• TABLE OF CONTENTS
HIDE
 Front Cover
 Epidemiology of papaya ringspot...
 Modelling yield losses due to cercospora...
 Epidemiological analysis of resistance...
 Yield loss assesment and economics...
 Evaluation of lowland potato (Solanum...
 Integrated control of club root...
 Abstracts of papers presented during...
 Information for contributors
 Republic of the Philippines Department...
 Back Matter
 Back Cover














Group Title: Journal of Tropical Plant Pathology
Title: Journal of tropical plant pathology
ALL VOLUMES CITATION THUMBNAILS PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00090520/00031
 Material Information
Title: Journal of tropical plant pathology
Series Title: Journal of tropical plant pathology.
Alternate Title: Journal of Philippine phytopathology
Philippine phytopathology
Physical Description: v. : ill. (some col.) ; 26 cm.
Language: English
Creator: Philippine Phytopathological Society
Publisher: Philippine Phytopathological Society
Place of Publication: Philippines
College Laguna
Publication Date: January-June 1989
Frequency: semiannual
regular
 Subjects
Subject: Plant diseases -- Periodicals -- Philippines   ( lcsh )
Plants, Protection of -- Periodicals -- Philippines   ( lcsh )
Genre: periodical   ( marcgt )
 Notes
Dates or Sequential Designation: v. 1, no. 1 (January 1965)-
General Note: Title from cover.
General Note: "Official publication of the Tropical Plant Pathology."
 Record Information
Bibliographic ID: UF00090520
Volume ID: VID00031
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 54382605
issn - 0115-0804

Table of Contents
    Front Cover
        Front Cover 1
        Front Cover 2
    Epidemiology of papaya ringspot in the Philippines
        Page 1
        Page 2
        Page 3
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
    Modelling yield losses due to cercospora leafspots [cercospora arachidicola Hori and cercosporidium personatum Berk. and Curt. (Deighton)] of peanut
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
    Epidemiological analysis of resistance to Philippine corn downy mildew
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
    Yield loss assesment and economics of control of sorghum tar spot
        Page 25
        Page 26
        Page 27
        Page 28
        Page 29
        Page 30
        Page 31
        Page 32
        Page 33
    Evaluation of lowland potato (Solanum spp.) Germplasm against early blight
        Page 34
        Page 35
        Page 36
        Page 37
        Page 38
        Page 39
        Page 40
        Page 41
        Page 42
        Page 43
        Page 44
        Page 45
        Page 46
        Page 47
        Page 48
    Integrated control of club root of crucifers caused by plasmodiophora brassicae
        Page 49
        Page 50
        Page 51
        Page 52
    Abstracts of papers presented during the annual convention of the pest control council of the Philippines, Baguio City, May 9-12, 1989
        Page 53
        Page 54
        Page 55
        Page 56
        Page 57
        Page 58
        Page 59
        Page 60
        Page 61
        Page 62
        Page 63
        Page 64
        Page 65
        Page 66
        Page 67
        Page 68
        Page 69
        Page 70
    Information for contributors
        Page 71
    Republic of the Philippines Department of Public Works, Transportation and Communication. Bureau of posts, Manila
        Page 72
    Back Matter
        Page 73
        Page 74
    Back Cover
        Page 75
        Page 76
Full Text






a "I1JIIA, a ill J A A A
Official Organ of the Philippine


PHILIPPINE PHYTOPATHi
BOARD OF DIRI


AVELINO D. RAYMUNDO
MARINA P. NATURAL
RUSTICO A. ZORILLA
CASIANA M. VERA CRUZ
CEFERINO A. BANIQUED
JOSE M. BANDONG
TWNG WAH MEW
ARCADIO J. QUIMIO
SAMUEL C. DALMACIO


EDITORIAL


AVELINO D. RAYMUNDO
RIZALDO G. BAYOT
NARCEO B. BAJET
MYRNA Q. SEVILLA




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hytopathological Society, Inc.


LOGICAL SOCIETY, INC.
:TORS 1988-89


President
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BOARD


Editor-in-chief
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IlLS. INC.


dressed to the TREASURER, P.P.S. c/o Depart-
720. Philippine Phytopathology, published semi-
lytopathological Society, Inc. It is sent free to
. For others, it is P50.00 per copy (domestic) and
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^~___, *- __.. _.J^ !.. *!;.; TA,.* I nrt w *h*






m -y F.


EPIDEMIOLOGY
IN TH



P.M. Magdalita, O.
at


Respectively, University Researct
Professor, Department of Plant Patholo
and Researcher, IPB, College of Agrii
(UPLB), College, Laguna, Philippines, 4(
Portion of M.S. Thesis of the senior
Given the Best Paper Award by the
Annual Convention of the Pest Control (
Hotel, Baguio City on May 9-12,1989.


This research was jointly sul
Forestry and Natural Resources
Institute of Plant Breeding (IPB) a
College, Laguna. The authors thank
and Elizabeth M. Libas for their value






Papaya ringspot (PRS) exhibited a foc
distance showed a shallow curve indicating
between incidence and distance was explain
Gregory's and Kiyosawa and Shiyomi's mode
X A sigmoid curve was depicted by PRS ar
logistic growth model. The relationship of thi
defined as Y = -11.84 + 0.74 X.
Infection rates were highly variable dui
0.74 per unit per week. Infection rate was r
elements together with aphid population sam
Integration of relative isolation, rigid
three-fold and delayed the epidemic by as mi
of vectors was ineffective in suppressing the ,
as 0.16.



INTRODUCTION

.1 ~ .


Y OF PAPAYA RINGSPOT
F PHILIPPINES



i. Opina, R.R.C. Espino
I V.N. Villegas


-r, Institute of Plant Breeding (IPB); Assc
,y, Assistant Professor, Department of Horticu]
culture, University of the Philippines at Los E
31.
author submitted to UPLB.
Philippine Phytopathological Society during the
councill of the Philippines, Inc. held at Hyatt Ter



ported by the Philippine Council for Agriculture
Research and Development (PCARRD), tht
id the Department of Plant Pathology, UPLB
Dr. Rizaldo G. Bayot, Ms. Hosanna H. Espantc
ible contributions.




ABSTRACT

il pattern of spread. A plot between disease incidence ani
long distance dispersal of the disease. The relationship]
ted by a a second-degree polynomial model better thai
i. The relationship was defined as Y = -4.12 + 3.52 X 0.7
1 the progression with time was accurately described by th,
transformed disease incidence (Y) relative to time (X), wa

Ition the epidemic. Apparent infection rate was estimated a
)t correlated with the number of trapped aphids. Weathe
le were similarly non-correlated with the rate of infection.
anitation and vector control reduced the infection rate b
:h as 15 weeks compared with the control. Chemical contrc
)read of PRS. Vander Plank's sanitation ratio was calculate,




national production reached 90 metric t(
1986 (Ministry of Agriculture and Food,
Sthe but production has been declining due
nnp nipu annd tPvetatQntr delae;Cp whieh ha.


Irebi pilpdyd kk_"
r . AI___








production in the Southern Tagalog region.
Based on symptoms, host, host range,
transmissibility, physical properties, and
electron microscopy, the disease in the
Philippines is probably caused by papaya
ringspot virus (PRSV) (Opina, 1986). Papaya
ringspot-infected plants first exhibited vein
clearing and chlorotic spots followed by
mottling and distortion of leaves, ringspots
on fruits and on the upper portion of the
stem, as well as elongated oily streaks on
petioles and stems (Opina, 1986).
The exact origin of PRS in the
Philippines is still uncertain. However, it was
first observed in the Island of Oahu, Hawaii
in 1945 (Lindner et al., 1945). In the 1950's,
diseases of similar symptoms were reported
in Bangladesh, Colombia, Cuba, El Salvador,
Sri Lanka and Venezuela. It became
prevalent throughout Central and South
America as well as in the Caribbean Islands
and is now widespread in tropical America
from Brazil to Florida (Hamilton, 1986). It
was recorded in Taiwan in 1975 (Yeh et al.,
1988) and recently in Thailand (Hamilton,
1986).
In the Philippines, PRS has been
observed as early as 1982 in Silang, Cavite
but it did not attract attention because it was
confined only to very few plants. However, in
the middle of 1984 the disease spread like
wild fire. About 200 ha of papaya were
affected with 60 to 100% incidence and an
estimated yield loss of about P6,309,000. The
disease has developed in epidemic proportion
in Cavite, Batangas and Laguna (Opina,
1986). It has spread in sone areas of Quezon,
Bulacan, Rizal, Pampanga, Nueva Ecija,
Tarlac, Pangasinan and Metro Manila
(Opina, 1986).
The control of PRS was limited to the
use of tolerant varieties (Conover et al., 1986;
Huang, 1988) and cross-protection techniques
(Yeh et al., 1988). However, one of the
limitations of these methods is the
maintenance of a reservoir of the, virus in
which mutations to more virulent strains are
likely to occur. One of the strategies in most
disease management programs is slowing
down the apparent infection rate via
sanitation and application of pesticides
(Berger, 1977). Miller et al. 1969 reported
that Dutch elm disease progressed at the rate


tlopatology Vol.25
of 0.012 per unit per month but
discontinuance of sanitation after seven years
resulted to a three-fold (0.039 per unit per
month) increase of infection rate.
Studies on various aspects of PRS has
been well documented but information on
the dynamics of the disease is still wanting.
This information may be of prime
importance in the development of a
meaningful disease management strategy.
Thus, this study was conducted to (a)
determine the dynamics of the disease; (b)
establish the relationship of infection rate
with weather elements and vector population
and (c) quantify the epidemiological impact
of relative isolation, sanitation and vector
control on disease development.

MATERIALS AND METHODS

Source and Preparation of Experimental
Plants

'Cavite Special' fruits free of PRS were
collected from an isolated papaya farm in
Ternate, Cavite. The seeds were extracted,
washed thoroughly in running water and air-
dried for one week. They were sown in bags
of disinfested soil and allowed to germinate
inside fine nylon nets in the greenhouse. The
seedlings were watered thrice a week and
drenched weekly with a solution of 0.05%
urea. After 1.5 months, the seedlings were
transplanted in the field, spaced at 2.0 mn
apart. All recommended cultural practices
were followed except insecticidal spray for
Fields 1 and 2. The study was conducted at
the Central Experiment Station, College of
Agriculture, University of the Philippines at
Los Bafios (UPLB).

Field Experiments

The study comprised three 0.25 ha
papaya fields characterized as follows:

Field 1. Relatively isolated; inoculum source
introduced; no sanitation and
insecticidal control; inoculum
sources within the vicinity were
removed. Field 1 was used to
generate data to establish
epidemiological parameters.







rieia L. Keiauveiy isolated; moculum source mie increase or r"~ wirn lime


,Ywu uJ -,, ^-,-,UU- ",- -"ui .w,. o time intervals ana c average lor Ltie CnLIr
)y the total number of trees within each duration of the epidemic was taken.
concentric line. The pattern of disease spread
n space was likewise determined by visually Effect of Ecological Factors
assessing diseased and healthy trees at
weekly intervals. Disease incidence was Aphid Population and Weather Elements
Allotted against distance in meters (m) to


--~~~---~~~ ---







amount of detergent were mounted on where ,o is the proportion of the disease in
wooden blocks supported with wooden stakes the field without sanitation and Xos is the
and were maintained at tree canopy level, amount of the disease in the field where
Likewise, aphids carried by wind were sanitation was applied.
trapped using fine nylon nets (1.5 m x 6.0 m)
attached to bamboo poles (6.0 m). The RESULTS AND'DISCUSSION
intercept traps were located at the front,
center and rear portion of the field against Spread and Increase of PRS in Space
the general direction of the wind. The traps
were adjusted to the level of the tree canopy Spatial distribution of the disease
as it increased in height. showed a focal pattern of spread during the
The trapped aphids were collected and early phase of epidemic which was about 3 to
placed in vials containing 75% ethyl alcohol, 9 weeks after introduction of initial inoculum.
cleared using 70% sodium hydroxide Towards the terminal phase of the epidemic
followed by chloral-phenol. The aphids were (about 14 to 15 weeks after introduction of
mounted on glass slides using Hoyer's initial inoculum), the disease was evenly
mounting medium were later identified by distributed within the field (Fig. 1). The
Dr. Venus J. Calilung, Department of incidence of PRS was inversely related to
Entomology, UPLB. distance from the inoculum point source. The
The data of the different weather plot of disease incidence versus distance
elements (windspeed, rainfall, relative showed a flattened gradient from 5.0 m to
humidity, sunshine, evaporation and 20.0 m radius from the initial inoculum but
temperature) were obtained from the UPLB beyond 20.0 m the gradient decreased with
Agrometeorological Station, College, increasing distance. A second-degree
Laguna. polynomial model explained better the
The weekly average uam. ,n trapped spread of PRS as shown by the higher
aphid population and weather elements were coefficient of determination (R2 = 94.6%)
regressed with infection rates. Since PRSV compared to Gregory's (1968) and Kiyo awa
required at least two weeks incubation period and Shiyomi's (1972) models with R of
(Opina, 1986), aphid population and weather 56.2% and 63.3%, respectively. This model
elements taken two weeks earlier, were used defined the spatial spread of the disease as Y
in the regression analysis. = -4.12 + 3.52X 0.79X2 (Fig. 2). Based on
this model, the isolation distance as disease
Epidemiological Evaluation of Relative incidence approaches zero was estimated as
Isolation, Sanitation and Vector Control 1230 m radius from the inoculum source.
In the focal pattern of spread of PRS,
Papaya trees in Fields 2 and 3 were the infected plants appeared to be aggregated
individually inspected daily for initial near the noint source of inncullm Inw.ve.r


Phlllppimn Phytopatholog


Vol. 25


1 -. --.\ r











* = Inoculum source
* = Diseased tree


:"'
*.



:;
:..:.-...:

"" ". "-: '..-..
...... .: .....:

;,.-: ";' ': ": .:.



"i



E


... .
t.... oJa e
:.':::'::'.'::"'

l****** * **** *







F


Fig. 1. Diagrammatic representation of a 0.25 ha papaya field showing (A to C) the focal pattern of spatial spread of
papaya ringshot about 3 to 9 weeks after introduction of inoculum and (D to F) disappearance of this pattern
towards the terminal phase (Field 1).


6


" "'

"' '"
.....,..
.............
...
""""
..........
..
..
""' :.: "::







PM#~ Phytopeliology Vol 25


10 20 30


Linear distance (m)

Fig. 2. Estimated relationship of transformed values and distance in Field 1.


practices ineffective in controlling the
disease.

The Increase of PRS with Time

Disease Progress Curve

A typical sigmoid curve, typical of a
polycyclic disease was obtained when disease
incidences were plotted against time (Fig. 3).
The onset of the epidemic started at about 10
weeks after transplanting and reached the
perception threshold (Y = 0.05) at about 13
weeks after transplanting. Mid-time epidemic
was attained at the 15th to 16th week while
the terminal phase was recorded on the 23rd
week.

Disease Growth Model

The logistic growth- model, better
explained the nature of progress of PRS
where an R of 943% was obtained
compared to the simple interest model, with
an R of only 82.6%. According to this
model, the logit transformed value of disease
incidence (Y) relative to time (X) was
defined as Y = -11.84 + 0.74X (Fig. 4).


Infection Rate

The average rate of infection was
estimated as 0.74 per unit per week based on
the logistic growth model. This indicates a
two-fold increase of PRS within three weeks,
suggesting that the disease is capable of
causing an explosive epidemic within a short
period of time. The infection rates at weekly
intervals during the entire duration of the
epidemic were highly variable (Fig. 5).
The rapid progression of PRS once
introduced in the field poses a serious
problem in managing the disease. Also, any
control measure designed to reduce the
initial inoculum would render it theoretically
ineffective.

Effect of Ecological Factors

Aphid Population and Weather Elements

Twenty-seven species of alate aphids
belonging to 13 genera were identified
throughout the 28-week trapping period
(Table 1). However, the proportion of
viruliferous aphids was not assessed. Stepwise
multiple regression analysis showed that the


Vol. 25


PhlHppine Phytopathology







Ian. ~~ & ue90Flmonv fPfaaRnao


1.0 no. of diseased trees
DP = ------------------
total no. of trees
0.8



0.6
a
0


0.4 -



0.2 -




10 12 14
Weeks after


Fig. 3. Disease progress curve of papaya ring



number of trapped aphid population together
with the various weather elements failed to
explain the variations of infection rates. This
result suggests that further investigation on
the ability of the 27 species of aphids trapped
to transmit PRSV should be undertaken.
Also, traps that could register the density of
viruliferous vectors must be devised.

Epidemiological Evaluation of Relative
Isolation, Sanitation and Vector Control

Relative crop isolation, rigid sanitation,
and vector control suppressed the
progression of PRS as compared to the
control (Fig. 6). The rate of infection was
reduced by three-fold and delayed epidemic
development by as much as 15 weeks under
relative isolation and rigid sanitation.
However, integration of chemical control of


I I I I I
16 18 20 22 24
insplanting


iot in Field 1.



:he suppression of the spread of PRS.
Vander Plank's sanitation ratio was
calculated as 0.16 suggesting that sanitation is
evidently a worthwhile strategy in suppressing
the spread of PRS.
While relative isolation and strict
sanitation are worthwhile measures in
delaying epidemic development, they could
not totally control the progression of PRS


weeKs aelay oI rIK epidemic ma
meaningful for perennial crops


lot oc too


isolated, sanitized and vector-controuea
fields were kept healthy only up to 14.4 weeks
ifter transplanting while those in the
insanitized field were already chlorotic. This
finding implies that the control of spread of
'RS within acceptable duration calls for the
integration of other control measures.


Fnidamnlnav ofa Panava RInnanot


Ian. A June 1989








hIrpn htpehlg o.2


Logistic Model


2.0


S4.0
u




-4.0


-8.0



10 12 14
Weeks after I

Fig. 4. Estimated relationship of transformed




2.0


1.8


S 1.6


1.4


S1.2


S1.0-

0
I 0.8


0.6


0.4 -


02



10 12 14 1(

Weeks after ti


Y = -11.84 +
074X
I = 94.38**



S 18 20 22 24
rsplanting

values to time in field 1.



































18 20 22 24

isplanting


hlllpplne Phytopathology


fol. 25





1.0 -

0*-**- No sanitation and vector )r
control
0.8 -r-*A- Sanitation + vector
ao I control
0C-0- Sanitation

0.6 -



g 0.4



0.2 -





10 12 14 16 18 -20 22 24 26 28 30 32 3
Weeks after transplanting


Fig. 6. Effect of non-sanitation, sanitation and sanitation including vector control o0
incidence of papaya ringspo.


.mr- O' -"" r~WY n-I4pr>







ilp.PyS~~yi.2


Fable 1. Twenty-seven species of aphids trapped
trapping period.


SPECIES


4phis citicola Van der Goot*
4phis craccivora Koch*
4phis eugeniae Van der Goot*
4phis glycines Matsumura
4phis gossypii Glover*
4phis nerii (B. de Fonsc.)
Branchycaudus helichrysi (Kaltenbach)
Brachysiphoniella montana (Van der Goot)
Cerathapis variabilis Hill Ris Lambers
Hysteroneura setariae (Thomas)*
Lipaphis erysimi (Kaltenbach)
Melanaphis sacchari (Zehntner)
Pentalonia gavarrai Eastop
Pentalonia nigronervosa Coquerel*
Rhopalosiphum maidis (Fitch)*
Rhopalosiphum nymphasae (Linn.)*
Rhopalosiphum rufiabdominalis (Sasaki)*
Schizaphis graminum (Rondani)
Schizaphis minute Van der Goot*
Schizaphis rotundiventris (Signoret)
Sitobion takahaski (Takahaski)
Tetraneura nigriabdominalis (Sasaki)*
Tetraneura polychaeta Hille Ris Lambers*
Tetraneura radicicola Strand
Toxoptera aurantii (B. de Fonsc.)
Toxoptera citricidus (Kirkaldy)*
Toxoptera odinae (B. de Fonsc.)


*Trapped in Field 1


the three fields during the seven month



NO. OF INDIVIDUALS


110
667
48
4
215
7
1
8
3
66
1
22
5
39
98
7
297
20
13
32
1
3977
18
1
4
136
2


ilppRt Pnyopanoiogy


1L.a8









Jan.&Jsuie im EpIdemIology ol Papaya Ringapos


LITERATURE CITED

BERGER, R.D. 1977. Application of epidemiological
principles to achieve plant disease control. Ann.
Rev. Phytopathol. 7: 31-50.

BUREAU OF AGRICULTURAL RESEARCH
(BAR). 1989. Papaya ringspot virus: the newest
enemy in the papaya industry.l: 10-11.

CONOVER, RA., RE. LITZ and S.E. MALO. 1986.
Cariflora-a poapaya ringspot virus tolerant
papaya for South Florida and the Caribbean.
Hort. Sci. 21: 1072.

GILL, C.C. 1970. Epidemiology of the barley yellow
dwarf in Manitoba and effect of the virus on yield
of cereals. Phytopathology 60: 1826-1830.

GREGORY, P.H. 1968. Interpreting plant disease
dispersal gradients. Ann. Rev. Phytopathol. 6:
189-212.

HAMILTON, RA. 1986. A preliminary report on
occurrence and control of papaya mosaic virus in
the Philippines. Consultancy report submitted to
the Philippine Council for Agriculture, Forestry,
and Natural Resourtces Research and
Development (PCARRD), Los Bafios, Laguna.
11 p.

HUANG, C.H. 1988. Superior crop varieties in lalwan.
Food and Fert. Technol. Center Bull. Taiwan,
R.O.C.

KIYOSAWA, S. and M. SHIYOMI. 1972. A
theoretical evaluation of mixing resistant variety


with susceptible variety for controlling plant
disease. Ann. Phytopathol. Soc. Japan. 38: 41-45.

LINDNER, R.C., D.D. JENSEN and W. IKEDA. 1945.
Ringspot: new papaya plunderer. Hawaii Farm
and Home. 8: 10-14.

MILLER, H.C., S.B. SILVERBORG and R.G.
CAMPANA. 1969. Dutch elm disease: Relation
of spread and intensification to control by
sanitation in Syracuse, New York. Pit. Dis. Reptr.
53: 551-555.

MINISTRY OF AGRICULTURE AND FOOD
(MAF). 1987. 1986. Crop Statistics. Quezon City.

OPINA, O.S. 1986. Studies on a new virus disease of
papaya in the Philippines. Food Fert. Technol.
Center Bull. 33. Taiwan, RO.C.

VANDER PLANK, J.E. 1963. Plant disease: Epidemics
and control. Acad. Press, New York, U.S.A. 3-49
pp.

YEH, S.D., H.L. WANG, R.J. CHUI and D.
GONZALVES. 1984. Evaluation of induced
mutants of papaya ringspot virus for control by
cross protection. Phytopathology 74: 1086-1091.

YEH, S.D., D. GONZALVES, H.L. WANG, R.
NAMBA and R.J. CHUI. 1988. Control of
papaya ringspot virus by cross protection. Pit.
Dis. 22: 375-380.


Jan. & June 1989


Fold I a loy of Pejm~a Rl~ngeWot





Philppin Phyloprhologioal Sooety, Inc.
19 PhI. Phytoplh. 25:12.17









MODELLING YIELD LOSSES DUE TO CERCOSPORA LEAFSPOTS
[CERCOSPORA ARACHIDICOLA HORI AND
CERCOSPORIDIUM PERSONATUM BERK. AND CURT.
(DEIGHTON)]
OF PEANUT

M.D. Ebuenga and O.S. Opina

A portion of the M.S. Thesis of the senior author, University of the Philippines
at Los Banos, College, Laguna, Philippines.

Research Associate, National Crop Protection Center, and Associate Professor,
Department of Plant Pathology, respectively, University of the Philippines at Los
Banos, College, Laguna, Philippines.

ABSTRACT

The critical point, area under the disease progress curve (AUDPC), and
multiple point models, were evaluated and fitted to the peanut leafspots yield loss
data during the 1988 cropping seasons. Diverse disease progress curves were
generated in the field by varying severity levels and inoculation time using
fungicidal sprays.
Correlation analyses of yield loss and disease severities in various growth
stages revealed that the most critical stage for estimating yield loss was at 70 days
after planting (DAP) which is approximately the R7 beginning maturity stage. The
best model for explaining the relationship between yield loss and disease severity
(in proportion) was a multiple point model between yield loss (Y) and disease
severities at 50 DAP (X50), 60 DAP (X60) and 70 DAP (X70).

Y = .0638 52.6753 X50 5.1211 X60 + 4.5433 X70
(r2 = .85, s.e. = .072)

The model was better than the critical point and AUDPC models in terms of
coefficient of determination, standard error and residual analysis. In addition, the
model is appropriate based on the epidemic behavior of peanut leafspots and
physiological characteristics of the peanut plant.







Jan. & June 1969 Modelling Yield Losses Due to Leafepots of Peanut


INTRODUCTION

The full exploitation of peanut as a
commercial crop has not been fully realized
in the Philippines. The reasons for this
apparent slow pace in the local peanut
industry are numerous physical,
technological and socio-economic
constraints. Among the technological
constraints, the presence of diseases and the
high yield losses that they cause are the most
perplexing. At present, peanut could not be
planted beyond certain hectarage because of
diseases (Opina, 1983).
The most common and serious diseases
of peanut in the Philippines are black spots,
or Cercospora leafspots caused by
Cercosporidiumpersonatum (Berk. & Curt.)
Deighton and Cercospora arachidicola Hori.
The perfect stages of these fungi are
Mycosphaerella berkeleyii W.A. Jenkins and
M. arachidis (W.A. Jenkins) Deighton,
respectively.
Severe infection of these diseases can
lead to defoliation and death of young plants.
Yield and quality of nuts may also be
drastically reduced when conditions favor
infection (Feakin, 1973). In some areas of the
world, economic losses from black spots
were estimated to be from 15 to 50 percent
of the yield (Garren and Jackson, 1973). The
leafspot pathogens cause loss of about 3
million tons of peanuts per year (Gibbons,
1980).
In the Philippines, Paningbatan (1976)
assessed yield loss of peanut due to leafspot
and rust to be 28% when complete
defoliation and drying of leaves occur.
Similarly, up to 68% reduction in peanut
yield was reported (NCPC, 1983). Damage
potential could reach 50% and 80% for
leafspots caused by C. arachidicola and C.
personatum, respectively (Cadapan, 1985).
In addition, these diseases are particularly
important in the Philippines where rainfed
cropping accounts for a significant
proportion of peanut production. Conditions
during the growing season are favorable for a
high severity of leafspots.
Quantitative assessment of the overall
impact of peanut leafspots is wanting. This is
important not only in predicting yield losses
and assessment of the disease, but also in the


formulation of management strategies for the
disease.
Yield loss models are appropriate tools
in this premise. Various workers have
investigated and proposed models of yield
losses (James, 1974; Zadoks and Schein,
1976; Teng, 1987; Chong Hoe-Kim and
Mckenzie, 1987). In peanut, Backman and
Crawford (1984) developed models of yield
loss due to leafspots utilizing quadratic
equations.
This study, therefore, aims to establish a
model or models for predicting yield losses
due to Cercospora leafspots and to
determine the critical growth stage fo,
assessing yield losses due to the disease.

MATERIALS AND METHODS

Experimental Design and Treatments

A two-factor split plot was the
experimental design used in the experiments.
Three and four replications were laid-out
during the dry and wet seasons, respectively.
Treatments were designed solely for the
purpose of generating diverse disease
severity levels and varying inoculation time in
accordance with the methods reviewed by
Sah and Mackenzie (1987). Appropriate
application of fungicides, mancozeb and
plantvax, was utilized to vary disease level of
leafspots and to minimize the development of
peanut rust, respectively. Disease infection
was facilitated using the spreader row
technique. The mainplot (factor A)
corresponded to the different times of
disease onset or time when disease initially
exhibited symptoms, e.g. leafspots while
varying levels of disease severity were
assigned to the subplots. Disease-free
subplots served as control.


Cultural Practices and
Experimental Plants


Care of


The experimental area was thoroughly
prepared. Pendimethalin was used as a pre-
emergence, soil-incorporated herbicide at a
recommended rate (1 kg a.i./ha).
The leafspot-disease susceptible variety,
BPI P9, was planted in all experimental plots.
Prior to planting, the seeds were treated with



Modelling Yield Losses Due to Lealfspots of Peanut


Jan. & June 1989







Phlppn Phtoatalg Vol.35


Captan (50% WP) at a rate of 230 g/100 kg
during the dry season and Brassicol (75%
PCNB) at 1 tablespoon FP/kg during the wet
season to minimize soil pathogen infestation.
Handweeding was done at 30 days after
planting (DAP) to keep the area free of
weeds. Cultivation with a machine operated
cultivator was resorted to at 40 DAP to
loosen the soil for hilling-up. As a routine
activity, hilling up using hand-held hoe was
done during 42 to 44 DAP.
The peanut crop was maintained with
minimal insect damage by frequent sprays of
monocrotophos at a rate of 1 li FP/ha. To
prevent rust disease, Plantvax was applied (1
k) during 50, 60 and 70 DAPs.
Experimental plants were irrigated by
perforain irrigation whenever necessary.

Disease Assessment

Twenty plants from the inner four rows
were selected at random in each sub-plot and
assessed for disease severity using a standard
area diagram (0-no disease, 100-100%
infection). Only the main stem was sampled
in each plant.
Sampling or data gathering was done
once disease initially occurred and every 5
days thereafter up to 90 DAP. Recorded data
on disease severity per sampling time were
averaged. Mean severity of 20 plants was
tabulated in each sub-plot.
Plant growth stages according to Boote
(1982) were also observed and noted.

Harvesting and Gathering of Yield Daata

At maturity (100 DAP), 20 plants in the
inner rows of all plots were harvested using
spading forks or hand shovels and dried
under the sun for half a day. Nuts were
detached and placed in double-tagged net
bags. The bags were properly secured with
rubber bands.
After 3 days of sun drying, the sampled
peanuts were cleaned and weighed using a
triple beam balance. The shelled weight and
moisture content in each sample. Yield data
were adjusted to 14% moisture using the
method of Gomez (1972).


Ilela losses were calculated using the
allowing formula:
% YL = [ (C-A)/C)
were % YL = percent yield loss; C = yield
of control plots;
k = yield of treatment plots.

Yield Loss Models of Peanut Leafspots

Various methods of quantifying the
relationship of loss in yield and peanut
leafspots disease were utilized in an attempt
to derive a yield loss model or models that
could best characterize such relationship.
The critical point (CP), areas under the
disease progress curve (AUDPC) and multiple
point (MP) models (Zadoks and Schein,
1976) were applied and evaluated in
modelling yield loss due to peanut leafspots.
Critical Point and Multiple Point
Models. Average disease severities and
transformed values in each treatment
combination per sampling time were
correlated and regressed with the
corresponding yield loss data. Correlation
matrix of the disease severities and yield loss
were computed and tabulated. Those
showing high correlation with yield loss were
quantified and models of the form:
Y = a + bX
where Y is yield loss (in proportion), a is the
intercept, b is the slope and x is the disease
proportion,were derived.
In addition, multiple point models were
also obtained. The stepwise regression
analysis was employed to obtain multiple
point models. All computations used were
the correlation and regression analyses
software package of the Hewlett-Packard
9845 and 9816 desktop-computers of the
National Crop Protection Center.
Area Under the Disease Progress Curve
(AUDPC) Model. The AUDPC in each
treatment combination was calculated based
on the method employed by Johnson and
Beute (1986).
The values of the AUDPC's were
correlated and regressed with the
corresponding yield loss data and possible
models were derived using regression and
correlation analyses.


Philippine Phykqmdhology


Vol. 25









RESULTS AND DISCUSSION where Y = proportion of yield loss and X =
disease proportion at 70 DAP. This equation
Correlation analysis between yield loss explained 74% of the variation in yield loss
and disease proportions showed that higher with a standard error of prediction of 9.1%.
correlation coefficients were derived by
combining the dry season and wet season The derived critical point model is a
data than by correlating the dry or wet critical time model according to the
season variables alone (Table 1). It was classification of Zadoks and Schein (1976)


Table 1. Correlation coefficients of disease proportion and yield loss using the
dry, wet and combined dry and wet season da*^

YIELD LOSS
DISEASE
PROPORTION Wet Dry Combined Wet and
Season Season Dry Season


30 DAP .004

40 DAP .004 -.115 .221

45 DAP .293 -.069 .387

50 DAP .107 -.201 .560

55 DAP .386 -.262 .754


65 DAP .086

70 DAP .561








Philippine Phytopathology Vol.25


confirmed that this closely approximates 70
DAP. At this stage, development of pods is at
its peak and accumulated effects of the
disease to the crop is maximally sustained.
Quantification of yield loss and AUDPC
of peanut leafspots showed that the following
regression model using the combined dry
and wet season data could best explain their
relationship:

Y = .03945 + .0287X

in which Y = Yield loss (in proportion) and X
is the AUDPC. The model is capable of
explaining 67% of the variation in yield loss
with a standard error of 10.29%.
The AUDPC model obtained is
comparable with that of Schneider et al.
(1976) where the AUDPC model for
Cercospora leafspots of cowpea explained
70.2% of the variations in yield.
However, comparison of the critical
point and AUDPC models showed that the
former explained 7% more variations in yield
than the latter.
The search for the "best" set of
independent variables for estimating yield
loss was achieved using the stepwise
regression search method. The method
showed that the best set of independent
variables is a combination of disease
proportions at 50, 60 and 70 DAPs. As a
result, the multiple point model equation to
estimate yield loss due to peanut leafspot
becomes:

Y = .0638 52.6753X50 5.1211X60 +
4.5433X70.

where Y = estimated yield loss (in
proportion) and X50, X60 and X70 are the
disease severities at 50, 60 and 70 DAP,
respectively. The equation explained 85% of
the variation in yield loss with a 7.2%
standard error. Autocorrelation between
these variables is not significant using the
Durbin-Watson test for autocorrelation.
Compared with the critical and AUDPC
models, the multiple point model obtained in
this study resulted in an improved fit as
indicated by an increase in R of 11% and
18% over the critical point and AUDPC


models, respectively. In addition, comparing
the predictive ability of the 3 models revealed
that residuals (actual-predicted yield) are
nearer to zero in the multiple point model
than in either the critical or AUDPC models.
Results in this study support the
advantages of the multiple point model over
the critical or AUDPC models. The
epidemiologic behavior of peanut leafspots
and physiological characteristic of peanut
supports the criteria outlined by James
(1974) that will necessitate the use of
multiple point model: 1) high variability in
infection rates or in shape of disease
progress, 2) early and/or long duration
epidemics and 3) a long period for
accumulation of yield.
Although there are indications that a
critical point model is workable, still several
readings of disease severity proved to be
superior to just one. The growth stages that
were pin-pointed as important for yield loss
determination could be easily distinguished
physiologically or visually. This makes the
possibility of assessing yield loss based on
physiological indicators of the peanut plant.


LITERATURE CITED

BACKMAN, PA. and M.A. CRAWFORD. 1984.
Relationship between yield loss and severity
of early and late leaf spot diseases of peanut.
Phytopathology 74:1101-1103.

BOOTE, K.J. 1982. Growth stages of peanut (Arachis
bypogaea L.). Peanut Sci. 9: 35-40.
CADAPAN, E.P. 1985. Pest management studies for
peanut in the Philippines. Paper presented at
the First National Peanut Consultation and
Peanut CRSP Review. Feb. 7-8, 1985,
PCARRD, Los Banos, Laguna, Philippines.

CHOONG-HOE KIM and D.R. MACKENZIE. 1987.
Empirical models for predicting yield loss
caused by a single disease. In Teng, P.S. Crop
Loss Assessment and Pest Management. St..
Paul, MN: Amer. Phytopathol. Soc. 270 pp.

ENYI, B.A. 1975. Effect of defoliation on growth and
yield in groundnut (Arachts hypogaea L.),
cowpea (Vigna unguiculata).
soybeans (Glycine max) and green gram
(Vigna aurens). Ann. Appl. Biol. 79: 55-66.

FEAKIN, S. (ed). 1973. Pest control in groundnuts.
Centre for Overseas Pest Research, Foreign
and Commonwealth Office, Overseas
Development Administration, London.


Philippine Phytopsthology


Vol. 25









Jan. & June 1969 Modelling YIeld Lasses Due to Lealsoots of Peanut


GARREN, K.H. and C.K. JACKSON. 1973. Peanut
diseases. In: peanut-culture and uses.
American Peanut Research and Education
Association.

GIBBONS, R.W. 1980. The ICRISAT groundnut program.
In: ICRISAT (International Crops Research
Institute for the Semi-Arid Tropics). 1980.
Proc. Intern. Workshop on Groundnuts. 13-
17 October 1980, Patancheru, A.P., India.

GOMEZ, K.A. 1972. Techniques for field experiments
with rice. The International Rice Research
Institute, Los Banos, Philippines.

JAMES, W.C. 1974. Assessment of plant disease and
losses. Ann. Rev. Phytopathol. 12: 27-48.

IOHNSON, C.S. and M.K. BEUTE. 1986. The role of
partial resistance in the management of
Cercospora leafspot of peanut in North
Carolina. Phytopathology 76: 468-472.

NCPC. 1983. Annual Report for 1982. National Crop
Protection Center, UPLB, College, Laguna,
Philippines.

3PINA, O.S. 1983. Management studies for the control
of legume diseases. Terminal Report, PCARRD
Project No. 652, Philippine Council for
Agriculture and Resources Research and
Development, Los Banos, Laguna,
Philiopines.


,PANINGBATAN, RA. 1976. Yield assessments in peanut
as affected by leafspots and leafrust.
Unpublished B.S. Thesis, University of the
Philippines at Los Banos, College, Laguna

SAH, D.N. and D.R. MACKENZIE. 1987. Methods of
generating different levels of disease
epidemics in loss experiments. In Teng, P.S.
(ed.). 1987. Crop loss assessment and pest
management. St. Paul, MN: Amer.
Phytopathol. Soc. 270 pp.

SCHNEIDER, R.W., R.J. WILLIAMS and J.B. SINCLAIR.
1976. Cercospora leafspot of cowpea: model
for estimating yield loss. Phytopathology 66:
384-388.

TENG, P.S. 1987. Quantifying the relationship between
disease intensity and yield loss. In: Teng, P.S.
(ed.). 1987. Crop loss assessment and pest
management. St. Paul, MN: American
Phytopathological Society. 270 pp.

WILLIAMS, J.H., J.H. WILSON and G.C. BATE. 1975. The
growth and development of four groundnut
(Arachis hypogaea L.) cultivars in Rhodesia.
Rhod. J. Agric. Res. 13: 131-144.

ZADOKS, J.C. ard K.D. SCHEIN. 1976. Epidemiology
and plant disease management. New York:
Oxford University Press. 427 pp.


Modelling Yield Lose"r Due to Lehatapols o ftnut


Jan. & June 1989






Philippine Phytopathological Society, Inc.
1988 Phil. Phytopath. 25:18-24







EPIDEMIOLOGICAL ANALYSIS OF RESISTANCE
TO PHILIPPINE CORN DOWNY MILDEW


A.R. Baria and A.D. Raymundo

Supported by the Institute of Plant Breeding (IPB), University of the PhilipDines at Los


ly, former undergraduate thesis student and Assistant Professor, Department
gy, UPLB, College, Laguna.



ABSTRACT


development, percent i
resistance reactions. Sor


"






Jan. & June 1989 EpidemI


A. unset of systemic symptoms. hrle time For example, in the first trial, the mean
from germination to systemic symptom of initial appearance of systemic sympt
appearance. were 22.6 and 21.1 days on P10 and Ph 1C
B. Rate of increase of chlorosis. The rate of Lower disease severity is manife
increase was calculated using Vander vhen there is delay in the appearance
Plank's model (1963). systemic symptoms. For instance, P10
C. Number of days it took for the first four infection of 8.9% produced over a n
leaves to succumb to systemic infection, period of 22.6 days. The early appearance
D. Percent systemic infection taken at 15, 30 systemic infection in test populations ca:
and 45 days after emergence (DAE) per the occurrence of higher number of dise
entry. Based on the number of plants plants. Ebron and Raymundo (1
showing systemic symptoms divided by observed the same trend.
the number of total plants by 100. Small chlorotic stripes arising from
base of the leaf moving towards the u
RESULTS AND DISCUSSION portion characterized the systemic sympt
of the disease.
Resistance component parameters Based on the number of p]
varied among the inbred lines and corn systemically infected, infection was high
populations tested (Table 1). These the corn population than in the inbred
components include: onset of initial systemic in both trials (Fig. la and Ib). X\
infection, percentage of systemic infection, obtained the highest percentage systb
rate of downy mildew development and infection during first trial while Ph 109-:
length and rate of chlorosis development, inbred line, obtained the highest infectic
Localized symptoms characterized by 60 percent in the second trial.
small, pale green dots to light green areas The final proportion of systemic
running parallel to the veins were observed in infected plants in the populations is refle
ll ^ -- -- -. -- i r .1 i. *r


varieties. Localized symptoms, however,
unreliable basis for classifying host react
since they may appear at a relatively h
proportion in plant genotypes but may fail
develop into visible systemic sympte
(Ebron and Raymundo, 1987b). Jover (19
and Josue (1976) observed similar effects
studies under controlled conditions. I
apparent failure of the hyphae to reach
growing point accounts for the reason v
local infections sometimes do not deve
into systemic symptoms. Significant variat
on the onset of systemic symptoms fr
germination was observed among cert
genotypes (Table 1). For instance, in Tria
inbred P10 had an onset of systemic sympt
significantly different from inbred P8
I- C *I -I -I I


S corn populations PDC-1 with appa
n infection rates of 0.128 and 0.150 for trii
h and 2, respectively; and XVH-5 with 0
3 and 0.130 per unit/day, respectively.
s inbred lines showed slower disease prog
) especially during Trial 1. This indicates
1 resistance which reduces the appa
e infection rate (r) reduces the amount
e disease that develops in the host.Ne
y (1973) reported that this type of resists
3 affects the colonization of the hosts by
n pathogen following successful infection
I that the rate r reflects the field resistance
i variety. Ebron and Raymundo (1987b) fo
slower apparent infection rates in I
n resistant to Philippine corn downy mildew
1 Chlorosis rates varied among







Philinlnne Phvtooatholoav


osis development were obtained in test
populations than in inbred lines (Table
EBI
The mean number of leaves
nically-infected 15, 30 and 45 days after
gence and the mean number of days it
for the first four leaves to show systemic EBI
:oms are significantly different in
ation as well as in inbred lines (Table
iese parameters appear to be important
ne involved in infection is the key IPB.
ieter. These should be studied further
firm their importance relative to the
parameters.
Several epidemiological parameters
influence the resistance of corn
nations and inbred lines to P. JOV
oinensis are quantified These
onents were studied primarily in
)n to their relevance in selection of
itative resistance to downy mildew. NEL
variation among the corn genotypes
on these components was significant, it
I be possible to develop resistance RA'
ng these parameters.


VAr


LITERATURE CITED

RON, L.A. and A.D. RAYMUNDO. 1987a.
Multilocation test for variations in Philippine
corn downy mildew caused by Peronosclerospora
philippinensis (Weston) Shaw. Phil. Phytopathol.
23: 13-17.

RON, LA. and A.D. RAYMUNDO. 1987b.
Quantitative resistance to Philippine corn downy
mildew caused by Peronosclerospora philippinensis
(Weston) Shaw. Phil. Agric. 70: 217-224.

1988. Annual Report. Institute of Plant Breeding,
UP at Los Bafios, College, Laguna.

UE, A.R. 1976. Virulence pattern and gross
morphology of isolates of Sclerospora
philippinensis Weston on maize in Bukidnon.
M.S. Thesis. UPLB, College, Laguna. pp. 115.

'ER, EM. 1977. Virulence pattern, comparative and
gross morphology of isolates of Sclerospora
philippinentsis corn from Isabela and College,
Laguna: pp. 130.

SON, R.R. (ed.) 1973. Breeding plants for disease
resistance: concepts and applications. The
Pennsylvania State Univ. Univ. Park, London.

(MUNDO, A.D. 1989. Multiple disease resistance
in corn and sorghum. Proc. First Corn and
Sorghum Crop Improvement Conference,
Zamboanga City, April 24-25, 1989.

4DERPLANK, J.E. 1963. Plant Diseases:
Epidemics and control. Academic Press, New
York. 363 p.













Onset of
Systematic Symptoms
enotypes (DAE)


Trial 13 Trial 22 T


I Lines

P8 15.8a 13.1b 0(
PIO 22.6b 13.2b 0.'
P12 18.4ab 14.2b 0.
Ph109-1 21.lab 15.6bc 0.'
I-5 16.4ab 15.6bc 0.'

itions
XVH-5 18.3ab 13.3bc 0.
PDC-1 17.lab 14.2bc 0.
SUWAN 2 15.7a 16.1c 0.
XV4 184.ab 9.6a 0.
EL3 20.6ab 12.4a 0.



Mean of five replications 10-15 plants per replication.
Means with the same letters are not significantly different
DAE, days after emergence.
Rates computer using Vander Plan's equation: r =
where x and x are disease seveties at times t land t 2
where xl and x 2are disease severities at times t land t 2rr


Z.-.UU 1o. / U
22.0c 16.7 de
24.6a 19.3b
22.8bc 20.5a
21.3a 14.6g

21.0d 15.6f
19.2e 16.2e
18.3f 13.2h
S 17.6f 17.4d
)1 7 -A 17)


- r


--


- -M~:






Philippine Phytopathology Vol. 25


2. Correlation coefficients among parameters affecting development of Philippine cor
downy mildew.

IPONENTS1 PASS15DAE PSS30DAE PSS45DAE AIRATE CL


DAE Trial I --
Trial II



DAE Trial I
Trial II -- -



DAE Trial I -
Trial II -- -- --



FE Trial I 0.743* 0.712* 0.625*
Trial II 0.865* 0.709* 0.719* --



Trial 0.943* 0.735** 0.657* 0.787*
Trial II 0.623* 0.663* 0.559* 0.783*



s (*) indicate statistical significance at p = 0.05
15DAE Percent Systemic Infection 15 Days after Emergence
ODAE Percent Systemic Infection 30 Days after Emergence
5DAE Percent Systemic Infection 45 Days after Emergence
ATE Apparent Infection Rate
Chlorosis length






Epidemiological Analysis of Corn Downy Mildew


TRANSFORMED DISEASE VALUE


0.2-

0.0
0.2-

0.4-

0.6-

0.8

1.0-

1.2-

1.4

1.6-

1.8 -

2.0

2.2

2.4-

2.6

2.8

3.0

3.2

3.4

3.6

3.8

4.0


SUWAN 2


AXVH
5/


V EL-3

q PB
19 PhlOS
/ Pio

/A 1-5
-/ P12


i I I I | i
10 15 20 25 30 35
Days after emergence

Fig. la. Rate of Downy mildew Development on Selected Corn Genotypes Based on Van
Der Plank's Model.


Jan. & June 1989








PhIlIppIne Phytopathology Vol.25


TRANSFORMED DISEASED VALUE


0.4

0.2

0.0


0.2

0.4

0.6


0.8
1.0


1.2

1.4

1.6

1.8

2.0

2.2

2.4


- 2.6

2.8
- 3.0


- 3.2

- 3.4

3.6

3.8


20 25 30 35


Days after emergence

Fig. lb. Rate of Downy mildew Development on Selected Corn Genotypes Based on Van
Der Plank's Model.


SUWAN2






V EL-3


Philippine Phytopathology


Vol. 25






1wo rml. r-nywqMM. dw; dKWr"







YIELD LOSS ASSESSMENT AND ECONOMICS OF CONTROL
OF SORGHUM TAR SPOT



B T.-Dionio and S.C. Dalmacio

Portion of M:S. thesis of senior author submitted to the University of the Philippine
Los Bafios, College, Laguna.
Respectively, Assistant Professor, Department of Plant Pathology, University of Sout]
Mindanao, Kabacan, North Cotabato, and Plant Pathologist, Pioneer Overseas Corp.,
Isidro, Cabuyao, Laguna (formerly Associate Professor, Department of Plant Pathol
College of Agriculture, University of the Philippines at Los Bafios College, Laguna, Philipp



ABSTRACT

A susceptible sorghum variety, UPL Sg-5, and a resistant sorghum line, BTx 623, were sprayed with
Benlate at varying frequencies to generate different levels of tar spot infection in the field and relate these
levels to yield loss.
Significant yield losses of 37.5, 25.4 and 13.3% resulted from 95.4, 74.3 and 35.0% leaf area infected
(LAI), respectively, on UPL Sg-5. On BTx 623, yield losses of 31.8, 15.2 and 9.7% occurred at 75.6, 47.3
and 19.1% infection.
A significant negative correlation between yield and disease was noted from late boot to soft dough
stage in UPL Sg-5. However, no significant linear relationship, was noted between disease levels and yield
in all growth stages of BTx 623.
Based on cost and return analyses, highest net income was realized in UPL Sg-5 even without
fungicide application while one spray of Benlate at 30 DAP is most profitable for BTx 623.


INTRODUCTION Paderes (1984) obtained a disease sev
rating of 95.0% on the susceptible line,
Tar spot caused by Phyllachora sorghi v. U127 and 48.7% and 36.2% on resistant 1
Hoehnel is a disease of major concern in Ace. 2059 and BTx 623, respectively. No
sorghum in the Philippines (Dalmacio, data, however, was obtained. Further
1980a). Although its destructiveness in terms tar spot was noted at the Southern Mind
of yield loss has not yet been studied, field Agricultural Research Center (SMAJ
observations show that severe infection USM, Kabacan, Cotabato (Tangonan, 19
causes premature drying of the leaves Considered as a potential threa
resulting to reduction in yield (Paderes and sorghum production in the country, rese
Dalmacio, 1984). efforts have been geared towards the co:
In 1976, a severe outbreak of the disease of the disease. Screening for resi
was observed in sorghum plantings in Davao varieties has been carried out and Daln






Philippine Phytopathology Vol.25


This study, therefore, was undertaken at
the Southern Mindanao Agricultural
Research Center, University of Southern
Mindanao, Kabacan, North Cotabato to
estimate yield loss and to determine the
economics of using Benlate for control of tar
spot.

MATERIALS AND METHODS

One susceptible variety (UPL Sg-5) and
one resistant sorghum line (BTx 623) were
used to determine the effect of tar spot on
the yield of sorghum. The test materials were
planted in five-meter row plots with an area
of 15 m2. Seeds were drilled on furrows
spaced 0.75 m apart and thinned to 12-14
plants per linear meter at 14 days after
planting (DAP).
Each set-up was replicated four times in
Randomized Complete Block Design. The
treatments, consisting of different levels of
infection, were attained by varying the
frequencies of Benlate application (2 gm/li)
at 30, 45 and 60 DAP.
To simulate natural field infection the
pathogen was inoculated using the leaf clip
and whorl methods of inoculation on the
spreader rows which were planted around the
experimental area one month ahead of the
test varieties. The spreader rows were cut
down after the disease has developed in the
plots about four weeks after planting.
Fertilization, insecticide application and
other cultural practices for sorghum were
carried out uniformly in all plots.

Gathering of Data

Disease assessment. Disease was
evaluated at seven-day intervals for nine
consecutive weeks starting from 36 days after
emergence. Final disease rating, however,
was taken at 92 DAE. Fifteen sample plants
per plot were rated based on percentage leaf
area infected using a scale of 0-100%
Grain Yield. Plants were harvested at
physiological maturity about 35 days after
flowering. Only plants within the three
middle rows covering an area of 9 m2 were
considered for yield data. Yield was
computed using the formula:


actual
MC
Yield = Grain wt/plot x 10,000 x 100 M
(kg/ha) 9 m 86
Mean percentage yield losses at
different disease levels were computed based
on the average grain yield of plots sprayed
with benlate three times (D).
Economic analysis. Analysis of costs and
returns was done to determine the most
profitable frequency of Benlate application in
UPL Sg-5 and BTx 623. Computations made
involved the use of the following
relationships:
a) Gross Return (GR) = Yield (kg/ha)
x price support per kg of sorghum
b) Total Production Cost (TPC) =
Variable Cost + Fixed Cost
c) Net Return (NR) = Gross Return -
Total Production Cost
d) Return on Investment (ROI) =
Net Return
-------------x 100
Total Production Cost


RESULTS AND DISCUSSION

Effect of Tar Spot on Yield

UPL Sg-5. Significant differences in
yield were noted in all levels of infection
when compared to treatment D which had an
LAI of 10.5% (Table 1). Mean grain yield at
95.4, 74.3, 35.0 and 10.5% LAI were 3,865.6,
4,614.6, 5,360.7 and 6,182.6 kg/ha,
respectively. Consequently, percent yield
losses, relative to plots sprayed three times
(Treatment D), were significant in all levels
of infection with means of 37.5, 25.4 and
13.3% at 95.4, 74.3 and 35.0% LAI,
respectively.
A significant linear relationship (r-
values = -0.96 and -0.95) existed between
yield and disease at 64 and 71 DAE on the
unsprayed plots, respectively (Table 2). On
the treated plots, significant linear
relationship (r-value = -0.96) was likewise
noted at 64 and 71 DAE for plots sprayed at
30 DAP and at 78 DAE for plots sprayed at
30 and 45 DAP (r-value = -0.96). These
suggest that high levels of infection at or near


Philippine Phytopathology


Vol. 25








Table 1. Mean yield and mean percent yield loss of UPL Sg-5 at various levels of tar spot
infection..


PERCENT LEAF
AREA INFECTED2


MEAN YIELD
(KG/HA)


,AN PERCENT
YIELD LOSS
(%)3


37.5 a

25.4 b

13.3 c


Legend: A No spray
B One spray application (30 DAP)
C Two spray applications (30 and 45 DAP)
D Three spray applications (30,45 and 60 DAP)
1 Figures represent the mean of 4 replicates; means within a column followed by a common letter are not
significantly different ( = 0.05, DMRT)
2 Figures represent final disease assessment (i.e. at 92 DAE).
3 Relative to treatment D.


these growth stages would adversely affect
yield.
BTx 623. Yield and the subsequent
yield losses were not significantly different at
47.3 and 19.1% LAI with mean yield of
5,919.5 and 6,298.7 kg/ha, respectively (Table
3). Corresponding yield losses at 75.6, 47.3
and 19.1% LAI were 31.8, 15.2 and 9.7%.
Simple linear correlation revealed a
non-significant relationship between yield
and disease in all stages of growth (Table 4).
Highest r-values of -0.89 and -0.82 were
noted at 64 and 71 DAE for the unsprayed
plots and plots subjected to one spraying of
Benlate, respectively. Plots sprayed twice, on
the other hand, have highest r-values of -0.75
at 50 and 64 DAE while plots sprayed three
times at 57 and 92 DAE with r-values of -
0.58.
The lower yields and subsequently
higher yield reductions in the unsprayed plots
of UPL Sg-5 and BTx 623 could be attributed
to the early occurrence and uninhibited


development of tar spot in these spots. High
levels of tar spot infection at early stages of
growth would result to premature drying of
'leaves (Paderes and Dalmacio, 1984).
Inevitably, this would reduce photosynthetic
area and activity of the plant important
during grain formation.
It is interesting to note that higher r-
values were obtained at the reproductive
stages and early grain formation in both UPL
Sg-5 and BTx 623. This suggests that
sorghum is most sensitive to tar spot and
probably to other diseases at these stages.
This would further suggests that when
disease is high at these stages, greater
reduction in yield would result. A similar
observation on the effect of drought injury
has been cited (Sullivan and Yoshikama,
1972). They noted that sorghum, like many
other cereal crops, is most susceptible to
drought injury during the period of flowering
and early grain formation.


TREATMENT


A 95.4 3,865.6 d

B 74.3 4,614.6 c

C 35.0 5,360.7 b

D 10.5 6,182.6 a


Jan. & June 1989


Yield Loss Due to Sorghum Tar Spot


ME







efficient of yield and percent leaf area infect


varying frequencies or nenlate appiicatlor







TMENT S1 S2
(36 DAE) (43 DAE) (50



-ay Y 0.87 ns 0.93 ns -0.
pray Y 0.88 ns 0.85 ns 0.
prays Y 0.26 ns 0.59 ns 0,
sprays Y 0.46 ns 0.78 ns 0,



/
nd: S1 Late vegetative stage
S3 Near reproductive stage
S4 Pre-booting stage
S5 Booting stage
S6 Late flowering
S7 Soft dough
S8 Near hard dough
S9 Hard dough


- Days after emergence


,....


PERCENT LEAF AREA INFECTED

Growth Stages 1


S3 S4 S5
)AE) (57 DAE) (64 DAE) (71 1



Sns 0.94 ns 0.96* 0.
Sns 0.86 ns 0.96* 0.
Lns 0.89 ns 0.87 ns -0.
Sns 0.82 ns 0.85 ns -0.




ri


"I--- ---l,"







Viad I A&* fhn- o eMwk.


Table 3 Mean yield and mean percent yield loss of BTx 623 at various levels of ta
infection.1


TREATMENT PERCENT LEAF MEAN YIELD MEAN PEI
AREA INFECTED2 (KG/HA) YIED I
(%)



A 75.6 4,759.90 c 31.8 a
B 47.3 5,919.50 b 15.2 b
C 19.1 6,298.70 b 9.7 b
D 5.2 6.977.20 a





Legend: A No spray
B One spray application (30 DAP)
C Two spray applications (30 and 45 DAP)
D Three spray applications (30, 45 and 60 DAP)
1 Figures represent the mean of 4 replicates; means within a column followed by a common letter are
significantly different ( = 0.05, DMRT)
2 Figures represent final disease assessment (i.e. at 92 DAE).
3 Relative to treatment D.



Furthermore, the lower and non- and 45 DAP with net income of P2
significant r-values at later stages signify that (ROI of 51.1%) and P2,194.50 per hE
higher proportions of disease at later stages, of 34.4%), respectively (Table 5).
i.e., after grain formation, would not spray applications at 30, 45 and 60 DA
adversely affect yield. In grain sorghum the lowest net income of P1,665.49/hi
grown for forage or sugar, considerable of 20.2%).
damage to foliage can be sustained without BTx 623. Highest profit was r
yield losses unless this damage occurs in the from one spray application followed t
upper leaves at the time of grain-filling spray, two sprays and three sprays w
(Edmunds and Zummo, 1975). income of P4,495.78, P3,984.58, P3
Where chemical control is concerned, and P2,882.39/ha with corresponding
the results imply that plants should be on investment of 90.4, 109.7, 56.3 and
protected from the disease before these respectively (Table 6).
eotical stages are reached to minimize losses Although higher gross income
in yield, derived by subjecting the plants to
frequencies of Benlate application,
Economic Analysis costs exceeded added returns, hence
realized were lower.
UPL Sg-5. Highest profit of The above results show that zer(
P2,614.97/ha with a corresponding return on would give the highest net income h
investment (ROI) of 73.3% was derived from Sg-5. while one spraying of Benlate
I. f A_ T% Ali, r\AJ:- _* ,-- fU nt < );2







if Rpnlti annlication.


PERCENT LEAF AREA INFECTED

1, Growth Stages 1
LTMENT
S1 S2 S3 S4 S5 S6
(36 DAE) (43 DAE) (50 DAE) (57 DAE) (64 DAE) (71 DAE


,ray Y -0.60 ns 0.54 ns 0.48 ns 0.84 ns 0.89 ns 0.81 ns
spray Y -0.62ns 0.51 ns 0.77 ns 0.81 ns 0.76 ns 0.82 ns
;prays Y 0.40 ns 0.64 ns 0.75 ns 0.64 ns 0.75 ns 0.62 ns
Sprays Y 0.36 ns 0.53 ns 0.57 ns -0.58 ns 0.42 ns 0.52 ns


i/
gend: S1 Late vegetative stage NS -
S2 Early reproductive stage
S3 Early booting stage
S4 Late booting
S5 Flowering
S6 Soft dough
S7 Late soft dough
Sg Hard dough
S9 Near maturity
2/
E Days after emergence


. - -..








Table 5. Estimated cost and return per hectare of sorghum (UPL Sg-5) subjected to different frequencies of Benlate application, USM,
Kabacan, Cotabato.



ITEMS TREATMENTS2
A B C D


Gross Return3 P 6,184.99 P 7,383.31 P 8,577.10 P 9,892.22
Production Cost
Variable C st4 3,389.26 4,638.67 6,059.43 7,810.19
Fixed Cost 180.76 247.40 323.17 416.54
Total Production Cost 3,570.02 4,886.07 6,382.60 8,226.73
Average Production Cost/kg 0.92 1.06 1.19 1.33
Net Return (Profit) 2,614.97 2,497.24 2,194.50 1,665.49
Return on Investment (%) 73.25 51.11 34.38 20.24



1
Computation as of Nov. 1984

2
A no spray
B 1 spray application at 30 DAP
C 2 spray applications at 30 and 45 DAP
d 3 spray applications at 30,45 and 60 DAP
3
Gross income was based on the quantity of harvest and on the Nov. 1984 NFA price support for sorghum valued at P 1.60/kg (Kabacan, Noth Cotabato).
4
Includes labor spent in land preparation, planting and care of the crop harvesting and processing and inputs utilized. Labor requirements for land preparation, planting and care of
the crop expressed in man-days and man-animal days were based on PCARR (1975). Labor requirements of harvesting and processing were based on one (1) hectare sorghum
production at SMARC, USM.

5
Interest in capital based on 16% per annum of total cash expenses.






Table 6. Estimated cost and return per hectare of sorghum (BTx 623)
Kabacan, Cotabato.


subjected to different frequencies of Benlate application, USM,


TEMS TREATMENTS2
A B C D


Gross Return3

Production Cost
Variable Cpst
Fixed Cost
Total Production Cost
Average Production Cost/kg
Net Return (Profit)
Return on Investment (%)



1
Computation as of Nov. 1984


P 7,615.84


3,447.40
183.86
3,631.26
0.76
3,984.58
109.73


P 9,471.2C


4,723.50
251.92
4,975.42
0.84
4,495.78
90.36


P 10,077.92


6,120.40
326.42
6,446.82
1.02
3,631.10
56.32


P 11,163.52


7,861.83
419.30
8,281.13
1.19
2,882.39
34.81


2
A no spray
B 1 spray application at 30 DAP
C 2 spray applications at 30 and 45 DAP
D 3 spray applications at 30, 45 and 60 DAP
3
Gross income was based on the quantity of harvest and on the Nov. 1984 NFA price support for sorghum valued at P 1.60/kg (Kabacan, Noth Cotabato).
4
Includes labor spent in land preparation, planting and care of the crop harvesting and processing and inputs utilized. Labor requirements for land preparation, planting and care of
the crop expressed in man-days and man-animal days were based on PCARR (1975). Labor requirements of harvesting and processing were based on one (1) hectare sorghum
production at SMARC, USM.
5
Interest in capital based on 16% per annum of total cash expenses.







Jan. & June 1989 Yeld Los Due to Sorghum Tar Spot

LITERATURE CITED UPLB, College, Laguna. 71 p.

DALMACIO, S.C. 1980a. Sorghum diseases in the PADERES, E.P. and S.C. DALMACIO. 191
Philippines. pp. 70-71. In ICRISAT Proc. Intern. Comparative rate of development of tar sp
Workshop on Sorghum Diseases, Hyderabad, caused by Phyllachora sorghi v. Hoehnel,
India, 468 p. susceptible and resistant sorghum lines. PI
Agric. 67: 337-343.
DALMACIO, S.C. 1980b. Studies on sorghum diseases
in the Philippines. NSDB Terminal Report SULLIVAN, C.Y. and F. YOSHIKAMA. 1972. Stage
(Mimeographed), UPLB, College, Laguna. 26 p. plant development and the effect on droul
tolerance in sorghum. pp. 164-167. In I
DALMACIO, S.C. and M.P. DAYAN. 1980. Sorghum Physiology of Yield and Management of Sorghi
diseases, pp. 107-117. In Proc. Symposium. Phil. in Relation to Genetic Improvement. Ann. Re
Phytopathol. Dec. 14-15, 1977, UPLB, College, No. 6, Univ. of Nebr., ARC, USDA, I
Laguna. Rockefeller Foundation, Lincoln, Nebraska.

EDMUNDS, L.K. and N. ZUMMO. 1975. Sorghum TANGONAN, N.G. 1977. Sorghum foliar fun
diseases in the U.S. and their control. Agr. diseases: etiology and index ratings in Southo
Handbook No. 468. Agr. Res. Service. USDA. 46 Mindanao. M.S. Thesis, UPLB, College, Lagu
p. 44p.

PADERES, E.P. 1984. Resistance to tar spot and its
components in some sorghum lines. M.S. Thesis,






piiw roiymup|uI,


EVALUATION OF LOWLAND PC
GERMPLASM AGAINST




I.P. Ona1, T.H. Quimi


Early bl
:tion in t
ins of th
am Dece
eriments
In both
Howeve
aturing 4
s385249
early ma
38-6, CF
ity. The


FATO (SOLANUM SPP.)
EARLY BLIGHT




2, P. Vander Zaag1


ABSTRACT

used by Altenaria solani (Jones & Grout) Sorauer is a constraint in ]
and tropics of Southeast Asia and the Pacific. Experiments were done at two
opines, namely, Mt. Banahaw, Quezon (800 m asl) and Canlubang, Laguna (
986-June 1988). Natural field infection was relied upon as the source of inocu

ns, late maturing clones/progenies were observed to be more resistant tc
e were early maturing clones/progenies that had lower disease incidence than
progenies. Low early blight infection was observed from early maturing pro
na x LT-7), both a medium maturing parental clones and 385410 (MS35.4 x L
progeny. Likewise, disease incidence was low on early maturing clones like 25
27.1, DTO-2 and 1-822. Disease incidence also varied among cultivars with -
iber bulking period of the early maturing susceptible clones/progenies exp
field than resistant clones/progenies. Statistical analyses showed no sign
irly blight infection and canopy duration, maturity or tuber yield.



)UCTION (1986) and Pelletier and Pry (1986)


he late maturing cultivars are generally and Pavek, 1972).
resistant and early maturing clones are Although early primary symptom
nely susceptible. Harrison et al. (1965b) development and secondary spread were
ved that symptom development was initiated simultaneously in early, medium and
rapid and more spores were produced late-maturing potato varieties, symptom
;no thh hp innina of penndarv snread development was more ranid and more


\ I ____ __


"Yo IFM.






Evaluation of Lowland Potato Against Early Blight


to early blight, none was found immune.
The correlation between the length of
the growing period and resistance to early
blight is not absolute such that it would be
possible to shorten the growing period while
still maintaining an adequate level of
resistance (CIP, 1987).
Evaluation of the degree of infection of
A. solani on potato cultivars is usually based
on: percentage defoliation, disease severity,
lesion size and number, percentage leaf area
infected and maturity with the use of certain
scales (Chauhan, 1985; Douglas and Pavek,
1972; Reifschneider et al., 1984). Arzuaga
(1985) recommended the 1 (healthy) to 9
(dead) scale for screening large quantities of
breeding materials. Since the disease
develops at different rates in different
cultivars, Holley et al. (1983) suggested that
cultivar resistance needs to be considered in
the control of potato early blight particularly
in attempts to develop forecast systems and
effective rates of fungicide application.
The objective of this work was to
evaluate true potato seed (TPS) progenies
and advanced germplasm (clones and
cultivars) for the identification of early
maturing genotypes with early blight
resistance.


MATERIALS AND METHODS

The experiments were conducted at the
Regional Germplasm and Training Center
(800 m asl) of the International Potato
Center located in Mt. Banahaw, Quezon and
at the Canlubang Sugar Estate (150 m asl),
Canlubang, Laguna from December 1986 to
June 1988. Natural infection was relied upon
as source of inoculum.
Furadan at the recommended rate was
applied in furrow prior to planting and
insecticides were sprayed in all experiments
during the growing season. Apical shoot
cuttings and tuber seeds were used as
planting materials in Mt. Banahaw and
Canlubang, respectively. The recommended
cultural management practices for the potato
were followed in both locations (Escobar and,
Vander Zaag, 1988; Vander Zaag and
Demagante, 1987).


Screening True Potato Seed (TPS) for Field
Resistance to Early Blight at Mt. Banahaw,
Quezon

Forty-nine (49) TPS families were
transplanted in double row beds (1 x 12 m)
with 27 to 164 seedlings per progeny totalling
5,401 clones, in an unreplicated trial
conducted in Mt. Banahaw. The susceptible
cultivar LT-2 was transplanted around the
perimeter to serve as an early source of
inoculum.
Screening of Advanced Potato Clones
for Field Resistance to Early Blight
In the second trial, heat-tolerant, early
and late maturing potato clones were
evaluated at both locations in an Augmented
Block Design with 2 replications.
At Mt. Banahaw 35 and 30 potato
clones from cuttings were evaluated in 1987
and 1988 trials, respectively. The cuttings
were transplanted in double-row beds (1 x
6m plot) with 40 plants/plot/clone. At
Canlubang, 47 potato cultivars/progenies as
tuber seed were planted in double-row beds
(1.2 x 6.2 m plot) using 40 plants/plot/clone.
A susceptible cultivar LT-2 was
transplanted/planted around the area in both
sites to serve as early source of inoculum.
Data collection included early blight
infection by progeny using a scale of 0-9
where 0 = no blight and 9 = plant dead at
60, 75 and 86 days after transplanting (DAT).
Maturity rating was recorded at 86 DAT with
the use of scale 1-9: 1 = very early, all plants
senescent; 3 = early, majority of plants
senescent; 5 = medium, senescent and green
plants are in similar proportion; 7 = late,
majority of plants green; 9 = very late, all
plants green.
Canopy cover was measured using a
wooden grid (1.0 x 0.6 m) with 100 equally-
sized squares. The number of squares
covered by functional leaves was taken as %
canopy cover. Observation taken at weekly
interval was based on 2
readings/clone/replication using 4
plants/reading. The sum of the weekly
canopy cover readings was defined as canopy
duration.


Jan. & June 1989








Philippine Phytopathology Vol.25


RESULTS AND DISCUSSION


Screening True Potato Seed (TPS) Families
for Field Resistance to Early Blight at Mt.
Banahaw

Early blight development was generally
slow in all TPS progenies even after 75 DAT
(Table 1). Resistance was observed from the
following late maturing TPS progenies:


385416 (India 931 x 575049), 385406 (Murca
x LT-9), 385402 (India 1039 x AVRDC
1287.19), 385401 (India 1035 x AVRDC
1287.19), 385419 (MS42.3 x BL2.9). However,
low early blight infection was also observed
from early maturing progenies such as
385249 (Serrana x LT-7) and 385410 (MS35.4
x LT-9) (Table 1, Fig. 1). A negative but
insignificant correlation (R = 0.55) was


Table 1. Growth of 49 TPS families evaluated for field resistance to early blight at Mt.
Banahaw, Quezon (transplanted March 18, 1987, harvested June 25, 1987).


EB INFECTION"* TOTAL MATU- YIELD
CODE*C R PEDIGREE DAT EB RITY *
CODE* NUMBER 60 75 98 SCORE 86 DAT g plant


india 931 x 575049
Murca x LT-9
1-1039 x AVRDC 1287.19
1-1035 x AVRDC 1287.19
MS-42.3 x BL2.9
7XY.1 xBL2.9
Maine-28 x 377888.8
C83-367 x LT-9
PW-31 x LT-9
Serrana x LT-7
CFK69.1 x AVRDC 1287.19
C83-386 x AVRDC 1287.19
BR63.65 x LT-9
Bzura x LT-9
NY 61 x 377964.5
BR63.74 x LT-9
MS35.4 x LT-9
CFK69.1 x LT-9
Maine 28 x AVRDC 1287.19
C83.119 x LT-9
CFS69.1 x AVRDC 1287.19
CFK69.1 x AVRDC 1287.19
379703.37 x AVRDC 1287.19
389420.1 x AVRDC 1287.19
379676.6 x AVRDC 1287.19
C83.119 x AVRDC 1287.19
377887.25 x LT-9
AVRDC 1287.19 x LT-7
F73008 x AVRDC 1287.19
MS35.4 x AVRDC 1287.19
BL2.2 x LT-9
Montsana X LT-9
Bzura x AVRDC 1287.19
MS35.33 x AVRDC 1287.19
377887.25 x ACRDC 1287.19
C83387 x AVRDC 1287.19
Tollocan x LT-9
7XY.1 x AVRDC 1287.19
C83.115 x 37888.8
579702.6 x AVRDC 1287.19
LR3.2 x AVRDC 1287.19
LT-7 x AVRDC 1287.19
Tollocan x AVRDC 1287.19
BR63.15 x 377888.8
Atzimba x AVRDC 1287.19
BL2.2 x AVRDC 1287.19
575049 x AVRDC 1287.19
Mex75049 x AVRDC 1287.19
Mex750815 x AVRDC 1287.19


385416
385406
385402
385401
385419
385418
385415
385414
385412
385249
385384
385377
385256
385306
385306
385417
385407
385410
385409
385399
385386
385385
385383
385381
385380
385376
385403
385408
385392
385387
385411
385404
385398
385388
385379.
385378
385405
385393
385377
385382
385395
385396
384597
384549
384556
385394
385391
385390
385389


* Code number for the different progenies used in Figs. 3 and 4.
** 0 = no blight 9 = plants dead due to early blight.
*** Maturity scale: 1 = plants complete dead; 9 = all plants green.


Vol. 25


Philippine Phytopathology






Evaluation of Lowland Potato Against Early Blight


20 -






15-






10-


-17



5-







1 3
MATUI



Figure 1. Relationship between mati
families at Mt. Banahaw, Quezon
graph).


observed between early blight infection and
maturity (Fig. 1).
Tuber yield was low with the highest
yield of 225 and 211 g/plant obtained from
385391 (47) and 385249 (10), respectively
(Fig. 2). From the progenies 385249, 385410
(17) and 385391, selections could be made
for clones which are high yielding, resistant
to early blight and early maturing. Very low
correlation was observed between early blight
infection and yield (R = 0.21). Many
susceptible progenies like 384556, 384549,
385397, 385398 and 385376 gave the highest
tuber yield
(Table 1).


*46
S41, 42,43,44


S34,35,36,37,39
.31,33 .30,32,38
21,22,23,24,25.
26,27,28, 29
S18,19,20
*16 *11,12,13,
14.15
.9 '16,17,18
2,3,4,5


RITY


irity and early blight infection of 49 TPS
(see Table 1 for pedigrees of numbers in



Screening of Advanced Potato Clones for
Field Resistance to Early Blight

Early blight lesions appeared on the
lower leaves of all cultivars at 65 DAT (Table
2). The slope (b) of early blight infection was
calculated to show the rate at which the
disease developed among the different
cultivars. The slope was highest on Kufri
Sheetman (.62), Nooksack (.50), 380573.2
(.48), Kufri Leukar (.42) and Serrana (.40)
indicating rapid increase in disease severity.
These cultivars were infected later compared
to other cultivars but when infected with
early blight after 60 DAT, the disease


Jan. & June 1989








Philippine Phytopathology Vol.25


250






200






150






100-






50 -


.44,45


.20.23 *35
.1 *27*30



^3 It:4.22 *37
S.1721
.4 *15 34
.6,8
*16
.24*.31
*10*20
:5 *25
2 .14


-




.42
.40
.441.46
.49
.48


SI I I I
5 10 15 '20)

TOTAL EARLY BLIGHT INFECTION



Figure 2. Relationship between early blight infection and yield of 49 TPS families
at Mt. Banahaw, Quezon (see Table 1 for pedigress of numbers in graph).


developed fast. On the other hand, the most
susceptible cultivars such as LT-7, B71-240.2
and 378711.7 were infected earlier than 60
DAT so that after 65 DAT infection rate was
slow due to limited infectible tissues
remaining. Hence, slope (b) of these
susceptible cultivars was lower. The cultivars
P-7, 38-6, 1-1039, CFK69.1 and 28-7 had the
lowest slope (.06) indicating that rate of
disease development was slow on these
cultivars. The clones P-7, 380584.3 and 1-1085


had low early blight infection in 1987.
However, in 1988 trial, these cultivars were
among the susceptible cultivars (Table 3).
The clones 378597.1 and Ackersegen which
were very susceptible in 1987 trial had the
lowest level of early blight infection in 1988
trial. Clones which appeared very susceptible
in both trials were LT-7, 378711.7, 7XY.1,
Huinkul and 379686.3.
Canopy duration was not significantly
correlated with early blight infection (R = -


Philippine Phytopathology


Vol. 25






Jan. & June 1989 Evaluation of Lowland Potato Against Early Blight 39
Table 2. Early blight infection of 35 potato clones from cuttings screened for field
resistance to early blight at Mt. Banahaw, Quezon (800 m asl) from March 27 to
June 25, 1987.


EARLY BLIGHT INFECTION*** TOTAL SLOPE
CODE** CLONE DAT (b)
60 65 70 75

1 P-7 2 1 1 1 5 -.06
2 38-6 2 2 2 2 8 .06
3 29.8 0 2 3 3 8 .20
4 Lal Pakri 1 2 3 3 9 .14
5 380584.3 0 2 2 5 9 .30
6 1-1085 0 1 3 5 9 .34
7 1-1039 1 2 3 3 9 .06
8 CFK69.1 2 2 2 3 9 .06
9 28-7 2 2 3 4 11 .06
10 27.1 0 2 4 5 11 .34
11 (AVRDC 1287.19 x 1-931).5 2 2 3 4 11 .14
12 K. Leukar* 0 1 4 6 11 .42
13 1-1035 x Atzimba 2 3 3 4 12 .12
14 42-1 1 3 4 5 13 .26
15 R. Burbank 0 4 4 5 13 .30
16 Serrana 0 3 5 5 6 .40
17 24-14 1 4 4 5 14 .24
18 Kufri Jyoti 1 4 4 5 14 .24
19 381064.10 2 2 5 6 15 .30
20 Ackersegen 3 4 4 5 16 .12
21 380573.2* 0 3 6 7 16 .48
22 DTO-2 3 4 5 5 17 .14
23 K. Sheetman 0 2 6 9 17 .62
24 7XY.1* 1 4 5 7 17 .38
25 379686.3 3 4 5 6 18 .20
26 378597.1 2 5 5 7 19 30
27 Monza 3 4 6 6 19 .22
28 Up-to-Date 3 4 5 7 19 .26
29 Nooksack 1 3 7 8 19 .50
30 P-3 3 5 5 7 20 .24
31 (Conchita x K. Jyoti).1 4 5 5 7 20 .12
32. Huinkul 3 5 6 6 20 .20
33 B71.240.2 2 5 6 8 21 .38
34 378711.7 3 6 6 7 22 .24
35 LT-7* 3 7 7 8 25 .30

Mean 1.7 3.5 4.3 5.4
CV (%) 71 34 24 19
LSD (0.05) Rep ns 3.0 2.0 2.0
Unrep ns 3.7 3.1 3.0
Rep/Unrep ns 3.2 2.7 2.5

Not replicated
S Code number for the different clones/progenies used in Figs. 5 to 8.
(0 no blight; 9 = plants dead due to early blight







40 Philippine Phytopathology Vol. 25
Table 3. Early blight infection of 30 potato cultivars from cuttings screened for field
resistance to early blight at Mt. Banahaw, Quezon from February 18 to May 11,
1988.


EARLY BLIGHT INFECTION TOTAL SLOPE
CULTIVAR DAP (b)
63 72 81

Ackersegen 0 2 5 7 .28
388597.1 0 2 5 7 .28
1-1039 3 3 4 10 .06
P. Inta 3 3 4 10 .04
I. Sirena 2 4 5 11 .17
Monserrate 3 4 5 12 .11
379697.13 2 4 6 12 .22
AVRDC 1287.19 2 4 7 13 .28
G-1 3 4 6 13 .17
Capiro 4 4 5 13 .06
Yungay 4 4 5 13 .06
TM-1 3 4 7 14 .22
Muziranzara 3 5 8 16 .28
1-1035 5 5 6 16 .06
Serrana 5 5 6 16 .06
Norchip 5 5 6 16 .06
Mex-32 4 6 9 19 .28
Huinkul 5 6 8 19 .17
381064.7 5 6 8 19 .17
BR112-113 5 6 8 19 .17
P-7 6 6 8 20 .11
7XY.1 6 6 8 20 .11
379693.110 7 6 7 20 0
Up-to-Date 8 7 6 31 .11
379686.3 8 7 6 21 -.11
K Jyoti 6 7 8 21 .11
1-1085 5 7 9 21 .22
380584.3 9 7 6 22 -.17
378711.7 9 8 7 24 -.11
LT-7 8 9 9 26 .06



Mean 4.6 5.2 6.6
LSD (0.05) 5 3 3






auon or Lowlana roTtto Agi


early blight infection had low ca
duration while susceptible clones
Ackersegen and 379686.3 had the hil
canopy duration (Table 4). The clones
Lal Pakri, 1-1039 and 28-7 had low
blight infection with moderately high ca
duration. Under field conditions, pos
interactions between organisms should n
overlooked. Evidence for the intera
between some pests of potato was show
Harrison (1974) and Johnson et al. (198(
this experiment, the presence of I
aggravated defoliation particularly during
later stages of growth. The leaf dai
caused by mites compounded the
canopy duration of most cultivars.
Resistance was observed both in
and late maturing clones. P-7 which ha(
lowest early blight infection is late matu
Early maturing clones like Lal Pakri, 29.9
6, and CFK69.1 also showed slight resist
to the disease. However, there were
maturing clones like P-3, Conchita x ]
Jyoti.1, 378711.7 and 380584.3 that
susceptible. Apparently, susceptibility
potato clones to early blight was
significantly correlated with maturity (
0.16). This result agrees with the reI
by Christ (1986) that
maturing potato clones and proge
respectively, exhibited resistance to
blight. The slope (b) given for each cu]
further indicates that the disease devel
at different rates even among cultivars h;
the same maturity score (Table 4).
example, the cultivars Kufri Sheet
Nooksack and DTO-2 having maturity ,
of 5 had a slope of 0.62, 0.50 and
respectively. Similar result was obtain
Holley et al. (1983). They who observe
potato cultivars with similar maturity
that responded very differently to na
infection by A. solani. Nevertheless, d
relationship between late maturity and
blight resistance can not be ruled out
late maturing varieties are physiology
vigorous for a longer period as compare
early maturing ones. The vigour-depen,
resistance to early blight is related tc
delay in the development of initial infe
sites on late maturing varieties. No vari
were immune to early blight confirm


Ow caril WUl iLuouglas anu raveK, 1y/9
ipy Chauhan, 1985).
ike Tuber yield was not affected by earl
est blight infection (R = 0.09). The clones LT-
'.8, and 378711.7 gave a higher yield of 8.9 an
rly 7.5 t/ha, respectively, despite high earl
1py blight infection while clone 38.6 and L,
ble Pakri which had low early blight infection
be gave low yield with 0.8 and 1.5 t/h;
on respectively (Table 4). This result support
by Livescu et al. (1987) who observed n
In correlation between disease severity
tes (expressed as percentage leaf coverage) an
he yield reduction. In most cases high yield wa
ige obtainedrom susceptible early maturin
art cultivars 'lie LT-7 and 378711.7. These earl
maturing cultivars had a high tuber bulkin
rly rate so as to avoid the disease late in th
he season. Adaptation of the cultivar is another
ng. factor which influenced yield (Vander Zaa
38- and Demagante, 1988). Further, yiel
ice reduction due to early blight depends on th
ite stage of plant growth when the disease
Ifri epidemic occurs. Late occurrence of th
:re disease during the growing season does nc
of cause significant yield reduction
lot (Weingartner, 1981).
S In the 1988 trial, early maturing clone
rts such as Ackersegen and 378597.1 had th
rly lowest level of early blight infection (Tabl
es, 5). The slope showed that disease severit
rly increased at different rates even among
tar cultivars having similar maturity level. This i
'ed exemplified by Ackersegen, Capiro an
ng BR112-113. Maturity, canopy duration an
'or tuber yield were not directly related to earl
in, blight infection. Susceptible clones like TM-]
>re Capiro, BR112-113 and G-1 had a canop
14, duration of 701, 673, 659 and 60'
by respectively which were higher than clone
3 with low early blight infection such a
tes Ackersegen, 378597.1 and 1-1039 (Table 5;
ral Likewise, yield was better from susceptible
ect clones like BR112-113 (18.4 t/ha) an
rly AVRDC 1287.19 (16.1 t/ha).
ice At Canlubang the lower leaves of th

illy plants were the first to be infected by earl
to blight. The disease started approximately a
nt- 53 DAP and increased rapidly after 60 DA]
:he (Table 6). Resistance was observed most
on from late maturing clones. A significant
ies correlation was observed between early bligh
ng susceptibility and early maturity (R = -0.69)


003 ?-7 as-o and C? k


4







Philippine Phytopathology Vol. 25


* CLONE CANOPY MATURITY*** YIELD
DURATION 80 DAP t/ha


P-7 183 7 11.3
38-6 201 5 0.8


0 I-1vbJ 1A 47
7 1-1039 251
8 CFK69.1 208
9 28-7 256
0 27.1 233
1 (AVRDC 1287.19 x 1-931).5 215
2 K. Leukar* 189
3 I-1035 x Atzimba 173
4 42-1 193
5 R. Burbank 181
6 Serrana 242
7 24-14 233
8 K. Jyoti 232
9 381064.10 283
0 Ackersegen 440
.1 380573.2* 131
2 DTO-2 298
3 K. Sheetman 197
4 7XY.1* 70
5 379686.3 417
6 378597.1 342
;7 Monza 339
8 Up-to-Date 211
9 Nooksack 170
0 P-3 357
1 (Conchita x K. Jyoti). 1 229
12 Huinkul 164
3 B71-240.2 140
4 378711.7 228
5 LT-7* 358

lean 244
:V (%) 21
SD (0.05) Rep 117
Unrep 169
Rep/Unrep 144


Not replicated
* Code number for the different clones used in
** Maturity scale: 1 = plants completely senesce
CT ..... .. -


7
7 3.2
5 4.8
5 5.6
5 1.8
7 1.4
5 6.1
7 2.4
3 2.4
5 5.1
5 5.8
3 3.4
5 6.3
6 8.8
5 3.2
7 5.0
5 7.2
5 5.2
5 1.0
7 5.1
7 5.8
7 4.0
5 3.4
5 2.4
7 3.7
7 1.7
5 3.5
7 5.5
7 7.5
5 8.9

5 4.4
24 29
2 2.8
ns 3.5
3 4.1



g. 5 to Fig. 8.
;9 = the tops area are green with







,n nf I nulmand Pntatn Annlne


Table 5. Maturity, canopy duration and yiel
for field resistance to early blight
May 11, 1988.


MATU
CULTIVAR DA
65

Ackersegen 5
378597.1 7
1-1039 5
P. Inta 5
I. Sirena 4
Monserrate 7
37967.13 6
AVRDC 1287.19 7
G-1 6
Capiro 5
Yungay 5
TM-1 7
Muziranzara 7
1-1035 5
Serrana 5
Norchip 3
Mex-32 6
Huinkul 5
381064.7 5
BR112-113 5
P-7 7
7XY.1 5
379693.110 6
Up-to-Date 4
379686.3 7
K. Jyoti 6
1-1085 5
380584.3 6
378711.7 4
LT-7 2



Mean 5.4
LSD (0.05) 2.3


d of 30 potato cultivars from cuttings screened
at Mt. Banahaw, Quezon from February 18 to



RITY CANOPY
P DURATION YIELD
(t/ha)
80

5 535 10.8
5 383 14.7
2 344 6.5
4 263 6.5
4 291 11.8
5 539 0
5 113 10.7
5 433 16.1
3 605 7.2
5 673 10.3
5 287 10.1
4 701 11.2
3 479 14.4
4 372 10.4
5 402 12.0
1 161 4.4
5 599 11.7
2 261 12.4
2 330 12.8
5 659 18.4
3 521 10.4
4 336 14.2
3 453 14.7
4 383 9.5
5 357 11.3
5 369 13.9
3 473 14.4
3 335 12.1
4 266 12.1
3 390 12.9



3.9 410 11.3
ns 160 6


1J







44 Philippine Phytopathology Vol. 25

Table 6. Early blight infection ot 4/ potato clones/ pi ugci:es irom tuoers screereu for field resistance
to early blight in Canlubang, Laguna (150 m asl) from Dec. 27, 1986 to March 24, 1987.



CODE** CLONE/PROGENY EB INFECTION*** TOTAL SLOPE
(#) DAP (b)
53 60 72

1 (Greta x BR63.65) x AVRDC
1287.19).3 1 1 2 4 .06
2 K. Sindhuri 1 1 3 5 .11
3 Cruza 148 2 2 3 7 .06
4 AVRDC 1287.19 x BR63.5 1 2 5 8 .22
5 BR63.65 x R128.6 1 2 5 8 .22
6 F-6 2 2 4 8 .11
7 27.1 2 2 4 8 .11
8 Greta x AVRDC 1287.19 1 2 5 8 .22
9 432.1 2 3 4 9 .10
10 MS35.22 2 3 4 9 .10
11 (AVRDC 1287.19 x BR63.65).2 2 2 5 9 .17
12 1-1039 2 3 4 9 .10
13 AVRDC 1287.19 x Atzimba* 2 3 4 9 .10
14 LT-2 x (BR63.65 x AVRDC 2 3 5 10 .16
1287.19).3 2 3 5 10 .16
15 A140-11* 2 3 5 11 .22
16 DTO-2 4 5 II .15
17 I. Sirena 2 3 5 II .22
18 381064.10 3 3 5 II II
19 381064.12 I 3 7 11 32
20 408.17* 2 4 5 11 15
21 430.7 2 4 (, 12 21
22 BR63.76 3 4 5 12 11)
23 BR63.74 x R128.6 2 4 6 12 .21
24 1-822 2 4 7 13 .26
25 490.2* 3 4 6 13 .16
26 Greta 2 4 7 13 .26
27 P-7 2 4 7 13 .26
28 BR112-113 2 4 7 13 .26
29 381064.3 3 5 (, 13 .16
30 R. Burbank 3 4 7 15 .22
31 Pirola* 3 4 7 14 .22
32 Serrana x DTO-33 3 4 7 14 .22
33 B71-240.2 3 5 0 14 .1
34 Huinkul 2 5 x 15 .31
35 Cosima 2 5 8 15 .31
36 Serrana 3 5 7 15 .21
37 444 3 5 7 15 .21
38 BR63.65 x AVRDC 1287.19 3 7 8 15 .24
39 1-1035 3 6 8 17 .25
40 P-3 4 5 8 17 .22
41 465 3 6 9 18 31
42 378597.1 3 7 8 18 .24
43 LT-5 3 7 9 19 .30
44 Gasore* 3 7 9 19 .30
45 P005-16* 4 7 8 19 .20
46 442* 6 7 9 22 .16
47 S. Feng*


Mean 2.4 3.9 6.1
CV (%) 46 44 32
LSD (0.05) Rep ns ns 4
Unrep 2.6 ns ns
Rep/ Unrep 2.2 3.7 ns


S Unreplicated
Code number for the different clones/progenies used in Fig. 9 to Fig. 12
CIP scale: 0 = no blight; 9 = plants due to blight.







Evaluation of Lowland Potato Against Early Blight


The clone (Greta x BR63.65) x AVRDC
1287.19).3 was the most resistant followed by
Kufri Sindhuri and Cruza 148. In contrast,
the clones S. Feng, 445 and P005-16 were the
most susceptible. P-7, which had the lowest
disease level in 1987 trial in Mt. Banahaw,
was susceptible in the 1988 trial at Mt.
Banahaw and also at this site. According to
Harrison et al. (1965b), other factors such as
temperature, moisture, light intensity and
daylength may play important roles in
overcoming the vigour-dependent plant
resistance to early blight. No early maturing


0
U


~ 15-I





o) 10
F-f


cultivars were observed to be resistant.
However, early maturing clones like 27.1,
DTO-2 and 1-822 had lower early blight
infection as compared to late maturing clones
like BR112-113, P-7 and BR63.76 (Table 6,
Fig. 3). The disease developed at different
rates on different clones and progenies as
indicated by the slope (Table 6). Clones
having similar maturity score like 381064.10,
381064.12 and 408.17 had a slope of 0.22, 0.11
and 0.32, respectively. The slope obtained at
this site was lower than those obtained at Mt.
Banahaw. This may be attributed to a longer


.46 .45
.42.43 .44
.41 .40
.39
35,36,37 .38
.31,32 .34
S .26 .25,28.30 .27
.24 *22 *23
.24 18.19,20,212 2
*16 17






*1
.7 .4,4 .5.6
.3 6

.2
*I


MATURITY


Figure 3. Relationship between maturity and early blight infection of 47
clones/progenies from tubers in Canlubang, Laguna (150 m asl) (see Table 6 for
clones related to numbers in graph).


_


Jan. & June 1989








Philippine Phytopathologv


period of dew formation in Mt. Banahaw
which is the principal moisture source for
early blight epidemic (Rotem and Reichert,
1964). In addition, Mt. Banahaw had mean
minimum/maximum temperature of
17.9/31.10C with 1080 mm of rain in 24 days
during the growing season. Canlubang, on
the other hand, had mean
minimum/maximum temperature of
20.5/290C with 191 mm of rain in 3 days


during the growing season. Bambawale and
Bedi (1982) observed that heavy dew
formation, infrequent rains but longer
periods of >80% relative humidity and
moderate mean temperature (13.6-23.60C)
were favourable to the faster development of
the disease.
Short canopy duration was observed in
most clones even from late maturing
clones/progenies (Table 7). The most


Table 7. Canopy duration, maturity and yield of 47 potato clones/progenies from tubers screened for
field resistance to early blight in Canlubang, Laguna from Dec. 27, 1986 to March 24,1987.


CODE** CLONE/PROGENY CANOPY MATURITY YIELD
(#) DURATION 80 DAP t/ha


(Greta x BR63.65) x
AVRDC 1287.19).3
K. Sindhuri
Cruza 148
AVRDC 1287.19 x
BR63.65 x R128.6


6 F-6
7 V-2
8 Greta x AVRDC
9 432.1
10 MS35.22
11 (AVRDC 1287.1'
12 1-1039
13 AVRDC 1287.19
14 LT-2 x (BR63.65
15 A140-11*
16 DTO-2
17 I. Sircna
18 3810164.10
19 381164.12
20 408.17'
21 430.7
22 BR63.76
23 BR63.74 x R 12.(,
24 1-822
25 490.2"
26 Grcia
27 P-7
28 BRII2 113
29 381064.3
30 R. Burbank
31 Pirola*
32 Serrana x DTO-32
33 B71-240.2
34 Huinkul
35 Cosima
36 Serrana
37 444
38 BR63.65 x AVRD
39 1-1035
40 P-3
41 465
42 378597.1
43 LT-5
44 Gasore'
45 P005-16"
46 442'
47 S. Feng*

Mean
CV (%)
LSD (0.05) Rep
Unrcp
Rep/Unrep


tX
xi

























C


266 7 17.3
414 6 18.0
495 7 9.9
BR63.5 229 6 30.4
436 7 20.7
424 7 19.3
265 5 17.0
.7.19 360 6 15.2
336 6 23.7
401 7 23.2
BR63.65).2 377 7 21.9
344 6 15.4
4Atimba* 227 6 11.8
AVRDC 1287.19).3 294 6 14.7
344 6 12.9
2(,7 4 21.1
253 7 20.7
354 6 20.3
341 6 15.9
224 6 15.8
37t. 6 14.9
31s 7 21.6
42?5 21.5
241 4 20.5
2741 6 25.0
27( 5 2'.9
440 7 20.7
3,1I I' 20.3
21S s 4 18.3
274 4 173
354 4 19f4
313 4 1S.3
48 4 16.9
28, 5 4 14.5
28,, 4 23.1
311' 4 23.0
237( 4 16.5
1287.19 289 4.5
266< 4 I'.8
217 6 2011.
183 4 15.
217 3 1 I
193 3 I.1
148 4 7.4
25i0 5 10.6
271 4 A 7
120 3 5,

299 5 17.7
19 20 31
118 2 as
169 16.5
144 14.2


Vol. 25


( Nrd N bun 4e, for tin different cloncn. rtgnnle- u-ed in V W Flitg 12.
Matuilly scl,, I .- plants completely aelseeint;9 the 1ftc amRlignn uith fIi1nt


_ __ _ __








JiUl. a JUl uw I1AN Fa-VIuvMUII u L.VIUFIU rvU

resistant clone (Greta x BR63.65) x AVRDC
1287.19).3 had only a canopy duration value
of 266 units while susceptible cultivars such
as P-7, Pirola and Serrana had a canopy
duration of 440, 354 and 319, respectively.
Statistical analysis showed a negative
correlation between early blight infection and
canopy duration (R = -0.55). Nonetheless,
canopy duration of 414, 495, 436 and 424 was
observed from Kufri Sindhuri, Cruza 148,
BR63.65 x R128.6 and F-6, respectively,
which had low early blight infection (Fig. 4).
Although not significantly correlated (R
= -0.18), yield was better from clones that
have low early blight infection. Yield of more
than 20 t/ha was obtained from
progenies/clones which had low early blight
infection such as AVRDC 1287.19 x BR63.5,
BR63.65 x R128.6, 432.1, MS35-22 and
(AVRDC 1287.19 x BR63.65).2. The most



500- .






S12.*
4 300. "





00





200-











I 2 3 4
EARLY BLI


Figure 4. Relationship between early b
clones/progenies from tubers in Ca


ao isgnalm rcay algr1 47

susceptible clones: Gasore, P005-16, 442 and
S. Feng gave the lowest yield with 7.4, 10.6,
5.6 and 4.7 t/ha, respectively (Tabe 7). In a
hot environment like Canlubang and under
field conditions, yield of potatoes is
influenced by environmental factors such as
solar radiation, temperature and photoperiod
(Demagante and Vander Zaag, 1988). The
overriding effect of any of these factors might
have masked the effect of early blight
infection on yld. This was further indicated
by a positive insignificant correlation between
canopy duration and yield.
In conclusion tuber yield of the different
TPS progenies and advanced clones was not
affected by early blight infection. In most
cases, the susceptible clones gave the highest
tuber yield due to their high tuber bulking
rate.












*. *7
o.I.
X.2
13 1 *


,14 .34 .O 3

















5 6 7 8 9
T INFECTION N
.24 .41
-41

.44
.4y








HT INFECrION I ON


eight infection and canopy duration of 47
lubang, Laguna (see Table 6 for clones


--~ ----~ML C-IY^- ^I url--~ CI-L~- I--I---~_-)~~ r_L-









48 Philippine PI


LITERATURE CITED

ARZUAGA, J. 1985. Comparison by several methods
of evaluating to Alternaria solani (Ellis and
Martin) Sorauer. Cultivos Tropicales 7: 141-146.

BAMBAWALE, O.M. and P.S. BEDI. 1982.
Epidemiology of early blight in the Punjab.
Indian Phytopathol. 35: 574-584.

CHAUHAN, M.S. 1985. Reaction of potato varieties
and hybrids to early blight disease. Haryana
Agric. Univ. J. Res. 15(4): 465-6.

CHRIST, B.J. 1986. Early blight susceptibility, of
potatoes as affected by early maturity and late
blight resistance. Phytopathology 76: 651.

CIP. 1987. Annual Report. 210 pp. Lima, Peru.

DEMAGANTE, A.L. and P. VANDER ZAAG. 1988.
The response of potato (Solanum spp.) to
photoperiod and light intensity under high
temperatures. Potato Res. 31: 73-83.

DOUGLAS, D.R. and J.J. PAVEK. 1972. Screening
potatoes for field resistance to early blight. Am.
Potato J. 49: 1-6.

EASTON, G.D. and M.E. NAGLE. 1985. Lack of
economic benefits by fungicides applied center-
point irrigation systems for control of Alternaria
solani on potato plant. Pit. Dis. 69: 152-153.

ESCOBAR, V. and P. VANDER ZAAG. 1988. Field
performance of potato (Solanum spp.) cuttings in
the warm tropics: Influence of plant system,
hilling, density and pruning. Am. Potato J. 65: 1-
10.

HARRISON, M.D. 1974. Interactions between foliar
sprays and soil fumigation in the yield response
of potatoes. Phytopathology 64: 860-864.

HARRISON, M.D., C.H. LIVINGTON and N.
OSHIMA. 1965a. Control of potato early blight


topathology Vol. 25


in Colorado. I. Fungicidal spray schedules 'in
relation to the epidemiology of the disease. Am.
Potato J. 43: 319-327.

HARRISON, M,D., C.H. LIVINGTON and N.
OSHIMA. 1965b. Epidemiology of potato early
blight in Colorado. I. Initial infection, disease
development and the influence of environmental
factors. Am. Potato J. 42: 279-291.

HOLLEY, J.D., R. HALL an G. HOSTRA. 1983.
Identification of rate reducing resistance to early
blight of potato. Can. J. Pit. Pathol. 5: 111-114.

JOHNSON, K.B., C.B. RADCLIFFE and P.S. TENG.
1986. Effects of interacting populations of
Alternaria solani, Verticillium dahliae and the
potato leafhopper (Empoasca fabae) on potato
yield. Phytopathology 76: 1046-1052.

PELLETIER, J.R. and N.E. FRY. 1986. Age-related
changes in receptivity of potato leaves to
Alternaria solani in 3 potato cultivars.
Phytopathology 76: 657.

ROTEM, J. and I. REICHERT. 1964. Dew A
principal moisture factor enabling early blight
epidemics in a semi-arid region of Israel. Pit. Dis.
Rept. 48: 211-215.

VANDER ZAAG, P. and A.L. DEMAGANTE. 1987.
Potato (Solanum spp.) in an isohyperthermic
environment. I. Agronomic management. Field
Crops Res. 17: 199-217.

VANDER ZAAG, P. and A.L. DEMAGANTE. 1988.
Potato (Solanum spp.) in an isohyperthermic
environment. III. Evaluation of clones. Field
Crops Res. 19: 167-181.

WEINGARTNER, D.P. 1981. In: Compendium of
Potato Diseases. W.J. Hooker (ed.). The Amer.
Phytopathol. Soc. USA. 125 p.














INTEGRATED CONTROL OF
CAUSED BY PLASMOD

L.M. Villanueva a

Professor and Researcn Assistant, respe
Benguet State University, La Trinidad, Bet

ABST
The treatments Paecilomyces 'ilacinus ale
tons/ha); Benlate 50 WP (0.5 kg ai/ha); combination
P. lilacinus + Benlate and the integration
determine their efficacy in controlling club root q
Untreated plants were provided to serve as control
area at the Benguet State University Experiment S
arranged in a randomized complete block design w
Based on club root severity rating, combine
followed by lime alone, integration of P. lilacir
percentage disease control of 70.3, 58.8, 57.5 and
was comparable to Benlate 50WP alone. The con
percentage control of 30.0. The disease rating of th
of the untreated plants. In terms of growth depress
among the treatments.


INTRODUCTION

Cabbage, Brassica oleracea L.. (Capitata
.oup), locally known as "repollo" in the
hilippines, is one of the widely- grown crops
i Benguet and Mt. Province. In Benguet
,one around 2,000 hectares are planted
nmually to this crop. However, inspite of the
ide area planted to it, the present
reduction is not sufficient to meet the
creasing demand for the crop. Maximum
reduction is often not attained due to the
Ltack of pests and diseases.
Before 1986, club root of cabbage
used by Plasmodiophora brassicae
Toronin was of minor importance in the
ighlands. Recently, Tad-awan and Villanueva
1986) conducted a survey of club root in
rucifer growing areas in Benguet. Three
municipalities, Atok, Buguias and La Trinidad
rere found to have high incidence of the
disease. All the barangays surveyed in Atok
ad 100% disease incidence. Other places
having the same incidence of club root
icluded the lower Natubleng area in


:LUB ROOT OF CRUCIFERS
OPHORA BRASSICAE

id G.B. Binaliw

tively, Department of Crop Protection,
guet.

ACT

ke (2.8 x 107 spores/ml); agricultural lime (4
ofP. lilacinus + lime; Benlate + lime;
P.lilacinus, lime and Benlate, were evaluated to
crucifers caused by Plasmodiopbora brassicae.
The study was conducted in a naturally -infested
ition, La Trinidad, Benguet. The treatments were
h three replications.
on of P. lilacinus + lime was the most effective
!s, lime and Benlate, and Benlate + lime with
i.3, respectively. The efficacy ofP. lilacinus alone
nationn of fungus and Benlate gave the lowest
said treatment was significantly lower than those
)n, however, the same trend of efficacy was noted



Buguias and in Balili (North), La Trinidad.
Apart from the places surveyed, other areas
where the disease occur include Bokkig,
Pasdong, Bosleng and Pitdao of Atok and
Balili, Mankayan.
There are only few methods to
effectively control the disease. Under field
conditions, Brassicol (PCNB) applied at 70 kg
ai/ha followed closely by burnt lime
effectively controlled club root disease as
shown by lesser crop growth depression,
club root severity and higher yield (Tad-awan
.and Villanueva, 1986). Brassicol is now
withdrawn from the market; hence only
Benlate (Benomyl) and lime were left for
club root control. Resistance to the disease
may not be present in the locally grown
cultivars. Sagudan and Villanueva (1989)
studied the reaction of eleven varieties of
head cabbage against the disease. Out of the
eleven varieties tested none showed
resistance to the disease. In the same study.
Paecilomyces lilacinus applied before
transplanting was as effective as Benlate SO
WP.








Lt present, chemicals other than Benlate
actively control the diseases are not
ble. Hence, this study was conducted to
Lte the efficacy of P. lilacinus, lime and
te 50 WP when applied alone or in
nation in controlling club root of
ge. This was done at the Benguet State
rsity (BSU), La Trinidad, Benguet from
aber, 1988 to March, 1989.

MATERIALS AND METHODS

eeds of cabbage var. Scorpio were
in a well prepared seeed bed. After a
1, they were transplanted in an area
Ily infested with P. brassicae. The area
prepared thoroughly and divided into
blocks. Each block was further
ided into eight plots with a dimension
10 m. The different treatments were
d before transplanting. Agricultural
:alcium carbonate) was mixed into the
ree weeks before transplanting at the
f 4 tons/ha. P. lilacinus cultured in
il agar was applied at a spore
itration of 2.8 x 107/ ml, using 2
.Benlate 50 WP, however, was diff
led into the soil at the rate of 0.5 kg gro
For the combination treatments with P. Plai
us, Benlate was sprayed into the cor
using th2 above rate. the
chicken dung was applied into the soil a sigi
before transplanting at the rate of 4 Bet
a. Split application of complete lim
er (14-14-14) at the rate of 450 kg/ha Mo
Iso done. Half of the amount was cat
I before transplanting the other half wit
administered during hilling-up (three alo.
after transplanting). All the proper Bet
tural practices necessary for cabbage mo
:tion were employed, viz, watering, will
ition, weeding and control of insects unt
leases.
ie different treatments were laid out in con
lomized complete block design with mo:
replications. The different parameters not
) evaluate the efficacy of the different aloi
nts were as follows: lila
coil
Rate of Growth Depression. The per
plants were evaluated on the resI
symptoms of stunting, wilting and con
plant death, all bound as growth con


_____^:_I 1~~ -^+^rr r~rt F-\r


depression. Iie Irat useu r
evaluation follows that of Anderson
(1976) with some modifications: 1 -
Normal aerial growth; 2 Slight
growth depression; 3 Moderate
growth depression with some
wilting; 4 Severe plant inhibition
and plant wilting and; 5 Plant dead.
Rate of Club Root Severity. The
plants were uprooted and the
severity of clubbing was rated
following the club root index of
Anderson (1976) with some
modifications: 1 Normal roots; 2 -
Minor lateral root clubbing with 0.5
cm diameter; 3 -Major lateral root
clubbing at 1-2 cm diameter; 4 -
Moderate clubbing on tap root; 5 -
Severe clubbing on tap root; and 6-
Roots decaying(ed) due to advanced
infection with plant dead.
Yield of the plant (tons/ha)

RESULTS AND DISCUSSION

Table 1 summarizes the effect of the
*ent treatments on club root infection,
th depression and yield of cabbage.
s grown in plots treated with the
nationn of P. lilacinus and lime showed
least growth depression, but was not
Scantly different with those treated with
ate alone, combination of Benlate and
and the integration of all the treatments.
rate growth depression was noted on
age transplanted in plots inoculated
P. lilacinus alone and agricultural lnme
:. The combination of P. lilacinus and
ite gave rise to plants that showed
!rate growth depression with some
ig and were comparable to the
:ated plants.
In terms of club root severity, the
nationn of P. lilacinus and lime was the
effective with 70.336 control, but did
liffer significantly, with agricultural lime
, the treatment that integrated P.
nus, Benlate and lime and the
nationn of Benlate and lime with
entage control of 58.83, 57.50 and 56.33,
actively P. lilacinus alone, however was
arable to Benlate alone and the


- -- -1








0ie 1. tnect or me amerem treatmemr


atment Club root
infection


cilomyces lilacinus
alone 3.6 bc

cultural
alone 2.5 cd

late 50 WP
ne 3.6 bc

lacinus -
P1.8 d 70.3

late 50 WP +
ie 2.6 cd

lacinus +
late 50 WP 4.2 b

lacinus +
e + Benlate 2.6 cd

created 6.0 a



Data are means of 3 replicates. Mans followed by 1
Test (DMRT).


on ciUD root inTection, grwm depression an


% Growth
Control Depression



39.8 2.9 bc


58.8 2.9 bc


40.7 2.2 cd


2.1 d 20.5 a


56.3 2.4 bcd


30.0 3.1 ab


57.5 2.5 bcd

3.7 a



milar letters are not significantly different at 5% level








hilippin. Ptiytopathology Vol.25


)ots of the untreated plants showed severe
ebbing and were already decayed due to
Ivanced infection.
A substantial increase in yield was noted
the combination of P. lilacinus and lime
7.32%) followed closely with agricultural
ne alone, integration of P. lilacinus,
latee and lime with percentage yield
crease of 79.56, 68.61 and 62.77,
spectively. However, the yield of the other
:atments were comparable to the untreated
ants. Evidently, the yield obtained in the
esent investigation was very low compared
the yield potential of cabbage var. Scorpio.
is is attributed to very high diamond
ckmoth (DBM) infestation. We were not
le to effectively control DBM even using
veral insecticides. Likewise, high relative
imidity and rainfall at the experimental site
ata not shown) induced faster growth and
velopment of the fungal pathogen. Dobson
'83) claimed that club root infection in
eir experiment was induced by repeated
.tering 7 to 10 days after seeding.
Generally, treatments with agricultural
te gave good results in terms of club root
rerity, growth depression and yield. The
ppressant effect of lime results from the
sing of the pH to 7 or higher (Anderson,
76; Dobson, 1983; Tate, 1980) wherein
der such condition, hypnospores of P.
assicae fail to germinate especially when
: soil pH is higher than 7.2. In the same
edition, myxamoebae of the pathogen do
t survive (Horsfall and Cowling, 1980). In
iwan, lime or calcium carbonate has also
en shown to effectively control club root
crucifers (Hsieh and Yang, 1984).
The efficacy of P. lilacinus alone was
parable to Benlate and the combination
the fungus and Benlate confirming our
hlier results (Sagudan and Villanueva,
19). Dyachina and Chaban (1981),
ever, reported that Benomyl (0.2%) was
most effective against P. brassicae on
)bage seedlings followed by Zineb (0.5%)
1 Daconil (0.2%). Although not
nificantly different, a slight reduction in
cacy was noted when the fungus was
nbined with Benlate. This could be
ibuted to the fact that during spraying
ne of the fungicide droplets might have


affected the biological control agent, or the
two might have some antagonistic effects. It is
also interesting to note that application of P.
lilacinus greatly improved the efficacy of
lime in controlling club root. The mechanism
by which the fungus controls the pathogen is
still unknown.
The combination of P. lilacinus and
lime could be a good substitute for soil
fungicides. Soil fumigation is very effective for
controlling root pathogens but it is
expensive, impractical and creates problems
like environmental contamination. Also, since
P. lilacinus could be easily grown in coconut
water and lime is cheaper than fungicides,
the prospect of using these locally available
materials for the control of club root disease
of cabbage deserves careful consideration.


LITERATURE CITED


ANDERSON, W.C. 1976. Club root control in crucifers
with hydrated lime and PCNB. Plant Dis.
Reptr. 60: 561-565.

DYACHINA, Z.S. and V.S. CHABAN. 1981. Comparative
effectiveness of new fungicides against club
root and black leg of cabbage on peat soil.
Rev. Pit. Pathol. 60: 97.
DOBSON, R.L. 1983. Effects of lime, particle size and
distribution and fertilizer formulation on club
root diseases caused by Plasmodiopbora
brassicae. Plant Dis. Reptr. 67: 50-52.

HORSFALL, J.G. and E.B. COWLING. 1980. Plant
Diseases: An Advanced Treatise. Vol. 5.
Academic Press, Inc. (London) Ltd: p. 32.
HSIEAH, W.H. and H. YANG. 1984. The incidence of
club root and its control in Taiwan. In: Soil-
Borne Crop Diseases in Asia. Food and
Fertilizer Technology Center for the Asian
and Pacific Region. Book Series No. 26, Taipe,
Taiwan.

SAGUDAN, C.B. and L.M. VILLANUEVA. 1989. Control of
club root of cabbage. Undergraduate Thesis.
Benguet State University La Trinidad,
Benguet. 35 pp.
TAD-AWAN., B.S. and L.M. VILLANUEVA. 1986. Survey,
pathogenicicy and chemical control of club
root on Chinese cabbage. M.S. Thesis.
Benguet State University, La Trinidad,
Benguet. 74 pp.

TATE, K.G. 1980. Club root control in cauliflower and
brussel sprout with benzimidazole,
transplanting drenches, and soil


hlllppine Phytopathology


Vol. 25






Philippine Phytol


PHILIPPINE PHYTOPATI

ABSTRACTS OF PAPERS PRE
CONVENTION OF THE PES1
PHILIPPINES, BAGU



Control of Tomato Seedling Damping-off
Caused by Sclerotium rolfsii Sace, with Ash,
Microbial Antagonist and Animal Manure.
B.K. Batsa and E.P. Paderes. Central Luzon
State University (CLSU)


A series of laboratory, greenhouse anc
field experiments was conducted tc
determine the effect of ash, Aspergillus niger
and animal manure on the mycelial growth
sclerotial body formation, disease
development of Sclerotium rolfsii and theii
effect on the yield on tomato.
In vitro test using modified disc bioassa3
technique showed that wood ash, A. niger and
animal manure from goat, buffalo and
chicken significantly reduced the mycelial
growth and sclerotial body formation from 9%
to 31%. Sclerotial bodies mean diameter was
suppressed from 42 to 32%.
In artificially inoculated tomato plants
in greenhouse, A. niger and animal manure
significantly reduced disease damping-off
from 96 to 15%. Chicken manure was
comp-:able to PCNB when applied at
10g/90g of soil. Chicken manure treated so;i
had the lowest viable sclerotia of 4%, in
contrast to 69.83% viability in PCNB treated
soil.
Utilization of ash, animal manure and
A. niger in field experiment also gave a highly
significantt disease reduction from 100 to
61%. Chicken manure applied at lOt/ha gave
a 100% disease suppression. Yield was
significantly high in plots treated with chicken
manure.


)LOGICAL SOCIETY, INC.

ENlTED DURING THE ANNUAL
CONTROL COUNCIL OF THE
) CITY, MAY 9-12, 1989



Epidemiology of Papaya Ringspot in the
Philippines. P.M. Magdalita, O.S. Opina
R.R.C. Espino, and V.N. Villegas. Institute ol
Plant Breeding, University of the Philippines
at Los Banos (IPB, UPLB)


Papaya ringspot (PRS) exhibited a foca
pattern of spread. Disease gradient flattened
from 5.0m to 20.0m radius from the initial
inoculum source but tend to decrease a
increasing distance. A plot between disease
incidence and distance showed a shallow
curve indicating long distance dispersal of the
virus. The relationship of incidence an
distance was poorly explained by Gregory'
and Kiyosawa and Shiyomi's models but
second-degree polynomial model bette:
explained such relationship. The relationship
was defined as Y = 4.72 + 3.52X 0.72 X
Based on this model, the isolation distance o
PRS as incidence approaches zero wa:
estimated to be 1230m from the inoculun
source.
A sigmoid curve, typical of a polycyclii
disease was depicted by papaya ringspot
Disease progression with time was accurately
described by the logistic growth model. The
relationship of the transformed disease
proportion (Y) relative to time (X)
according to this model was defined as Y =
11.84 + 0.74X.
The infection rate of PRS was highl)
variable within the entire duration of the






no Phytopathology


lemic within a short period.
Infection rate was not correlated with E
number of trapped aphid vectors. C
ather elements together with aphid
ulation sample were similarly not- ii
related with the rate of s,
ction.Integration of relative isolation, o
d sanitation and vector control reduced s
infection rate by three-fold and delayed
onset of epidemic by as much as 15 weeks e
pared to the control. However, chemical v
trol of vectors was ineffective in 8
pressing the spread of papaya ringspot. 7
under Plank's sanitation ratio was d
:ulated as 0.16. n
d
ti
grated Control of Clubroot of Crucifers s
used by Plasmodiophora brassicae. L.M. s
lanueva and G.B. Binaliw. Benguet State a
diversity (BSU).
d
sl
Different treatments namely" r
cilomyces lilacinus alone (2.8 x 10 p
res/ml), agricultural lime (4 tons/ha), si
late 50 WP (1g/liter water), combination a
P. lilacinus + lime, Benlate + lime, P. r;
:inus + Benlate and the integration of P. yi
:inus, lime and Benlate were evaluated to
:rmine their efficacy in controlling tr
>root of crucifers. Untreated plants were
vided to serve as control. The study was
ducted in a naturally-infected area at M
J Experiment Station, La Trinidad, C
guet. The treatments were arranged in a w
idomized Complete Block Design with pi
e replications. M
Based on clubroot severity rating, U
bination of P. lilacinus + lime was the
t effective followed closely by lime alone,
gration of P. lilacinus + lime + Benlate,
Benlate + lime with percentage disease di
rol of 70.3, 58.8, 57.5 and 56.3, m
ectively. The efficacy of P. lilacinus fil
.e, on the other hand, was comparable to di
late 50 WP. Among 'the Adifferent di
tments, combination of the fungus and fic
late gave the lowest percentage disease in
rol of 30.0.
However, plants treated with this di
bination were less severely infected than re


Yield Loss in Rice Due to Sheath Blight at
Terent Growth Stages. F.L. Nuque, S.B.
Ivero, Jr and P.S. Teng (IRRI)
Two experiments on the effect of
iculating rice plants with Rhizoctonia
ani at different growth stages on yield loss
rice were conducted in 1987 wet and dry
sons.
Results of the 1987 wet season
)eriment showed that disease incidence
ied from 4.1 to 86.3%; intensity from 2 to
8%, and relative lesion length from 5.2 to
5%. Percentage relative lesion length
feared significantly among treatments but
t among replications. Computed yield from
ferent treatments ranged from 2.2 to 3.1
is/ha. The mean yield of the control plot
-ayed weekly with iprodione differed
nificantly with those of the plots inoculated
different growth stages.
Dry season (1988) results revealed that
ease intensity varied from 50 to 100%;
erity from 3.0 to 100%, and percentage
native lesion length from 0 to 70.1%.
rcentage relative lesion length differed
nificantly among treatment means but not
ong replications. Calculated mean yield
ged from 3.3 to 4.2 tons/ha. The mean
Id of the control plots differed significantly
h those of the other inoculation
itments.


delling Yield Loss in Peanut Due to
cospora Leafspots [Cercospora
:hidicola Hori and Cercosporidium
onatum (Berk and Curt.) Deighton].
). Ebuenga and O.S. Opina (NCPC,
LB)


The critical point, area under the
ase progress curve (AUDPC) and
tiple point models were evaluated and
d to the peanut leafspot yield loss data
ing the 1988 cropping seasons. Diverse
ase progress curves were generated in the
Is by varying severity levels and
:ulation time using fungicidal sprays.
Correlation analysis of yield loss and
ase severities in various growth stages
Walked that the most critical stage for






Ak.4r4. -f D0.


planting (DAP) which is approximately,
R7 beginning maturity stage. The
model for explaining the relation
between yield loss and disease severity
proportion) was a multiple point m
between yield loss (Y) and disease sever
at 50 DAP (X50), 60 DAP (X60) an
DAP (X70):
Y = .0638 52.6753 X50 5.1211 X(
4.5433 X70
r = .85, s.e. = .072
This model was better than the cri
point and AUDPC models in term!
coefficient of determination, standard e
and residual analysis. In addition, the m
is practical for yield loss estimation in
field since the growth stages included in
model are highly apparent
distinguishable.

Association of Some Cultural Practices
Physical Factors on Rice Diseases
Bulacan, Pampanga, and Nueva Ecija.
Elazegui, R.S. Dy, A.J.P. Magnaye, and
Teng (IRRI)


Associations among diseases, s
cultural practices and physical factors
determined from disease surveys condu
on 90 farmers' fields in the three provi
during 1987-'88 wet season as part of I
Integrated Pest Survey. In all observat
diseases prevailed more in Nueva Ecij
IR64 variety, in irrigated rice culture typ
transplanted method, and in fields with
soil with water. At 30 days after plan
bacterial leaf streak incidence was high
Nueva Ecija in "Rio" variety, in wet-see
method, and in fields with soft soil
water. Bacterial leaf streak occurred onl
irrigated fields. High narrow brown
incidence was not affected by province,
culture type, and planting method
observation at 60 days after planting. Ne3
narrow brown spot was bacterial blight w
was high in Nueva Ecija, in irrigated, an
transplanted fields. Rainfed fields
significantly higher sheath blight incidc
than irrigated fields. During observation
harvest, narrow brown spot incidence
Pampanga was significantly higher thai


, the Bulacan. Severity at 60-day observation
best highest in bacterial blight from a Nueva I
ship field which was at milk stage, transplant
S(in IR64, irrigated, and had soft soil with w,
odel Although tungro was not observed in
*ities field, tungro virus particles were m,
d 70 detected, through serology, in IR42 an
reproductive growth stages of the c
60 + Planting date and date of visit did not a
diseases in all observations. No disease
considered serious during this season.
itical
s of Retrieval System for Rice Disease Su
error Data. R.S. Dy, AJ.P. Magnaye,
odel Elazegui, and P.S. Teng (IRRI)
the
the
and Disease data from ninety farmers' I
in Bulacan, Pampanga, and Nueva ]
during 1987-'88 wet season were collect<
and part of the IRRI Integrated Pest Survey.
in data were stored in a microcomputer-i
FA. system developed through Rbase V
P.S. retrieval system was designed to access,
encoded and edited data and the summal
data.through built-in application procec
implemented on Foxbase + /Dbase II
ome Data retrieval is facilitated by mean
were menus and formatted screens.
Lcted
inces Influence of Nitrogen, Rice Straw
RRI Bacterization on the Population
ions, Physiological Activity of Microorganisn
a, in Lowland Soil. E.D. Imolehin, T.W. Mew
e, in T.S. Teng (IRRI)
soft
ting, In a greenhouse experiment, nitr(
:r in (N), source rate and rice straw but
eded bacterization, had significant effects on
with population of bacteria in !he rice rhizosp.
ly in under flooded condition. Bacterial popular
spot ranged between 11 to 31; 13 to 40 and 5 t
rice x 10 for soils receiving ammonium supl
in at the rate of 60, 120 and 180 kg N
xt to respectively. With urea at the same i
which bacteria numbers were between 8 to 22;
d in 16 and 13 to 35 x 104, while those recoi
had for calcium nitrate ranged between 10 to
ence 11 to 28 and 13 to 28 x 104, respectil
n at Aspergillus flavus was the most abun<
in fungus (6-21 x 104) in the rice rhizosph








-4 x 10T4 and Fusarium spp. (0-2 x 10). s
lere were differences between N source r
th the highest fungal population occurring c
soil treated with urea, followed by calcium i
:rate and ammonium sulphate, respectively, i
source, N rate, and straw application had
;nificant effects on microbial activities as I
termined by percent carbon dioxide (CO2) I
olved. The highest CO2 evolved was I
trained at 0 kg N/ha; 1.32 1.9% at 120 kg
/ha and 0.88 1.25 at 180 kg N/ha. Straw
plicationn tends to increase CO2 evolution.
1
ming of and Synchronous Planting for 7
ce Tungro Disease Control: The Indonesia I
experience. R.C. Cabunagan, H. Hibino and I
W. Mew (IRRI); S. Sama and A. t
asanuddin (MORIF, Indonesia) i


In Indonesia, tungro (called locally I
enyakit habang') caused serious damage in
of 27 provinces in 1984 and 16 provinces in I
85. Tungro incidence was at low level in
iuth Sulawesi during this period, where a 1
ngro management scheme developed by
ORIF had been practiced since 1983. The
heme involves timing of planting, synchrony
planting, variety rotation and use of I
secticides.
Studies conducted by MORIF between
74-1983 indicated a fairly uniform
actuation and green leafhopper (GLH)
nsity and tungro incidence year to year in
>uth Sulawesi. The annual fluctuation
Ittern generally has two peaks, one each in
e wet and dry seasons.
The recommended planting time for the i
-t season crop is at the peak of rainfall !
ien GLH population is very low, and the
y season crop is about 6-7 months later.
according to the maturity of the varieties to 1
planted, planting date is also adjusted to
incide the peak time of GLH density after
e late tillering stage or flowering stage.
ost critical period for tungro infection is
e first 30-45 DAT, plants after this critical
ige are less susceptible and suffered less
image when infected.
In 1985 and 1986, 90% or more rice
:lds were planted .following the'
commended schedule. Thus, rice


ichrony with definite fallow periods of 1-2
). between crops. With this practice,
mbined with variety rotation and use of
tecticides tungro disease has been managed
the region.

management of Potato Late Blight Using
domil 58 WP. L.M. Villanueva.
*nguet State University (BSU)


Field trials were conducted from 1986 to
88 at Benguet State University, La
inidad, Benguet and Bucao (Km. 44) Atok,
:nguet to determine the best time of
domil MZ application and best sequential
satment in controlling potato late blight
sectionn and consequently assess their
fects on yield. Granola, a susceptible potato
riety was used in Randomized Complete
ock Design with four replications.
Generally, application of RIDOMIL
Z 14 days after emergence or early in the
owing season followed by contact
ngicides namely, Dithane M-45, Curzate-M
d Daconil 75 WP effectively controlled the
ease. However, these did not significantly
fer with those sprayed first with contact
ngicides followed by RIDOMIL MZ.
apparently, sequential treatments were
mparable to if not better than spraying the
andard fungicides alone. Although not
;nificantly different, sequential treatment
th Daconil 75 WP gave numerically higher
rcentage control than sequential spraying
th Dithane M-45 and Curzate M.
In terms of yield, however, a substantial
:rease was noted in most of the sequential
:atments compared with the application of
e standard fungicides alone except Daconil
WP. Untreated plants, however, gave the
west mean yield.

Tect of Weed Control on Crop Growth and
development of Blast and Sheath Blight
disease in Upland Rice. E.M. Kuerschner,
.O. Silla and J.M. Bonman (IRRI)


Weeds and diseases are two of the key
anstraints to increased upland rice yield and
eld stability. The effects of weed control on


4






Abtracts of Paper


blast (Bl) and sheath blight (S
development were studied in fic
experiments at Sto. Tomas, Batangas in 19
and 1988. Diseases and crop growth we
monitored in treatments either kept wec
free or hand-weeded twice. In 1987 t'
improved upland rice varieties C22 and Ul
Ri5 were used, while in 1988 only C22 v
planted. In both years, leaf BI severity (
DLA) and collar BI infection (% infectic
observed in C22 were significantly higher
the weed-free plots. BI infection was lower
variety UPL Ri5 compared to C22 and we
control did not affect Bl in UPL Ri5.
infection was observed only in 1987. At
DAS both varieties showed significantly me
SB in the weed-free treatment. Can<
height (cm) and crop cover (%) w
significantly higher (35, 58, 79 DAS) in we
free plots both years. However, total
matter (15.3 vs. 13.7 t/ha) and grain yie
(3.2 vs. 3.2 t/ha) did not differ significai
between the weed-free treatment and
treatment handweeded twice.

Comparison of Virulence of Xanthomo
campestris pv. oryzae in North China and
the Philippines. Zhang Qi, C.M. Cruz
T.W. Mew (IRRI)

The seven selected differential varied
Kinmaze, Kogyoku, Shennong 1033, Chug
45, Tetep, Java 14 and IR26 were evalum
in North China (Beijing) and in
Philippines for differential response to h
races. Twenty isolates from North Cl
were classified into 4 groups. The isolate:
group IV may correspond to Philippine r
1.
The International differential varie
which included Japanese Kinmn
Kogyoku, Tetep, ;Wase Aikoku 3, and J
14; IRRI IR8, IR20, IR1545-339, DV85
Cas 209; and Chinese differential varieties
Kinmaze, Shennong 1033, Tetep, Nang
15, Java 14 and IR26 were evaluated
differential reaction to 62 isolates from Nc
China. Among 4 susceptible variel
Shennong 1033 was the most susceptibk
almost all of the isolates tested. The tl
others, Kinmaze, IR8 and Cas 209 v
susceptible to 53, 50, and 42 isola


S respectively. Wase Aikoku 3, IR1545-3:
I and DV 85 were resistant to all isolat
1 Reactions on IR20, IR26 and Java 14 wc
e either similar, resistant, or moderate
resistant. The results indicated that neitl
) the IRRI nor the Japanese different
systems can differentiate more than t
s pathotypes virulent or avirulent to thi
9 cultivars, except Tetep which shove
) different reactions to isolates in North Chi
i Chinese differentials showed some
a different reactions. However, the he
d pathogen response in rice X. c. pv. ory
3 system in North China was still not as de
8 cut as those in the Philippines or Japan.
e The difference between the ratio
*y lesion with leaf length and percent les
e area was also studied and was significi
I- The assessment of percent lesion area
y visual estimation and leaf area meter w
Is similar.
ly
ie
Screening of Peanut Genotypes Against
and Other Diseases. N.G. Tangonan, I
rs Miral, and JA. Arguelles (USMARC, US
n
Id Twenty-five introduced pe
genotypes were screened against peanut
and other prevailing diseases in Cotal
The most serious disease observed
s, peanut wilt. Percentage infections (
;u varied from 3.70 to 100%. Only
4d genotype, ICG 8710 (from Malaysia)
ie found resistant to the disease. TI
al genotypes, namely: ICGs 221, 799, and 1
ia all from India, were moderately suscepi
of with PIs that ranged 23.91 to 50%; all ot]
e were susceptible with PIs that ranged fror
to 100%. The fungal organisms isolated f
es wilt-infected plants were: Scleroti
e, Fusarium Rhizoctonia, and a bacteria
ia Pseudomonas sp. was also isolated. 0i
id diseases observed were leaf rust with seven
ratings (SRs) from 1.3 to 4.6 and blacl
ig late leaf spot with 1.0 to 3.6. A virus.disc
:r which has symptoms similar to peanut mc
th infected two genotypes: ICGs 2157 and 1!
s, with PIs of 4 and 8%, respectively.
to Yield (kg/row) ranged from .05 to i
ee with the resistant genotypes giving the hig
-2-1-1- -I --_J_ 1_








fm.I-lIrtIiU IIUI DICI i 1. _I /-i I. ai wIrn scnrp.o nr s m0nflpra tlv rPcictint KA rv


Idhra Pradesh, India.

Method for Scoring Resistance to Rice
ngro. A. Hasanuddin, R.D. Daquioag, and
Hibino (IRRI)

Correlations between symptom severity
d grain yield reduction were used to
velop an effective scoring method for
iluating varieties for resistance to or
erance for RTV infection.
Seedlings of nine varieties exposed to
'V-viruliferous green leafhoppers (GLHs)
re transplanted in pots. Plants infected
:h both rice tungro bacilliform virus and
e tungro spherical virus (RTBV + RTSV),
:h RTBV alone, and with RTSV alone
re identified by latex serology 1 or 2 wk
er inoculation (WAI). Plant height was
lasured and symptoms were recorded 3
AI.
Irrespective of varieties, plants infected
th RTBV + RTSV had the greatest
auction in height and yield followed by
'BV-infected plants. The correlations
tween yield and height reductions among
nts infected with RTBV + RTSV or with
'BV or RTSV alone were significant in
V272-6B, FK135, and TN1, but not in
limau Putih, Sigadis, and Utri Rajapan.
ants with severe symptoms had greater
Id reduction.
These results indicate that the level of
erance for RTV can be scored at about 3-4
AI on the basis of plant height reduction
I degree of leaf discoloration.
Using these results, the modified
rring method is as follows:
= no symptom
= 1-10% plant height reduction with no
leaf discoloration
= 11-30% plant height reduction with no
distinct leaf discoloration
= 31-50% plant height reduction and/or
yellow to orange leaf discoloration
= more than 50% plant height reduction
and yellow to orange leaf
discoloration

Cultivars with scores lower than 3 were
asidered resistant (or tolerant); cultivars


an 1,000 rice germplasm were tested using
is modified mass screening method. Nine
percent had score 0-3. Tjempo Kijik (Acc. no.
i602) and Utri Merah (Acc. no. 16682)
Aibited very mild symptoms but had high
fection with RTBV and/or RTSV.


he Development of Soft Rot and Dry Rot in
otato Tubers as Affected by Storage
temperature. R.C. Gesmundo and M.P.
natural (BPI-Manila and UPLB)

Potato tubers were inoculated with
isarium sp. and Erwinia sp. either singly or
combination and stored at different
mperature levels, namely: 0-5 C, 15 C, 25 C
id 30 C. Rotting became severe as the
mperature and length of storage increased.
abers inoculated with Fusarium sp. alone,
'winia sp. alone and with both pathogens
itted rapidly under high temperature (25
id 30 C). Rotting was minimal when treated
bers were stored at low temperatures (0-5
and 15 C).
The presence of Fusarium sp. did not
crease the severity of rotting. It only
*ovided a favorable entry point for the soft
t bacteria. Therefore, the combined action
the two pathogens did not surpass the
dividual effect ofErwinia sp.
Cultural and morphological
aracteristics of the organisms
responded well to Fusarium solani,
using dry rot and Erwinia carotovora
using soft rot in potato tubers.

occurrence of Field and Storage Fungi at
different Panicle Positions of Amaranthus
udatus L. J.S. Bartolini (BPI-Manila)

Among the fungi found associated with
naranthus caudatus, Altemaria altemata
is most frequently observed at 10-64 days
ter peak flowering (DAPF), although its
cidence remained at less than 10% until 62
APF. This slow build up of Altemaria
lowed Fusarium spp. and Penicillium spp.
proliferate up to 24 and 37 DAPF,
spectively.
Incidence of A. altemata, Phoma sp. and


I I _-- _-.. ..







Abstracts of Papel


utaetolntuni sp. was round signitic,
higher in the top panicles than in the botl
Low incidence of Penicillium and Asperg
was found at all panicle positions.

Estimation of Rice Yield Loss Causec
Sheath Blighit ijsing a Modified Single I
Method. F.L. Nuque, AJ.P. Magnaye
P.S. Teng (IRRI)

An experiment on the auantit;


:ly dry season but generally low in the
n. season. Density was especially high in
us when IR36 was planted. N. nigropictus de
was ger rally low but high on ratoon stag
In Mabitac, incidence of RTSV an
by virescens was high in 1986 first crop UP
er 10, but generally low in other sea
id especially when leafhopper resistant
was planted. N. nigropictus density was
on ratoon and in 1986 second crop.
ve Results showed the occurrence










s and nine fluorescent bacteria wi


mortality and infection were, in (seedling and booting stage), and in
order, the biovar 4 isolates T6, phytotron with a day/night temperature of
5 followed by the biovar 3 isolates 20/15 C and 98% relative humidity (seedling
WP12 and P15. Among the three stage). Several pathogenic bacteria had been
tto isolates, WP12 (B3) was the isolated. Their relation to Pseudomonas
:nt followed by WP14 (B4) and the fuscovaginae and other bacterial pathogens
nt was the biovar 2 isolate WP112 affecting the rice sheath and grains were
highly specific to white potato and investigated.

ig the nine weed species cross-
with the nine isolates of P. Growth Behaviour and Cultural
im, Vemonia cinerea, Emilia Characteristics of Some Fungal Pathogens
i and Portulaca oleracea were the of Rice at Varying Temperatures and Media.
ptible hosts to all isolates, except J.K. Misra, E. Gergon, and T.W. Mew
WP112. Synedrella nodiflora, (IRRI)
conyzoides and Amaranthus
ere infected at a low degree only Growth behaviour and cultural
), P10 (B4) and E18 (B3). Cleome characteristics of seven fungal genera viz.,
ta was infected at a very low Dreshclera oryzae, Fusarium moniliforne,
WP12 (B3) only with no mortality. Gerlachia oryzae, Pyricularia oryzae,
sava, sweet potato, Trianthema Sarocladium oryzae and Trichoconiella
rum and Commelina benghalensis padwickii isolated from rice seeds were
ifected by any of the isolates. studied using Malt-extract agar (MEA),
.e test isolates were highly virulent Potato-dextrose agar (PDA), and Czapek-
iginal hosts. Percent infection was Dox agar (CzA) media at 20, 25 and 30 C.
:r than percent mortality and some Varying colony diameter and cultural
lants did not manifest the wilt characteristics of the genera were noted.
Among the media tested PDA was found to
be the best for all genera except for F.
es of Rice Sheath and Grain moniliforme. Except for D. oryzae and S.
ion in the Philippines. M.F. Van oryzae which grew best at 30 C, all isolates
[.T. Cerez and T.W. Mew (IRRI) grew best at 25 C. However, the intensity of
sporulation of the isolates was quite variable
literature on bacteria causing in different media and temperature.
grain discoloration on rice has not
n very clear especially the role of
tas fuscovaginae which has been Clubroot Disease of Crucifers in Benguet
s a subject of controversy. The and Mountain Province. J.S. Mariano and E.
causes sheath brown rot of rice Verzola (BPI-Baguio)
en isolated from diseased rice in
regions of Japan, Madagascar and Clubroot of crucifers caused by the
he pathogen has also been isolated fungus Plasmodiophora brassicae Woronin
; obtained from the Philippines. was observed in five barangays in Atok, and
until now it has never been in three barangays in Buguias, namely:
iat Pseudomonas fuscovaginae is Madaymen, Kibungan and Kabayanan,
agent of severe damage on rice in Benguet. Approximately 650 hectares were









.dUd, Daulu, EVIL. rIuvIINc. VdIIUUs mHuiua Was UoLauLCU aL J I~. 10
The disease occurred in epidemic by 30 and 20. Nitrogen source x I
proportion in Paoay, Bosleng, Sayangan and interactions were significant at
longlo, Atok with disease incidence as high temperatures. Sclerotial production
s 60-75 per cent. three N sources also differed significant
to 58 at 20 C; 16-37 at 25 C and 12.3:
C). The highest number of scleroti
urvey and Chemical Control of Vascular produced at 20 C followed by 25 and 3(
treak Die-back of Cacao. I.C. Tandingan each N source while urea produce
nd A.E. Ampo (USM) highest number of sclerotia follow
calcium nitrate and ammonium sulpl
Surveys of vascular streak die-back each test temperature. Nitrogen sour
icidence and severity were conducted in five rate had no significant effect on scl
different cacao farms/areas in Southern viability and germination in all tempt
4indanao. regimes tested. However, nitrogen soul


another two loc
ease incidence c
observed. An incil
d at the USMA]
17 A0C, f;v mnn'


Ltions at CII, germinated sclerotia. Greenhouse
S43.47% and showed that nitrogen source and
ence of 4.43% application to soil but not N rate
. ,i mi .. .. _^ .. -1 -- -A-*-1 C"-.. .*--


lean disease severity of 6.9%.
An experiment was conducted at
JSMARC cacao experimental area to Screening of Fungicides Against
determine the effect of different dosages of Stripe of Rubber. T.B. Bayaron an
-iadimenol in the control of vascular streak Rivera (USM)
ie-back. The fungicide was applied as soil
rench and as spraying using three dosages Thirteen fungicides were sci
5, 10, and 15 ml/15 liters of water). All the against black stripe of rubber caus
treatments did not show any significant Phytopthora palmivora under field coni
education in disease severity compared with using their recommended rates. Rubbe
he control, three months after treatment. with severity rating of 4.0 were used.
trees showed symptoms of brown to
flect of Nitrogen, Temperature and lesions on top of the tapping panel.
esidue Management of Rhizoctonia solani Fungicides were applied three tim
uhn. E.D. Imolehin, T.W. Mew and P.S. days interval by brushing them on the s
sng (IRRI) of the tapping panels. After 7 days of tl


The effect c
mperature an4
lerotial formal
owth of R. so.


1 rates, determined.
nt on Maneb was found very
y and controlling the disease as sh
in the reduction of the disease sever


solani in media amended with different reduced disease severity






Philippine Phytopathology
he control, personata produced 7,168 conidi
which denotes a remarkable differ
factor of seven times. Under the ,
ixyl and Copper Hydroxide as Seed of the experiment, C. arachidicoi
ient Fungicides Against Root and personata attained average net reI
Rots of Sorghum. C.C. Evangelista and rates of 98 and 916 and maximum,
angonan (USM) growth rates of 0.203 and 0.225 un
across cultivars, respectively. F
sed treatment with metalaxyl (Ridomil individual reproductivity statistics,
I) and copper hydroxide (Kocide) at 4 shorter mean generation time, the
significantly reduced incidence of root less gross reproduction per le
stalk rots in two susceptible ninefold less net reproductive rn
descent sorghum genotypes, PQ 56 and arachidicola stand for marked diff
t. Grain yield of 3 to 3.07 tons/ha were pathogen capacity relative to P. j
ed in treated seeds for the two Taken altogether, however, the sh
pes, while the untreated control generation time of C an
I only 1.42 to 1.69 tons/ha. Infected compensated for its inferior net ref
ms gave rise to poorly developed rate or gross reproduction per lesi
s with lesser grains; otherwise, eventually resulted in statistical
y infected plants die prematurely. maximum relative growth rates.


luctivity of Cercospora arachidicola Populations of Plants Singly oi
and Phaeoisariopsis personata (Berk. Infected with Rice Tungro Bacillil
:urt.) v. Arx on Different Peanut Rice Tungro Spherical Virus Sol
irs. R.A. Paningbatan and O.S. Opina Their Role on Disease Spret
k and UPLB) Chowdhury, P.S. Teng and H.Hibint
A-
eproductity tables were constructed Spread of rice tungro virus (RI
alyzed to compare conidial production different proportion of source plant:
arachidicola Hori and P. personata with rice tungro bacilliform virus
and Curt.) V. Arx lesions on intact and rice tungro spherical virus (RI
of susceptible and resistant peanut evaluated in caged method under g
-s. Lesions of C. arachidicola and P. conditions. Percentage of tungro
ita initiated conidial production at 15- increased as the number of sour
Is and 21-26 days after inoculation, increased irrespective of RTBV c
ively. Consequently, the mean cohort infected source plants used. Transn
t-n times of C. arachidicola and P. RTSV was comparatively much hig
rta reached 19-23 and 20-32 days, that of RTBV or by both RTBV ai
ively, with susceptible BPI P9 cultivar infection with the increasing nu
ting shorter generation time. Gross RTSV infected source with fixed ni
active rates per lesion of C RTBV infected plants in each pr
'irenin and P nowrnnata varied frnm CnrrP.eronndinolv n-.rrpntaop nf


sustaining the highest rate. When plants infected individually by RTBV
Shorter reproductive period of lesions or RTSV were mixed with a fixed number of
on susceptible cultivar was compensated for plants infected by both viruses, transmission
by higher reproductive capacity of lesions, of RTSV was also higher than that of RTBV.
and vice-versa on resistant cultivar. Across Plants infected by both viruses did not differ
cultivars, C arachidicola produced an significantly with different proportion of






Jan. & June 1989 Abstracts of Papers 63
In a separate experiment, cv. TNI plants Survival of Rhizoctonia solani Kuhn In
infected individually by RTBV and RTSV Relation to Nitrogen Source, Temperature
were mixed equally in cage. Two to three and Fungicide Application. E.D. Imolehin,
virus-free green leafhoppers (GLH) per plant B.L. Candole, P.S. Teng and T.W. Mew
were released for acquisition-inoculation (IRRI)
feeding for 2 days to examine the rate of
cross infection within the infected plants. The Sclerotia of Rhizoctonia solani Kuhn are
results indicated that the chances of cross at first non-buoyant but become buoyant
infection are not so pronounced within this after 15-30 days. Such sclerotia float on
time period. irrigation water to initiate infection. The
effects of nitrogen sources and temperature
on the survival of such sclerotia were
The Relationship Between Inoculum Level investigated. Nitrogen sources had significant
and Damping-off Incidence in Tobacco effects on the survival of the sclerotia of R.
Seedlings. P.N. Dipon and T.T. Reyes (UEP solani when incubated at a constant
and UPLB) temperature of 20 C (30-53%), 25 C (27-
53%), and 30 C (23-40%) for one month.
Greenhouse studies were conducted to The survival was significantly reduced to 10-
determine damping-off incidence at different 30%, 10-30% and 3-20%, respectively by the
inoculum levels and to compare the inoculum third month. There were significant
efficiency of four soilborne pathogens causing differences between temperature and
damping-off of tobacco. interactions between temperature and
Disease incidence was directly nitrogen sources were significant. Incubation
correlated with inoculum level. Continuous temperature had significant effects on the.
increase of inoculum did not result in germination of retrieved sclerotia only when
proportional increase in damping-off incubated for 2-3 months while N source only
incidence. Only at lower inoculum significantly affected the germination of those
concentration that proportional increase in incubated for one month.
disease incidence was noted with increased The survival (germination %) of
inoculum concentration. Pythium sclerotia produced under various N sources
aphanidennatum (Edson) Fitzpatrick was the and temperature decreased significantly with
major pathogen causing both pre- and post- storage. Percent sclerotial survival was
emergence damping-off. It had high significantly influenced by the temperature
inoculum efficiency and caused serious under which they were produced.
damage to tobacco seedlings even at low Germination of sclerotia produced at 20, 25
inoculum concentration. Pre-emergence and 30 C was reduced from 100 to 70%; 100
damping-off of 78% to 92% was noted at to 0% and 100 to 70%, respectively after 8
inoculum levels of 1:20 to 1:4 (v inoculum/v 1/2 months of storage. Nitrogen source also
soil). Seedlings were nearly wiped out during significantly affected sclerotial survival.
the post-emergence phase of infection. Sclerotia from ammonium sulphate
Sclerotium rolfsii Kuhn, Rhizoctonia solani amended media had the least survival rate
Sacc. and Fusarium o:ysporum f. sp. followed by calcium nitrate, urea and the
nicotianae (Breda de Haan) Tucker caused control. Greenhouse studies showed that the
significant damage only at very high survival of sclerotia buried in soils treated
inoculum. These pathogens were less active with Benomyl, Brestan, Validamycin and
during the pre-emergence phase but more three N sources did not differ significantly.
active during the post-emergence phase of However, the germination of retrieved
infection. sclerotia was significantly affected by N
Tobacco seedlings showed some degree sources.
of resistance to P. aphanidermatum with age
but became more susceptible to infection by
ihe other damping-off pathogens.









iroid on Coconut Embryos Grown In Vit
.P. Rillo, M.B.F. Paloma, MJ. Rodrigu
id M.T. Ignacio (PCA-Albay)

This paper describes an asel
oculation technique of Coconut Cadai
adang Viroid (CCCV) for coconut embr,
*own by in vitro method. The inoculum w
concentration of 20 ug/ml was filt
erilized in 0.22 u nitrocellulose membri
Iters after filtration in 0.45 u filters. Seve


sprayed with spore suspension contain
marmit solution than in plants sprayed w
spore suspension containing beef extra
peptone solution.

Analysis of DNA Introgression from Or,
minute to Oryza sativa. N.P. Oliva,
Nelson, A.D. Amante, H. Leung, and L


3-10) isolated from C
be highly repetitive ii
I only in low copv y


g indicator strains; however, this was
h observed when assay temperature
lowered from 30 C to 22 C. Therefore
results do not indicate a correlation bet
bacteriocin specificities and races. Gene
a lower assay temperatures caused larger:
S of clearing.
I.


Sitch (IRRI)

Repetitive DNA sequences specific to


- .. r 11 1_L____1 _r -I.-- I\VTA !-1






Jan. & June 1989 Abstracts of Papers 65
Starch Test of Leaf Sections from Tungro- better than Penicillium anatolicum with
Recovered Rice Plants. A. Pizarro (GAUF) 63.2% and Penicillium oxalicum with 57.1%
control. On the other hand, the soil-mix
Tungro is one of the most widespread treatment of these fungi generally provided
and destructive diseases of rice in the lower nematode control than the tuber-dip
country. Recently, recovery of rice plants method.
from tungro infection has been reported. The The test also showed that all isolates of
sole limiting factor for recovery to occur is P. lilacinus gave higher yield increase of
the freedom of infected plants from the potato than P. oxalicum, P. anatolicum and
leafhopper vectors of the virus. Recovered M. anisopliae. Likewise, the tuber dip
rice plants appear healthy and normal application gave higher yield increase than
without the external visual symptoms the soil-mix application of the fungi.
associated with tungro, Recovery occurs en BIOCON and Peru isolates provided the
masse, naturally and permanently. highest first class yield increase (86.5% and
Decolorized leaf sections from 78.4%, respectively) followed by Furadan 3G
recovered plants, either dipped in cold treatment with 54.0% increase. ViSCA and
rubbing alcohol or boiled showed negative Abuyog P. lilacinus gave higher second class
reactions with Lugol's or diluted tincture of yield with 57.7% and 50.0% as compared
iodine solutions. The disappearance of the with 30.8% of both BIOCON and Peru
external visual symptoms of tungro, the isolates using the tuber dip method. There
permanent healthy appearance with non- was not much difference in the first and
recurrence of the disease, and the starch- second class yield increase in P. oxalicum and
negative reactions are evidences of total and P. anatolicum treatments, but in M.
complete recovery, anisopliae, the second class yield increase
(76.9%) was much higher than the first class
yield. Generally, the plants under treatments
Field Evaluation of More Effective with BIOCON and Peru isolates had bigger
Paccilomyces lilacinus Isolates and Three tubers than those with treatments of ViSCA
Other Nematophagous Fungi for the Control and Abuyog isolates.
of Potato Cyst Nematode Globodera
rostochiensis in Atok, Ilenguet. R.G. Davide
and R.A. Zorilla (NCPC, UPLB) Field Evaluation of Bacterial Strains for
Biological Control of Sheath Blight of Rice.
More effective Paecilomyces lilacinus S. Gnanamanickam, B.L. Candole and T.W.
isolates and three other nematophagous fungi Mew (IRRI)
were evaluated under field conditions against
potato cyst nematode (Globodera Bacterial strains isolated from rice
rostochiensis) in severely cyst-infested potato rhizosphere samples from IRRI farm
farm in Atok, Benguet showing in vitro antagonism towards
Based on cyst counts per 100 cc soil Rhizoctonia solani cause the sheath blight
sarrples taken before treatment at 45 and 90 (ShB) of rice and at the same time showing
day, after treatment, the P. lilacinus isolates other desirable traits were selected for field
(BIOCON, Peru, ViSCA and Abuyog) were evaluation during the dry (DS) and wet (WS)
relatively more effective than the Furadan 3G seasons of 1988. During DS, 1988 one
nematicide treatment. In the tuber-dip fluorescent (In-b-784), three nonfluorescent
treatment, both the BIOCON and Peru (In-b-33, 3,and 655) and a combination of
isolates gave the highest control with 79.3% strains In-b-33 and In-b-748 were used as
md 78.7% control, respectively, whereas seed treatments along with fungicides
I ',se of the ViSCA and Abuyog isolates Validamycin and pentachloronitrobenzene






Philippine Phytopathology Vol.25


strains In-b-1-14-1 and In-b-714 provided
98% and 84% ShB control, respectively.
Results suggest that bacterial seed treatments
are far more effective in suppressing ShB in
direct-seeded than in transplanted rice crops.


Biological Control of Root-knot Nematodes
in Ramie Using Paecilomyces. lilacinus. I.C.
Tandingan and E.V. Asuncion (USM)

Biological control of root-knot
nematodes (Meloidogyne incognita) in ramie
was conducted at the USMARC
experimental area using P. lilacinus in
organic substrate as soil mix (1:2 rice hull
and rice bran or RHRB); sterile substrate,
RHRB alone; P. lilacinus as soil drench (200
x 106 spores/ml); non-treated control; and
nematicide (phenamiphos, 100 ppm).
All treatments of P. lilacinus, with or
without substrate, organic substrate alone,
and phenamiphos significantly reduced root-
knot nematodes in the soil, number of galls
and egg masses in roots of ramie three
months after treatment.
Decrease in nematode population
ranged from 54 to 85%, with P. lilacinus-
treated plots showing the highest reduction.
Degree of galling was severe in the non-
treated control, slight in the RHRB-
ammended plots, and trace in P. lilacinus-
and phenamiphos-treated plots. Population
of egg masses decreased by 87% in
phenamiphos-treated plots; 80 and 82% in
plots with P. lilacinus treatments as soil mix
and soil drench, respectively; and 62% in
RHRB-amended plots.


Host Range, Method of Transmission and
Properties of Peanut Stripe Virus in the
Philippines. F.L. Mangaban, M.P. Natural,
and R.B. Valdez. (IPB and UPLB)

Characterization of the Philippine
isolate of peanut stripe virus (PStV) was
done based on symptomatology, method of
transmission, host range, physical and
serological properties.
PStV is serologically related to blackeye
cowpea mosaic virus (BICMV) and soybean
mosaic virus (SMV) but not to peanut mottle


virus (PMV) and tomato spotted wilt virus
(TSWV).
The disease appears as green islands or
blotches, oakleaf pattern and stripes along
the lateral veins of infected peanut leaves.
The virus is readily transmitted to peanut and
to some species of Papilionaceae and
Chenopodiaceae by mechanical inoculations,
grafting and with five aphid species with
Aphis craccivora as the most efficient vector.
The virus remained infective in crude
sap up to a dilution of 104. It can be stored
up to 3 days at 0C and is inactivated at
650C.
Three peanut accessions were identified
with some degree of resistance to PStV from
among 107 lines and accessions evaluated.


Twelve Corn Entries Found Highly Resistant
to Downy Mildew. N.G. Tangonan, B.T.
Dionio, F.R. Alejandro, P.R. Miral, JA.
Arguelles, and J.G. Elarde (USMARC,
USM)

Fifty-five corn entries were screened
and evaluated for reactions to downy mildew
at USMARC-USM, Kabacan, Cotabato.
Twelve entries or 21.82% showed complete
resistance against the disease. The corn
entries were: P7, P10, P14, SMC 305, CPX
8403, P3224, P3228, PY8g62, SMC 317, SMC
308, SX 747, and CPX 3605 with percentage
infection ranging from 0 to .72%. On the
other hand, 13 other entries or 23.64% were
found resistant to downy mildew with
infection of 1.51 to 9.67%; six or 10.90%
were moderately susceptible and 24 corn
entries or 43.64% susceptible to downy
mildew.


Resistance of. Traditional Varieties and
Lines to Ten Isolates of Pyricularia oryzae.
F.L. Nuque and P.S. Teng (IRRI)
A total of 194 traditional varieties and
lines grown during the pre-1920s, pre-World
War II, post World War II, late 50's and 60's,
etc. were separately inoculated with 10
isolates of Pyricularia oryzae artificially to
determine varietal resistance and virulence of
the isolates.


Philippine Phytopathology


Vol. 25







me 1989 Abstracts of Papers
rietics differed in their resistance to The Chinese cabbage cultivars, (
isolates used. Milagrosa, Raminad Str and Esperanza, when screened aga
Balibud, IR3259-PP5-169-1, IR4547- virulent isolates of P. solana
15533-PP584-1, were highly resistant representing biovars 1, 2, 3, 4 were r
instancee index of 1.00. Varieties that to the nechav and Chinese cahhanaee


.. uC dllU lllaIUOy Wllla ULSe;
2.5000, 2.6000 and, 2.66
.Calibo and Taal, IR3941-9
yang were susceptible w
induced of 3.5000, 3.8880 a
ectively.
g reactions to the isolates wi
ed on the same cultivars hav
sessionn numbers. Milagrosa (A
has a resistance index of 0.(
) Milagrosa (Acc. no. 44634) w
ndex of 3.3000. Similar rest


irom tomato, eggplant, p
ia.

lance and Diseases of Pt
stum glaucum (L.) R
WC-USM, Kabacan, Cota
an, P.R. Miral and JA.
RC, USM)

renty-four pearl millet gent
at USMARC-USM,
o to test their adantabili


A-p-nctr',


1 0.8351 to 2.9569. The lea
B 840106) and the most virulei
B 849106) collected from Banal
ce indices of 0.8351 and 2.956


leter-row followil
s. No control mi
the pearl millet!
- nc, t-

K.t.. vaiaez (lirt, ufLti) Diseases observed were spots and blight,
the leaves, leaf sheaths, and stems include
Bacterial wilt of crucifers, caused by grain molds in the panicle heads. Isolati
domonas solanacearum was observed at from infected parts yielded species
UPLB Experiment Station and vicinity. Curvularia, Fusarium, and Helminthosporiz
isolates belonged to biovar 3 (race 1). Pathogenicity tests are underway to asceri
Of the 50 pechay accessions screened whether they are the causal agents of
resistance to eight virulent isolates of P. diseases noted. Resistant genotypes were:
tacearum, A-226 and A-243 were 9287, 9260, 9478, 4763, 9255, and 8554.
tant to biovar isolates 1, 3, and 4
ined from tomato, eggplant and
alaya, respectively, but were susceptible POSTER PRESENTATION
ie pechay isolate. Accessions A-248 and
.2 were resistant to the pechay isolate but A Preliminary Investigation of a Funj
susceptible to the other isolates. Six Attacking Nematodes in Leyte. R
r accessions showed resistance to one Gapasin and J.L. Lim (ViSCA)
te. The cultivar, Black Behi, is
eptible to all the isolates. In a survey made in six localities
In another screening test, K-K cross was Leyte where corn is grown, it was obser
best among seven cabbage cultivars with that plant parasitic and free-living nemato,
ifection, followed by Yr Summer 50 and were parasitized by a fungus. Aver;
ess 60. None of the cultivars of Chinese parasitism based on dead nematodes ranj
age, mustard, radish, cauliflower, from 0.5-1.5 and 3.6-12.2, respectively. 1
coli and lettuce nrnoed rensltanit plant parasitic nematodes attacked w






Philippine Phytopathology Vol. 25
ylenchus, Helicotylenchus, Criconenmoides, in both. Results showed that the simulated
lolaimus, Xiphinema and Longidons, values from the blast model did not
e the free-living ones were Dorylainus correspond well with the actual data. The
Rhabditis. All the parasitized nematodes blast-RICE model was used to predict bulk
Dead. yield, yield components and biomass changes
Microscopic examination revealed that when exposed to epidemics with different
fungus under study was totally different disease progress curves in the field. Predicted
i previously reported ones. It occupied yield values approximated estimates of the
whole body length of the nematodes and observed; however, there was general
luced thick-walled round or ovoid spores overestimation by the model. Bulk yield and
le the nematode body. yield component values were decreased with
Attempts to isolate the fungus from the increasing severity rates observed in the
nematode and grow it using tryptone validation exercise. This suggests that losses
ose yeast extract agar (TGYA) and due to blast may to a large extent be caused
ito dextrose agar (PDA) failed, by reduction in photosynthetically active leaf
tissue alone.
nation and Pathogen Specialization of
aceloma batatas (Saw) in Leyte. C.E. Avidin-Biotin ELISA for Sensitive Detection
ze and M.B. Capuno (PRCRTC, ViSCA) of Rice Tungro-Associated Viruses. P.Q.
Cabauatan and H. Hibino (IRRI)
Eight isolates of Sphaceloma batatas
collected from Baybay and Abuyog, A standard avidin-biotin enzyme-link
te were tested for their virulence on 40 immunosorbent assay (AB-ELISA) protocol
et potato cultivars in the screenhouse. was developed and its sensitivity in detecting
.e determination involved inoculating each RTBV and RTSV in plant/ s p was
ate to a series of 40 differential hosts. compared with double antibody sandwich
Based on the differential response of ELISA (DAS-ELISA). The sap dilution end
test cultivars, the isolates were grouped point and absorbance at 410 nm (A410 nm)
four races designated as races 1, 2, 3 and were used as criteria for comparing the
wo isolates (V11-398 and V3-158) were sensitivity of the two serological tests. Rice
sified as race 1 and two other isolates plants infected artificially or naturally with
.S 387 and G145r4) belonged to race 2. either or both rice tungro bacilliform virus
:e 3 was composed of 3 isolates (Vll-148, (RTBV) and rice tungro spherical virus
-253, PRS 182) while race 4 was (RTSV) were used in the test.
-esented by a single isolate (BNAS 51). Results showed that AB-ELISA was
lificant differences in virulence were eight and thirty times more sensitive than
-d among the isolates. Some of the DAS-ELISA in detecting RTBV and RTSV,
ates were highly virulent on some respectively. Absorbance values at 410 nm
ivars and less on other. was three to five times higher in AB-ELISA
than in DAS-ELISA. Some field collected
liminary Validation of the Blast ano samples from different varieties reacted
st-Coupled IBSNAT Ceres Rice Models. negatively in DAS-ELISA but gave positive
. Calvero, Jr., C.Q. Torres, N.G. Fabellar reaction in AB-ELISA. These samples had
P.S. Teng (IRRI) low virus concentration and escaped
detection in DAS-ELISA. These results
Validation of a blast model and a blast- demonstrated the advantage of AB-ELISA in
pled version of the IBSNAT Ceres-Rice detecting low concentrations of RTBV and
lel was conducted at IRRI, using data RTSV in infected plants and may be useful
n 1988 wet season experiments. Blast for routine screening for resistance and in
crities predicted by the blast model were epidemiological studies of the disease.
pared with observed severities in
plots using the same environmental data








Biological Control of Rice Blast Usi
Antagonistic Bacteria. S.S. Gnanamanicka
R.C. Reyes and T.W. Mew (IRRI)

Strains of bacteria isolated from IR:
rice fields were screenedffor their antagoni,
towards the blast fungus, Pyricularia oryzi
From more than one hundred bacter
strains initially used in the laboratc
screening, 4 strains (2 fluorescent and
nonfluorescent) that caused maxima
inhibition of P. oryzae were chosen for a fic
test. The average diameter of inhibit
zones were 38.5 mm for strain 7.
(fluorescent), 30.4 mm for strain 4.
(fluorescent), 26.3 mm for strain 33 and 2:
mm for strain 4.03. The field experiment m
done in RCBD with 4 replications v
conducted at the IRRI site for upland ri
research at Cavinti, Laguna. Seeds
UPLRi-5 rice were coated with bacteria [1
colony forming unit (CFU) per g seed]
with fungarin and were sown in field pih
along with nontreated seeds. The crops al
received three additional sprays with bactel
(10 cfu per ml) or fungarin when the plai
were 20, 30, and 40 days old. Root and she
samples collected at 10-day intervals
monitor the bacterial populations suggest
that the nonfluorescent strains had a high
level of population (10 to 106 cfu per
tissue) than the fluorescent strains until 1
days after planting. Fungarin and all bacter
treatments caused significant reductions
leaf blast severity and also margin
reductions in neck blast severities.


Biological Control of Sheath Blight of R
in Korea by Antagonistic Bacteria. A.
Rosales, Y.H. Lee, G.Y. Shim, E.J. Lee, a
T.W. Mew. (IRRI and RDA, Korea)

Three isolates of bacteria showi
antagonism to Rhizoctonia solani in vitro a
greenhouse tests were selected for field tri
at Icheon, Korea. Seeds of rice cultil
Chucheonbyeo were bacterized and w(
sown in seedboxes. Seedlings we
transplanted in plots 3 x 4 m. Results show
that seed bacterization and spray applicati
of bacteria on rice plants reduce


cts of Papers
g weeks after transplanting.
i, Pseudomonas aureofaciens (P62) \
more effective in sheath blight supress
than P. fluorescens (P55) and P. putida (P(
I The grain yield of bacterized plants 1
n higher than non-bacterized plants. I
. populations of these bacteria w
>l determined at various stages of plant grove
y Prior to transplanting in the field,
2 population of P. fluorescens, P. putida and
a aureofaciens were 1.7, 2.4 and 1.2 x 10 CI
d res ectively, then decreased to 8 x 102,
n 10 and 1.7 x 103, respectively, six weeks al
4 transpslanting. Plating the washings from
5 roots, stems and leaves of bacteria-trea
1 plants showed that the bacterial populat
s was concentrated on roots and stem port
Is after seed treatment. Eleven weeks al
e transplanting, the populations of
>f fluorescens, P. putida and P. aureofaciens \
Higher on stem than on roots and leaves.
ir
;s
o Effect of Resistance on Cercospora sorgl
a Sorghum Interaction. C.B. Pascual and A
.s Raymundo (IPB, UPLB)
)t
o Results of inoculation of C. sorghi
d resistant (Acc. 898) and susceptible (UPL
xr 5) sorghum genotypes suggest that C sot
g undergoes a dormancy period before
0 germinates. This fungus exhibited h
11 percent germination on both genotypes
n hours and 8 hours after inoculation using
11 vitro and in vivo inoculation techniqt
respectively.
More lateral germ tubes, branching a
elongation were observed in susceptible tl
:e in resistant genotype. Branching of thi
[. lateral germ tubes are equal to the number
d infecting hyphae and consequently to I
number of lesion.There was no signific;
difference between the R and S genotype
g the inhibitory effect of toxin extracted fr&
d C. sorghi on root elongation.
Is
tr
e Histopathology of Host and Non-I
e Responses to Pyricularia oryzae Cavi
;d MA. Bernardo, H. Kaku, and H. Le
n (IRRI)
d
- To studv host and non-host response





I IIIId r I *JV |
iogen infection, rice variety C039 and a (c
d, Leersia hexandra were inoculated with bi
cularia oryzae isolate P06-6 from rice and nq
ite NLH from L. hexandra. Scanning ni
tron microscopy showed that spore bi
nination in the compatible interactions, in
39-PO6-6 (98%) and L. hexandra-NLH in
Po), was significantly higher than in the bi
impatible interactions C039-NLH. AT 72 sl
96 hours after inoculation, transverse leaf re
ions of C039 inoculated with P06-6 ol


uiww~y T IM
mpatible) showed mycelial growth in the
inform cells, and in the lumens of the
m vessels. The infected parenchyma cells
r the bulliform cells collapsed into dark
wn necrotic cells. In C039-NLH
action (incompatible), the penetrating
action hyphae did not colonize the
liform and neighboring cells, instead, a
ht browning at the infection sites,
:ricted to a few parenchyma cells, was
erved.











INFORMATION FOR CONTRIBUTORS

1. Membership in the Philippine Phytopathological Society is prerequisite to publish-
ing in Philippine Phytopathology or at least one author must be a member of this
society. The Editorial Board, however, may relax this rule in the case to contribu-
tions of exceptional merit. It may also invite distinguished scientists to contribute
articles of interest to the Society.

2. Manuscripts must be reports of original research, except meritorious reviews, and
should have not been published elsewhere. The decision of the Editorial Board to
accept or reject the manuscript is final.

3. The manuscript should be typed on one side of 8% x I1 inch paper, double spaced
throughout.

4. The author's name should follow the title. Author's position and institutional ad-
dress.

5. Papers other than Notes may be organized conveniently under: Abstract, Introduc-
tion, Materials and Methods, Results, Discussion, (or Results and Discussion) and
Literature Cited.

6. In the text, citations should be by name-and-number system, e.g. Ou and Nuque (1).
With 3 or more authors, use et al. (e.g. Ou, Nuque and Silva (1) should appear Ou,
et al. (1); the number in parenthesis should correspond to the number of the article
cited (or referred to in the text) under literature cited.

7. Literature citation should be in alphabetical order and with numbers. Do not cite un-
published work; it should appear as footnote. Biological Abstracts' 1968 List of
Serials with Title Abbreviations must be consulted in abbreviating the names of
journals. Examples of abbreviation: Philipp. Entomol., Philipp. Phytopathol., J.
Mol. Biol., Plant Dis. Reptr., J. Agr. Res., Amer. J. Bot.

8. Acknowledgements should be placed at the end of the article i.e. after Literature
Cited.

9. Tables should be numbered consecutively, and each typed on a separate page. They
must have descriptive headings and should be understandable without reference to
the text. Lower case superscript letters are to be used for footnotes to tables. Pages
containing tables should follow Literature Cited and should be numbered accord-
ingly.

10. Figures should add clearly to an understanding of the paper. The size and arrange-
ments of figures (graphs, line, drawings, and photographs) should correspond to
Journal page. Combine illustrations in composite cuts when possible, and number
each unit to correspond with the text figure reference, using consecutive Arabic
numerals. Label each illustration in pencil on the reverse side with the figure number
and author's name. Legends for figures should be typed together on a separate num-
bered page following the tables.

11. See latest journal of Philippine Phytopathology for more details on the format of
papers to be submitted to the journal.

12. Articles published are not paid but authors foot the bill for reprints






























Owner : PHIL. PHYTOPATHOLOGICAL SOCIETY, INC.
Printer : PHINELLPRINTING
Office of
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In case of publication other than daily, total number of copies printed and circu-
lated at the last issue date June 1985.

I. Sent to paid subscribers ...... 120


SUBSCRIBED AND SWORN to before
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Los Banos, Laguna on January 31, 1987.

Doc. No. 44 SGD. A
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Series of 1987

NOTE: This form is exempt from the payment


SGD. AVELINO D. RAYMUNDO
Editor-in-Chief

me this _-_- day of May 1989 at
lence Certificate No. 10087677 issued at


IY. LORENZO C. MENESES, JR.
Until Dec. 31, 1987
PTR No. 1174223
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if documentary stamp tax.








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