (G) g 1 M2 2 e + R 2 g Error (g 1)(r 1) M3 2 e Table 6-3. Expected mean squares fo r turfgrass performance traits of zoysiagrass genotypes evaluated on multiple dates. Source of variation df Mean squares Expected mean squares Replication (R) r 1 M1 2 e + D 2 gr + GD 2 r Genotype (G) g 1 M2 2 e + R 2 dg + D 2 gr + RD 2 g G R (g 1)(r 1) M3 2 e + D 2 gr Date (D) d 1 M4 2 e + R 2 dg + RG 2 d D G (d 1)(g 1) M5 2 e + R 2 dg Error g(d 1)(r 1) M6 2 e 109

PAGE 110

Table 6-4. Variance component estimates, descrip tive statistics, and broad-sense heritabilities (H2) for turfgrass performance characteristics of zoysia grass genotypes with very fine, fine or coarse leaf texture evaluated during 2006, 2007, and 2008. Variance estimates % plot coverage Turf density Turf quality Source Fine Coarse Very Fine Fine Coarse Very Fine Fine Coarse Replication (R) 35.4 35.8 10.6 10.9 0.09 0.10 0.21 0.22 0.00 0.00 0.05 0.06 0.18 0.19 0.00 0.01 Genotype (G) 58.8 10.4 66.9 12.1 1.39 0.25 0.90 0.17 1.04 0.19 0.95 0.19 0.65 0.13 0.97 0.16 G R 29.2 4.3 31.7 4.3 0.24 0.05 0.53 0.09 0.77 0.10 0.18 0.05 0.36 0.07 0.45 0.07 Date (D) 631.2 892.8 658.2 931.2 0.17 0.15 0.11 0.09 0.13 0.11 0.86 0.71 0.50 0.41 0.44 0.36 D G 4.6 2.0 23.4 4.2 0.50 0.07 0.10 0.06 0.28 0.06 0.66 0.09 0.19 0.06 0.24 0.05 Error 26.0 2.5 28.0 2.5 0.92 0.06 1.54 0.08 1.29 0.07 1.07 0.06 1.36 0.08 1.24 0.06 Mean 52.8% 39.9% 5.5 4.2 5.0 4.7 4.3 4.8 Min. 21.2% 17.2% 2.1 1.6 1.5 1.8 1.5 1.5 Max 69.3% 65.7% 8.2 6.6 7.8 6.9 6.3 6.8 Variance 457.9 486.0 3.2 3.3 3.5 3.5 3.0 3.2 H2 0.78 0.14 0.71 0.13 0.83 0.15 0.73 0.14 0.70 0.13 0.75 0.15 0.70 0.14 0.76 0.13 Estimates derived from two evaluation dates. Variance components and heritabilities standard errors. Estimates derived from four evaluation dates. 110

PAGE 111

Table 6-5. Variance component estimates, descrip tive statistics, and broad-sense heritabilities (H2) for turfgrass color characteristics of zoysiagra ss genotypes with very fine, fine, or coarse leaf texture evaluated during 2006 and 2007. Variance estimates Genetic color Fall dormancy Spring greenup Source Very Fine Fine Coarse Very Fine Fine Coarse Very Fine Fine Coarse Replication (R) 0.00 0.00 0.24 0.25 0.06 0.06 0.18 0.20 0.30 0.31 0.01 0.01 0.06 0.06 0.04 0.05 0.04 0.04 Genotype (G) 1.30 0.24 0.52 0.12 0.68 0.12 1.66 0.34 0.47 0.12 0.45 0.12 0.28 0.14 0.36 0.10 0.20 0.09 G R 0.17 0.05 0.42 0.06 0.33 0.06 1.75 0.18 0.28 0.09 0.04 0.06 0.38 0.09 0.06 0.08 0.00 0.05 Date (D) 0.30 0.26 0.52 0.43 0.12 0.10 0.55 0.78 1.44 2.05 0.06 0.10 0.10 0.14 0.00 0.00 D G 0.45 0.07 0.40 0.06 0.39 0.06 0.14 0.08 0.52 0.11 0.51 0.12 0.16 0.08 0.49 0.11 Error 1.08 0.06 0.94 0.05 1.10 0.06 1.06 0.10 0.92 0.08 0.82 0.09 1.16 0.11 0.97 0.08 Mean 5.7 5.4 5.4 5.6 5.3 5.0 6.2 6.1 5.8 Min. 2.4 2.8 2.2 2.7 3.2 2.5 3.3 3.5 3.7 Max 8.3 7.2 7.5 8.7 7.3 7.3 8.8 8.3 7.5 Variance 3.2 2.8 2.6 3.5 2.4 2.7 2.0 1.8 1.6 H2 0.83 0.15 0.62 0.14 0.69 0.13 0.74 0.15 0.58 0.15 0.51 0.14 0.35 0.17 0.55 0.15 0.32 0.15 Estimates derived from four evaluation dates. Variance components and heritabilities standard errors. Estimates derived from one evaluation date. Estimates derived from two evaluation dates. 111

PAGE 112

Table 6-6. Variance component estimates, descrip tive statistics, and broad-sense heritabilities (H2) for turfgrass performance characteristics of zoysiagra ss genotypes with very fine, fine, or coarse leaf texture evaluated during 2006 and 2007. Variance estimates Turf quality (glufosinate) Turf quality ( Bipolaris spp.) Turf quality ( Scapteriscus spp.) Seedhead density# Source Fine Coarse Fine Coarse Very Fine Fine Coarse Very Fine Coarse Replication (R) 0.09 0.09 0.02 0.02 2.53 2.55 0.08 0.08 0.03 0.04 0.13 0.16 0.04 0.04 0.04 0.04 0.00 0.00 Genotype (G) 0.09 0.04 0.08 0.05 0.92 0.38 0.10 0.08 0.00 0.04 0.28 0.21 0.22 0.09 1.56 0.25 1.26 0.18 G R 0.04 0.04 0.23 0.07 0.00 0.36 0.03 0.10 0.12 0.07 1.76 0.30 0.00 0.10 0.31 0.03 0.41 0.04 Date (D) 0.90 0.90 0.20 0.21 0.33 0.50 0.14 0.20 0.06 0.09 0.48 0.68 0.07 0.11 D G 0.25 0.05 0.13 0.06 0.98 0.42 0.18 0.10 0.00 0.05 0.06 0.14 0.15 0.10 Error 0.83 0.06 1.47 0.09 5.35 0.51 1.55 0.14 0.85 0.09 2.35 0.22 1.63 0.14 Mean 3.4 4.7 7.0 8.7 8.8 7.6 8.5 3.0 3.0 Min. 2.6 3.0 3.5 5.3 7.2 3.3 5.7 1.0 1.0 Max 5.3 6.1 9.0 9.0 9.0 9.0 9.0 5.0 5.0 Variance 1.9 2.0 9.0 2.0 1.0 4.8 2.0 1.9 1.7 H2 0.33 0.16 NA 0.40 0.16 NA NA NA 0.38 0.16 0.94 0.15 0.90 0.13 Estimates derived from three evaluation dates. Variance components and heritabilities standard errors. Broad-sense heritability not calculated due to lack of genetic variation. Estimates derived from two evaluation dates. #Estimates derived from one evaluation date. 112

PAGE 113

REFERENCES Anderson, S.J. 2000. Taxonomy of Zoysia (Poaceae): morphological an d molecular variation, Ph.D. dissertation. Texas A&M Univ., College Station, TX. Anonymous. 1993. USGA recommendation for a method of putting green construction: The 1993 revision. USGA Green Section Record 31:1-3. Arumuganathan, K., and E.D. Earle. 1991a. Estimation of nuclear DNA content of plants by flow cytometry. Plant Mol. Biol. Rep. 9:229-233. Arumuganathan, K., and E.D. Earle. 1991b. Nu clear DNA content of some important plant species. Plant Mol. Biol. Rep. 9:208-218. Arumuganathan, K., S.P. Tallury, M.L. Fraser A.H. Bruneau, and R. Qu. 1999. Nuclear DNA content of thirteen turfgrass species by flow cytometry. Crop Sci. 39:1518-1521. Banziger, M., and M. Cooper. 2001. Breeding fo r low input conditions and consequences for participatory plant breeding: examples from tropical maize and wheat. Euphytica 122:503-519. Barcaccia, G., A. Mazzucato, A. Belardinelli, M. Pezzotti, S. Lucretti, and M. Falcinelli. 1997. Inheritance of parental genomes in progenies of Poa pratensis L. from sexual and apomictic genotypes as assessed by RAPD mark ers and flow cytometry. Theor. Appl. Genet. 95:516-524. Barker, R.E., J.A. Kilgore, R.L. Cook, A.E. Garay, and S.E. Warnke. 2001. Use of flow cytometry to determine ploidy level of ryegrass. Seed Sci. Technol. 29:493-502. Beard, J.B., and S.I. Sifers. 1997. Genetic di versity in dehydration avoidance and drought resistance within the Cynodon and Zoysia species. Int. Turfgrass Soc. Res. J. 8:603-610. Bekal, S., and J.O. Becker. 2000. Host range of a California sting nematode population. HortScience 35:1276-1278. Bennett, M.D., and I.J. Leitch. 1995. Nuclear DNA amounts in angiosperms. Ann. Bot. 76:113176. Betran, F.J., D. Beck, M. Banziger, and G.O. Ed meades. 2003. Genetic analysis of inbred and hybrid grain yield under stress and nonstress environments in tropical maize. Crop Sci. 43:807-817. Bonos, S.A., M.D. Casler, and W.A. Meyer. 2003 Inheritance of dollar spot resistance in creeping bentgrass. Crop Sci. 43:2189-2196. Bonos, S.A., K.A. Plumley, and W.A. Meyer. 2002. Ploidy determination in Agrostis using flow cytometry and morphological traits. Crop Sci. 42:192-196. 113

PAGE 114

Bowman, D.C., C.T. Cherney, and T.W. Rufty, Jr. 2002. Fate and transport of nitrogen applied to six warm-season turfgrasses. Crop Sci. 42:833-841. Braman, S.K., R.R. Duncan, and M.C. Engelke. 2000. Evaluation of turfgrass selections for resistance to fall armyworms (Lepidopter a: Noctuidae). HortScience 35:1268-1270. Brede, A.D., and S. Sun. 1995. Diversity of turfgrass germplasm in the Asian Pacific rim countries and potential for reducing gene tic vulnerability. Crop Sci. 35:317-321. Bunnell, B.T., L.B. McCarty, and W.C. Bridge s, Jr. 2005. Evaluation of three bermudagrass cultivars and Meyer Japanese z oysiagrass grown in shade. In t. Turfgrass Soc. Res. J. 10:826-833. Burton, G.W. 1972. Registration of 'Coast cross-1' bermudagrass. Crop Sci. 12:125. Burton, G.W. 1974. Breeding bermudagrass for turf, p. 18-22, In E. C. Roberts, ed. Proc. 2nd Int. Turfgrass Res. Conf. Int. Turfgrass Soc., Blacksburg, VA. Burton, G.W., C.W. McBeth, and J.L. Stephens. 1946. The growth of Kobe Lespedeza as influenced by the root-knot nematode resistan ce of the bermuda grass strain with which it is associated. J. Am. Soc. Agron 38:651-656. Busey, P. 1977. Turfgrasses for the 1980's. Proc. Fla. State Hortic. Soc. 90:111-114. Busey, P. 2003. Cultural management of weeds in turfgrass: a review. Crop Sci. 43:1899-1911. Busey, P., and B.J. Myers. 1979. Growth rates of turfgrasses propagated vegetatively. Agron. J. 71:817-821. Busey, P., J.A. Reinert, and R.A. Atilano. 1982. Genetic and environmental determinations of zoysiagrass adaptation in a subtropical regi on. J. Am. Soc. Hortic. Sci. 107:79-82. Busey, P., R.M. Giblin-Davis, and B.J. Center. 1993. Resistance in Stenotaphrum to the sting nematode. Crop Sci. 33:1066-1070. Busey, P., R.M. Giblin-Davis, C.W. Riger, and E.I. Zaenker. 1991. Susceptibility of diploid St. Augustinegrasses to Belonolaimus longicaudatus J. Nematol. 23:604-610. Bush, E.W., A.D. Owings, D.P. Shepard, and J.N. McCrimmon. 2000. Mowing height and nitrogen rate affect turf quality and vegetative growth of common carpetgrass. HortScience 35:760-762. Cai, H., M. Inoue, N. Yuyama, and S. Nakayama. 2004. An AFLP-based linkage map of zoysiagrass (Zoysia japonica ). Plant Breed. 123:543-548. Cai, H.W., M. Inoue, N. Yuyama, W. Takahashi, M. Hirata, and T. Sasaki. 2005. Isolation, characterization and mapping of simple sequence repeat markers in zoysiagrass (Zoysia spp.). Theor. Appl. Genet. 112:158-166. 114

PAGE 115

Carroll, M.J., P.H. Dernoeden, and J.M. Krouse. 1996. Zoysiagrass establishment from sprigs following application of herbicides, nitrogen and a biostimulator. HortScience 31:972975. Chalmers, D.R., K. Steinke, R. White, J. Thom as, and G. Fipps. 2008. Evaluation of sixty-day drought survival in San Antonio of establishe d turfgrass species a nd cultivars [Online] http://itc.tamu.edu/60day.php (verified 1 Oct. 2008). Chen, C.C., and C.C. Hsu. 1962. Cytological studies on Taiwan grasses. 2. Chromosome numbers of some miscellaneous tr ibes. J. Jap. Bot. 37:300-313. Childers, N.F., and D.G. White. 1947. Manila grass fo r lawns. Puerto Rico Agric. Exp. Stn. Circ. No. 26:1-16. Choi, J., B. Ahn, and G. Yang. 1997. Classification of zoysiagrasses (Zoysia spp.) native to the southwest coastal regions of Korea using RAPD s. J. Korean Soc. Hortic. Sci. 38:789-795. Christie, J.R., J.M. Good, Jr., and G.C. Nutter. 1 954. Nematodes associated with injury to turf. Proc. Soil Sci. Soc. Fla. 14:167-169. Christopher, J., and A. Abraham. 1974. Studies on the cytology and phylogeny of South Indian grasses. II. Sub-family Eragrostoideae Cytologia 39:561-571. Cockerham, S.T., V.A. Gibeault, S.B. Ries, a nd R.A. Khan. 1997. Verticutting frequency and mowing height for management of 'Deanza' and 'Victoria' Zoysia Int. Turfgrass Soc. Res. J. 8:419-425. Colbaugh, P.F., S.P. Metz, and M.C. Engelke. 1994. Pythium blight on inoculated zoysiagrasses. TX Turfgrass Res. 1993, Consolidated Prog. Rep. PR-5131:86-87. Costich, D.E., T.R. Meagher, and E.J. Yurkow 1991. A rapid means of sex identification in Silene latifolia by use of flow cytometry. Plant Mol. Biol. Rep. 9:359-370. Crow, W.T. 2005a. Alternatives to fenamiphos fo r management of plant-parasitic nematodes on bermudagrass. J. Nematol. 37:477-482. Crow, W.T. 2005b. How bad are nematode problems on Florida's golf courses. Fla. Turf Digest 22(1):10-12. Crow, W.T. 2005c. Plant-parasiti c nematodes on golf course turf. Outlooks on Pest Manage. 16:10-15. Crow, W.T., and J.K. Welch. 2004. Root reductions of St. Augustinegrass ( Stenotaphrum secundatum ) and hybrid bermudagrass ( Cynodon dactylon C. transvaalensis ) induced by Trichodorus obtusus and Paratrichodorus minor Nematropica 34:31-37. 115

PAGE 116

Crow, W.T., R.M. Giblin-Davis, and D.W. Lickfe ldt. 2003. Slit injection of 1,3-dichloropropene for management of Belonolaimus longicaudatus on established bermudagrass. J. Nematol. 35:302-305. Crow, W.T., D.L. Porazinska, R.M. Giblin-D avis, and P.S. Grewal. 2006. Entomopathogenic nematodes are not an alternative to fena miphos for management of plant-parasitic nematodes on golf courses in Florida. J. Nematol. 38:52-58. Daday, H., F.E. Binet, A. Grassia, and J.W. P eak. 1973. The effect of environment on heritability and predicted selection response in Medicago sativa Heredity 31:293-308. Diesburg, K.L. 2000. Expanded germplasm collec tions set stage for increased zoysiagrass breeding for turf use. Diversity 16:49-50. Dolezel, J., P. Binarova, and S. Lucretti. 1989. Analysis of nuclear DNA content in plant cells by flow cytometry. Biol. Plant. 31:113-120. Dolezel, P., J. Greilhuber, S. Lucretti, A. Meiste r, M.A. Lysak, L. Nardi, and R. Obermayer. 1998. Plant genome size estimation by flow cy tometry: inter-laboratory comparison. Ann. Bot. 82:17-26. Dudley, J.W., and R.H. Moll. 1969. Interpretation and use of estimates of heritability and genetic variances in plant breeding. Crop Sci. 9:257-262. Dunn, J.H., K.M. Sheffer, and P.M. Halisky. 1981. Thatch and quality of 'Meyer' Zoysia in relation to management. Agron. J. 73:949-952. Dunn, J.H., D.D. Minner, B.F. Fresenburg, a nd S.S. Bughrara. 1993. Fall fertilization of zoysiagrass. Int. Turfgrass Soc. Res. J. 7:565-571. Dunn, J.H., D.D. Minner, B.F. Fresenburg, S.S. Bughrara, and C.H. Hohnstrater. 1995. Influence of core aerification, topdre ssing, and nitrogen on mats, r oots, and quality of 'Meyer' zoysiagrass. Agron. J. 87:891-894. Eaton, T.D., J. Curley, R.C. Williamson, and G. Jung. 2004. Determination of the level of variation in polyploidy among Kent ucky bluegrass cultivars by means of flow cytometry. Crop Sci. 44:2168-2174. Engelke, M.C. 2000. Widely used for centuries, z oysiagrass is a time-teste d reservoir of genetic diversity. Diversity 16:48-49. Engelke, M.C., and S. Anderson. 2003. Turfgrass biology, genetics a nd breeding, p. 271-285, In M. D. Casler and R. R. Duncan, eds. Turfgrass biology, genetics and breeding. Engelke, M.C., S.J. Morton, and R.H. White. 1992. Nitrogen enrichment and mowing height effects on zoysiagrass performance. Texas Agric. Exp. Stn. Prog. Rep. 5003:67-72. 116

PAGE 117

Engelke, M.C., R.H. White, P.F. Colbaugh, J.A. Reinert, K. Marcum, B.A. Ruemmele, and S.J. Anderson. 2002a. Registration of 'Palisades zoysiagrass. Crop Sci. 42:305-306. Engelke, M.C., J.A. Reinert, P.F. Colbaugh, R.H. White, B.A. Ruemmele, K.B. Marcum, and S.J. Anderson. 2002b. Registration of 'Cav alier' zoysiagrass. Crop Sci. 42:302-303. Engelke, M.C., P.F. Colbaugh, J.A. Reinert, K.B. Marcum, R.H. White, B. Ruemmele, and S.J. Anderson. 2002c. Registration of 'Diamond zoysiagrass. Crop Sci. 42:304-305. Fehr, W.R. 1987. Principles of cultivar deve lopment. Macmillan Publishing Company, New York. Forbes, I., B.P. Robinson, and J.M. Latham. 1955. Emerald Zoysia -an improved hybrid lawn grass for the South. U.S. Golf. Ass. J. 7:23-26. Forbes, I., Jr. 1952. Chromosome numbers and hybrids in Zoysia Agron. J. 44:194-199. Frank, K.W., R.E. Gaussoin, T.P. Riordan, R.C. Shearman, J.D. Fry, E.D. Miltner, and P.G. Johnson. 2004. Nitrogen rate and mowing height effects on turf-type buffalograss. Crop Sci. 44:1615-1621. Fry, J.D., and P.H. Dernoeden. 1987. Growth of zoysiagrass from vegetative plugs in response to fertilizers. J. Am. Soc. Hortic. Sci. 112:286-289. Galbraith, D.W. 1990. Flow cytometric analysis of plant genomes. Methods Cell Biol. 33:549562. Galbraith, D.W., K.R. Harkins, J.M. Maddox, N. M. Ayres, D.P. Sharma, and E. Firoozabady. 1983. Rapid flow cytometric analysis of the cell-cycle in intact plant-tissues. Science 220:1049-1051. Gibeault, V.A., S.T. Cockerham, R. Autio, and S.B. Ries. 1997. The enhancement of Zoysia winter colour. Int. Turfgrass Soc. Res. J. 8:445-453. Giblin-Davis, R.M., P. Busey, and B.J. Center. 1992a. Dynamics of Belonolaimus longicaudatus parasitism on a susceptible St. Augus tinegrass host. J. Nematol. 24:432-437. Giblin-Davis, R.M., J.L. Cisar, F.G. Bilz, and K.E. Williams. 1991. Management practices affecting phytoparasitic nematodes in 'Tif green' bermudagrass. Nematropica 21:59-69. Giblin-Davis, R.M., J.L. Cisar, F.G. Bilz, a nd K.E. Williams. 1992b. Host status of different bermudagrasses ( Cynodon spp.) for the sting nematode, Belonolaimus longicaudatus J. Nematol. 24:749-756. Good, J.M. 1959. Occurrence of plant parasitic ne matodes in Georgia turf nurseries. Plant Dis. Rep. 43:236-238. 117

PAGE 118

Good, J.M., J.R. Christie, and J.C. Nutter. 1956. Identification and distribution of plant parasitic nematodes in Florida and Geor gia. Phytopathology 46:13-13. Good, J.M., N.A. Minton, and C.A. Jaworski. 19 65. Relative susceptibilit y of selected cover crops and 'Coastal' bermuda grass to plant nematodes. Phytopathology 55:1026-1030. Gould, F.W. 1968. Grass systematics. McGraw-Hill Book Company, New York. Gould, F.W., and T.R. Soderstrom. 1974. Chromoso me numbers of some Ceylon grasses. Can. J. Bot. 52:1075-1090. Grau, F.V., and A.M. Radko. 1951. 'Meyer' (Z-52) Zoysia U.S. Golf. Ass. J. 4:30-31. Green, D.E., J.D. Fry, J.C. Pair, and N.A. Tisserat. 1993. Pathogenicity of Rhizoctonia solani AG-2-2 and Ophiosphaerella herpotricha on zoysiagrass. Plant Dis. 77:1040-1044. Green, D.E., II, J.D. Fry, J.C. Pair, and N.A. Tisserat. 1994. Influence of management practices on rhizoctonia large patc h disease in zoysiagra ss. HortScience 29:186-188. Green, R.L., S.I. Sifers, C.E. Atkins, and J.B. Beard. 1991. Evapotranspiration rates of eleven zoysiagrass genotypes. Hortscience 26:264-266. Greene, N.V., K.E. Kenworthy, K.H. Quesenberry, J.B. Unruh, and J.B. Sartain. 2008. Variation and heritability estimates of co mmon carpetgrass. Crop Sci. 48:2017-2025. Greilhuber, J. 1998. Intraspecific variation in ge nome size: a critical re assessment. Ann. Bot. 82:27-35. Grime, J.P., and M.A. Mowforth. 1982. Variation in genome sizean ecol ogical interpretation. Nature, UK 299:151-153. Guertal, E.A., and D.L. Evans. 2006. Nitrogen rate and mowing height effects on TifEagle bermudagrass establishment. Crop Sci. 46:1772-1778. Hale, T. 2006. Zoysiagrass management trial. TPI Turf News Janua ry/February:79-80. Hallauer, A.R. 1970. Genetic variability for yiel d after four cycles of reciprocal recurrent selections in maize. Crop Sci. 10:482-485. Hallauer, A.R., and J.B. Miranda. 1981. Quantitative genetics in maize breeding. Iowa State Univ. Press, Ames, IA. Han, Y., S.A. Bonos, B.B. Clarke, and W.A. Meyer. 2006. Inheritance of resi stance to gray leaf spot disease in perennial ry egrass. Crop Sci. 46:1143-1148. Hanna, W.W., and J.E. Elsner. 1999. Registration of 'TifEagle' bermudagra ss. Crop Sci. 39:1258. Hanna, W.W., and W.F. Anderson. 2008. Developm ent and impact of ve getative propagation in forage and turf bermudagrasses. Agron. J. 100:S-103-S-107. 118

PAGE 119

Hanson, A.A. 1966. 'Meyer' Zoysia (Reg. No. 12). Crop Sci. 6:99. Hawes, D.T. 1979. Zoysia : For the transition zone. USGA Gr een Section Record 17(3):1-4. Haydu, J.J., L.N. Satterthwaite, and J.L. Cisar. 2005. An economic and agronomic profile of Florida's sod industry in 2003 [Online]. Ava ilable by The University of Florida Food & Economics Department, Agricultural Experiment Station, and Cooperative Extension Service IFAS. http://edis.ifas .ufl.edu/pdffiles/FE/FE56100.pdf. Heald, C.M., and G.W. Burton. 1968. Effect of organic and inorgani c nitrogen on nematode populations on turf. Plant Dis. Rep. 51:46-48. Heald, C.M., and H.D. Wells. 1967. Control of endoand ecto-parasitic nematodes in turf by hot water treatments. Plant Dis. Rep. 51:905-907. Henry, J.M., V.A. Gibeault, M.K. Leonard, and S.T. Cockerham. 1989. Response of zoysiagrass to nitrogen fertilization for winter color and ge neral performance. Int. Turfgrass Soc. Res. J. 6:213-215. Hixson, A.C., W.T. Crow, R. McSorley, and L.E. Trenholm. 2004. Host status of 'Sealsle 1' seashore paspalum ( Paspalum vaginatum ) to Belonolaimus longicaudatus and Hoplolaimus galeatus. J. Nematol. 36:493-498. Holdeman, Q.L., and T.W. Graham. 1953. The eff ect of different plant species on the population trends of the sting nematode. Plant Dis. Rep. 37:497-500. Hollingsworth, B.S., E.A. Guertal, and R.H. Walker. 2005. Cultural management and nitrogen source effects on ultradwarf bermudag rass cultivars. Crop Sci. 45:486-493. Hong, K.H., and D.Y. Yeam. 1985. Studies on inters pecific hybridization in Korean lawn grasses ( Zoysia spp.). J. Korean Soc. Hortic. Sci. 26:169-178. Horn, G.C., A.E. Dudeck, and R.W. Toler. 1973. 'Floratam' St. Augustinegrass: A fast growing new variety for ornamental turf resistant to St. Augustine decline and chinch bugs. Fla. Agric. Exp. Stn. Circ. S-224. Huang, X., and J.O. Becker. 1999. Li fe cycle and mating behavior of Belonolaimus longicaudatus in gnotobiotic culture. J. Nematol. 31:70-74. Huff, D.R., and J.M. Bara. 1993. Determining genetic origins of aberrant progeny from facultative apomictic Kentucky bluegrass us ing a combination of flow cytometry and silver-stained RAPD markers. Theor. Appl. Genet. 87:201-208. Huff, D.R., and A.J. Palazzo. 1998. Fine fescue species determination by laser flow cytometry. Crop Sci. 38:445-450. 119

PAGE 120

Hultquist, S.J., K.P. Vogel, D.J. Lee, K. Ar umuganathan, and S. Kaeppler. 1997. DNA content and chloroplast DNA polymorphisms among switchgrasses from remnant midwestern prairies. Crop Sci. 37:595-598. Jarret, R.L., P. Ozias-Akins, S. Phatak, R. Nadimpalli, R. Duncan, and S. Hiliard. 1995. DNA contents in Paspalum spp. determined by flow cytometry. Genet. Resources and Crop Evolution 42:237-242. Jenkins, W.R. 1964. A rapid centrifugal-flotation t echnique for separating nematodes from soil. Plant Dis. Rep. 48:692. Johnson, A.W. 1970a. Pathogenicity and intera ction of three nematode species on six bermudagrasses. J. Nematol. 2:36-41. Johnson, A.W. 1970b. Control of lance nematode, Hoplolaimus galeatus, on 'Tifdwarf' bermudagrass by chemical dips. J. Nematol. 2:179-181. Johnson, B.J., R.N. Carrow, and R.E. Burns. 1987. Bermudagrass turf response to mowing practices and fertilizer Agron. J. 79:677-680. Johnson, P.G., T.P. Riordan, and K. Arumuga nathan. 1998. Ploidy level determinations in buffalograss clones and populat ions. Crop Sci. 38:478-482. Joo, Y.K., J.P. Lee, and N.E. Christia ns. 1999. Mowing effects on the growth of Zoysia japonica Steud 'wild type' under low maintenance. J. of Turfgrass Manage. 3:15-20. Juska, F.V. 1959. Response of 'Meyer' Zoysia to lime and fertilizer treatments. Agron. J. 51:8183. Juska, F.V. 1972. Nematodes, a contributing fact or to zoysiagrass dec line in Maryland. Plant Dis. Rep. 56:568-572. Karcher, D., M. Richardson, J. Landreth, a nd J. McCalla. 2006. Vari ety selection affects bermudagrass and zoysiagrass divot recovery time. Golf Course Managment 74(12):8387. Karcher, D.E., and M.D. Richardson. 2003. Quantifying turfgrass colo r using digital image analysis. Crop Sci. 43:943-951. Kelsheimer, E.G., and A.J. Overman. 1953. Notes on some ectoparasitic nematodes found attacking lawns in the Tampa Bay area. Pr oc. Fla. State Hortic. Soc. 66:301-303. Kenworthy, K.E., and M.C. Engelke. 1999. Aerifi cation and fertilization of zoysiagrass fairways. Agron. Abstr.:126. Kenworthy, K.E., C.M. Taliaferro, B.F. Carver D.L. Martin, J.A. Anderson, and G.E. Bell. 2006. Genetic variation in Cynodon transvaalensis Burtt-Davy. Crop Sci. 46:2376-2381. 120

PAGE 121

Kim, J.H. 1983. A taxonomic study of the genus Zoysia Willd. in Korea. Kor. J. Plant Taxon. 13:41-53. Kim, K.S., J.B. Beard, and S.I. Sifers. 1988. Drought resistance comparisons among major warm-season turfgrasses. USGA Green Section Record 26(5):12-15. Knight, C.A., N.A. Molinari, and D.A. Petrov. 2005. The large genome constraint hypothesis: evolution, ecology and phenotype. Ann. Bot. 95:177-190. Kopec, D.M., J.L. Walworth, J.J. Gilbert, G. M. Sower, and M. Pessarakli. 2007. 'SeaIsle 2000' paspalum putting surface response to mowing he ight and nitrogen fertilizer. Agron. J. 99:133-140. Laat, A.M.M.d., W. Gohde, and M.J.D.C. Vogel zang. 1987. Determination of ploidy of single plants and plant populations by flow cytometry. Plant Breed. 99:303-307. Lautz, W.H. 1959. Increase of Belonolaimus longicaudatus on various plant species in artificially inoculated soil. Plant Dis. Rep. 43:48-50. Leitch, I.J., and M.D. Bennett. 2004. Genome do wnsizing in polyploid plan ts. Biol. J. Linnean Soc. 82:651-663. Loch, D.S., B.K. Simon, and R.E. Poulter. 2005. Taxonomy, distribut ion, and ecology of Zoysia macrantha Desv., an Australian native species with turf breeding potential. Int. Turfgrass Soc. Res. J. 10:593-599. Luc, J.E., W.T. Crow, J.L. Stimac, J.B. Sartai n, and R.M. Giblin-Davis. 2006. Influence of Belonolaimus longicaudatus on nitrate leaching in turf. J. Nematol. 38:461-465. Luc, J.E., W.T. Crow, J.L. Stimac, J.B. Sart ain, and R.M. Giblin-D avis. 2007. Effects of Belonolaimus longicaudatus management and nitrogen fertility on turf quality of golf course fairways. J. Nematol. 39:62-66. Marcum, K.B., S.J. Anderson, and M.C. Engelke. 1998. Salt gland ion secretion: a salinity tolerance mechanism among five zoysia grass species. Crop Sci. 38:806-810. Marcum, K.B., M.C. Engelke, S.J. Morton, an d R.H. White. 1995. Rooti ng characteristics and associated drought resistance on zoys iagrasses. Agron. J. 87:534-538. Mayr, E. 1948. The bearing of the new systematic s on genetical problems. The nature of species. Adv. Genet. 2:205-237. McSorley, R., and J.J. Frederick. 1991. Extraction efficiency of Belonolaimus longicaudatus from sandy soil. J. Nematol. 23:511-518. Metz, S.P., P.F. Colbaugh, and M.C. Engelke. 1994. Rhizoctonia blight susceptibility among commercial and experimental zoysiagrasses. TX Turfgrass Res. 1993, Consolidated Prog. Rep. PR-5129:82-83. 121

PAGE 122

Morris, K.N. 2000. National Zoysiagrass Te st 1996, Final Report 1997, NTEP No. 01 15, National Turfgrass Evaluation Program, USDA-ARS, Beltsville, MD. Morris, K.N. 2006. National Zoysiagrass Te st 2002, Final Report 2003, NTEP No. 07 11, National Turfgrass Evaluation Program, USDA-ARS, Beltsville, MD. Morris, K.N., and R. Shearman. 1995. National Zoysiagrass Test 1991, Final Report 1992 1995, NTEP No. 96, National Turfgrass Eval uation Program, USDA-ARS, Beltsville, MD. Morton, S.J., M.C. Engelke, and R.H. White. 1991. Performance of four warm-season turfgrass genera cultured in dense shade III. Zoysia spp. Texas Agric. Exp. Stn. Prog. Rep. 4894:51-52. Murray, B.G. 2005. When does intraspecific C-value variation become taxonomically significant? Ann. Bot. 95:119-125. Murray, B.G., P.J.d. Lange, and A.R. Fergus on. 2005. Nuclear DNA variation, chromosome numbers and polyploidy in the endemic and i ndigenous grass flora of New Zealand. Ann. Bot. 96:1293-1305. Murray, J.J., and M.C. Engelke. 1983. Explorati on for zoysiagrass in Ea stern Asia. USGA Green Section Record 21:8-12. Ohri, D. 1998. Genome size variation and plant systematics. Ann. Bot. 82:75-83. Patton, A.J., and Z.J. Reicher. 2007. Zoysiagras s species and genotypes di ffer in their winter injury and freeze tolerance. Crop Sci. 47:1619-1627. Patton, A.J., J.J. Volenec, and Z.J. Reicher. 2007. Stolon growth and dry matter partitioning explain differences in zo ysiagrass establishment rates. Crop Sci. 47:1237-1245. Perry, V.G. 1974. The nematode problems of turfgrass and their control, p. 131-134, In C. W. D. Brathwaite, et al., eds. Crop protection in the Caribbean, proceedings of a symposium on the protection of horticultural crops in the Caribbean, University of the West Indies, St. Augustine, Trinidad. Perry, V.G., G.C. Smart, Jr., and G.C. Horn. 1970. Nematode problems of turfgrasses in Florida and their control, p. 489-492 Proceedings of the 83rd Annual Meeting of the Florida State Horticultural Society. Miami Beach, USA. Qian, Y.L., and M.C. Engelke. 1997. Evaluation of zoysiagrass genotypes for shade tolerance. TX Turfgrass Res. 1997, Consolid ated Prog. Rep. TURF 97-24:1-11. Qian, Y.L., M.C. Engelke, and M.J.V. Foster. 2000. Salinity effects on zoysiagrass cultivars and experimental lines. Crop Sci. 40:488-492. 122

PAGE 123

Rasch, E.M. 1985. DNA "standards" and the range of accurate DNA estimates by Feulgen aborption microspectrophotometry, p. 137-166, In R. R. Cowden and F. W. Harrison, eds. Advances in Microscopy. Alan R. Liss Inc., New York. Rayburn, A.L., J.A. Auger, and L.M. McMur phy. 1992. Estimating percentage constitutive Heterochromatin by flow cytometry. Exp. Cell Res. 198:175-178. Reinert, J.A., and M.C. Engelke. 2001. Resistance in zoysiagrass, Zoysia spp., to the tropical sod webworm, Herpetogramma phaeopteralis Guenee. Int. Turfgrass Soc. Res. J. 9:798-801. Reinert, J.A., M.C. Engelke, and S.J. Morton. 1993. Zoysiagrass resistance to the zoysiagrass mite, Eriophyes zoysiae (Acari: Eriophyidae). Int. Turf grass Soc. Res. J. 7:349-352. Reinert, J.A., M.C. Engelke, R.L. Crocker, S. J. Morton, P.S. Graff, and B.R. Wiseman. 1994. Resistance in zoysiagrass ( Zoysia spp.) to the fall armyworm ( Spodoptera frugiperda ). TX Turfgrass Res. 1994, Consolidated Prog. Rep. PR-5248:39-42. Reinert, J.A., M.C. Engelke, J.C. Read, S.T. Ma ranz, and B.R. Wiseman. 1997. Susceptibility of cool and warm season turfgr asses to fall army worm ( Spodoptera frugiperda). Int. Turfgrass Soc. Res. J. 8:1003-1011. Rhoades, H.L. 1962. Effects of sting and stubby-root nematodes on St. Augustine grass. Plant Dis. Rep. 46:424-427. Richardson, M.D., and J.W. Boyd. 2001. Establishing Zoysia japonica from sprigs: effects of topdressing and nitrogen fertil ity. HortScience 36:377-379. Richardson, M.D., D.E. Karcher, and L.C. Purcell. 2001. Quantifying turfgrass cover using digital image analysis. Crop Sci. 41:1884-1888. Riggs, R.D., J.L. Dale, and M.L. Hamblen. 1962. Reaction of bermuda grass varieties and lines to root-knot nematodes. Phytopathology 52:587-588. Robbins, R.T., and K.R. Barker. 1973. Comp arisons of host range and reproduction among populations of Belonolaimus longicaudatus from North Carolina and Georgia. Plant Dis. Rep. 57:750-754. Rogers, R.A., J.H. Dunn, and C.J. Nelson. 1977. Photosynthesis and cold hardening in zoysia and bermudagrass. Crop Sci. 17:727-732. Rose, L.W., IV, M.K. Das, R.G. Fuentes, and C.M. Taliaferro. 2007. Effects of highvs. lowyield environments on selection for increas ed biomass yield in switchgrass. Euphytica 156:407-415. Ruemmele, B.A., and M.C. Engelke. 1990. Zoysiagrass cultivars toda y and tomorrow. Grounds Maintenance 25:92,94,96,124,126. 123

PAGE 124

Samudio, S.H. 1996. Whatever became of the improved seeded Zoysia varieties? Golf Course Management 64(8):57-60. SAS Institute. 2008. The SAS system for Windows: Release 9.1.3. SAS Inst., Cary, NC. Schwartz, B.M., K.E. Kenworthy, and W.T. Crow. 2006. Methods for screening zoysiagrass cultivars for sting nematode response. In ASA-CSSA-SSSA Abstracts 68:23. Amer. Soc. Agron., Madison, WI. Sledge, E.B. 1962. Preliminary report on a Meloidogyne sp. parasite of grass in Florida. Plant Dis. Rep. 46:52-54. Soper, D.Z., J.H. Dunn, D.D. Minner, and D. A. Sleper. 1988. Effects of clipping disposal, nitrogen, and growth retardants on thatch a nd tiller density in z oysiagrass. Crop Sci. 28:325-328. Taliaferro, C.M., A.A. Hopkins, J.C. Henthorn, C.D. Murphy, and R.M. Edwards. 1997. Use of flow cytometry to estimate ploidy level in Cynodon species. Int. Turfgrass Soc. Res. J. 8:385-392. Tarjan, A.C., and P. Busey. 1985. Genotypic variability in bermudagrass damage by ectoparasitic nematodes. HortScience 20:675-676. Tateoka, T. 1955. Karyotaxonomy in Poaceae III. Further studies of somatic chromosomes. Cytologia 20:296-306. Taylor, M.G., and I.K. Vasil. 1987. Analysis of DNA size, content and cell-cycle in leaves of Napier grass ( Pennisetum purpureum Schum). Theor. Appl. Genet. 74:681-686. Tiersch, T.R., R.W. Chandler, S.S. Wachtel, an d S. Elias. 1989. Reference standards for flow cytometry and application in comparative studies of nuclear DNA content. Cytometry 10:706-710. Toler, J.E., J.K. Higingbottom, and L.B. McCarty. 2007. Influence of fertility and mowing height on performance of established centipedegrass. HortScience 42:678-681. Trenholm, L.E., D.W. Lickfeldt, and W.T. Cr ow. 2005. Use of 1,3-dichloropropene to reduce irrigation requirements of sting nematode-infested bermudagrass. HortScience 40:15431548. Tsuruta, S.-I., M. Hashiguchi, M. Ebina, T. Matsuo, T. Yamamoto, M. Kobayashi, M. Takahara, H. Nakagawa, and R. Akashi. 2005. Devel opment and characterization of simple sequence repeat markers in Zoysia japonica Steud. Grassland Sci. 51:249-257. Tucker, B.J., L.B. McCarty, H. Liu, C.E. We lls, and J.R. Rieck. 2006. Mowing height, nitrogen rate, and biostimulant influence root de velopment of field-grown 'TifEagle' bermudagrass. HortScience 41:805-807. 124

PAGE 125

Unruh, J.B., L.E. Trenholm, and K.E. Kenwort hy. 2007. Zoysiagrass for Florida lawns: a passing fancy or here to stay. Fla. Turf Digest 24(2):12-19. USDA-ARS. 2007. Germplasm Resources Inform ation Network: National Plant Germplasm System. Available at http://www.ars-grin. gov/cgi-bin/npgs/html/tax_search.pl (verified 2 October 2008). USDA-ARS, Beltsville, MD. Vaio, M., C. Mazzella, V. Porro, P. Speranza, B. Lopez-Carro, E. Estramil, and G.A. Folle. 2007. Nuclear DNA content in allopolyploid sp ecies and synthetic hybrids in the grass genus Paspalum Plant Systematics and Evolution 265:109-121. Watson, L., and M.J. Dallwitz. 1992. The grass genera of the world. C.A.B. International, Wallingford Oxon, UK. Weng, J.H., M.J. Fan, C.Y. Lin, Y.H. Liu, and S.Y. Huang. 2007. Genetic variation of Zoysia as revealed by random amplified polymorphic DNA (RAPD) and isozyme pattern. Plant Production Sci. 10:80-85. Weston, J.B., and J.H. Dunn. 1985. Thatch and quality of Meyer Zoysia in response to mechanical cultivation and nitr ogen fertilization. Int. Turf grass Soc. Res. J. 5:449-458. White, R.H., and R. Dickens. 1984. Plant-parasitic nematode populations in bermudagrass as influenced by cultural-practices. Agron. J. 76:41-43. White, R.H., and M.C. Engelke. 1990. Shade adaptation of zoysiagrass cultivars and elite DALZ experimental lines. TX Turfgrass Res. 1990, Consolidated Prog. Rep. PR-4744:26-27. White, R.H., M.C. Engelke, S.J. Anderson, B.A. Ruemmele, K.B. Marcum, and G.R. Taylor, II. 2001. Zoysiagrass water relations. Crop Sci. 41:133-138. Wieners, R.R., S.Z. Fei, and R.C. Johns on. 2006. Characterization of a USDA Kentucky bluegrass (Poa pratensis L.) core collection for reproduc tive mode and DNA content by flow cytometry. Genet. Resources and Crop Evolution 53:1531-1541. Winchester, J.A., and E.O. Burt. 1964. The effect and control of sti ng nematodes on 'Ormond' bermuda grass. Plant Dis. Rep. 48:625-628. Wofford, D.S., and A.A. Baltensperger. 1985. Herita bility estimates for turfgrass characteristics in bermudagrass. Crop Sci. 25:133-136. Wu, Y.Q., C.M. Taliaferro, G.H. Bai, D.L. Martin, J.A. Anderson, M.P. Anderson, and R.M. Edwards. 2006. Genetic analyses of Chinese Cynodon accessions by flow cytometry and AFLP markers. Crop Sci. 46:917-926. Yaneshita, M., S. Kaneko, and T. Sa sakuma. 1999. Allotetraploidy of Zoysia species with 2n=40 based on a RFLP genetic map. Theor. Appl. Genet. 98:751-756. 125

PAGE 126

126 Yaneshita, M., R. Nagasawa, M.C. Engelke, and T. Sasakuma. 1997. Genetic variation and interspecific hybridization among natural popula tions of zoysiagrasses detected by RFLP analyses of chloroplast and nuclear DNA. Genes and Genet. Systems 72:173-179. Youngner, V.B. 1961. Accelerated wear tests on turfgrasses. Agron. J. 53:217-218.

PAGE 127

BIOGRAPHICAL SKETCH Brian M. Schwartz earned his B.S. and M.S. degrees from Texas A&M University in Plant and Environmental Soil Science and Plant Breeding, respectively. His interests in plant breeding and genetics have taken him from corn and cotton fields to the tu rf plots. Upon graduation from the University of Florida with a Ph.D., he will take on the turf breeding responsibilities at the University of Georgia, Tifton Campus as an assistant professor. 127