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Influence of Calcium on Postharvest Quality and Yield of Strawberry Fruit (Fragaria x ananassa Duch.)

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Influence of Calcium on Postharvest Quality and Yield of Strawberry Fruit (Fragaria x ananassa Duch.)
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2008

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Acidity ( jstor )
Apples ( jstor )
Botrytis ( jstor )
Calcium ( jstor )
Fruits ( jstor )
Growing seasons ( jstor )
Gypsum ( jstor )
P values ( jstor )
Soils ( jstor )
Strawberries ( jstor )

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University of Florida
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INFLUENCE OF CALCIUM ON POSTHARVEST QUALITY AND YIELD OF STRAWBERRY FRUIT ( Fragaria×ananassa Duch.) By CAMILLE ELIZABETH ESMEL A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2005

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Copyright 2005 by Camille Elizabeth Esmel

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To my family and friends who gave their unwavering support to me during this gritty and sometimes crazy process. I appreciate all their candid advice, jokes, and laughter in attempt to keep me sane and smiling

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iv ACKNOWLEDGMENTS I thank my parents (Lydia and George Fortier) for their support (albeit unusual at times, but always present). I would also like to express my deepest appreciation to Boo and Butter. My furry, four-legged friends always reminded me that journal articles do not belong on the floor; blanket and carpet monsters do exist; and if I am not attentive, I will become a scratching post. They had true dedication to my cause, and remained by my side through all the tough times. Finally, I would like to express my thanks to the members of my supervisory committee for all their assistance and insight on this project.

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v TABLE OF CONTENTS page ACKNOWLEDGMENTS..................................................................................................iv LIST OF TABLES............................................................................................................vii LIST OF FIGURES.............................................................................................................x ABSTRACT....................................................................................................................... xi CHAPTER 1 INTRODUCTION TO FLORIDA’S STRAWBERRY INDUSTRY..........................1 Production....................................................................................................................1 Harvest Operations.......................................................................................................2 Postharvest Operations.................................................................................................2 Maintaining Postharvest Quality..................................................................................3 Quality of Florida Strawberry......................................................................................4 2 INFLUENCE OF CALCIUM ON FRESH PRODUCE QUALITY...........................9 Introduction..................................................................................................................9 Causes of Calcium-Related Disorders.........................................................................9 Quality Issues Related to Calcium.............................................................................12 Minimizing Quality Loss....................................................................................12 Postharvest Storage Extension............................................................................15 Increasing Firmness with Calcium Treatments..................................................19 Correlation of Tissue Calcium and Fruit Firmness....................................................24 Improving Strawberry Fruit Quality with Calcium....................................................28 Conclusions................................................................................................................30 3 EFFECT OF CULTIVAR ON CALCIUM CONTENT AND FIRMNESS IN STRAWBERRY FRUIT ( Fragaria ananassa Duch.).............................................34 Introduction................................................................................................................34 Materials and Methods...............................................................................................36 Results and Discussion...............................................................................................39 Conclusions................................................................................................................43

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vi 4 EFFECT OF SUPPLEMENTAL CALCIUM APPLICATIONS ON YIELD AND POSTHARVEST QUALITY OF ‘SWEET CHARLIE’ STRAWBERRY ( Fragaria × ananassa Duch.)......................................................................................60 Introduction................................................................................................................60 Materials and Methods...............................................................................................64 Results and Discussion...............................................................................................72 Conclusions................................................................................................................79 5 INFLUENCE OF CALCIUM SOURCE ON YIELD AND POSTHARVEST QUALITY OF ‘SWEET CHARLIE’ STRAWBERRY ( Fragaria × ananassa Duch.)......................................................................................................................... 95 Introduction................................................................................................................95 Materials and Methods...............................................................................................98 Results and Discussion.............................................................................................103 Conclusions..............................................................................................................105 6 CONCLUSIONS......................................................................................................114 LIST OF REFERENCES................................................................................................118 BIOGRAPHICAL SKETCH..........................................................................................128

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vii LIST OF TABLES Table page 2-1. Calcium-related disorders by commodity and investigator.....................................33 3-1. Description and existing use of strawberry ( Fragariaananassa Duch.) cultivars grown in Florida during 1998-2003 from both the University of Florida (UF) and University of California (UC) breeding programs..................................................45 3-2. Dates of strawberry ( Fragariaananassa Duch.) cultivar and numbered line tissue collection for measurements pertaining to the correlation of calcium content to textural attributes at GCREC-Dover........................................................................46 3-3. Calcium content of strawberry ( Fragariaananassa Duch.) tissues of selected cultivars for two seasons at GCREC-Dover............................................................47 3-4. Strawberry ( Fragariaananassa Duch.) cultivar effect on calcium content of calyces, fruit and leaf tissues for two sampling dates during 2003-04 season at GCREC-Dover.........................................................................................................48 3-5. Interaction of month with strawberry ( Fragariaananassa Duch.) cultivar for calcium content of leaves collected on 16 February and 17 March 2004 at GCREC-Dover.........................................................................................................49 3-6. Strawberry ( Fragariaananassa Duch.) cultivar effect on firmness in 2003-04 season at GCREC-Dover.........................................................................................50 3-7. Fruit calcium content and fruit firmness correlation coefficients for selected strawberry ( Fragariaananassa Duch.) cultivars grown at GCREC-Dover in 2003-04 season........................................................................................................51 3-8. Leaf calcium content and fruit firmness correlation coefficients for selected strawberry ( Fragariaananassa Duch.) cultivars in 2003-04 season at GCRECDover.......................................................................................................................52 4-1. Horsfall-Barratt scale used to evaluate surface area affected by postharvest pathogens on strawberry ( Fragariaananassa Duch.) stored at 1C for 2002-03 and 2003-04 seasons................................................................................................80 4-2. Bruising scale used to evaluate 'Sweet Charlie' strawberry ( Fragariaananassa Duch.) at 1C for 2002-03 and 2003-04 seasons....................................................81

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viii 4-3. Combined marketable yield of ‘Sweet Charlie’ strawberry ( Fragaria × ananassa Duch.) GCREC-Dover for 2002-03 and 2003-04 growing seasons as affected by calcium application..................................................................................................82 4-4. Percent unmarketable fruits of harvested ‘Sweet Charlie’ strawberry ( Fragaria×ananassa Duch.) fruits at GCREC-Dover for 2002-03 and 2003-04 growing seasons as affected by calcium application...............................................83 4-5. Monthly and season total of Botrytis fruit rot (caused by Botrytis cinerea Pers. ex Fr.) incidence on unmarketable fruits of ‘Sweet Charlie’ strawberry ( Fragaria×ananassa Duch.) at GCREC-Dover during 2002-03 and 2003-04 growing seasons as affected by calcium application...............................................84 4-6. Calcium concentration by month for ‘Sweet Charlie’ strawberry ( Fragaria×ananassa Duch.) at GCREC-Dover for 2002-03 and 2003-04 growing seasons as affected by calcium application.............................................................85 4-7. Seasons total for calcium concentration of ‘Sweet Charlie’ strawberry ( Fragaria×ananassa Duch.) tissues at GCREC-Dover as affected by calcium application...............................................................................................................86 4-8. Achenes and related tissues test for calcium concentration of ‘Sweet Charlie’ strawberry ( Fragaria×ananassa Duch.) at GCREC-Dover as affected by calcium application...............................................................................................................87 4-9. Postharvest quality of ‘Sweet Charlie’ strawberry ( Fragaria×ananassa Duch.) at GCREC-Dover during 2002-03 and 2003-04 growing seasons as affected by calcium application..................................................................................................88 4.10. Interaction of supplemental calcium applied as gypsum with foliar calcium source and rate on strawberry fruits ( Fragaria×ananassa Duch.) firmness at 3 mm deformation depth on 163 DAT 2003......................................................................89 4-11. Total moisture content of ‘Sweet Charlie’ strawberry fruits ( Fragaria×ananassa Duch.) at GCREC-Dover during 2002-03 and 2003-04 growing seasons as affected by calcium application...............................................................................90 4-12. Effect of supplemental calcium on storage of ‘Sweet Charlie’ strawberry fruits ( Fragaria×ananassa Duch.) at GCREC-Dover during 2002-03 and 2003-04 growing seasons as affected by calcium application...............................................91 4-13. Decay for 2002-03 and 2003-04 seasons and bruising for 2002-03 season stored at 1°C on 'Sweet Charlie' strawberry fruits ( Fragaria×ananassa Duch.) grown at GCREC-Dover.........................................................................................................92 4-14. End of growing season soil test (Mehlich-1 extraction method for calcium) in experimental area at GCREC-Dover for 2002-03 and 2003-04 growing seasons as affected by calcium application...............................................................................93

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ix 5-1. Calcium fertilizer and calcium supplemental source treatment combination on 'Sweet Charlie' strawberry ( Fragaria×ananassa Duch.) grown at GCREC-Dover 2003-04 season......................................................................................................106 5-2. Marketable yield (monthly and season total) of ‘Sweet Charlie’ strawberry fruits ( Fragaria×ananassa Duch.) grown at GCREC-Dover 2003-04 season with and without recommended calcium fertilizer source...................................................107 5-3. Percent unmarketable fruits (monthly and season total) of ‘Sweet Charlie’ strawberry fruits ( Fragaria×ananassa Duch.) grown at GCREC-Dover 2003-04 season with and without recommended calcium fertilizer source.........................108 5-4. Percent Botrytis fruit rot (caused by Botrytis cinerea Pers. ex Fr.) incidence occurring on unmarketable fruits (monthly and season total) ‘Sweet Charlie’ strawberry ( Fragaria×ananassa Duch.) at GCREC-Dover 2003-04 season with and without recommended calcium fertilizer source.............................................109 5-5. Postharvest quality of ‘Sweet Charlie’ strawberry fruits ( Fragaria×ananassa Duch.) grown at GCREC-Dover 2003-04 season with and without recommended calcium fertilizer source........................................................................................110 5-6. Moisture content of fruits of ‘Sweet Charlie’ strawberry ( Fragaria×ananassa Duch.) at GCREC-Dover 2003-04 season with and without recommended calcium fertilizer source........................................................................................111 5-7. Calcium concentration within fruit on dry weight basis of ‘Sweet Charlie’ strawberry ( Fragaria×ananassa Duch.) grown at GCREC-Dover 2003-04 season with and without recommended calcium fertilizer source.........................112 5-8. Soil test (Mehlich-1 extraction method for calcium) at the end of the season within area grown with ‘Sweet Charlie’ strawberry ( Fragaria×ananassa Duch.) at GCREC-Dover 2003-04 season with and without recommended calcium fertilizer source......................................................................................................113 6-1. Summary of strawberry ( Fragaria × ananassa Duch.) responses to additional calcium applied as foliar, soil amendment, or injection........................................116 6-2. Current prices (in US$) for calcium products on the market at recommended rates by the hectare................................................................................................117

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x LIST OF FIGURES Figure page 1-1. Wholesale value of strawberry ( Fragariaananassa Duch.) harvested in Florida from 1991 to 2003 ....................................................................................................6 1-2. Hectares of strawberries ( Fragaria ananassa Duch.) planted in Florida from 1991 to 2003.......................................................................................................................7 1-3. Strawberry ( Fragariaananassa Duch.) producing counties in Florida based on description.................................................................................................................8 3-1. 'Camino Real' strawberry ( Fragariaananassa Duch.) fruit firmness and calcium content association during 2003-04 season at GCREC-Dover................................53 3-2. 'Sweet Charlie' strawberry ( Fragariaananassa Duch.) fruit firmness and calcium content association during 2003-04 at GCREC-Dover...........................................54 3-3. 'Treasure' strawberry ( Fragariaananassa Duch.) fruit firmness and calcium content association during 2003-04 at GCREC-Dover...........................................55 3-4. 'Carmine' strawberry ( Fragariaananassa Duch.) fruit firmness and calcium content association during 2003-04 season at GCREC-Dover................................56 3-5. 'Strawberry Festival' strawberry ( Fragariaananassa Duch.) fruit firmness and calcium content association during 2003-04 season at GCREC-Dover .................57 3-6. 'Camarosa' strawberry ( Fragariaananassa Duch.) fruit firmness and calcium content association during 2003-04 season at GCREC-Dover................................58 3-7. University of Florida numbered line 97-39 strawberry ( Fragariaananassa Duch.) fruit firmness and calcium content association during 2003-04 season at GCRECDover.......................................................................................................................59 4-1. Interaction between soil and foliar calcium on strawberry ( Fragariaananassa Duch.) firmness at 3 mm deformation depth on 11 March 2003 with Fisher's least significant difference error bars...............................................................................94

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xi Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science INFLUENCE OF CALCIUM ON POSTHARVEST QUALITY AND YIELD OF STRAWBERRY FRUIT ( Fragaria × ananassa Duch.) By Camille Elizabeth Esmel May 2005 Chair: John R. Duval Co chair: Eric H. Simonne Major Department: Horticultural Sciences A typical Florida strawberry ( Fragaria × ananassa Duch.) grower uses Ca (NO3)2 (calcium nitrate) as the primary nitrogen source, which also provides Ca2+ (calcium) throughout the season. The limestone bedrock of Florida is karst topography can be a source of water-soluble Ca2+. In addition, many Florida strawberry growers apply supplemental Ca2+ to their crop, despite the lack of conclusive evidence of an increase in fruit quality or yield. The rationale for applying supplemental Ca2+ comes from calcium’s involvement in cell-wall integrity, and reduction of fruit quality when inadequately available at critical times. The association of Ca2+ with postharvest quality has not been well studied for Florida strawberries. Our objectives were to clarify the association of Ca2+ with postharvest quality attributes, and to determine the influence of supplemental Ca2+ on strawberry. A strong association between fruit firmness, and calcium content did not exist for strawberry. Few strong correlations were found between fruit firmness, and Ca2+ content. The negative

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xii correlation findings suggest that the increasing Ca2+ content of strawberry fruit could be detrimental to fruit firmness. This goes against the widely accepted concept that applying supplemental Ca2+ to strawberry fruit will increase firmness. Our findings make it obvious that leaf, and fruit Ca2+ content cannot be used to predict fruit firmness for the selected cultivars. It is apparent that these characteristics are independent of each other, and not linked. We found consistent insignificant results for preharvest supplemental Ca2+ on strawberry. Pre-plant applications to the soil (as gypsum), and foliar applications of Ca2+ (as calcium chloride or calcium sulfate) did not increase yield or improve postharvest quality of strawberry. These results are contrary to previous published studies in low Ca2+ environments, but consistent with studies conducted in high Ca2+ environments. We found that an injected fertilizer source of Ca2+ did not to influence postharvest quality, yield, or Ca2+ of strawberry. Therefore, any additional Ca2+ injected through the irrigation system from any source other than the Ca (NO3)2 was unnecessary, and financially wasteful. Plant growth and development did not increase with the additional Ca2+. Applying supplemental Ca2+ as a foliar spray, pre-plant soil amendment, or fertilizer injection did not improve postharvest quality or yield of strawberry fruit. Based on our findings, we recommend that cultivar choice be the first method for improving quality of strawberry fruits. Preharvest supplemental Ca2+ is not recommended as a method for improving postharvest quality of strawberry fruits.

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1 CHAPTER 1 INTRODUCTION TO FLORIDA’S STRAWBERRY INDUSTRY Production With 2,874 hectares of production at a total value of US$ 136 million (Figure 1-1) for the 2003 season (Florida Agricultural Statistics Service (FASS). 2003. http://www.nass.usda.gov/fl/ May 2004.), Florida is a major producer of fresh winter strawberries ( Fragaria × ananassa Duch.) in the United States. Average production has increased steadily over the past ten years (Figure 1-2). Of the 2,874 hectares of strawberries planted in Florida annually, 95% are located in Hillsborough and Manatee counties, while the remaining 5% are divided among Bradford, Dade, and Broward counties (Mossler, M.A. and O.N. Nesheim. Florida Crop/Pest Management Profiles: Strawberries. University of Florida Extension Publication CIR 1239 http://edis.ifas.ufl.edu/PI037 September 2004.) (Figure 1-3). Florida strawberry growers use the annual hill culture method for production. This method involves soil fumigation, formation of raised beds covered with black plastic, use of drip irrigation, and bare-root strawberry plants. Drip irrigation is primarily used to supply water and fertilizer. In early October, bare-root strawberry plants are established in the field, using overhead irrigation to reduce heat stress and ensure rapid establishment. Overhead irrigation is applied for approximately 7 to 12 days after transplanting (Simonne et al., 2003). The overhead irrigation system is also used for frost protection.

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2 Harvest Operations Harvesting of strawberries begins within 30 to 60 days after transplanting, based on location in Florida (Simonne et al., 2003). Strawberries are hand picked (starting in the morning, to minimize the amount of field heat that accumulates as the temperature increases during the day). Grading and packing occur in the field. Grading of strawberries is based on visual marketability of each individual fruit. Strawberries are not washed to remove residues, insects, or disease. The strawberries are packed into 0.55 or 1.1 L (pint or quart) containers, which can be closed clamshells or open containers. These containers are placed in corrugated cartons (flats) and directly stacked onto pallets. These pallets are transported to storage facilities for forced-air cooling, and shipment to consumers. Postharvest Operations Forced-air cooling for strawberries requires maintaining relative humidity between 90 and 95%, and temperature near 0°C (32°F). Forced-air cooling removes field heat by quickly forcing cool air through the palletized flats of strawberry fruits (Sargent, S.A., M.A. Ritenour and J.K. Brecht. Handling, cooling and sanitation techniques for maintaining postharvest quality. University of Florida Extension Publication. IFAS. http://edis.ifas.ufl.edu/CV115. October 2004.). The flow of air is stopped within a few degrees of the target temperature for the fruit tissue. Then the pallets can be wrapped in a sealed plastic film and injected with an elevated-carbon-dioxide gas mixture to retard microbial growth during shipment. Shipment of Florida strawberries begins in early December, peaks in March, and ends in late April or early May (Bertelsen, 1995). The length of time for shipment depends on the location of the destination market. For example, from Dover-Plant City,

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3 FL, to New York, estimated of shipment time is 20 h for travel alone. Including the harvesting, cooling, packing, and unpacking of the fruit, the best estimate of the time from the field to the consumer is between 48 h and 52 h. During shipment, strawberry fruits can experience shaking and bouncing within their packaging, which can cause bruising. Bruising allows an entry point for postharvest diseases, such as Rhizopus stolonifer Ehrenb. ex Fr. Before harvest, strawberries are inoculated with Botrytis cinerea Pers. ex Fr. (Botrytis fruit rot), which can remain dormant during postharvest storage conditions. Consumers want fresh, large, red, ripe fruits that are unblemished. Thus high quality is imperative for marketing. Maintaining Postharvest Quality Many factors determine the quality of any commodity. Cultivar, environmental conditions, and postharvest handling are important factors in determining postharvest quality. Cultivar selection is important in addressing postharvest quality issues such as firmness, because most postharvest factors are genetically controlled (Prange and DeEll, 1997; Sams, 1999). Environmental conditions can influence postharvest quality in strawberry and other commodities (Kader, 1991; Hancock, 1999; Prange and DeEll, 1997; Sams, 1999). Temperature has been shown to influence the soluble-solids content of muskmelon ( Cucumis melo L. subsp. melo var cantalupensis (Naudin)) (Welles and Buitelaar, 1988). Light quality and quantity influence postharvest fruit and vegetable flavor, composition, and texture (Mattheis and Fellman, 1999; Sams, 1999). Environmental conditions are not the only factors that can influence postharvest quality. Postharvest handling also influences the quality of a commodity. Prompt and rapid cooling (in addition to proper storage and transport temperatures) is critical for maintaining strawberry quality (Nunes et al., 1995). To maintain quality a commodity

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4 also must be harvested at the correct maturity stage. Postharvest physiological disorders are more likely in fruits picked too early or too late in their season than in fruits picked at the proper maturity (Kader, 1999). Despite the importance of these factors, the Ca2+ (calcium) level is most commonly associated with postharvest disorders and quality (Ferguson et al., 1999). Improving postharvest quality with Ca2+ applied as preor postharvest treatments has been successful in several commodities. Increased firmness has resulted from postharvest treatments of Ca2+ on apples ( Malus domestica Borkh.) and kiwifruit ( Actinidia chinesis Planch var deliciosa (A. Chev.)) (Gerasopoulos et al., 1996; Sams and Conway, 1993). Storage extension of honeydew ( Cucumis melo L. subsp. melo var inodorus (H. Jacq.)) and muskmelon has been achieved with preor postharvest treatments of Ca2+ (Lester and Grusak, 1999; 2001). A reduction in internal brown spot of potato ( Solanum tuberosum L.) tuber has been achieved with supplemental Ca2+ fertilization during the growing season (Clough, 1994). However, Hancock (1999) stated that improving strawberry fruit firmness with supplemental Ca2+ has had varied results. Quality of Florida Strawberry Strawberry production in Florida focuses on the window of November to February. The earlier the yield is produced, the higher the price. Introduced in 1992, 'Sweet Charlie' strawberry was the top cultivar in production until 2001. This cultivar produces high early yields, which are desirable to growers. Yet, it has soft tissue fruit and a disposition to damage at any point, from harvest to shipment. Foliar applications of Ca2+ have proven effective on numerous crops for improving firmness, but inconsistent scientific results have been reported for strawberry. Most studies conducted outside the United States have shown that increase in firmness can be attained with high CaCl2

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5 sprays. Within the United States, those claims of increased firmness have yet to be validated. Improving such a cultivar as 'Sweet Charlie' with foliar applications of Ca2+ would greatly benefit Florida strawberry growers, because it can be hypothesized that any cultivar (regardless of firmness attributes) could be improved with Ca2+ applications.

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6 Figure 1-1. Wholesale value of strawberry ( Fragariaananassa Duch.) harvested in Florida from 1991 to 2003 (based on data from Florida Agriculture Statistic Directory, 2004 http://www.floridaagriculture.com/pubs/pubform/pdf/Florida_Agriculture_Statistical_Directory_2004.pdf p.92. September 2004) 90000 100000 110000 120000 130000 140000 150000 160000 170000 180000 1991-92 1992-93 1993-94 1994-95 1995-96 1996-97 1997-98 1998-99 1999-00 2000-01 2001-02 2002-03 Production SeasonProduction Value (1,000 US $)

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7 Figure 1-2. Hectares of strawberries ( Fragaria ananassa Duch.) planted in Florida from 1991 to 2003 (based on data from Florida Agriculture Statistic Directory, 2004 http://www.floridaagriculture.com/pubs/pubform/pdf/Florida_Agriculture_Statistical_Directory_2004.pdf p.92. September 2004) 2000 2100 2200 2300 2400 2500 2600 2700 2800 2900 3000 1991-92 1992-93 1993-94 1994-95 1995-96 1996-97 1997-98 1998-99 1999-00 2000-01 2001-02 2002-03 Production Seaso nHectare

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8 Figure 1-3. Strawberry ( Fragariaananassa Duch.) producing counties in Florida based on description. Adapted to a map from Mossler, M.A. and O.N. Nesheim. 2003. Florida Crop/Pest Management Profiles: Strawberries. University of Florida Extension Publication CIR 1239 http://edis.ifas.ufl.edu/PI037 September 2004.

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CHAPTER 2 INFLUENCE OF CALCIUM ON FRESH PRODUCE QUALITY Introduction Calcium (Ca2+) has an important role in postharvest quality, because of its role in plant metabolism. The essentiality of this element has been extensively reviewed in the areas of maintaining cell-walls and membrane integrity, and its role in reducing the rate of senescence and softening (Demarty et al., 1984; Ferguson, 1984; Kirkby and Pilbeam, 1984; Marschner, 1995; Poovaiah et al., 1988). Calcium ranks as the seventh most abundant element in the earth’s crust and hydrosphere (Delwiche, 1975), but the physiological disorder of Ca2+ deficiency still reduces produce quality worldwide. The objective of this review is to critically examine the influence of Ca2+ on quality of fruits and vegetables by (1) presenting previous Ca2+ research in terms of consistency to benefit postharvest quality, (2) focusing on the correlation among Ca2+ content and quality attributes, and (3) evaluating Ca2+ applications on quality of strawberry. Causes of Calcium-Related Disorders Calcium deficiency in fruits and vegetables is the physiological disorder most associated with reduction in quality (Ferguson et al., 1999) (Table 2-1). It is also one of the best reviewed topics in the influence of an essential element on postharvest quality. The reduction in quality occurs when cell-wall and membrane integrity become reduced under inadequate Ca2+ supply. Conditions of deficiency are more likely to be related to inefficient Ca2+ distribution than poor uptake and supply (Bangerth, 1979). Factors that can negatively affect distribution of Ca2+ are (1) environmental conditions, (2) cultural 9

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10 practices, and (3) existing nutritional factors that affect Ca2+ uptake. Some environmental conditions contributing to Ca2+ related disorders are temperature, light, and humidity (Pavia et al., 1998; Saure, 1998; Weston and Barth, 1997). The impact of soil moisture on Ca2+ distribution has been often cited as a factor contributing to Ca2+ related disorders (Ho et al., 1999; Prange and DeEll, 1997; Shear, 1975b). Ca2+ uptake within the soil solution is done by young root tips and passively translocated through the plant with the transpirational stream. Under drier soil conditions, less Ca2+ is translocated. Cultural practices that may influence Ca2+ disorders include cultivar, row covers, and soil moisture regime. Genotypic differences in nutrient efficiency are related to the differences in efficiency in acquisition by the roots and in the utilization by the plant or both (Marschner, 1995). Calcium efficiency of cultivars has been investigated in tomato ( Lycopersicon esculentum Mill.) (Ho et al., 1993) and cauliflower ( Brassica oleracea var capitata L.) (Hochmuth, 1984). Regardless of commodity, identification cultivars that are tolerant to nutrient stress aids in the improving of cultivars to avoid nutrient related disorders. Ho et al. (1993) reported that the physiological basis of susceptibility to blossom-end rot (BER) was the interaction between fruit growth habit and the growing environment. Leaf transpiration determines the movement of Ca2+ within the plant and its availability to the fruit at times of rapid growth (Bangerth, 1979). Antitranspirants and row covers have the potential to reduce plant transpiration and therefore decrease the incidence of Ca2+ disorders. Row covers aim to minimize transpiration from the plant leaf surface and therefore reducing rapid growth. Alexander and Clough (1998)

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11 investigated spun bound row covers, Ca2+ and the influence on BER, a Ca2+ related disorder, of bell pepper ( Capsicum annum L.). Their study found that the row cover reduced BER incidence. Alexander and Clough (1998) suggest that the environment in which the study was conducted and the leaf/fruit transpiration ratio were involved in the development of BER. The level of soil moisture has been reported to influence BER in tomato. Water stress of tomato plants aggravated BER by Franco et al. (1999) and Taylor et al. (2004). Existing nutrition factors that can influence Ca2+ uptake are caused by other nutrients inducing growth or competition with Ca2+. Nitrogen, potassium (K+), magnesium (Mg2+), and salinity (Na+) have been studied for their ability to inhibit or influence the development of Ca2+-related disorders (Cubeta et al., 2000; Ehret and Ho, 1986; Richardson and Al-Ani, 1982; Sugar et al., 1992; Taylor et al., 2004; Weston and Barth, 1997). Nitrogen influences crop size, fruit size, and fruit/shoot ratios (Ferguson and Watkins, 1989) and nitrogen source as ammonium (NH4 +) can compete with Ca2+ for soil cation exchange sites. Magnesium and K+ both have been implicated in contributing to bitter pit in apple ( Malus domestica Borkh.) by competing for binding sites on cellwalls, membranes, and inhibiting Ca2+ uptake into cells (Ferguson and Watkins, 1989). In strawberry ( Fragaria × ananassa Duch.), high NaCl could induce Ca2+ deficiency in leaves and additional Ca2+ ameliorated and corrected the Ca2+ deficiency (Kaya et al., 2002). These factors have been extensively studied and reviewed for influence on Ca2+ distribution and uptake on crop as tomato, leafy crops, and pome fruits. This review will focus on soil and tissue Ca2+ content, and preand postharvest Ca2+ treatments and their effect on quality of commodities.

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12 Quality Issues Related to Calcium The application of Ca2+ to correct or prevent the reduction in quality associated with low Ca2+ levels is one part of the multifaceted approach to Ca2+ research and its connection to quality. Fruits respond to Ca2+ treatments for prolonged periods after harvest (Poovaiah et al., 1988). Research has concentrated on Ca2+ and its function in quality focuses on (1) minimizing the loss of quality, (2) storage extension, and (3) increasing a commodity's tissue firmness or textural attributes. These areas are often researched together, because the complex nature of Ca2+ on quality. Minimizing Quality Loss The incidence of specific Ca2+-related disorders have resulted in extensive research over many years on increasing Ca2+ in fruit, and on understanding the role Ca2+ plays in the ripening process (Ferguson et al., 1995). Apple, pear ( Pyrus communis L) pepper, tomato, leafy vegetables (lettuce ( Lactuca sativa L.), and collard greens ( Brassica oleraceae , var acephala ), are commodities have been reported to develop Ca2+ related disorders during crop growth or in postharvest storage. Reduction in quality at some point is expected when the level of Ca2+ drops below the critical concentration for development. The critical concentration is the level at which an essential plant nutrient becomes deficient and in tomatoes the critical concentration has not been determined (Saure, 2001; Taylor and Locascio, 2004). The critical concentration in apple is dependent on the type of sample and cultivar being sampled. A level of Ca2+ within 'Cox's Orange Pippin' apple in which the fruit could be rejected based on a prediction of bitter pit is 40 mgkg-1 Ca2+ fresh weight (Ferguson and Watkins, 1989). Calcium applications on apple and pear are a method to control bitter pit and cork spot, which can be exacerbated during the extended storage of fruit. Recommended rates

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13 of calcium chloride (CaCl2) for apples ranges from 17 to 56 kgha-1yr-1 based on the potential severity of nutritional disorders (Biggs, 1999). In pears, a reduction of black end and not a complete control of the disorder were obtained with foliar Ca2+ applications (Raese, 1994). Foliar applications of 610 mgL-1 Ca2+ from CaCl2 (34% Ca2+ as CaCl2 source at 681 g per 379 L rate) improved fruit quality and Ca2+ content of 'd'Anjou' pears (Raese and Drake, 2000a). Increasing fruit Ca2+ content in these commodities has reduced postharvest disorders. Several studies have focused on different formulations in comparison to CaCl2 for postharvest decay and bitter pit control (Bramlage et al., 1985; Raese and Drake, 2000b; 2002). Results from these studies have shown products with or based on CaCl2 increase quality. High rates of CaCl2 have shown to improve quality of apple, but in addition can cause leaf scorch and defoliation of trees. Fall sprays of 16,000 and 24, 000 mgL-1 Ca2+ from CaCl2 (16 and 24 kgha-1 of Ca2+) defoliated apple trees, therefore, timing and rate of foliar Ca2+ applications seem to be factors in leaf damage incidence (Wojcik, 2001b). Postharvest applications of Ca2+ have been researched as another way to permeate apple tissue with Ca2+. Postharvest applications of Ca2+ have reduced decay in apples. Sams and Conway (1993) reported pressure infiltration of Ca2+ into apples increased Ca2+ content of the fruit two to three times greater than with those fruit where were sprayed or dipped. A review of postharvest application of Ca2+ on apples and potatoes found that pressure infiltration was superior to both vacuum infiltration and dip methods of postharvest Ca2+ treatments (Conway et al., 1994). Postharvest applications allow Ca2+ solutions to have direct contact with the surface of the fruit. Conway et al. (1992), Conway et al. (1994), and Shear (1975a; 1975b), have cited this crucial component of

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14 preand postharvest Ca2+ treatments. However, undesirable injuries to the fruit and regulations in some countries have prompted researchers to focus on preharvest applications as the method to increase Ca2+ content and therefore fruit quality (Wojcik, 2001a; 2001b). Multiple factors have been implicated with the development of blossom end rot (BER) of tomato and pepper, and tipburn of leafy vegetables. Both of these localized Ca2+ deficiencies have been also called Ca2+ related disorders and physiological Ca2+ disorders (Marcelis and Ho, 1999; Saure 1998; 2001; Taylor and Locascio, 2004). Unlike tree fruits, tomatoes, peppers and leafy vegetables do not have shelf lives that can potentially last for greater than 6 months in controlled atmosphere storage. Immediate loss at harvest caused by BER or tipburn can and does occur. Saure (2001) stated that BER research has over emphasized the attainment of high Ca2+ levels in fruit and not explored the other possible environmental stressors on plant growth and development as casual agents of the disorder. Fluctuations in soil water, competitive cations, and salinity are stressors that can affect plant growth, development, and a plant's ability for Ca2+ uptake and distribution. In addition, recommendations for reducing incidence of BER and tipburn are based on choosing cultivars that are not susceptible to these disorders (Kinet and Peet, 1997; Johnson 1991; Rosen 1990; Taylor and Locascio 2004). Differences in cultivars to tolerate Ca2+ disorders can be linked to efficiency of Ca2+ distribution within the plant. Until the causes of cultivar susceptibility to Ca2+ disorders are elucidated, reduction of possible factors inducing Ca2+ disorders can be the only solution commonly available to minimize losses.

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15 Postharvest Storage Extension Kiwifruit ( Actinidia chinesis Planch var deliciosa (A.Chev.)), honeydew melon ( Cucumis melo L. subsp. melo var inodorus (H. Jacq.)), and muskmelon ( Cucumis melo L. subsp. melo var cantalupensis (Naudin)) have all shown increased storage with Ca2+ treatments. Gerasopoulos et al. (1996) reported an extension in storage of kiwifruit with foliar CaCl2 solutions of 2,710 and 5,420 mgL-1 Ca2+ from CaCl2 (0.75 and 1.5% CaCl2). The usual 5to 6-month storage-life was shown to be extended an additional 5 to 10 weeks with 2,710 mgL-1 Ca2+ and 10 to 18 weeks with 5,420 mgL-1 Ca2+ from CaCl2. In addition, our study found that titratable acidity increased by a range of 0.14 to 0.29% and soluble-solids content decreased by a range of 0.32 to1.4% over the control at 2,710 and 4,065 mgL-1 Ca2+ from CaCl2 (0.75 and 1.13% from CaCl2) (Gerasopoulos et al., 1996). In kiwifruit, high titratable acidity and low soluble-solids content show unripe and less mature fruits. Other studies conducted using preharvest foliar treatments of 22,392 mgL-1 Ca2+ from NutriCal (8% Ca2+, three applications at 9.33 Lha-1) in conjunction with control atmosphere (10% CO2 and 3% O2) on kiwifruit reported different results. Control atmosphere involves maintain an atmospheric composition that is different from ambient air composition (about 78% N2, 21% O2, and 0.03% CO2); generally, O2 below 8% and CO2 above 1% are used (Kader, 2003). Basiouny and Basiouny (2000) reported an increase in total titratable acidity of kiwifruit over the 8 weeks of cold storage, but no significance was found among treatments. Soluble-solids content significantly increased in kiwifruits treated with only controlled atmosphere by 82% over the control. In addition, those kiwifruits receiving the Ca2+ treatment alone had a minimum increase in soluble-solids content of 71.3% (Basiouny and Basiouny, 2000). In addition, supplemental Ca2+ and controlled atmosphere benefited kiwifruit during

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16 storage as determined by quality, but controlled atmosphere was more effective than supplemental Ca2+. Honeydew and netted muskmelon showed positive responses to Ca2+ treatments in which storage has been assessed. Honeydew melons and netted muskmelon have maturity indices for soluble-solids content of 8 to 10% and 9 to 11%, respectively (Lester and Shellie, 2003; Shellie and Lester, 2003). Expansion of the fresh produce market requires exploration of possible methods of storage-life extension for highly perishable commodities. An application of additional Ca2+ to commodities has been viewed as the potential non-fungicidal, senescence delaying treatment. Studies conducted on honeydew and netted muskmelon with pre and postharvest Ca2+ treatments (1215 and 1823 mg·L-1 Ca2+ from amino acid chelated Ca2+ (6% Ca2+ at 2.3L·ha-1 in 75.7 to 113.6 L of water), 3,038 and 2,025 mg·L-1 Ca2+ from mannitol-complexed Ca2+ (10% Ca2+ at 2.3L·ha-1 in 75.7 to 113.6 L of water); 160 and 240 mg·L-1 Ca2+ from CaCl2, amino acid chelated Ca2+, or EDTA chelated Ca2+(0.16 and 0.24 M Ca2+), respectively) did not significantly affect soluble-solids content (Lester and Grusak, 2001; 2004). Yet, in these studies storage was extended with chelated Ca2+ treatments. Honeydew melons are able to absorb preharvest applications of chelated Ca2+ in sufficient amounts to have an impact on quality, unlike netted muskmelon in which Ca2+ absorption was very poor (Lester and Grusak, 2004). In their study, observing the movement of labeled Ca2+, Lester and Grusak (1999) reported two significant findings on netted muskmelon. First, only 9% of the labeled Ca2+ was measured in the mesocarp tissues. The investigators suggested that the morphologically difference of the netted muskmelon attributed to the poor distribution of Ca2+ across the exocarp. Second, once

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17 the Ca2+ diffused to the hypodermal mesocarp tissues, it continued to diffuse to the middle and inner layers of the fruit. The investigators suggested that the continuation of the Ca2+ to diffuse to the inner portions of the melon (pepo) was caused by the seeds. Edible mushrooms have an extremely high respiration rate (Saltveit, 2003) and current research has focused on applying supplemental Ca2+ through CaCl2 treatments in irrigation water. With the addition of 361 and 1,806 mg·L-1 Ca2+ from CaCl2 (0.1 and 0.5% CaCl2) in irrigation water mushrooms ( Agaricus bisporus ) were lighter in color and bacterial growth was reduced in storage (Barden et al., 1990). Low rates of CaCl2 in irrigation water have shown to improve color of A. bisporus . Mushroom color was improved in mushrooms irrigated with 903 mg·L-1 Ca2+ from CaCl2 (0.25% CaCl2) for white strains only (Diamantopoulou and Philippoussis, 2001). The addition of 1,265 mg·L-1 Ca2+ from CaCl2 (0.35 % CaCl2) in irrigation water had a positive influence on postharvest color in the reduction of browning during late flushes or after storage (Philippoussiss et al., 2001). In addition, it has been shown that, storage of mushrooms can be extended with CaCl2 treated irrigation water. Barden et al. (1990) reported treatment with CaCl2 delayed senescence, with cap opening and stripe growth at 4°C. Other researchers showed that the beneficial effect of high CaCl2 (2,710 and 3,613 mg·L-1 Ca2+ (0.75 and 1% CaCl2)) rates on mushroom could decrease softening in storage (Philippoussis et al., 2001). Despite these benefits of CaCl2 in irrigation water to extend storage and increase quality for commercial production, researchers have suggested further investigation for different mushroom strains (Diamantopoulou and Philippoussis, 2001).

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18 Commodities and cultivars with higher rates of respiration tend to have shorter storage life than those with low rates of respiration (Saltveit, 2003). Avocados ( Persea americana Mill.) and mangos ( Mangifera indica L.) are tropical fruits with high to moderate respiration rates at 20 to 50 and 10 to 22 mg CO2kg-1h-1 at 5C, respectively (Paull and Chen, 2003; Woolfe et al., 2003). Tingwa and Young (1974) first reported both 4008 mgL-1 Ca2+ from CaSO4 and CaCl2 (0.1 M CaSO4 and 0.1 M CaCl2) inhibited the rate of respiration in intact and sliced avocado fruit. For a climacteric fruit such as avocado, the inhibition of respiration of intact fruit suggests that storage can be extended with Ca2+ treatments. The avocados in this investigation containing high Ca2+ were always late in ripening and produced less CO2 and ethylene (C2H4) at the climacteric peak (Tingwa and Young, 1974). Wills and Tirmazi (1982) confirmed results of previous studies on CaCl2 treatments to delay ripening of avocados. This investigation used 375 and 250 mm Hg pressure and 3,613, 7,226, 14,453, and 28,905 mgL-1 Ca2+ from CaCl2 (1, 2, 4, and 8% CaCl2) on 'Hass' and 'Fuerte' avocados. Respiration and external attributes were focused on in these studies and the affect of Ca2+ treatments. Commercial application of 2,004 and 4,008 mgL-1 Ca2+ from CaCl2 (0.05 and 0.1 M Ca2+ from CaCl2) are not feasible, because vacuum-infiltration (50 mm Hg for one minute) and its adverse effect on external quality after storage (Eaks, 1985). Similar results on external quality and delayed ripening of 'Monroe' and 'Reed' avocados with 14,453 mgL-1 Ca2+ from CaCl2 (4% CaCl2) vacuum infiltrated (380 or 120 mm Hg pressure for 5 minutes) were reported by Davenport (1984). In this investigation, over 60% of the fruits were found with some decay at ripening with the surface affected ranging from 25 to 75%. Davenport (1984) cited that surface

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19 sterilization did not inhibit breakdown associated with Ca2+ treatments and further did not recommend vacuum infiltration on avocados to increase storage-life. Preand postharvest treatments with CaCl2 have both been inconsistent in increasing Ca2+ content and extending storage of mangos. Singh et al. (1993) reported storage extension in mangoes treated with of 6,000 mg·L-1 Ca2+ from CaCl2 (0.6% Ca2+ from CaCl2) as a preharvest foliar spray. Postharvest applications of Ca2+ as CaCl2 had variable results in extending storage, Ca2+ content, and respiration rate. Shorter and Joyce (1998) applied 4,000 mg·L-1 Ca2+ (4 g·L-1 Ca2+ from CaCl2) at 247, 495, and 742 mm of Hg to mangos which resulted in no respiratory climacteric. This investigation also found an increase in Ca2+ content of the skin caused by treatments. In comparison to this investigation, postharvest application of 28,905 mg·L-1 Ca2+ from CaCl2 (8% CaCl2), in conjunction with modified atmosphere packaging and surfactants, increased Ca2+ content, delayed ripening and prolonged storage of mangoes (Singh et al., 2000). In mango fruit, the method of the Ca2+ application can directly affect the response in terms of quality. Joyce et al. (2001) suggested that cultivar differences, level of maturity and inherent nutrients as factors affect the consistency of Ca2+ postharvest treatments on mangos. Increasing Firmness with Calcium Treatments Fruit texture is a collective term that encompasses the structural and mechanical properties of a food and their sensory perception in the hand or mouth (Abbott and Harker, 2003; Sams, 1999). Fruit firmness pertains to the strength of the fruit tissue to sustain a force. This one measurement is a part of the sensory perception of texture. Penetrometer measurements are moderately well correlated with human perception of firmness and with storage life, and consequently this technique has received widespread acceptance for a number of horticultural commodities, such as apple, cucumber ( Cucumis

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20 sativus L.), kiwifruit, peach ( Prunus persica L.), and pear (Abbott, 1999). Furthermore, human perception of quality is biased to individual preference for textural attributes, such as crispness, viscous and stringiness. Viscous can be a significant component to tomato, cherry, citrus and various small fruits and currently no commonly accepted commercial instrument for measuring this parameter of texture (Abbott, 1999). Calcium is the plant nutrient most frequently associated with fruit quality in general and firmness in particular (Sams, 1999). The greatest amount of research has been conducted on the influence of Ca2+ treatments on quality of apple. Firmness of apple fruit is used to determine quality and storability (Glenn and Poovaiah, 1990). Apples are a commodity that can have an extended storage of greater than 6 months in controlled atmosphere. Maintaining firmness with preharvest Ca2+ treatments has been welldocumented (Carbo et al., 1998; El-Ansary et al., 1994; Raese and Drake, 2000b; 2002; Wojcik, 2001b; 2002) and postharvest applications (Beavers et al., 1994; Glenn and Poovaiah, 1990; Picchioni et al., 1998; Saftner et al., 1998; Sams and Conway, 1993; Siddiqui and Bangerth, 1996) applications on apples. Raese and Drake (2002) showed that fruit firmness and fruit Ca2+ content were highest in fruit from trees sprayed with CaCl2. Other studies have showed that high fall applications of foliar Ca2+ cause leaf damage and tree defoliation at 8,000, 16,000, and 24,000 mgL-1 Ca2+ from CaCl2 (8, 16, and 24 kgha-1 Ca2+) (Wojcik, 2001b). This investigation also showed that fall foliar Ca2+ sprays had a positive effect on fruit firmness. Postharvest vacuum infiltration of 9,033 mgL-1 Ca2+ from CaCl2 (2.5% CaCl2) increased Ca2+ content, but rotting was more prevalent in fruits receiving vacuum infiltration (Hewett and Watkins, 1991).

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21 Kiwifruit have also benefited from preand postharvest Ca2+ treatments to improve firmness. Preharvest Ca2+ treatments resulted in retarded softening during storage at 0 and 20C (Gerasopoulos et al., 1996). The investigators reported that fruits sprayed with 5,419 mgL-1 Ca2+ from CaCl2 (1.5% CaCl2) had an increased Ca2+ content and exhibited the highest differences in firmness, soluble-solids content and titratable acidity compared to the control. Other studies have found similar results with postharvest applications of Ca2+. Hopkirk et al. (1990) reported that kiwifruit treated with a postharvest application of 10,839 mgL-1 Ca2+ from CaCl2 (3% CaCl2) were as firm as fruits treated with higher concentrations (14,453 and 18,066 mgL-1 Ca2+ from CaCl2 (4 and 5% CaCl2)). All postharvest Ca2+ treatments in this investigation retarded the rate of softening during the first 6 weeks of storage. However, Ca2+ treatments resulted in the development of small pits in the skin of fruit between 6 and 10 weeks after treatment, the most severe observed with 18,065.8 mgL-1 Ca2+ from CaCl2 treatment (5% CaCl2) (Hopkirk et al., 1990). Gerasopoulos et al. (1996) and Basiouny and Basiouny (2000) did not observe this pitting with preharvest Ca2+ treatments on kiwifruit during storage. The surface pitting can be associated with the submersion of fruit in postharvest Ca2+ treatments. In conclusion, Hopkirk et al. (1990) suggested that the total Ca2+ content of the fruit at harvest could not predict the storage of kiwifruit. Basiouny and Basiouny (2000) reported that controlled atmosphere storage was more effective than preharvest Ca2+ treatment in maintaining fruit quality in storage. Cherry ( Prunus avium L.), and blueberry ( Vaccinium ashei Reade) are commodities whose response to Ca2+ treatment varied. Surface pitting of cherry fruit is a

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22 disorder caused by bruising and directly related to fruit firmness (Facteau, 1982). Research has showed that preharvest treatments of 1,409 mg·L-1 Ca2+ from CaCl2 (3.9 g·L-1 CaCl2) and postharvest treatments of 10,839 mg·L-1 Ca2+ from CaCl2 (30 g·L-1 CaCl2) would reduce surface pitting on cherry fruit (Lidster et al., 1979). This investigation investigated the influence of Ca2+ on impact damage of cherry fruit. No firmness measurements were attained from fruit bruised and pitted in this investigation. Facteau (1982) reported that increasing firmness of cherry fruits might not necessarily be associated with a reduction in surface pitting. The author focused on the association of Ca2+ with firmness. Facteau et al. (1987) stated that increased fruit puncture force, and firmness was related to reduce mechanical damage, and each measurement system did not reflect similar responses to application of Ca2+. Within this investigation conflicting results were apparent for increasing firmness with preharvest applications of 950, 1,400, and 3,800 mg·L-1 Ca2+ from CaCl2 (950, 1,400, and 3,800 mg·L-1 Ca2+) applied as multiple sprays throughout the growing season. Calcium treatments did not contribute to increase cherry fruit firmness or the resistance to mechanical injury. Hanson et al. (1993) reported that high bush blueberries ( Vaccinium corymbosum L.) treated at postharvest with 3,613, 7,226, 10,839 or 14,453 mg·L-1 Ca2+ from CaCl2 (1, 2, 3, and 4% CaCl2) had improved firmness attributes. The flavor of the fruit was adversely affected with treatments that significantly improved postharvest quality (7,226 and 14,453 mg·L-1 Ca2+ from CaCl2 (2 and 4% CaCl2)). Increases in Ca2+ content were not evaluated in this investigation. Preharvest Ca2+ treatments on rabbiteye blueberries ( Vaccinium ashei Reade) as chelated Ca2+ increased firmness (Basiouny and Woods 1993; Basiouny 1994). These studies found foliar and soil applications of chelated Ca2+

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23 increased tissue Ca2+ content of high bush blueberries. A study conducted by Hanson (1995) using foliar CaCl2 of did not increase in firmness or Ca2+ content of blueberries. Environment and genetic factors may also be involved in blueberry fruit response to Ca2+. Perhaps as suggested by Facteau (1982) sweet cherry tree vigor and crop load can affect fruit firmness. Postharvest storage of mangoes has been successfully extended with postharvest Ca2+ treatments and modified atmosphere (Singh et al., 2000). Fruit firmness was increased with a postharvest treatment of 28,905 mgL-1 Ca2+ from CaCl2 (8% CaCl2) compared to the control in mango. Vacuum infiltration of Ca2+ into mangos has shown to have several negative effects. Injury has been reported to occur with partial pressure infiltration of Ca2+ (4,000 mgL-1 Ca2+ from CaCl2 (4 gL-1 Ca2+ from CaCl2)) at 247, 495, and 742 mm Hg for 5 minutes (Shorter and Joyce, 1998). This investigation concluded that small differences in firmness occurred midway during storage of the experiment. In addition to these results, further investigation of Ca2+ vacuum infiltration on mangoes concluded treatments (4,000 mg L-1 Ca2+ from CaCl2 (4 gL-1 Ca2+ from CaCl2) at 247 mm Hg for 5 minutes) did not affect firmness of fruit of 'Kensington', Sensation', 'Irwin', and 'Palmer' cultivars (Joyce et al., 2001). These results suggest that vacuum infiltration 4,000 mgL-1 Ca2+ from CaCl2 (4 gL-1 Ca2+ from CaCl2) at 247 mm Hg for 5 minutes does not increase firmness of mangoes, but submersing mangoes in solutions of 28,905.3 mgL-1 Ca2+ (8% CaCl2) from CaCl2 for 20 min does increase firmness. The pressure of infiltration can cause physiological damage within the mango preventing increases in firmness.

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24 Attainment of relatively high concentrations of Ca2+ in fruit is accepted as a desirable objective of horticultural production (Ferguson et al., 1995). A better understanding of the association between Ca2+ and firmness needs to be clarified for commodities in which Ca2+ can prove to be beneficial in altering firmness attributes. The use of correlations to understand the interaction between Ca2+ applications and fruit firmness is a tool and underused in these studies. Correlation of Tissue Calcium and Fruit Firmness Correlations between Ca2+ content and quality of a commodity are not published with any consistency in studies involving these two parameters. Most studies evaluated the increase in firmness and Ca2+ and concluded that they are related. A simple correlation to test the association can only strengthen the argument that Ca2+ is a major factor in improving firmness. Previous researchers have used both statistical correlations and regression models to help describe results obtained by Ca2+ treatments. Studies on kiwifruit, papaya ( Carica papaya L.), blueberry, apricot ( Prunus armeniaca L.), and apple have conducted correlations of Ca2+ and firmness. Gerasopoulus et al. (1996) found that additional Ca2+ and firmness in kiwifruit were highly positively correlated (R2 = 0.93, Intercept = 52.18, Slope = 0.105) for pericarp tissue, but other postharvest quality measures (titratable acidity and soluble-solids content) had a highly negative correlation with Ca2+ content. In contrast, Hopkirk et al. (1990) found for cultural variables such as crop load, fruit size, position on vine, that Ca2+ content and fruit firmness were poorly correlated (r2 = -0.28, n = 14) and that none of the correlations between fruit Ca2+ levels and firmness at harvest or at any other of the 6 measurements were significant. Both studies used ‘Hayward’ kiwifruit, but the studies were done in two different locations, Crete and New Zealand respectively. Climate has

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25 been cited in the past as a preharvest factor affecting postharvest quality (Prange and DeEll, 1997) and can be responsible for these differences. Qiu et al. (1995) found mesocarp Ca2+ concentration related to the rate of softening of papaya fruit. This investigation applied Ca2+ at four different stages of growth. The soil fertilizer treatments consisted of control, Ca2+ as CaCO3, Ca2+ and K+, K+ and N. The papaya trees received the Ca2+ treatment as a side dress of CaCO3 at 192 grams per tree every month. For each soil fertilizer treatment, five papaya trees were sprayed with 2 L of de-ionized water or 7,226 mgL-1 Ca2+ from CaCl2 (2% CaCl2) every 2 weeks for 3 months. After harvest, fruits were washed with de-ionized water or 7,226 mgL-1 Ca2+ from CaCl2 (2% CaCl2). For each treatment, a plug was extracted for firmness measurements and treated with either ETGA (Ethylene glycol-bis-(2aminoethyl)-N,N,N', N'-tetraacetic acid), 10 mgL-1 (10 mM); sodium citrate, 50 mgL-1 (50 mM); CaCl2, 18 mgL-1 (50 mM) Ca2+ at 500 mm Hg for 20 seconds. The papaya exhibited low mesocarp Ca2+ uptake from postharvest Ca2+ treatments. This was related to preharvest environmental conditions and fertilization (Qiu et al., 1995). Correlation between Ca2+ content and firmness on blueberry fruits are weak, despite the strong correlation between the rate of Ca2+ applied and firmness (Basiouny, 1994; Basiouny and Woods, 1992). No r2-value was published in either study for the correlations conducted between Ca2+ content and fruit firmness of blueberry. Other studies, conducted on blueberry lack statistical correlations between Ca2+ and firmness. Tzoutzoukou and Bouranis (1997) reported a significant increase in firmness with preharvest Ca2+ application of 1,806, 2,529, or 2,809 mgL-1 Ca2+ from CaCl2 (0.5, 0.7 and 0.8% CaCl2) and a strong positive correlation (r2 = 0.87) on apricot. Other

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26 commodities morphologically similar (peach and nectarine ( Prunus persica L.)) do not have clearly associated relationship between firmness and Ca2+. Crisosto et al. (2000) found no increase in fruit tissue Ca2+ or fruit firmness when preharvest Ca2+ as 744.5 mgL-1 Ca2+ from Link Calcium (6% Ca2+) in one, two, five, or six applications or 1,585 mgL-1 Ca2+ from Stopit (7% Ca2+ buffered CaCl2 solution) in eight applications over the growing season to nectarine and peach. In perspective, nectarine and peaches were reported to have 3.0 108 mgkg-1 Ca2+ dry weight compared to the range of 4,000 to 1,000 mgkg-1 Ca2+ dry weight reported for apricot. This suggest that fruit size is an important factor for Ca2+ distribution and the corresponding increase in fruit firmness in Prunus spp . Glenn and Poovaiah (1990) reported Ca2+ content of apple was positively associated with both tensile (r = 0.87, y =136x + 2.8 105) and compression (r2 =0.82, y = 0.0126x + 43.7) measurements used to determine textural attributes. This investigation used postharvest infiltration applications of 14,452 mgL-1 Ca2+ from CaCl2 (4% CaCl2) at 210 mm of Hg for 2 minutes. Beavers et al. (1994) obtained positive correlations between tissue Ca2+ content and firmness for all cultivars with postharvest infiltration applications of 7,300, 14,600, 29,100, 58,200 mgL-1 Ca2+ from CaCl2 or Ca2+ EDTA (Ethylenediamine-tetraacetic acid disodium salt) chelate (0.73, 1.46, 2.91, and 5.82% Ca2+ from CaCl2) (r2 =0.95, y = 52.83 + 0.01x -2.59x2) or Stopit (7% Ca2+) (r2 = 0.99, y = 49.19 + 0.02x-5.04x2) at 772 mm of Hg for 6 minutes. They also reported that chelated Ca2+ caused excessive fruit injury, preventing accurate textural data to be collected. Saftner et al. (1998) reported correlation coefficient of r2 = 0.95 for postharvest Ca2+ treatments (2,804, 5,609, 6,811, 8,014, 9,616, 10,818, 13,623 mgL-1

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27 Ca2+ from CaCl2 (0.07, 0.14, 0.17, 0.30, 0.24, 0.27, and 0.34 moleL-1 CaCl2) at 772 mm of Hg for 3 minutes) and fruit firmness. In contrast, Carbo et al. (1998) reported no significant effect between preharvest Ca2+ sprays (13,224 mgL-1 Ca2+ from CaCl2 (36.6% CaCl2 at 1.0 L per 100 L)) and fruit firmness. This investigation did not report a correlation coefficient (r2-value) for preharvest Ca2+ sprays on fruit firmness. Distinctively, Carbo et al. (1998) also reported that a negative correlation existed between the total number of preharvest Ca2+ applications and the percentage of bitter pit incidence (P-value = 0.01, r2 = 0.23). The authors stated that a significant linear trend was found on fruit firmness depending on the number of applications (P-value = 0.03, r2 = 0.19). Most of the studies correlated Ca2+ applications to fruit firmness, when a more accurate correlation could be conducted between Ca2+ content within the fruit and fruit firmness analysis. These studies establish a significant correlation relationship between postharvest Ca2+ applications and fruit firmness in apple. Excluding commodities that are very similar in morphology, taxonomy and culture (apples, peach, apricots, and nectarines), very few individual commodities have common trends in their response to supplemental Ca2+. Therefore, it is difficult to conclude that strawberry would benefit from supplemental Ca2+ based on research on other commodities not similar in morphology, taxonomy or culture. Strawberry plants are both cultivated as an annual and perennial crop and within the Rosaceae family (within the same family as apple, apricot, peach, nectarine, and cherry). The strawberry is actually a false fruit or a ripened floral receptacle (Hancock, 1999). Fig ( Ficus carica L.) is the only other commodity with similar to strawberry in anatomical portion considered edible. No extensive research has been conducted on this commodity for increasing fruit

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28 quality with Ca2+ treatments. Therefore, it is easy to hypothesize that strawberry fruit would have their own distinct response to supplemental Ca2+. Improving Strawberry Fruit Quality with Calcium Studies conducted on strawberry to improve postharvest quality with supplemental Ca2+ treatments have had inconsistent results. An early study conducted to improve strawberry quality used 'Sparkle' strawberry and four applications of 1,445 mg·L-1 Ca2+ from CaCl2 (0.4% CaCl2) before harvest (Eaves and Leefe, 1962). This simple study found a significant increase of 1.2% in strawberry fruit firmness of fruit sprayed with Ca2+ over the control on all four harvest dates. Levels of Ca2+ in the soil and water were not reported in this investigation. Calcium chloride sprays of 5, 10, 15, and 20 kg·ha-1 delayed softening, ripening, and mold development of 'Kent' and 'Tribute' strawberries (Cheour et al., 1990). Although the soil Ca2+ levels were determined to be15 and 20 mg·kg-1 Ca2+ dry weight, no interpretation of soil Ca2+ sufficiency for plant development was provided for their growing conditions. Water volume in which foliar applications was also not reported. Without the water volume, replicating the exact applied amount of Ca2+ within the application is difficult, because multiple dilutions of Ca2+ concentration within the solution can be calculated. Cheour et al. (1990) reported that Ca2+ levels in leaves and fruits were closely correlated, and Ca2+ determination in leaves can serve as a predictor for Ca2+ treatment efficacy. This is valuable information, but does not include correlations between firmness and Ca2+ content for the two selected cultivars. If these two variables were increased independently, the benefit of elucidating the relationship of Ca2+ and firmness on strawberry by a statistical correlation would further prove this point by eliminating other factors. Cheour et al. (1991) conducted a similar study using similar variables with

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29 0, 10, or 20 kg per hectare CaCl2, applied to 'Kent' and 'Glooscap' cultivars and reported 33.1 and 33.3 mgkg-1 Ca2+ dry weight This investigation also found CaCl2 sprays before harvest prolonged storage and delayed mold development. Cheour et al. (1991) did note the influence of cultivar on accumulation and distribution of Ca2+. This suggests that individual strawberry cultivars can respond differently to Ca2+ supplementation based on genetic factors. A more recent study involved 'Elsanta' strawberry, a common European cultivar, with 1,500 mgL-1 Ca2+ from CaCl2 (1.5 kgha-1 Ca2+ per spray) foliar spray with and without boron. This investigation concluded that CaCl2 or CaCl2 plus boron sprayed fruit were firmer, more resistant to decay, had higher soluble-solids content, and titratable acidity after 3 days holding at 18C than control fruit (Wojcik and Lewandowski, 2003). These investigators did not note the soil or water Ca2+ levels. The profile of environmental Ca2+ is important in clarifying level of potential benefit of supplemental foliar Ca2+ application. Wojcik and Lewandowski (2003) showed that yield was not increased with foliar applications CaCl2 or boron. This suggests that Ca2+ was not a limiting factor for yield and perhaps foliar applications are optimizing quality attributes in that study. Other studies have been conducted with supplemental foliar and soil Ca2+ applications to improve quality of strawberry. Results from these studies showed that Ca2+ treatments did not increase firmness (Erincik et al., 1998; Makus and Morris, 1989) or reduce grey mold ( Botrytis cinerea ) development (Erincik et al., 1998). Erincik et al. (1998) applied foliar Ca2+ treatments to 'Honeoye' strawberry at 1,902, and 3,797 Ca2+ mgL-1 Ca2+ from CaCl2 (5 and 10 kgha-1 CaCl2), and found no increase in firmness of

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30 strawberry fruit. Phytotoxicity occurred on plants treated with 3,797 mg·L-1 Ca2+ from CaCl2 (10 kg·ha-1 CaCl2). This investigation did showed that soil Ca2+ levels were 1,110 and 990 mg·kg-1 Ca2+ and water volume for foliar applications (sprayed at 275 kPa), but lacked Ca2+ determination of irrigation water and interpretation of soil Ca2+ to sufficiently meet plant development. Makus and Morris (1989) reported that foliar Ca2+ applications as chelated Ca2+ (Nutrical® 8% Ca2+), Ca(NO3)2 injected into drip irrigation, and pre-plant gypsum (CaSO4·2H2O) on 'Cardinal' and 'Fern' strawberries did not affect firmness, titratable acidity, or soluble-solids, but reduced storage decay. A reduction in fruit size was reported with the total treatment combined Ca2+ rate of 904 kg·ha-1 Ca2+ (Makus and Morris, 1989). This investigation showed that soil fertility was low, but did not state the soil Ca2+ level. Another study conducted by Makus and Morris (1998) on the distribution of Ca2+ within ripe fruit reported soil Ca2+ of 1,400 mg·kg-1. This investigation found that supplemental Ca2+ increased Ca2+ content in leaf blades but did not affect whole fruit Ca2+ content. It is possible that studies indicating positive results for additional Ca2+ have below or at a threshold of the strawberry plant's critical need for Ca2+. This is considering the lack of those studies to report environmental Ca2+ levels within soil and irrigation water at experimental sites. In addition, the inconsistent results for supplemental Ca2+ to improve postharvest quality of strawberry could be influenced by cultivar. Future studies conducted on improving postharvest quality of strawberry should annotate both environmental Ca2+ present and lineage of cultivar. Conclusions Differences in quality response that commodities exhibit to Ca2+ treatment are found. The explanation as to why each commodity can respond different is not obvious.

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31 The categories that commodities have been grouped into (e.g., climacteric, non-climacteric, respiration rate, taxonomic family) do not allow a coherent and predictable separation of positive responsiveness to Ca2+ treatment. Ferguson et al. (1999) and Wojcik (2001b) have both suggested that Ca2+ concentration in apple tissue can not be the only factor influencing bitter pit development. Improving postharvest quality, in particular firmness, can rely more on genetics and further investigation into the genetic link between Ca2+ and firmness is necessary to completely clarify the relationship between the these two variables. Prange and DeEll (1997) reported that from a quality standpoint, cultivar selection might be the most important management decision in berry crop production. Other factors influence textural quality besides Ca2+ content such as environment, genetics, cultural practices and physiological differences (Prange and DeEll, 1997; Sams, 1999). Investigators have cited some of these factors in studies on firmness (Hopkirk et al., 1990; Wojcik, 2001b). Despite additional external factors involved in textural quality, certain commodities are more responsive to Ca2+ treatments than others. No one study can investigate all the factors (light, temperature, soil moisture, fertilization, storage conditions, harvesting practices) involved in postharvest quality, although Ca2+ is frequently studied. Additional factors influencing quality need to be investigated more closely in conjunction with Ca2+ treatments. Many pre and postharvest factors have been identified as influencing postharvest quality. Calcium is the plant nutrient most associated with improving postharvest and harvest quality. The influence of Ca2+ on quality has been reviewed extensively for major fruit crops such as apples. Positive and consistent results obtained with Ca2+

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32 treatments are not wide spread through out all commodities. Preand postharvest applications of Ca2+ have proven to minimize loss, extend storage, and improve firmness of many commodities. A better understanding of calcium's role in postharvest quality is needs to be gained to determine those commodities best suited for quality supplementations with Ca2+. Improving postharvest quality of strawberry fruits with supplemental Ca2+ has had inconsistent in results. Despite the inconsistencies, commercial strawberry growers apply additional Ca2+ applications under high environmental Ca2+ conditions to improve postharvest quality. Our study seeks to probe and further our understanding of Ca2+ and its relationship to firmness in strawberry. Our study objectives were as follows: Review previous literature on improving postharvest and harvest quality with Ca2+. Ex plore the influence of cultivar on the relationship between firmness and Ca2+. Determine if supplemental Ca2+ improves postharvest quality in strawberry under Florida conditions. Determine if current fertilization regime for strawberries in Florida meets the strawberry critical requirement needs of Ca2+.

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33 Table 2-1. Calcium-related disorders by commodity and investigator Commodity Ca2+ related disordera Investigator Apple Bitter pit Water core Cork spot Bramlage et al., 1974 Carbo et al., 1998 Conway et al., 1992 Failla et al., 1990 Raese and Drake, 2000b; 2002 Redmond, 1975 Wojcik, 2001b; 2002 Cauliflower Whiptail Hochmuth, 1984 Wiebe and Krug, 1974 Cherry Cracking Surface pitting Facteau, 1982 Facteau et al., 1987 Lidster et al., 1979 Fig Surface cracking Sun scald Aksoy and Anac, 1994 Greens Tipburn Collier and Tibbitts, 1982 Cubeta et al., 2000 Johnson, 1991 Misaghi and Matyac, 1981 Saure, 1998 Orange Albedo breakdown Treeby and Storey, 2002 Pear Cork spot Richardson and Al-Ani, 1982 Pepper Blossom end rot Alexander and Clough, 1998 Marcelis and Ho, 1999 Toivonene and Bowen, 1999 Potato Internal browning Clough, 1994 Conway et al., 1992 Kleinhenz et al., 1999 Strawberry Tipburn Bradfield and Guttridge, 1979 Tomato Blossom-end rot Ehret and Ho, 1986 Ho et al., 1999 Paiva et al., 1998 Saure, 2001 Taylor and Locascio, 2004 Taylor et al., 2004 a Adapted from Shear, C.B. 1975b. Calcium-related disorders of fruits and vegetables. HortScience 10:361-365.

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34 CHAPTER 3 EFFECT OF CULTIVAR ON CALCIUM CONTENT AND FIRMNESS IN STRAWBERRY FRUIT ( Fragaria × ananassa Duch.) Introduction ‘Camarosa’, ‘Carmine’, ‘Earlibrite’, ‘Strawberry Festival’, and ‘Treasure’ are commonly grown strawberry cultivars in Florida (Simonne et al., 2003). Cultivar popularity has been driven by desirable characteristics for the particular cultivar, trends, and market windows (Table 3-1). Early yield is a significant factor for selection of cultivars for Florida. Storage and fruit firmness attributes are a driving force for current cultivar selection. Many Florida growers apply supplemental foliar Ca2+ to increase firmness without evidence of correlation between increase fruit Ca2+ content and firmness measurements. It is known that Ca2+ (calcium) has a role in membrane stability (Kirkby and Pilbeam, 1984), contributes to the linkages between pectic substances within the cell-wall (Demarty et al., 1984), and is involved in the rate of ripening and respiration (Ferguson, 1984). The rationale behind our study is that Ca2+ content within leaves and fruit tissues contributes to the textural qualities of strawberry fruits. Studies have not been conducted on the heritability of Ca2+ efficiency in relation to textural attributes. Prange and DeEll (1997) stated that postharvest quality is genetically controlled and cultivar selection can be the most important decision for quality in small fruit production. The heritability of firmness and relating other characteristics with firmness has been investigated continuously to improve strawberry fruit quality.

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35 Previous research on inherited strawberry characteristics, firmness appears to be connected to physical characteristics to a greater degree than it is connected to quality characteristics. Hortynski et al. (1991) reported that fruit firmness had a very high positive correlation with the number of achenes on a fruit and that this was caused by the dense dispersal of vascular bundles in the fruit tissue. The number of achenes on a fruit is the number of successful fertilized ovaries. The authors also noted the fruit core within the strawberry was larger on clones with greater firmness. Core size could be a quick index for determining fruit firmness for breeders (Hortynski et al., 1991). This observation has not been reported anywhere else in the literature on strawberry firmness. The correlation of yield and size of strawberry fruits with fruit firmness were found to be significantly different from zero and not significantly correlated (Hanshe et al., 1968). In contrast, Hortynski et al. (1991) reported results of an association between fruit size and firmness. This investigation found the associations between length (r2 = 0.49, r2 = 0.43), width (r2 = 0.47, r2 = 0.41), and fruit weight (r2 = 0.48, r2 = 0.39) with firmness at top and base of fruits. Yield or fruit size are much easier methods to measure as they are typical variables in studies compared to counting achenes. Quality traits are time-consuming and expensive to measure (Shaw et al., 1987), but important in the development of strawberry cultivars for consumer acceptability. Studies have been conducted on improving strawberry firmness with supplemental Ca2+ applications. Yet, a lack of genetic studies on the association between fruit firmness and Ca2+ content in fruits exists. Strawberry has variability of traits within a population and independence of desirable traits and this have been viewed as important factors in developing new cultivars (Shaw et al., 1987; Yashiro et al., 2002). Therefore, multiple

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36 cultivars from various breeding programs would need to be evaluated to determine if an association exists between these two variables. Previous studies have various in results for improving fruit firmness with supplemental foliar Ca2+. Those cultivars that respond to supplemental Ca2+ with an increase in firmness can have similar lineages. It is hypothesized that cultivar strongly influences the association of fruit firmness and Ca2+ content in strawberry. Our study aims to clarify the relationship between Ca2+ and firmness on multiple cultivars from 3 breeding programs by De termining Ca2+ content Analyzing firmness C orrelating calcium content with fruit firmness to interpret the reliability of improving firmness with Ca2+ on strawberry Evaluating similarities in firmness analysis and Ca2+ content with the available lineages Materials and Methods This 2-year study was located at the University of Florida, Gulf Coast Research Education Center at Dover (GCREC-Dover) on Seffner fine sand (sandy, siliceous, hyperthermic, Quartzipsammentic Haplumbrepts) from August 2002 to March 2003, and August 2003 to March 2004. Soil was fumigated to industry standards of 67% to 33% ratio (w: w, methyl bromide: chloropicrin) at 381.7 kgha-1. Experimentation was planted in annual hill method with drip irrigation and a double row set 1.2 m meters on center. Cultivars chosen for our study, included both University of California (UC) licensed cultivars of 'Camarosa', 'Gaviota', 'Aroma', and 'Camino Real', University of Florida (UF) licensed cultivars of 'Strawberry Festival' ('Festival'), 'Carmine', 'Earlibrite', 'Sweet Charlie' and six numbered lines from Dr. Craig Chandler's

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37 breeding program at GCREC-Dover (Table 3-2), and one cultivar from J & P Research, Inc. from Naples, FL called 'Treasure'. Each experimental plot consisted of an individual cultivar planted in an 8845 m2, except for 'Sweet Charlie' and 'Camino Real' strawberry. 'Sweet Charlie' samples were collected from a 441 m2 section for the 2003-04 season only. 'Camino Real' samples were collected from a 480 m2 section. In the 2003-04 season, 'Sweet Charlie' was being phased out as a general cultivar and 'Camino Real' was being planted for the first time at GCREC-Dover. Therefore, each of these cultivars was in small populations during the 2003-04 season. Four replicate samples of thirty recently matured leaves and ten U.S. number one grade (Mitcham, 2003) fruits were randomly collected from each experimental plot (Table 3-2). Calyces were collected and replications combined as outlined by Albregts and Howard (1978) for the 2003-04 season only. Samples were dried at 70ºC in a forced-air dryer. Once dried, leaf and calyx samples were ground using a tissue mill (Thomas Scientific Wiley mill (Swedesboro, NJ, USA) in 2002-03 and Foss Tecator Cyclotec Sample Mill (Sweden) in 2003-04), and fruit samples using a standard household electric coffee grinder to pass through a 20-mesh screen (7.8 openings per cm). In 2002-03, organic matter of the samples was digested with 1 N (Normal) solution of HCl (Hydrochloric acid). In 2003-04, 6 N solution of HCl was used for digestion of organic matter. Both procedures use one gram of dried tissue ashed in a muffle furnace (500°C for 4 h) and a final solution volume of 50 mL. For both years, prepared samples were sent to the Analytical Research Laboratory in Gainesville, FL for Ca2+ determination by an ICP (inductively coupled plasma) spectrophotometer (EPA Method

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38 200.7, CIROS, Spectro) (Mylavarapu, R.S., and E.D. Kennelley. UF/IFAS extension soil testing laboratory analytical procedures and training manual. University of Florida Extension Publication. http://edis.ifas.ufl.edu/SS312. October 2004.). All Ca2+ concentrations were expressed in mg·kg-1 based on a dry weight basis. On 11, 14 February and 14, 20 March 2004, strawberry fruits were harvested from each experimental plot to fill two 0.9 kg hinged clamshells and transported to the Postharvest Horticulture Laboratory, University of Florida, Gainesville, FL for measurements. Each sample consisted of ten representative fruits. Fruits selected for firmness were U.S. number one grade (Mitcham, 2003). Samples were stored at 1°C for a maximum period of 2 h until the destructive test was performed. Preparation for firmness consisted of slicing each fruit into an 11 mm equatorial section at room temperature (approximately 22°C). Each slice was orientated proximal end up for mechanical resistance measurement. The puncture measurements were taken using a penetrometer (Instron Universal Testing Instrument, Model 4411, Canton, Mass.) with a 5 kg load cell fitted with a 4 mm convex probe with a crosshead speed of 0.83 mm·s-1 to an end-point of 7 mm. Two measurements were taken within the cortex tissue of each fruit slice. Maximum force (bioyield point) was used to determine firmness of each sample. Calcium content and fruit firmness measurements were subjected to ANOVA for cultivar effects using a general linear model (SAS Version 9) as a randomized complete block design and mean separation by Fischer's LSD (least significant differences). The variables were analyzed with years combined and separated where an interaction of cultivar and year was significant. Variables were considered significant at a significance

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39 level of 5% or P<0.05. The coefficient of variation (CV) was calculated as 100 times the ratio between the standard deviation and the mean and was reported for each variable. Correlations were conducted using Pearson's correlation coefficients between fruit and leaf Ca2+ content and firmness for February, March, and 2004-season average. Variables were considered to have strong positive correlation at r2 = + 0.70. Results and Discussion Calcium content of selected cultivars was significantly different for year, and significant interaction between year and cultivar was found for fruit and leaf tissues only (Table 3-3). 'Treasure', 'Carmine', 'Camarosa', 'Earlibrite', 'Aroma', 96-59, and 99-140 fruit Ca2+ content in 2002-03 were significantly lower than that of 'Festival', 'Gaviota', 95-269, and 96-59. 'Rosa Linda' is a possible genetic source of low fruit Ca2+ characteristic, but 'Festival' also has 'Rosa Linda' as a parent. 'Camarosa' has 'Douglas' another UC cultivar as a parent and no other cultivar in our study has 'Douglas' as a parent. . 'Carmine' and 'Earlibrite' both have 'Rosa Linda' and other UF cultivar as a parent. Calcium content of leaves from 'Treasure', 'Carmine', 'Camarosa', 'Earlibrite', 'Aroma', 95-14, 95-269, and 99-140 were significantly lower than 'Festival', 'Sweet Charlie', and 99-56 for 2002-03. 'Sweet Charlie' has very similar lineage as 'Rosa Linda', which is one of the parent lines for 'Festival'. In 2003-04 fruits and leaf tissue Ca2+ content were both significant for month with P< 0.02 (Table 3-4). Leaf tissue Ca2+ content had the only significant interaction between month and cultivar (Table 3-5). Calyces were only significant for March 2004. Calcium content of 97-39 calyces was significantly higher than all other cultivars. Calcium content of 'Sweet Charlie' calyx tissue was significantly higher than all other cultivars, except 97-39. Calcium content of 'Camarosa' calyx tissue was significantly

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40 lower than of all other cultivars. 'Sweet Charlie' and 97-39 are from the UF strawberry breeding program at GCREC-Dover and 'Camarosa'. Calcium content of fruits in February 2004 for 'Treasure', 'Camarosa', 97-39, 99-140, and 99-56 were significantly less than Ca2+ content of fruits from 'Festival', 'Camino Real', 'Carmine', 'Sweet Charlie', and 95-269. In March 2004, 'Carmine' fruit Ca2+ content was not significantly different from any cultivar. Calcium content of 'Camino Real' and 'Sweet Charlie' fruits were significantly higher in than fruits from Treasure', 'Camarosa', and 97-39 for March. 'Sweet Charlie' has 'Parajo' a UC cultivar in it lineage which can be attributing to the similarities between these two cultivars for fruit Ca2+ content, but it is not certain. UC strawberry breeders do not publish their lineages beyond the parent cross. 'Camarosa' and 99-56 leaf tissue had significantly less Ca2+ content than all other cultivars in February 2004 (Table 3-4). Calcium content of 97-39 leaf tissue was significantly higher than all other cultivars for both February and March, except for 'Carmine' in March 2004 (Table 3-4). For 2003-04, Ca2+ content of leaves had a significant interaction between cultivar and month (Table 3-5). 'Sweet Charlie' and 97-39 were the only two cultivars in which February 2004 Ca2+ content of leaves were higher than March 2004. All other cultivars had higher Ca2+ content in leaves for March (Table 3-5). Albregts and Howard (1978) first described this pattern of increasing Ca2+ content over the season in Florida and it seems that most of the selected cultivars in our study followed this pattern. Firmness measurements were only collected during 2003-04 season (Table 3-6). The effect of month was not significant for firmness measurements and no interaction

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41 between month and cultivar were found. 'Treasure' was significantly higher in firmness than all other cultivars and 'Sweet Charlie' was significantly less firm than all other cultivars. 'Festival', 'Camino Real' and 'Carmine' were all similar in firmness measurements at 1.05 N. For 'Camino Real', the plant patent reported similar firmness to 'Camarosa'. However, our study found different results under Florida conditions; 'Camarosa' was more similar to 97-39, a UF breeding line. 'Festival' and 'Carmine' share 'Rosa Linda' as a parent and this is a possible parental source of textural characteristics. Yet, 'Treasure' and 'Festival' share a parent in 'Oso Grande' and surprisingly are not similar in firmness. Hence, the inheritability of firmness does not appear to be simple. Correlation between fruit Ca2+ content and fruit firmness for strawberries was analyzed by month, because the significant difference in month for fruit Ca2+ content (Table 3-7). 'Camino Real' (Figure 3-1) was the only cultivar to have strong positive correlations between fruit Ca2+ content and firmness in February and March 2004 at 0.72 and 0.95, respectively. 'Sweet Charlie' (Figure 3-2) had a strong positive correlation at 0.78 for February 2004 only. In February 2004, ' Treasure' (Figure 3-3), and 'Carmine' (Figure 3-4) have strong negative correlations at -0.70 and -0.78, respectively. Overall, for the month of February 2004, fruit Ca2+ content and firmness did not have a strong positive correlation. In March, 'Festival' had strong negative correlation between fruit Ca2+ content and firmness. Overall, March did not have a strong positive correlation between fruit Ca2+ content and firmness. Correlations were negative for 'Carmine' and 'Festival' (Figure 3-5) for both months. These cultivars are from the UF breeding program and can be distinct individuals in the population. Both 'Camarosa' (Figure 3-6) and 97-39 (Figures 3-7) did

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42 not have consistent strong correlations (negative or positive) between Ca2+ content and fruit firmness. These cultivars re-enforce the concept that firmness and Ca2+ content are not correlated to each other. Combining observations for each month for a total for the season, results in lowering the correlation values for all cultivars, except 'Camarosa' and 97-39. All correlation values were below r2 = 0.70 for the average of both months. These results were unexpected, because in February 2004 'Camino Real' and 'Sweet Charlie' had strong positive correlations. These cultivars are not similar in firmness or Ca2+ content, because the lack of consistency from month to month. In March 2004, 'Sweet Charlie' did not have a positive correlation between fruit Ca2+ content and firmness unlike 'Camino Real'. Perhaps, at that point, environmental conditions influenced firmness for 'Sweet Charlie', which is known for shorter storage once temperatures increase in March. Further evaluation of Ca2+ content within fruit tissues and firmness measurement are needed to accurately assess the influence of a relationship between these two variables. Leaf Ca2+ content and fruit firmness were not overall positively related to each other (Table 3-8). 'Sweet Charlie' was the only cultivar with similar pattern of association for both leaf and fruit Ca2+ content to fruit firmness. In February 2004, 'Camino Real' and 'Camarosa' both had strong positive correlations between leaf Ca2+ content and fruit firmness. Both of these cultivars are from the UC strawberry-breeding program and are progeny from different crosses. Overall, for February 2004, a strong association between leaf Ca2+ content and fruit firmness did not exist. In March 2004, 'Treasure' was the only cultivar with a strong positive correlation. 'Camino Real' and 'Carmine' had strong negative correlations between leaf tissue Ca2+ content and fruit

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43 firmness. These cultivars do not share any parents. Overall, for March 2004, a strong association did not exist between leaf Ca2+ content and fruit firmness. Over all the correlation, outcomes were largely unexpected. Many correlations were strongly negative or lacking strong associations between Ca2+ content and fruit firmness. The negative correlation findings suggest that increasing Ca2+ content of strawberry fruit could be detrimental to fruit firmness. This goes against the dominate concept that applying supplemental Ca2+ to strawberry fruit will increase firmness. Although, supplemental Ca2+ studies on strawberry fruits have been inconsistent on improving quality in particular fruit firmness. Yet, these previous studies have relied on positive results in other commodities to validate their hypothesis for strawberry. It is obvious based on our study's findings that leaf and fruit Ca2+ content cannot be used to predict fruit firmness for the selected cultivars. It is apparent that these characteristics are independent of each other. Conclusions Based on this 2-year study, no relationship exists between Ca2+ content and firmness for the selected strawberry cultivars. Calcium content and firmness characteristics were found to be dependent on each individual cultivar. The UF strawberry breeding program in several instances has cultivars or numbered lines that had similar Ca2+ content. Similarities in parent lines for the UF strawberry breeding program can be responsible for these results. Calcium content of fruit or leaves is not a factor in determining firmness in all cultivars. 'Camino Real' can be the exception within the population of cultivars currently available and in production. Future studies involving improving textural quality of strawberry cultivars with supplemental Ca2+ should not be

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44 conducted based on these results. No correlation existed between Ca2+ content and firmness measurements of strawberry fruit.

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45Table 3-1. Description and existing use of strawberry ( Fragaria×ananassa Duch.) cultivars grown in Florida during 1998-2003 from both the University of Florida (UF) and University of California (UC) breeding programs. Cultivar (Introduced) Desirable characteristics Limitations Origin Percent planted in Florida Firmness ratingx Publication Camarosa (1993) Vigorous, firm deep red fruit Even fruiting pattern Susceptible to anthracnose fruit rot and powdery mildew UC 22% 2002-03 45% 2001-02 35% 2000 Very firm Voth et al., 1994 Gaviota (1997) Rain tolerant fruit good eating quality Less aromatic flavor UC 6.5% 2001-02 Firm Shaw, 1996 Ventana (2001) Bright light red fruit, good yield, resistant to Phytophthora crown rot Can become rain damaged UC Unreported New in 2001 Firmer than 'Gaviota' Larson et al., 2003 Camino Real (2001) Rain tolerant, firm fruit Resistant to Phytophthora cactorum crown and root rot Sensitive to sulfur fertilization Low early yield UC Unreported New in 2001 Firm Shaw and Larson, 2002 Carmine (2001) Firm fruit, early yielding Moderate resistance to anthracnose fruit rot and Botrytis cinerea UF 3% 2002-03 Firm Chandler et al., 2004 Earlibrite (2000) High early yields Large firm fruits Misshapen primary fruits Easily water damage UF 6% 2001-02 & 2002-03 Firm Chandler et al., 2000a Sweet Charlie (1992) High early yields Resistant to anthracnose fruit rot Sweet and Flavorful Short storage in warm weather UF 9% 2001-02 40% 2000 Soft Chandler et al., 1997 Strawberry Festival (2000) Flavorful, firm deep red fruits High total yield Susceptible to Colletotrichum spp. UF 31% 2002-03 5.7% 2001-02 Firm Chandler et al., 2000b Treasure (2000) Resistant to Colletotrichum spp . and abrasion Uneven ripening pattern from tip to shoulders J & P Research 5.5% 2001-02 19% 2002-03 Firm Chang, 2000

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46 Table 3-2. Dates of strawberry ( Fragaria×ananassa Duch.) cultivar and numbered line tissue collection for measurements pertaining to the correlation of calcium content to textural attributes at GCREC-Dover Cultivar Leaves Fruit Calyces Treasure 11 Mar. 2003, 16 Feb. 2004, 17 Mar. 2004 11 Mar. 2003, 16 Feb. 2004, 17 Mar. 2004 16 Feb. 2004, 17 Mar. 2004 Strawberry Festival 11 Mar. 2003, 16 Feb. 2004, 17 Mar. 2004 11 Mar. 2003, 16 Feb. 2004, 17 Mar. 2004 16 Feb. 2004, 17 Mar. 2004 Carmine 11 Mar. 2003, 16 Feb. 2004, 17 Mar. 2004 11 Mar. 2003, 16 Feb. 2004, 17 Mar. 2004 16 Feb. 2004, 17 Mar. 2004 Sweet Charlie 11 Mar. 2003, 16 Feb. 2004, 17 Mar. 2004 11 Mar. 2003, 16 Feb. 2004, 17 Mar. 2004 16 Feb. 2004, 17 Mar. 2004 Earlibrite 11 Mar. 2003 11 Mar. 2003 95-269 11 Mar. 2003, 16 Feb. 2004 11 Mar. 2003, 16 Feb. 2004 16 Feb. 2004 96-59 11 Mar. 2003 11 Mar. 2003 97-39 11 Mar. 2003, 16 Feb. 2004, 17 Mar. 2004 11 Mar. 2003, 16 Feb. 2004, 17 Mar. 2004 16 Feb. 2004, 17 Mar. 2004 99-56 11 Mar. 2003, 16 Feb. 2004 11 Mar. 2003, 16 Feb. 2004 16 Feb. 2004 99-140 11 Mar. 2003, 16 Feb. 2004 11 Mar. 2003, 16 Feb. 2004 16 Feb. 2004 99-56 11 Mar. 2003, 16 Feb. 2004 11 Mar. 2003, 16 Feb. 2004 16 Feb. 2004 Camino Real 16 Feb. 2004, 17 Mar. 2004 16 Feb. 2004, 17 Mar. 2004 16 Feb. 2004, 17 Mar. 2004 Camarosa 11 Mar. 2003, 16 Feb. 2004, 17 Mar. 2004 11 Mar. 2003, 16 Feb. 2004, 17 Mar. 2004 16 Feb. 2004, 17 Mar. 2004 Aroma 11 Mar. 2003 11 Mar. 2003 Gaviota 11 Mar. 2003 11 Mar. 2003

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47Table 3-3. Calcium content of strawberry ( Fragariaananassa Duch.) tissues of selected cultivars for two seasons at GCREC-Dover n Fruit n Leavesd n Calyx n Fruit n Leavesd Cultivar Season 2002-03 (mgkg-1)c Season 2003-04 (mgkg-1)c Treasure 4 2678 def 4 10660 de 4 13270 bc 8 1489 d 8 8468 ef Strawberry Festival 4 3209 bc 4 13327 a 4 15361 bc 8 2069 ab 8 8924 def Camino Real 0 --0 --4 13647 bc 8 2217 ab 8 9430 cde Carmine 4 2383 f 4 10505 de 4 12298 bc 8 1896 bc 8 9736 bcd Camarosa 4 2384 f 4 11430 bcd 4 10447 b 8 1488 d 8 8389 f Sweet Charlie 4 2972 cd 4 13715 a 4 19166 ab 8 2255 a 8 10264 b Earlibrite 4 2421 f 4 10770 de 0 0 0 Gaviota 4 3181 bc 4 9757 e 0 0 0 Aromas 4 2662 def 4 11440 bcd 0 0 0 95-14 4 3435 ab 4 11245 bcd 0 0 0 95-269 4 3141 bc 4 11415 bcd 1 8037 c 4 2034 ab 4 9457 cd 96-59 4 2567 ef 4 11945 bc 0 0 0 97-39 4 3737 a 4 12140 b 4 26964 a 8 1373 d 8 12770 a 99-140 4 2586 def 4 10827 cde 2 13030 bc 4 1624 cd 4 10167 bc 99-56 4 2951 cde 4 13477 a 1 11945 bc 4 1614 cd 4 6625 g LSDb 395 1131 8323 321 984 Mean 2879 11618 14416 1806 9423 CV (%)a 9 6 26 15 9 P-values Cultivar <0.01 <0.01 <0.01 <0.01 <0.01 Year ----------Cultivar*Year ----------Month ----0.02 <0.01 <0.01 Cultivar*Month ----0.54 0.34 <0.01 dSufficency range for leaf tissue at first harvest 4,000 to 15,000 mgkg-1 (Simonne et al., 2003) cValues in columns are means separated with Fischer's Least Significant Difference bMean separation by Fischer's Least Significant Difference aCoefficient of variation

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48Table 3-4. Strawberry ( Fragariaananassa Duch.) cultivar effect on calcium content of calyces, fruit and leaf tissues for two sampling dates during 2003-04 season at GCREC-Dover n Calyx n Fruit n Leavesd n Calyx n Fruit n Leavesd Cultivar Feb. (mgkg-1)c Mar. (mgkg-1)c Treasure 2 12149 4 1506 c 4 8102 e 2 14391 d 4 1473 bc 4 8835 d Strawberry Festival 2 11484 4 2360 ab 4 8588 de 2 19238 c 4 1778 ab 4 9360 cd Camino Real 2 12600 4 2447 ab 4 8266 e 2 14171 d 4 1987 a 4 10595 bc Carmine 2 8586 4 2186 ab 4 8132 e 2 16010 d 4 1606 abc 4 11340 ab Camarosa 2 10447 4 1612 c 4 6559 f 2 12411 e 4 1365 bc 4 10220 bcd Sweet Charlie 2 15068 4 2250 a 4 11056 b 2 23264 b 4 1959 a 4 10000 bcd 95-269 1 8037 4 2034 b 4 9457 cd 0 0 0 97-39 2 28145 4 1572 c 4 13068 a 2 25783 a 4 1175 c 4 12472 a 99-140 2 13030 4 1624 c 4 10167 cb 0 0 0 99-56 1 11945 4 1614 c 4 6625 f 0 0 0 LSDb 14841 332 936 1878 457 1706 Mean 13149 1920 9002 17893 1620 10403 CV (%)a 42 13 7 4 18 11 P-values Cultivar 0.20 <0.01 <0.01 <0.01 0.01 <0.01 Month ------------Cultivar*Month ------------dSufficency range for leaf tissue at first harvest 4,000 to 15,000 mgkg-1 (Simonne et al., 2003) cValues in columns are means separated with Fischer's Least Significant Difference bMean separation by Fischer's Least Significant Difference aCoefficient of variation

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49 Table 3-5. Interaction of month with strawberry ( Fragariaananassa Duch.) cultivar for calcium content of leaves collected on 16 February and 17 March 2004 at GCREC-Dover dSufficency range for leaf tissue at first harvest 4,000 to 15,000 mgkg-1 (Simonne et al., 2003) cValues in columns are means separated with Fischer's Least Significant Difference bM ean separation by Fischer's Least Significant Difference aCoefficient of variation n Leaves d,c n Leaves d, c Cultivar Feb. (mgkg-1) Mar. (mgkg-1) Treasure 4 8102 e 4 8835 d Strawberry Festival 4 8588 de 4 9360 cd Camino Real 4 8266 e 4 10595 bc Carmine 4 8132 e 4 11340 ab Camarosa 4 6559 f 4 10220 bcd Sweet Charlie 4 11056 b 4 10000 bcd 95-269 4 9457 cd 0 97-39 4 13068 a 4 12472 a 99-140 4 10167 cb 0 99-56 4 6625 f 0 LSDb 936 1706 Mean 9002 10403 CV (%)a 7 11 P-values Cultivar <0.01 <0.01 Month Cultivar*Month

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50 Table 3-6. Strawberry ( Fragariaananassa Duch.) cultivar effect on firmness in 2003-04 season at GCREC-Dover Bioyield point (Newtons)c Cultivar n Feb. Mar. Mean Treasure 8 1.23 a 1.13 a 1.18 a Strawberry Festival 8 1.14 ab 0.96 bc 1.05 b Camino Real 8 1.10 b 1.01 abc 1.05 b Carmine 8 1.07 b 1.04 ab 1.05 b Camarosa 8 0.90 c 0.99 bc 0.95 c Sweet Charlie 8 0.72 d 0.71 d 0.72 d 97-39 8 0.85 c 0.88 c 0.86 c LSDb 0.13 0.13 0.08 Mean 1.00 0.96 0.98 CV (%)a 8 18 8 P-values Cultivar <0.01 <0.01 <0.01 Month 0.08 Cultivar*Month 0.05 cValues in columns are means for each treatment bMean separation by Fischer's Least Significant Difference aCoefficient of variation

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51 Table 3-7. Fruit calcium content and fruit firmness correlation coefficients for selected strawberry ( Fragaria×ananassa Duch.) cultivars grown at GCREC-Dover in 2003-04 season Pearson's Correlation Coefficient r values Cultivar n Feb. Mar. Mean Treasure 8 -0.70 +0.60 +0.04 Strawberry Festival 8 -0.59 -0.87 +0.21 Camino Real 8 +0.72 +0.95 +0.54 Carmine 8 -0.78 -0.64 -0.20 Camarosa 8 -0.30 +0.24 -0.48 Sweet Charlie 8 +0.78 -0.78 -0.12 97-39 8 +0.16 +0.01 -0.19 All cultivars combined 56 -0.13 -0.22 -0.09

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52 Table 3-8. Leaf calcium content and fruit firmness correlation coefficients for selected strawberry ( Fragaria×ananassa Duch.) cultivars in 2003-04 season at GCREC-Dover Pearson's Correlation Coefficient r values Cultivar n Feb. Mar. Mean Treasure 8 +0.37 +0.95 +0.08 Strawberry Festival 8 -0.43 -0.21 -0.38 Camino Real 8 +0.85 -0.80 -0.26 Carmine 8 -0.01 -0.70 -0.31 Camarosa 8 +0.90 +0.31 +0.67 Sweet Charlie 8 +0.68 -0.68 -0.51 97-39 8 +0.12 +0.43 +0.21 All cultivars combined 56 -0.46 -0.22 -0.37

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53 Figure 3-1. 'Camino Real' strawberry ( Fragariaananassa Duch.) fruit firmness and calcium content association during 2003-04 season at GCREC-Dover 0.9 0.95 1 1.05 1.1 1.15 1.2 1.25 1.3 85009000 950010000105001100011500 Calcium content (mgkg -1)Fruit Firmness (Newtons)

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54 Figure 3-2. 'Sweet Charlie' strawberry Fragariaananassa Duch.) fruit firmness and calcium content association during 2003-04 at GCREC-Dover 0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95 1 90009500 1000010500110001150012000-1)Fruit Firmness (Newtons)Calcium content (mgkg

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55 Figure 3-3. 'Treasure' strawberry ( Fragariaananassa Duch.) fruit firmness and calcium content association during 2003-04 at GCREC-Dover 1 1.05 1.1 1.15 1.2 1.25 1.3 1.35 7600 7800 8000820084008600 8800900092009400 Calcium content (mgkg -1 ) Fruit Firmness (Newtons)

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56 Figure 3-4. 'Carmine' strawberry ( Fragariaananassa Duch.) fruit firmness and calcium content association during 2003-04 season at GCREC-Dover 0.95 1 1.05 1.1 1.15 1.2 80008500 90009500100001050011000 11500120001250013000 Calcium content (mgkg -1)Fruit Firmness (Newtons)

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57 Figure 3-5. 'Strawberry Festival' strawberry ( Fragariaananassa Duch.) fruit firmness and calcium content association during 2003-04 season at GCREC-Dover 0.7 0.8 0.9 1 1.1 1.2 1.3 75008000 8500900095001000010500 Calcium content (mgkg -1)Fruit Firmness (Newtons)

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58 Figure 3-6. 'Camarosa' strawberry ( Fragariaananassa Duch.) fruit firmness and calcium content association during 2003-04 season at GCREC-Dover 0.7 0.75 0.8 0.85 0.9 0.95 1 1.05 1.1 75008000 85009000950010000 105001100011500 Calcium content (mgkg -1)Fruit Firmness (Newtons)

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59 Figure 3-7. University of Florida numbered line 97-39 strawberry ( Fragariaananassa Duch.) fruit firmness and calcium content association during 2003-04 season at GCREC-Dover 0.8 0.82 0.84 0.86 0.88 0.9 0.92 0.94 1000011000 1200013000140001500016000 Calcium content (mgkg -1)Fruit Firmness (Newtons)

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CHAPTER 4 EFFECT OF SUPPLEMENTAL CALCIUM APPLICATIONS ON YIELD AND POSTHARVEST QUALITY OF ‘SWEET CHARLIE’ STRAWBERRY ( Fragaria × ananassa Duch.) Introduction Calcium has been extensively reviewed as both an essential element and its potential role in maintaining postharvest quality of fruit and vegetable crops (Kirkby and Pilbeam, 1984; Shear, 1975a; Bangarth, 1979). It is accepted that the presence of Ca2+ ions increases the cohesion of cell-walls (Demarty et al., 1984). Cell-wall integrity is one part of the rationale behind applying Ca2+ for improving postharvest quality. In addition to the structural role in cell-wall integrity, Ca2+ is also involved in reducing the rate of senescence and fruit ripening (Ferguson, 1984). Strawberry responses to supplemental Ca2+ applications for improving postharvest quality have been inconsistent. Eaves and Leefe (1962) found that a 1,445 mg·L-1 Ca2+ (0.4% CaCl2) as foliar CaCl2 increased firmness in strawberry fruit. This investigation focused only on firmness and not any other postharvest quality attributes which Ca2+ can affect. Canadian investigators furthered the understanding of Ca2+ by focusing on the effect of CaCl2 on delaying attributes of ripening and decay (Cheour et al., 1990; 1991). They found that foliar 5, 10, 15, and 20 kg·ha-1 Ca2+ as CaCl2 applied before harvest reduced decay and increased firmness measurements. These treatments also reduced free sugars, and titratable acidity within strawberry fruits. The descriptive statistics for 'Kent' strawberry firmness showed initial firmness measurements started at about 9 N (Newtons) for 'Kent' strawberry, treated fruits softened to between 8.25 and 6.5 N, and

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61 the control softening to 5 N. Descriptive statistics for 'Tribute' strawberry were not reported, but storage, rate of application, linear, and contrast of control verses all treatments were significant. In this investigation, both 'Kent' and 'Tribute' fruits were stored for 23 to 28 days at 4C and 100% relative humidity to determine textural attributes over time. Another study conducted with the same methods by Cheour et al. (1991) had similar results for 'Kent' and 'Glooscap' cultivars for firmness, total titratable acidity, and soluble-solids content. Erincik et al. (1998) focused on the applicability of foliar 1,902, and 3,797 Ca2+ mgL-1 Ca2+ from CaCl2 (5 and 10 kgha-1 CaCl2) applications on postharvest quality of strawberry. This investigation was in direct response to Cheour et al. (1990; 1991) claims of reduced Botrytis fruit rot with foliar Ca2+ applications. These investigators in Ohio, found that foliar applications of CaCl2 had no consistent effects on Ca2+ content of fruit, yield, fruit firmness, soluble-solids content, fruit acidity, or external color of fruit in both field and greenhouse experiments (Erincik et al., 1998). Firmness measurement of 'Honeoye' strawberry in this investigation found skin firmness for both years and internal tissue firmness for one year of the study not to be affected by treatments. Firmness was assessed as puncture through the fruit at the equator of the fruit in this investigation. Average skin firmness was measured to be 2.89 and 2.30 N for the two years. The average internal tissue firmness was 6.40 N in which treatment was not significant. The second year in which treatment was significant, fruit firmness with CaCl2 treatment was 4.53 N where as the average of the control and fungicides were 4.09 N. Makus and Morris (1989) found that foliar and soil application of supplemental Ca2+ as foliar chelated Ca2+ (21 applications of 7 or 30 kgha-1 Ca2+ for 1986 and

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62 1987, respectively), 437 kgha-1 Ca2+ from pre-plant soil gypsum (CaSO4H2O) or 437 kgha-1 Ca2+ from drip irrigation applied Ca(NO3)2 (calcium nitrate) reduced decay in storage compared to the control. Firmness measurement of 'Fern' and 'Cardinal' strawberries were 212 and 258 N as shear in this investigation, but Ca2+ treatments did not influence firmness. This investigation found no significant increase postharvest quality measurement or Ca2+ content of fruit. Both Erincik et al. (1998) and Makus and Morris (1989) found inconsistent to minimal benefit for supplemental Ca2+ improving firmness compared to studies conducted outside of the United States. Wojcik and Lewandowski (2003) documented the benefit of foliar CaCl2 sprays in reducing Botrytis fruit rot development, increasing firmness and reducing soluble-solids content and titratable acidity. This investigation reported that 1,500 mgL-1 Ca2+ as CaCl2 (1.5 kgha-1 per spray) or CaCl2 plus boron treatment of increased firmness of 'Elsanta' strawberry to 1.22 and 1.25 N. The control fruits for this investigation were shown to be 1.05 N. Firmness was assessed as a puncture test at the equatorial point of the fruit. The investigators reported soil levels of nitrogen and phosphorus, but no reference to the amount of soil Ca2+. Studies conducted on strawberry for improving firmness through increasing Ca2+ content have found variable results. The uptake and distribution of existing soil Ca2+ can provide important insights to these inconsistent results. Makus and Morris (1998) reported that distribution of Ca2+ within strawberry fruit is not affected by preharvest supplementation by 21 applications of 1.4 kgha-1 Ca2+ as foliar chelated Ca2+ (Nutrical) spray, 437 kgha-1 Ca2+ from pre-plant soil gypsum (CaSO4H2O), 437 kgha-1 Ca2+ from drip irrigation applied Ca (NO3)2, or a combination of all three at 904 kgha-1 Ca2+. This suggests that additional preharvest

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63 Ca2+ supplied to strawberry fruits to improve firmness measurements was not being deposited into the reproductive sinks (achenes). Albregts and Howard (1978) reported that Ca2+ content of strawberry plants increased over the 4to 5-month growing season. Under such conditions for growth, an increase in Ca2+ content within the plant could be caused by the extensive root system developed. Root mass was not collected in either study, but based on the mode of uptake of Ca2+ by plants it can be hypothesized that bigger root systems equate to increased Ca2+ uptake. Cheour et al. (1990) were the only investigators to correlate soil and tissue Ca2+ as a method to determine the necessity of Ca2+ applications. The level of soil Ca2+ reported by Cheour et al. (1990) was 15 and 20 mgkg-1 Ca2+ (dry weight) and Cheour et al. (1991) reported 33 mgkg-1 Ca2+ (dry weight). An interpretation or recommendation of the sufficient level of soil Ca2+ was not provided in either study. Only two other studies reported soil Ca2+ levels for studies on strawberry and Ca2+, Erincik et al. (1998) and Makus and Morris (1998). Erincik et al. (1998) reported 1,110 and 990 mgkg-1 soil Ca2+ for their 2year study. These levels of soil Ca2+ were within the sufficient range for strawberry production in Ohio. Recommendations cited by Erincik et al. (1998) stated no supplemental treatment was required. The first study conducted by Makus and Morris (1989) reported soil fertility at "low" without any specific level of soil Ca2+ being cited. These investigators did, however, report soil Ca2+ in a different study conducted on supplementation of strawberry with Ca2+ to be 1,400 mgkg-1 (Makus and Morris, 1998). Neither of the two Makus and Morris (1989; 1998), studies mentioned a sufficiency range of Ca2+ for strawberry production in Arkansas.

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64 It is important to note that none of the studies focusing on Ca2+ and strawberry quality reported the level of Ca2+ in the irrigation water. Nutrients available in irrigation water are often over looked in field studies for supplying appreciable amounts of some elements. Florida has karst typography throughout the state and drinking and irrigation water are pumped from limestone aquifer. Calcium within irrigation water can be an additional source of Ca2+ for strawberry plantings. Strawberries are a high value crop with a short-storage-life. Many Florida strawberry growers apply supplemental Ca2+ as a foliar spray to their crop despite the lack of conclusive evidence of an increase in fruit quality or yield. The rationale for application of supplemental Ca2+ comes from Ca2+ involvement in cell-wall integrity and reduction of fruit quality. It is hypothesized that supplemental Ca2+ can improve postharvest quality based on previous research. The objectives of our study are to determine the effect of preharvest Ca2+ application on Yield Firmness and postharvest quality Ca2+content of strawberry Materials and Methods Experimentation was conducted at the Gulf Coast Research Education Center at Dover (GCREC-Dover) on a Seffner fine sand (sandy, siliceous, hyperthermic, Quartzipsammentic Haplumbrepts) from August 2002 to March 2003, and August 2003 to March 2004. Soil was fumigated with a 67% to 33% ratio (w:w, methyl bromide:chloropicrin) at 381.7 kgha-1, and planted in a double row set on 1.2 m center. ‘Sweet Charlie’ transplants were obtained from Kentville, Nova Scotia and

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65 planted on 8 October 2002, and 1 October 2003. ‘Sweet Charlie’ was selected, because its characteristics of resistance to anthracnose (caused by Colletotrichum spp .), susceptibility to (caused by Botrytis cinerea Pers. ex Fr.) , high early yields, short storage life, and fruits with soft-tissue. Existing soil Ca2+ within the experimental plot was determined by a pre-season soil test (EPA Method 200.7, Mehlich-1 extraction) (Mylavarapu, R.S., and E.D. Kennelley. UF/IFAS extension soil testing laboratory analytical procedures and training manual. University of Florida Extension Publication. http://edis.ifas.ufl.edu/SS312. October 2004.). The plots chosen for 2002-03 and 2003-04 had 471 and 623 mg·kg-1 Ca2+ respectively and both interpreted to be "very high" at greater than 400 mg·kg-1 (Simonne and Hochmuth, 2003). Irrigation water at the site was also tested and found to contain 53 mg·L-1 Ca2+. The comparison of pre-season and post season soil Ca2+ levels were used to present the combination environmental and treatment contribution of Ca2+ to the crop. Treatments were selected based on previous research conducted using additional Ca2+ on strawberry and other commodities. Treatments consisted of soil applications Ca2+ as gypsum (CaSO4·2H2O) and of a weekly-applied foliar Ca2+ as calcium sulfate (CaSO4), or calcium chloride (CaCl2). Soil application rates were zero (control), 224.5, and 449 kg·ha-1 Ca2+ from gypsum. The rate of foliar applications consisted of controlwater, 400 Ca2+ mg·L-1 from CaSO4, and 400 and 800 Ca2+ mg·L-1 from CaCl2 at 935 L·ha-1 rate (40 kPa pressure). Foliar applications were made to the point of run off. Foliar treatments were applied weekly starting at first bloom (35 DAT and 36 DAT). A spilt-plot design with four replications was used. The main plots (59.7 m2) were supplemental soil Ca2+, and foliar Ca2+ levels were subplots (14.6 m2).

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66 All cultural practices for both years followed the University of Florida, Institute of Food and Agricultural Science (IFAS) recommendations (Simonne et al., 2003). Overhead irrigation was applied for the standard 14 days for establishment of transplants at a rate of 63,464 Lh-1ha-1 for 8 h per day. Fertilization for N-P-K was fulfilled using a no Ca2+ fertilization source (6-0-6-0Ca-0S, Dyna-Flo, Chemical Dynamics Plant City, FL) and to the recommended schedule by Simonne et al. (2003). The nitrogen sources in the no Ca2+ fertilizer were urea ammonium nitrate and potassium nitrate. Harvest data were collected from twelve adjacent plants. Fruits were harvested twice a week for approximately 16 weeks starting in late November to early December until mid-March. Marketable U.S. number one grade fruits (Mitcham, 2003) and unmarketable fruits were harvested during this interval. Data collected were total number marketable and unmarketable fruit, weight of marketable fruit and type of unmarketable fruit. Marketable strawberry fruits were over 10 g in weight and fully ripe. Unmarketable fruits were based on low size, deformation, decay, or water damage. Leaves, fruit, and calyx were collected on 104 and 154 DAT (days after transplant) in 2003 and 96, 144, and 159 DAT in 2004 for Ca2+ content determination. Achenes of fruits were collected on 134 DAT in 2004 for Ca2+ content determination. Thirty recently matured leaves and ten U.S. number one grade fruits (Mitcham, 2003) were randomly selected within each experimental plot. Calyces were sampled as outlined by Albregts and Howard (1978). For achene Ca 2+ content determination, ten U.S. number one grade fruits (Mitcham, 2003) were randomly selected within each experimental plot. Fruits were peeled with a razor blade to remove the achenes, which were dried on paper bags.

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67 Total moisture content of fruit was measured to determine the total moisture for each treatment as an estimate of quality. Fresh weight and dry weight data were collected simultaneously for Ca2+ content and total moisture content. This eliminated the need to collect two separate samples for each variable. Samples were dried at 70C in an air dryer, ground with a Wiley mill (Thomas Scientific (Swedesboro, NJ, USA) in 2002-03 and Foss Tecator Cyclotec Sample Mill (Sweden) in 2003-04) to pass through a 20-mesh screen (7.8 openings per cm). A half gram aliquot was ashed at 550C for 4 h in a muffle furnace. After cooling ashes were diluted to final volume of 100 mL a 1 N (Normal) solution of HCl (Hydrochloric acid). All samples were sent to the Analytical Research Laboratory in Gainesville, FL for Ca2+ determination by an ICP (inductively coupled plasma) spectrophotometer (EPA Method 200.7, CIROS, Spectro) (Mylavarapu, R.S., and E.D. Kennelley. UF/IFAS extension soil testing laboratory analytical procedures and training manual. University of Florida Extension Publication. http://edis.ifas.ufl.edu/SS312. October 2004.). In 2003-04 season, samples were directly sent to the Analytical Research Laboratory in Gainesville, FL for oxidative acid digestion according to Extension Soil Testing Laboratory Analytical Procedures and Ca2+ determination by ICP (EPA Method 200.7, CIROS, Spectro) (Mylavarapu, R.S., and E.D. Kennelley. UF/IFAS extension soil testing laboratory analytical procedures and training manual. University of Florida Extension Publication. http://edis.ifas.ufl.edu/SS312. October 2004.). All Ca2+ concentrations were expressed in mgkg-1 based on Ca2+ percent dry weight Soil samples were randomly collected from the experimental plots on 183 DAT 2003 and 181 DAT 2004. Samples were air dried and sent to the Analytical Research

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68 Laboratory in Gainesville, FL for soil Ca2+ content and soil pH (2003-04 only) determination according to Extension Soil Testing Laboratory Analytical Procedures and Ca2+ determination by Mehlich-1 extraction method (EPA Method 200.7, Mehlich-1 extraction) (Mylavarapu, R.S., and E.D. Kennelley. UF/IFAS extension soil testing laboratory analytical procedures and training manual. University of Florida Extension Publication. http://edis.ifas.ufl.edu/SS312. October 2004.). Fruit firmness was assessed in March 2003 as a nondestructive compression test to replicate a strawberry fruit being squeezed during the picking process. In February and March of 2004, firmness was assessed by using a puncture test assessing the bioyield point of the fruit tissue. This test was destructive and aimed at determining the strength of the internal tissue. Both measurements reflect fruit firmness at harvest. Fruits selected for the nondestructive compression firmness test were U.S. number one grade (Mitcham, 2003), greater than 10 g in weight and collected on 163 DAT in 2003. Forty fruits were selected from each experimental plot. These fruits were placed directly into labeled 0.9 kg containers for immediate transport to the Postharvest Horticulture Laboratory at the University of Florida in Gainesville, FL. Replicate samples of each treatment were combined into a pooled sample for a final composite selection for nondestructive mechanical resistance. Final selection of 20 fruits for each treatment for the nondestructive compression was performed at 5C. Compression measurements were taken using a penetrometer (Instron Universal Testing Instrument, Model 4411, Canton, Mass.) with a 5 kg load cell fitted with an 11 mm convex probe and a crosshead speed of 0.83 mms-1. Deformation force was recorded at 2 and 3 mm depths

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69 of each fruit. Samples were frozen immediately after measurements for later quality measurement measurements. Fruits selected for bioyield point were uniform U.S. number one grade (Mitcham, 2003), and greater than 10 g in weight. Samples were collected on 136 and 157 DAT in 2004. Fruits collected for each experimental plot were placed into 0.9 kg container and transported to the Postharvest Horticulture Laboratory at the University of Florida in Gainesville, Florida for measurements. Samples were placed into a 1°C until destructive preparation could occur. The maximum amount of time for any one treatment to be at 1°C was 24 h. Fruit temperature was always raised to room temperature (approximately 22°C) before preparation for bioyield point. Each sample for bioyield point consisted of four replicates of ten fruits from the pooled population representing each treatment. The destructive preparation for bioyield point consisted of slicing each fruit in the sample into an 11 mm section at the equator. Each slice was orientated proximal end up for mechanical resistance measurement. The puncture measurements were taken with a penetrometer (Instron Universal Testing Instrument, Model 4411, Canton, Mass.) with a 5 kg load cell fitted with a 4 mm convex probe to 7 mm end-point with a crosshead speed of 0.83 mm·s-1. Each fruit was measured twice within the red tissue area (outer receptacle tissue). Postharvest quality measurements of pH, titratable acidity, and soluble-solids content were conducted on frozen fruits collected during the growing season on 163 DAT in 2003, and 136 and 157 DAT in 2004. Frozen fruits were separated into four replications for each treatment and placed into containers to thaw at room temperature (approximately 22°C). Once at room temperature, fruits were homogenized in a blender,

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70 centrifuged at the force of 17,600 gn for 20 min, and filtered. The filtered supernatant was used for all postharvest quality measurements. The total supernatant sample was directly measured for pH using a Corning 140 pH meter standardized with pH 4.0 and 7.0 buffer solutions. Between each sample, the electrode was rinsed with de-ionized water and dried with laboratory wipes. Titratable acidity represents the buffering capacity of the fruit, and is generally expressed in terms of predominate organic acid (Perkins-Veazie and Collins, 1995). Total titratable acidity measurements were taken using a sub-sample of 6 g of supernatant plus 50 mL of de-ionized water. The measurements were performed using an electrode meter, using a burette/dispenser and a titrate demand using 0.1 N solution of NaOH (sodium hydroxide) to an endpoint pH of 8.2. Titratable acidity measurements were recorded as milliliters of NaOH dispensed. Milliliters of NaOH dispensed was used to calculate total titratable acidity by using the initial volume of the sample, normality of the base, and the milli-equilivant for citric acid equal to 0.064. Total titratable acidity is reported as percent citric acid based on the calculation. Soluble-solids content were measured using an ABBE Mark II Digital Refractometer using the refractive index range of Brix for sucrose. Two drops of supernatant were used on the prism at room temperature (approximately 22C) to determine soluble-solids content. Soluble-solids content measurements were recorded as the concentration percentage of soluble-solids (sucrose) within a solution (sample). Between each sample, the prism was rinsed with de-ionized water and dried with a laboratory wipe.

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71 Storage evaluations were conducted in 2002-03 and 2003-04 in a similar manner. The Horsfall-Barratt scale (Horsfall and Barratt, 1945) (Table 4-1) and bruising scale (Table 4-2) were used to evaluate each individual fruit in storage. For 2002-03, fruits were collected from the same pool (DAT 163) as firmness measurements and were U.S. number one grade (Mitcham, 2003). Samples consisted of 20 fruits for each treatment. Egg cartons were used as storage containers. Samples were held at 1C for 12 days with observations on Day 4, Day 8, and Day 12. On these observation days, weight loss and development of postharvest pathogens were measured. Samples were moved to a 5C on those 3 days for a maximum of 2 h for weight loss, bruise and decay observations. For 2003-04, U.S. Number one grade fruits (Mitcham, 2003) were randomly collected from the experimental plots and placed directly in to 454 g clamshell containers on 142 and 159 DAT. All clamshell containers were packed to commercial standards and removed from the field within a maximum time of 45 minutes. These clamshell containers were placed at 1C for 1 h with lids open to remove field heat before closing each container. Evaluation for weight loss measurement occurred as described above with samples held at a constant 1C. Marketable and unmarketable yield, Botrytis fruit rot affected fruit, Ca2+ content, total moisture content, firmness, titratable acidity, soluble-solids content, pH, storage, soil Ca2+ content, and soil pH were subjected to ANOVA for treatment effects using a general linear model (SAS, 2003, Version 9) with an alternative hypothesis tested for split-block, and mean separation by Fischer's LSD (least significant differences). Variables were considered significant at the level of 5% or P<0.05. The variables were analyzed with

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72 years combined and separated when a significant interaction between year and factor persisted. The exception to this was with firmness measurements caused by the differences in methodology. Orthogonal linear contrasts were used where appropriate for ascertaining the relationship of soil Ca2+, foliar source of Ca2+ and foliar CaCl2. The coefficient of variation (CV) was calculated as 100 times the ratio between the standard deviation and the mean and reported for each variable. Results and Discussion Season total and monthly yield for 2002-03 and 2003-04 seasons were not significantly different, except for the month of January. Therefore, yield results for both seasons were combined for every month excluding January (Table 4-3). The average marketable yield for both seasons combined was17,968 kgha-1. February accounted for44% of total yield produced. January 2004 produced 21% of the yield that was produced in January 2003. The significance between the two seasons for just the month of January can be related to the initial bloom flush dropping off earlier in the 2003-04 season than in the 2002-03 season. It is also possible that the minimum (January 2003, -2.93C and January 2004, 0.49C) and maximum temperatures (January 2003, 24.9C and January 2004, 29C) between the two years had an effect (Florida Automated Weather Network (FAWN). http://www.fawn.ifas.ufl.edu. June 2004.). Unmarketable fruit were not significantly decreased by source or rate of Ca2+ (Table 4-4). O f the marketable fruit, 39% was unmarketable in March, because of low fruit size, disease, or malformation. For both seasons combined, 25% of the fruits harvested were unmarketable. No interactions between foliar and soil Ca2+ applications were found for unmarketable fruits. The CV values for unmarketable fruits (greater than 30%) can be interpreted as a relatively high variability around the mean.

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73 Source and rate of foliar Ca2+ did not significantly affect the percentage of unmarketable fruit having visual symptoms of Botrytis fruit rot at harvest. Soil applications of Ca2+ as gypsum had no significant affect on the percent of unmarketable fruit being categorized as having Botrytis fruit rot (Table 4-5). February and March yield contributed to 75% of the unmarketable fruit with visible Botrytis fruit rot at harvest. The CV values for unmarketable fruits with visible Botrytis fruit rot (greater than 60%) can be interpreted as a relatively high variability around the mean. Supplemental Ca2+ applications did not significantly increase Ca2+ content of fruit or calyces analyzed in any month (Table 4-6). Calcium content of leaf tissue was significantly increased with soil applications of Ca2+ for the combined seasons. Despite, the P-value for this variable being less than 0.05, the means for the control, 224.5, 449 mg·kg-1 soil Ca2+ from gypsum rate were not separated by Fischer's LSD (Table 4-7). Calcium content within achenes was not significantly affected by additional Ca2+ applications (Table 4-8). This suggests that the achenes are not a strong sink for Ca2+. Any extra Ca2+ applied to the strawberry fruit would not be directly translocated into the achenes. The hypothesis that seeds or other fertilized embryos (such as achenes) would be a sink for additional Ca2+ applied to a commodity was suggested by Lester and Grusak (1999). Soluble-solids content and total titratable acidity were not significantly affected by soil or foliar Ca2+ applications (Table 4-9). The averages for soluble-solids content and total titratable acidity were 5.4 °Brix, and 0.61% citric acid, respectively. Soil applications of Ca2+ as gypsum significantly affected pH of fruit juice extracted from processed frozen fruits (Table 4-9). The control soil Ca2+ pH of fruit juice extracted from

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74 processed frozen fruits was significantly higher than the 449 mg·kg-1 Ca2+ from gypsum. No linear effects of soil or foliar applications of total titratable acidity, soluble-solids content and pH were found. Fruit firmness results were presented by year, because the different analytical methods used (Table 4-9). In 2002-03, fruits receiving the 449 mg·kg-1 Ca2+ from gypsum rate were significantly firmer than fruits receiving the control soil Ca2+ and the 224.5 mg·kg-1 soil Ca2+ (from gypsum) rate at the 2 mm depth of compression. A significant linear contrast response to soil Ca2+ was found for this depth (Table 4-9). For the 3mm depth of compression, foliar Ca2+ significantly increased fruit firmness (Table 4-9). Fruits treated with either 400 or 800 mg·L-1 were firmer than those treated with the foliar application of water. A significant linear contrast was found for CaCl2 at this depth. An interaction of foliar and soil Ca2+ applications was found at 3 mm (Table 4-10 and Figure 4-1). Fruits firmness increased with the combination of foliar water and soil Ca2+ from control to 449 mg·kg-1 Ca2+ from gypsum. Fruit firmness was decreased with foliar Ca2+ as 800 mg·L-1 from CaCl2 as soil Ca2+ applications increased from control to 449 mg·kg-1 Ca2+ from gypsum. Both CaSO4 and CaCl2 at 400 mg·L-1 rate in combination with the 224.5 mg·kg-1 Ca2+ from gypsum had higher firmness measurements than their respective combinations with control soil and 449 mg·kg-1 Ca2+ from gypsum. In the 2003-04 season, firmness was assessed as bioyield point of the internal tissue. Supplemental soil and foliar Ca2+ did not significantly affect firmness measured as bioyield (Table 4-9). Supplemental soil and foliar applications Ca2+ did not significantly affect total percent moisture attained by fruit (Table 4-11). No significant interaction between soil and foliar Ca2+ for total percent moisture was found.

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75 Foliar and soil Ca2+ application significantly affected postharvest weight loss in storage on Day 4 and Day 8 for 2003 only with no interactions present (Table 4-12). Bruising and decay ratings in storage were inconsistent and minimal for storage at 1C for 2002-03 and 2003-04 seasons. Basic statistics consisting of maximum observations, minimum observations, means, variance, range of bruising rating and postharvest pathogen are presented for Day 4 and D ay 8 of storage in 2002-03; Day 8 and only postharvest pathogen ratings for Day 12 of storage in 2003-04 (Table 4-13). Weight loss in storage on Day 12 was not significant influenced by foliar or soil Ca2+ application. A significant linear contrast of soil Ca2+ was found for Day 4 and D ay 8 of storage at 1C. Soil Ca2+ on both observation days at 449 mgkg-1 Ca2+ from gypsum had higher weight loss over the 224.5 mgkg-1 Ca2+ from gypsum and control soil treatments. Day 8 of storage was the only observation date in which soil application significantly affected weight loss. Fruits from plants treated with soil Ca2+ as 449 mgkg-1 Ca2+ from gypsum loss more weight in storage than either the control or 224.5 mgkg-1 Ca2+ from gypsum. On Day 4 foliar Ca2+ as 800 mg/L from CaCl2 significantly increased weight loss in storage. On Day 8, fruits from plants treated with 400 or 800 mgL-1 from CaCl2 had high weight loss. Both rates of foliar CaCl2 were significantly different from the 400 mgL-1 from CaSO4. On Day 4 of storage, a significant linear contrast of foliar Ca2+ as CaCl2 was found. The linear trend of increasing levels of CaCl2 increased weight loss of strawberry fruit in storage. On Day 8 of storage, a significant linear contrast of source of foliar Ca2+ was found. Foliar Ca2+ as CaSO4 and the control application lost less weight than the low rate of CaCl2. Foliar CaCl2 and supplemental soil Ca2+ increased weight loss in the initial

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76 Day 8 of storage. The increased weight loss caused by soil and foliar Ca2+ at Day 4 is a serious detrimental effect. Strawberry fruits are sold by weight in a corrugated cardboard container called a flat (weighing approximately 4.5 kg) and depending on the market could be held for 2 days in storage before shipment. Based on our storage test, a 4% weight loss by Day 4 could result in a loss of 180 g. Soil Ca2+ levels after the growing season, at depths of 15.2 and 30.4 cm were not significantly affected by supplemental Ca2+ applied throughout the season. The 30.4 cm depth had a significant linear contrast of soil Ca2+ treatment. Both soil application rates had more Ca2+ than the control, but were not significantly different from each other (Table 4-13). The mean for the control was 369 mgkg-1 higher than the average of the two pre-season soil test results. Soil pH was significantly influenced by soil Ca2+ treatment at 30.4 cm. Both soil gypsum rates (224.5 and 449 kgha-1 Ca2+) were significantly higher than the control soil treatment. This response was unexpected, because the rationale of using gypsum on the basis that it does not influence soil pH. A significant positive linear contrast was found for soil pH at 30.4 cm. Supplemental foliar Ca2+ significantly increased soil pH at 15.2 cm. The 800 mg/L of Ca2+ from CaCl2 had a higher soil pH than 400 mgL-1 of Ca2+ from CaCl2. Soil pH of the water control spray was not significantly different from either of the CaCl2 foliar sprays. A significant positive linear contrast was found for foliar CaCl2. The non-significant results of marketable yield were similar to results to the study conducted in Ohio. The study found no increase in yield with additional foliar Ca2+ when soil Ca2+ levels were 990 and 1,110 kgha-1 (Erincik et al., 1998). The levels of Ca2+ are at or higher than sufficiency levels for strawberry production, therefore, it is not

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77 unexpected that yield did not respond to additional Ca2+. The number of unmarketable fruit was not significantly affected by additional Ca2+ applications. Wojcik and Lewandowski (2003) had similar results with foliar Ca2+ affecting deformed fruit. Visible symptoms of Botrytis fruit rot at harvest were not significantly affected by Ca2+ applications. These results are very similar to the study conducted by Erincik et al. (1998), in which foliar Ca2+ was compared to traditional fungicides for Botrytis fruit rot control. Soil Ca2+ applications increased total Ca2+ content of leaves for our study. These results validate the findings of previous studies conducted by Makus and Morris (1989), Cheour et al. (1990; 1991), and Wojcik and Lewandowski (2003). Arkansas investigators used foliar, fertigation, soil applications of Ca2+; Canadian investigators used foliar Ca2+ application at different rates, and the Polish investigators used foliar Ca2+ applications in conjunction with boron. Makus and Morris (1989) did not observe an increase in fruit tissue, but did observe an increase in leaf tissue Ca2+ content. Cheour et al. (1990; 1991) and Wojcik and Lewandowski (2003) both found increased Ca2+ in leaf and fruit tissue with foliar Ca2+ treatments. In particular, Cheour et al. (1990; 1991) found cultivar differences for Ca2+ uptake and assimilation into leaves, green and pink fruit. Results for our study were not consistent with those studies conducted outside of the United States. Environment, cultural management, and cultivar choice are potential explanation for these results by influencing Ca2+ availability for plant uptake. Postharvest measurements of total titratable acidity, and soluble-solids content were not significantly increased by supplemental Ca2+ applications. These results were

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78 similar to the studies conducted in Ohio, and Arkansas in which additional Ca2+ did not affect soluble-solids content and total titratable acidity. Fruit pH was significantly decreased by supplemental soil Ca2+ applications. Previous studies do not coincide with these results. A possible explanation for the decrease in pH with additional Ca2+ could be transportation into the vacuole from the cytosol for enzyme functionality purposes (Marschner, 1995). Fruit firmness was significantly increased by additional soil and foliar Ca2+ for March 2003. These results were similar to all other studies, except for those studies conducted in Ohio and Arkansas. Firmness was increased with foliar CaCl2 over the control, but the rates were not different from each other. This does not coincide with results from the Canadian studies. Cheour et al. (1990; 1991) found significant increase in fruit firmness with different rates foliar 5, 10, 15, or 20 kgha-1 Ca2+ as CaCl2. Wojcik and Lewandowski (2003) used one rate of CaCl2 and observed increase in firmness at harvest. Soil supplementation with Ca2+ significantly increased firmness of strawberry fruit at 2 mm depth of compression. This effect has not been previously documented with soil applied Ca2+ on strawberries. An interaction between soil and foliar Ca2+ was found for strawberry firmness during the 2003-04 season. With increasing soil Ca2+, foliar Ca2+ was less effective in increasing strawberry firmness. In 2004, strawberry firmness was not affected by supplementation with Ca2+. The split between significance in the first year compared to the second year of our study may be caused by the type of measurement taken. The surface firmness of strawberry is an important factor in determining firmness.

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79 Percent moisture accumulated by strawberry fruit was not significantly increased with additional Ca2+. The moisture content of a fruit can be important in determining quality, because some fruits are compost moistly of water and sugars. This variable has not previously been measured in other studies. Weight loss in storage was significantly increased with the addition of soil or foliar Ca2+. Previous studies have not reported weight loss being negatively affected by applications of soil or foliar Ca2+. The companion ion within the foliar sprays could be an influencing factor weight loss of strawberry fruit in storage. Previous studies have shown the additional Ca2+ to reduce decay by Botrytis fruit rot in storage (Makus and Morris, 1989; Cheour et al., 1990; 1991; Wojcik and Lewandowski, 2003). This 2-year study found no decrease in decay caused by Botrytis fruit rot with applications of soil or foliar Ca2+ while strawberry fruit were in storage. Conclusions In this 2-year study, preharvest Ca2+ applications offer did not offer any benefit to the Florida strawberry. Supplemental Ca2+ did not significantly affect marketable yield, Botrytis fruit rot at harvest, fruit firmness for both years. Weight loss was significantly increased by supplemental Ca2+ applications after day 4 and day 8 of storage. When soil Ca2+ is sufficient, additional Ca2+ applications are not recommended for strawberry growers. The practice of applying additional Ca2+ as a foliar spray decreases the final quality of fully ripe strawberry fruits at postharvest. These results do not support the current practice of applying foliar Ca2+ to strawberry throughout the season.

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Table 4-1. Horsfall-Barratt scale used to evaluate surface area affected by postharvest pathogens on strawberry ( Fragaria×ananassa Duch.) stored at 1°C for 2002-03 and 2003-04 seasons Percentage affecteda Evaluation number 0 1 0 to 3 2 3 to 6 3 6 to 12 4 12 to 25 5 25 to 50 6 50 to 75 7 75 to 87 8 87 to 94 9 94 to 97 10 97 to 100 11 100 12 aAdapted to table a form from Horsfall, J.C. and R.W. Barratt. 1945. An improved grading system for measuring plant diseases. Phytopathology 35:655-655.

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Table 4-2. Bruising scale used to evaluate 'Sweet Charlie' strawberry ( Fragariaananassa Duch.) at 1C for 2002-03 and 2003-04 seasons Subjective degree of bruising Evaluation number Bruise free 1 Slight bruising 2 Moderate bruising 3 Severe bruising 4 Disfiguring or very severe bruising 5

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82Table 4-3. Combined marketable yield of ‘Sweet Charlie’ strawberry ( Fragaria ananassa Duch.) GCREC-Dover for 2002-03 and 2003-04 growing seasons as affected by calcium application Nov. Dec. Jan. Feb. Mar. Season (kgha-1)c Ca2+Source 2003 2004 Ca2+ from Gypsum (kgha-1) 0 1317 2766 2349 608 7849 5078 17748 224.5 1302 2848 2589 427 7708 5176 18054 449 1327 2807 2241 501 8265 4936 18112 LSDb 315 337 740 421 804 542 3739 P-value 0.92 0.98 0.69 0.58 0.39 0.43 0.37 Linear Contrast Soil 0.95 0.97 0.76 0.69 0.18 0.58 0.88 Foliar (mgL-1 Ca2+) 0 1239 2624 2488 499 8155 5217 17995 400 CaSO4 1417 2978 2325 448 8274 5134 18580 400 CaCl2 1239 2817 2524 495 7615 5136 17802 800 CaCl2 1382 2812 2236 624 7716 4755 17491 LSDb 364 389 855 486 928 626 4315 Mean 1317 2807 2393 514 7940 5061 17968 CV (%)a 32 23 42 108 19 21 88 P-value 0.82 0.49 0.88 0.78 0.38 0.36 0.97 Linear Contrast Source Ca2+ 0.51 0.55 0.63 0.73 0.10 0.77 0.77 Linear Contrast CaCl2 0.50 0.51 0.58 0.53 0.59 0.14 0.80 cValues in columns are means for each treatment bMean separation by Fischer's Least Significant Difference aCoefficient of variation

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83Table 4-4. Percent unmarketable fruits of harvested ‘Sweet Charlie’ strawberry ( Fragariaananassa Duch.) fruits at GCREC-Dover for 2002-03 and 2003-04 growing seasons as affected by calcium application Nov. Dec. Jan. Feb. Mar. Season Ca2+ Source Percent unmarketablec Ca2+ from Gypsum (kgha-1) 0 20.9 22.5 35.0 22.5 40.3 26.4 224.5 14.8 20.0 41.3 21.2 38.3 24.9 449 15.5 14.7 46.2 22.3 39.7 25.2 LSDb 8.0 6.3 13.4 5.8 4.8 3.8 P-value 0.39 0.44 0.40 0.95 0.54 0.91 Linear Contrast Soil 0.48 0.31 0.55 0.81 0.36 0.83 Foliar (mgL-1 Ca2+) 0 18.5 18.8 40.6 21.2 35.6 24.8 400 CaSO4 15.1 18.2 45.1 23.1 41.4 26.4 400 CaCl2 21.9 21.8 43.5 23.8 40.9 28.2 800 CaCl2 13.4 17.7 33.2 20.1 39.9 23.0 LSDb 9.3 7.3 15.4 6.7 5.6 4.4 Mean 17.1 19.1 40.7 22.0 39.4 25.5 CV(%)a 124 125 93 99 29 105 P-value 0.50 0.93 0.92 0.96 0.63 0.68 Linear Contrast Source Ca2+ 0.40 0.60 0.74 0.99 0.79 0.74 Linear Contrast CaCl2 0.21 0.95 0.88 0.59 0.95 0.60 cValues in columns are means for each treatment bMean separation by Fischer's Least Significant Difference aCoefficient of variation

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84Table 4-5. Monthly and season total of Botrytis fruit rot (caused by Botrytis cinerea Pers. ex Fr.) incidence on unmarketable fruits of ‘Sweet Charlie’ strawberry ( Fragariaananassa Duch.) at GCREC-Dover during 2002-03 and 2003-04 growing seasons as affected by calcium application Nov. Dec. Jan. Feb. Mar. Season Ca2+ Source Percent with Botrytis fruit rotc Ca2+ from Gypsum (kgha-1) 0 8.0 2.2 4.1 16.8 18.1 45.0 224.5 7.3 2.2 0 13.3 16.8 40.5 449 1.3 2.5 2.6 14.4 20.9 36.4 LSDb 9.3 3.1 3.7 7.2 7.0 3.0 P-value 0.41 0.98 0.10 0.13 0.75 0.24 Linear Contrast Soil 0.09 0.79 0.25 0.42 0.71 0.28 Foliar (mgL-1 Ca2+) 0 5.3 1.3 3.7 14.5 18.3 40.5 400 CaSO4 5.3 2.6 0.3 14.7 18.6 38.7 400 CaCl2 6.3 3.6 3.7 13.8 17.2 41.4 800 CaCl2 5.6 2.0 1.5 16.5 20.4 43.6 LSDb 10.7 3.6 4.3 8.3 8.1 3.5 Mean 5 2 2 14 18 40 CV(%)a 197 243 272 59 45 115 P-value 0.99 0.60 0.18 0.97 0.87 0.98 Linear Contrast Source Ca2+ 0.78 0.50 0.07 0.84 0.58 0.75 Linear Contrast CaCl2 0.90 0.78 0.18 0.86 0.55 0.87 cValues in columns are presented as untransformed means for each treatment bMean separation by Fischer's Least Significant Difference aCoefficient of variation

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85Table 4-6. Calcium concentration by month for ‘Sweet Charlie’ strawberry ( Fragariaananassa Duch.) at GCREC-Dover for 2002-03 and 2003-04 growing seasons as affected by calcium application Leavesd Fruit Calyx Leavesd Fruit Calyx Leavesd Fruit Calyx Ca2+ Source 104 DAT 2003 & 96 DAT 2004 144 DAT 2004 154 DAT 2003 & 159 DAT 2004 Ca2+ from Gypsum (kgha-1) (mgkg-1)c 0 7837 1387 12040 11451 2650 13373 11924 3057 18655 224.5 7738 1412 11905 11265 2679 12569 11335 3088 19258 449 8032 1445 11840 11605 2739 13426 12036 3083 19315 LSDb 1166 146 1240 694 131 3010 1149 148 2708 P-value 0.32 0.68 0.81 0.27 0.39 0.66 0.21 0.32 0.14 Linear Contrast Soil 0.72 0.42 0.72 0.67 0.26 0.96 0.84 0.77 0 .60 Foliar ( mgL-1 Ca2+) 0 7768 1416 11760 11637 2732 13513 11265 3084 18794 400 CaSO4 7469 1373 11370 11403 2683 12708 11745 2987 18854 400 CaCl2 7794 1427 12106 10881 2632 13602 11738 3099 18091 800 CaCl2 8453 1443 12476 11839 2704 12668 12426 3132 20526 LSDb 1346 168 1432 801 151 3475 1326 171 3128 Mean 7870 1414 11928 11440 2688 13122 11781 3075 19070 CV(%)a 29 20 9 8 6 20 15 9 19 P-value 0.52 0.85 0.39 0.09 0.48 0.88 0.42 0.32 0.44 Linear Contrast Source Ca2+ 0.59 0.53 0.27 0.25 0.65 0.57 0.92 0.13 0.58 Linear Contrast CaCl2 0.31 0.74 0.28 0.67 0.52 0.59 0.10 0.65 0.26 dSufficency range for leaf tissue at first harvest 4,000 to 15,000 mgkg-1 (Simonne et al., 2003) cValues in columns are means for each treatment bMean separation by Fischer's Least Significant Difference aCoefficient of variation

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86 Table 4-7. Seasons total for calcium concentration of ‘Sweet Charlie’ strawberry ( Fragariaananassa Duch.) tissues at GCREC-Dover as affected by calcium application Leavesd Fruit Calyx Ca2+ Source (mgkg-1)c Ca2+ from Gypsum (kgha-1) 0 10195a 2308 15681 224.5 9823a 2331 15747 449 10340a 2357 15866 LSDb 861 275 2407 P-value 0.04 0.54 0.74 Linear Contrast Soil 0.76 0.74 0.60 Foliar (mgL-1 Ca2+) 0 9941 2346 15715 400 CaSO4 9922 2277 15299 400 CaCl2 9981 2334 15473 800 CaCl2 10679 2368 16549 LSDb 994 317 2780 Mean 10125 2028 15761 CV(%)a 26 37 30 P-value 0.33 0.93 0.83 Linear Contrast Source Ca2+ 0.78 0.64 0.94 Linear Contrast CaCl2 0.14 0.95 0.54 dSufficency range for leaf tissue at first harvest 4,000 to 15,000 mgkg-1 (Simonne et al., 2003) cValues in columns are means for each treatment bMean separation by Fischer's Least Significant Difference aCoefficient of variation

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87 Table 4-8. Achenes and related tissues test for calcium concentration of ‘Sweet Charlie’ strawberry ( Fragariaananassa Duch.) at GCREC-Dover as affected by calcium application Achenes Fruit Calyx Ca2+ Source 134 DAT (mgkg-1)c Ca2+ from Gypsum (kgha-1) 0 2783 2347 13221 224.5 2693 2329 13347 449 2797 2448 14168 LSDb 258 167 2180 P-value 0.28 0.12 0.53 Linear Contrast Soil 0.87 0.17 0.31 Foliar ( mgL-1 Ca2+) 0 2739 2428 13321 400 CaSO4 2729 2313 13189 400 CaCl2 2749 2443 14305 800 CaCl2 2825 2313 13528 LSDb 298 192 2508 Mean 2759 2374 13582 CV(%)a 9 12 12 P-value 0.80 0.40 0.69 Linear Contrast Source Ca2+ 0.91 0.15 0.29 Linear Contrast CaCl2 0.53 0.35 0.74 cValues in column are means for each treatment bM ean separation by Fischer's Least Significant Difference aCoefficient of variation

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88Table 4-9. Postharvest quality of ‘Sweet Charlie’ strawberry ( Fragariaananassa Duch.) at GCREC-Dover during 2002-03 and 2003-04 growing seasons as affected by calcium application Firmness (Newtons)f Quality Measurementf Ca2+Source Deformation Force Bioyield point pH TTAe,d SSCc 163 DAT 2003 136 DAT 2004 157 DAT 2004 2002-03 & 2003-04 Ca2+ from Gypsum (kgha-1) 2 mm 3 mm 0 2.17 b 3.22 0.62 0.55 3.72 b 0.61 5.5 224.5 2.10 b 3.32 0.63 0.54 3.70 ab 0.62 5.5 449 2.33 a 3.25 0.63 0.54 3.69 a 0.61 5.4 LSDb 0.09 0.11 0.01 0.04 0.02 0.03 0.28 P-value 0.02 0.34 0.38 0.56 0.02 0.33 0.90 Linear Contrast Soil <0.01 0.54 0.23 0.42 0.51 0.51 0.91 Foliar (mgL-1 Ca2+) 0 2.17 3.17 b 0.63 0.56 3.71 0.60 5.5 400 CaSO4 2.28 3.22 ab 0.63 0.54 3.70 0.60 5.5 400 CaCl2 2.17 3.32 a 0.63 0.53 3.70 0.61 5.5 800 CaCl2 2.17 3.32 a 0.62 0.55 3.69 0.62 5.3 LSDb 0.11 0.12 0.02 0.04 0.02 0.04 0.33 Mean 2.19 3.26 0.62 0.54 3.27 0.61 5.4 CV(%)a 6 4 6 10 1.5 8 12 P-value 0.16 0.05 0.39 0.79 0.80 0.46 0.74 Linear Contrast Source Ca2+ 0.07 0.11 0.66 0.78 0.84 0.11 0.87 Linear Contrast CaCl2 0.94 0.02 0.10 0.75 0.33 0.81 0.44 fValues in columns are means for each treatment eTotal titratable acidity as percent citric acid dPresented as untransformed means cPercent soluble-solids content measured using the Brix refractive index range bMean separation by Fischer's Least Significant Difference aCoefficient of variation

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89Table 4.10. Interaction of supplemental calcium applied as gypsum with foliar calcium source and rate on strawberry fruits ( Fragariaananassa Duch.) firmness at 3 mm deformation depth on 163 DAT 2003 Deformation Forces (Newtons)a,b Gypsum (kgha-1) Ca2+ Source 0 224.5 449 Foliar (mgL-1 Ca2+) 0 2.84 ab 3.13 ab 3.55 ab 400 CaSO4 3.18 ab 3.46 ab 3.02 ab 400 CaCl2 3.34 a 3.41 a 3.22 a 800 CaCl2 3.51 a 3.26 a 3.20 a bValues in columns are means for each treatment aMean separation by Fischer's Least Significant Difference

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90 Table 4-11. Total moisture content of ‘Sweet Charlie’ strawberry fruits ( Fragariaananassa Duch.) at GCREC-Dover during 2002-03 and 2003-04 growing seasons as affected by calcium application Jan. Feb. 2004 Mar. Season Ca2+Source Percent fresh weightc Ca2+ from Gypsum (kgha-1) 0 90.4 94.3 94.0 92.6 224.5 90.3 94.6 94.1 92.6 449 90.0 94.6 93.9 92.5 LSDb 0.4 0.5 0.2 0.7 P-value 0.73 0.25 0.25 0.63 Linear Contrast Soil 0.37 0.17 0.25 0.81 Foliar (mgL-1 Ca2+) 0 90.4 94.4 93.9 92.6 400 CaSO4 90.2 94.3 93.9 92.5 400 CaCl2 90.2 94.5 94.1 92.6 800 CaCl2 90.3 94.9 94.1 92.7 LSDb 0.5 0.5 0.2 0.8 Mean 90.0 94.0 93.5 92.0 CV(%)a 1 1 1 3 P-value 0.73 0.08 0.64 0.92 Linear Contrast Source Ca2+ 0.73 0.24 0.30 0.68 Linear Contrast CaCl2 0.91 0.05 0.50 0.74 cValues in columns are presented as untransformed means for each treatment bM ean separation by Fischer's Least Significant Difference aCoefficient of variation

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91Table 4-12. Effect of supplemental calcium on storage of ‘Sweet Charlie’ strawberry fruits ( Fragariaananassa Duch.) at GCREC-Dover during 2002-03 and 2003-04 growing seasons as affected by calcium application Percent weight lossc 2003 2004 Ca2+Source Day 4 Day 8 Day 12 Day 4 Day 8 Day 12 Ca2+ from Gypsum (kgha-1) 0 1.9 4.0 b 6.6 1.8 4.2 7.3 224.5 2.3 4.3 b 7.3 1.8 4.3 7.3 449 3.0 7.6 a 10.4 1.7 4.2 8.3 LSDb 0.6 2.5 3.6 0.2 0.5 1.7 P-value 0.11 0.01 0.07 0.45 0.84 0.60 Linear Contrast Soil <0.01 <0.01 0.12 0.27 0.96 0.38 Foliar ( mgL-1 Ca2+) 0 1.9 b 4.0 b 7.2 1.9 4.5 7.7 400 CaSO4 1.6 b 4.3 ab 6.5 1.6 4.3 7.3 400 CaCl2 2.4 b 6.9 a 9.2 1.7 4.0 8.3 800 CaCl2 3.6 a 5.8 ab 9.2 1.9 4.1 7.3 LSDb 0.7 2.9 3.6 0.3 0.5 1.9 Mean 2.3 5.2 8.0 1.7 4.2 7.6 CV(%)a 27 25 32 18 11 18 P-value <0.01 0.04 0.24 0.50 0.42 0.82 Linear Contrast Source Ca2+ 0.09 0.03 0.23 0.66 0.23 0.51 Linear Contrast CaCl2 <0.01 0.06 0.10 0.97 0.27 0.60 cValues are presented as untransformed means for each treatment bMean separation by Fischer's Least Significant Difference aCoefficient of variation

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92Table 4-13. Decay for 2002-03 and 2003-04 seasons and bruising for 2002-03 season stored at 1C on 'Sweet Charlie' strawberry fruits ( Fragariaananassa Duch.) grown at GCREC-Dover Decayb Bruisingc 2002-03 2003-04 2002-03 & 2003-04 Mar. Feb. Mar. 4 d 8 d 8 d 12 d 12 d 4 d 8 d Range 2.0 2.0 4.0 3.0 3.0 3.0 4.0 Min. 0 0 0 0 0 0 0 Max. 2.0 2.0 4.0 3.0 3.0 3.0 4.0 N 45 48 45 48 48 239 239 Variance 0.16 0.23 0.86 0.57 0.26 0.35 0.47 Standard Deviation 0.40 0.48 0.93 0.75 0.51 0.59 0.69 Mean 0.08 0.13 0.33 0.25 0.10 1.36 1.5 bHorsfall Barrett scale in which the percentage affected equals an evaluation number. Therefore, 0%=1, 0% to 3% = 2, 3% to 6 % = 3, 6% to 12 % = 4, 12% to 25% = 5, 25% to 50% = 6, 50% to 75% = 7, 75% to 87% = 8, 87% to 94% = 9, 94% to 97% = 10, 97% to 100% = 11, 100% = 12 aBruising scale evaluation: bruise free = 1, slight bruising = 2, moderate bruising = 3, severe bruising = 4, disfiguring or ve ry severe bruising = 5

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93 Table 4-14. End of growing season soil test (Mehlich-1 extraction method for calcium) in experimental area at GCREC-Dover for 2002-03 and 2003-04 growing seasons as affected by calcium application Soil Calciume,d (mgkg-1) Soil pHe,c 183 DAT 2003 & 181 DAT 2004 181 DAT 2004 Ca2+Source Depth Depth 15.2 cm 30.4 cm 15.2 cm 30.4 cm Ca2+ from Gypsum (kgha-1) 0 995 916 b 6.13 6.42 a 224.5 930 1002 ab 6.20 6.17 b 449 993 1085 a 6.10 6.09 b LSDb 149 159 0.11 0.16 P-value 0.70 0.34 0.56 0.01 Linear Contrast Soil 0.87 0.03 0.78 <0.01 Foliar (mgL-1 Ca2+) 0 976 1053 6.12 ab 6.27 400 CaSO4 964 958 6.15 ab 6.26 400 CaCl2 951 908 6.06 b 6.17 800 CaCl2 1001 1079 6.25 a 6.23 LSDb 172 184 0.13 0.18 Mean 972 1000 6.14 6.23 CV(%)a 30 31 2 3 P-value 0.89 0.28 0.04 0.68 Linear Contrast Source Ca2+ 0.75 0.56 0.22 0.41 Linear Contrast CaCl2 0.61 0.73 0.04 0.62 eValues are means for each treatment d>400 mgkg-1 soil Ca2+ interpreted as "very high" by Hochmuth and Simonne (2003) cTarget pH 6.5 for strawberries grown on mineral soils bM ean separation by Fischer's Least Significant Difference aCoefficient of variation

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94 Figure 4-1. Interaction between soil and foliar calcium on strawberry ( Fragariaananassa Duch.) firmness at 3 mm deformation depth on 11 March 2003 with Fisher's least significant difference error bars 2.7 2.8 2.9 3 3.1 3.2 3.3 3.4 3.5 3.6 3.7 0 mgkg-1 224.5 mgkg-1449 mgkg-1Soil applied Ca2+ from gypsum (CaSO 4 ) N ewtons water 400 mgL-1 CaSO4 400 mgL-1CaCl2 800 mgL-1CaCl2

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95 CHAPTER 5 INFLUENCE OF CALCIUM SOURCE ON YIELD AND POSTHARVEST QUALITY OF ‘SWEET CHARLIE’ STRAWBERRY ( Fragaria × ananassa Duch.) Introduction Annual hill production of strawberries in Florida uses calcium nitrate (Ca(NO3)2) as the primary nitrogen source, which also provides calcium (Ca2+) throughout the season. Florida has a karst topography, limestone bedrock, which can be a soluble Ca2+ source. Therefore, up to 60 mg·L-1 soluble Ca2+ is present in Florida irrigation water. Many Florida strawberry growers apply additional Ca2+ to their crop despite the lack of conclusive evidence of an increase in fruit quality or yield. The rationale for application of supplemental Ca2+ comes from calcium’s involvement in cell-wall integrity and reduction of fruit quality when inadequately available at critical times. Calcium has been extensively reviewed as both an essential element and with regard to its role in maintaining postharvest quality of fruit and vegetable crops. Calcium is known to have a role in membrane stability (Kirkby and Pilbeam, 1984). Calcium contributes to the linkages between pectic substances within the cell-wall (Demarty et al., 1984). The implication of Ca2+ involved in improving postharvest quality under relatively high concentrations in fruit tissue has resulted in a slower rate of ripening, and reduced respiration, ethylene production and softening of fruit tissue (Ferguson, 1984). Calcium is absorbed in the plant by young root tips and translocated via the transpirational stream (Mengel and Kirkby, 1987). Applying preharvest Ca2+ as a supplement to the root zone as part of a regular fertigation event can improve postharvest quality of strawberry.

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96 Results from preharvest applications of Ca2+ to improve strawberry fruit yield and quality have been inconclusive. Eaves and Leefe (1962) found that a foliar spray of 1,445 mg·L-1 Ca2 from CaCl2 (0.4% CaCl2) increased firmness in strawberry fruit. This finding was supported by Canadian investigators Cheour et al. (1990; 1991), who found that foliar treatments of 5, 10, 15, and 20 kg·ha-1 Ca2+ as CaCl2 delayed the ripening of strawberry fruit and mold development. These treatments also increased firmness of fruit at harvest and during storage. Soil Ca2+ was reported as 15 and 20 mg·kg-1 Ca2+ in 1990 study and 33 mg·kg-1 Ca2+ in 1991 study. These investigators did not interpret the reported soil Ca2+ levels to be sufficient for strawberry growth and development in either study. An interpretation of the sufficiency of the current soil Ca2+ level would be beneficial to understanding the need for additional Ca2+ from any source. Wojcik and Lewandowski (2003) found no significant effect of supplemental foliar Ca2+ on yield and the number of misshapen fruit, but report favorable effects on fruit postharvest quality. Fruit firmness was increased with both Ca2+ and Ca2+ and boron applications. Foliar Ca2+ applications increased both titratable acidity and soluble-solids content of fruit in our study. These investigators reported soil levels of nitrogen and phosphorus, but no reference to soil Ca2+ content. In our study, both leaf and fruit Ca2+ content were increased with foliar Ca2+ over the control treatment. In contrast, research conducted in Ohio, found that foliar applications of CaCl2 had no consistent effects on Ca2+content of fruit, yield, fruit firmness, soluble-solids content, fruit acidity and external color of fruit in field and greenhouse experiments (Erincik et al., 1998). This investigation also found that foliar applications of CaCl2 did not control Botrytis fruit rot at harvest or during postharvest. These results were contrary to previous

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97 studies conducted which found a reduction in Botrytis fruit rot with foliar CaCl2 applications. This investigation was conducted under high Ca2+ environment at 990 and 1100 mgkg-1 Ca2+ in the soil. The level of soil Ca2+ was interpreted by the investigators to be within the sufficiency range for strawberry production. Makus and Morris (1989; 1998) supported of the conclusion that foliar, soil, and drip irrigation injected applications of supplemental Ca2+ as chelated Ca2+, gypsum, or Ca (NO3)2 did not significantly increase postharvest quality measurement or Ca2+ content of strawberry fruits. The first study focused on postharvest attributes and Ca2+ of the fruits and leaves, but did not report the influence on total yield. The second study focused only on fruit Ca2+ content. Postharvest quality measurements of soluble-solids content, fruit pH, titratable acidity, and firmness were not influenced by Ca2+ treatment (Makus and Morris, 1989). Leaf Ca2+ content was significantly increased in this investigation with Ca2+ application. All sources of additional Ca2+ increased leaf Ca2+ content over the control, but fruit Ca2+ content was not increased in our study. Makus and Morris (1998) furthered the conclusion of a lack of fruit accumulation of Ca2+. In this investigation, additional Ca2+ applied in the same manner of the investigator's previous study was found not to increase Ca2+ distribution. Soil fertility and Ca2+ level were reported in this investigation. In pervious studies conducted by these investigators only an interpretation of the over all fertility was reported as "low" without a soil Ca2+ level. In Makus and Morris (1998) soil fertility was again reported as "low", but the inclusion of 1400 kgha-1 as soil Ca2+ seems to contradict this measurement. No previous studies have not focused on Ca (NO3)2 as a Ca2+ source except for Makus and Morris (1989; 1998). No previous studies exist for calcium thiosulfate

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98 (CaS2O3), an additional Ca2+ source, on improving strawberry quality. Yet, CaS2O3 has been sold as an alternative to soil amending with gypsum based on its ease of use. The product can be injected through the drip irrigation system with the regular fertilizer application. Yet, very little published information on the benefits of CaS2O3 exists on increasing yield or postharvest quality of any commodity. Calcium thiosulfate has been found to not increase yield or reduce BER (blossom-end rot) of tomato fruit (Taylor et al., 2004). This investigation also found that CaS2O3 did not to increase calcium content of tomato fruit when applied through drip irrigation. Taylor et al. (2004) focused on the Ca2+ deficiency of tomato fruits and improvement with Ca2+, K+, and irrigation. They did not focus on postharvest quality aspects of tomato fruits. Therefore, it is unknown how CaS2O3 will affect quality of fruit. It is hypothesized that supplemental Ca2+ applied to the root system through the drip irrigation, as CaS2O3 will increase yield, Ca2+ in fruit tissue, and improve fruit postharvest quality. The objectives of our study were to determine the effects of Ca2+ supplied as CaS2O3 when applied supplemental to a grower’s standard fertilization regime and as sole source of Ca2+ through fertigation on Yield of strawberry G rowth and Ca2+ content of strawberry fruit Postharvest quality . Materials and Methods An experiment was conducted at the Gulf Coast Research Education Center at Dover (GCREC-Dover) on a Seffner fine sand (sandy, siliceous, hyperthermic, Quartzipsammentic Haplumbrepts) from August 2003 to March 2004. Soil was

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99 fumigated to industry standards of 67% to 33% ratio (w: w, methyl bromide: chloropicrin) at 381.7 kgha-1, and planted in a double row set on 1.2 m center. ‘Sweet Charlie’ transplants were obtained from Kentville, Nova Scotia and planted on 3 Oct. 2003. ‘Sweet Charlie’ was selected, because its characteristics of resistance to anthracnose ( Colletotrichum spp .), susceptibility to Botrytis fruit rot, high early yields, short storage-life, and soft-tissue fruit. Existing soil Ca2+ within the experimental plot was determined by a pre-season soil test (EPA Method 200.7, Mehlich-1 extraction) (Mylavarapu, R.S., and E.D. Kennelley. UF/IFAS extension soil testing laboratory analytical procedures and training manual. University of Florida Extension Publication. http://edis.ifas.ufl.edu/SS312. October 2004.). Within the plots chosen for 2003-04 soil Ca2+ was 675 mgkg-1 Ca2+, and interpreted to be "very high" at greater than 400 mgkg-1 (Simonne and Hochmuth, 2003). The pH of the soil was 5.9, which is below target pH of 6.5 for strawberries (Simonne et al., 2003) (EPA Method 200.7) (Mylavarapu, R.S., and E.D. Kennelley. UF/IFAS extension soil testing laboratory analytical procedures and training manual. University of Florida Extension Publication. http://edis.ifas.ufl.edu/SS312. October 2004.). Irrigation water at the site contained 53 mgL-1 Ca2+. The comparison of pre-season and post season soil Ca2+ levels were used to present the combination environmental and treatment contribution of Ca2+ to the crop. The experimental design was a randomized complete block with two factors replicated four times (Table 5-1). Each experimental plot measured 160 m2. Fertilizer treatments were the recommended grower’s standard fertilization method and source of Ca (NO3)2 (5-0-7-3Ca-0S, Chemical Dynamics Plant City, FL) and a no-Ca2+ fertilization

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100 source (6-0-6-0Ca-0S Dyna-Flo, Chemical Dynamics Plant City, FL) both injected through the drip irrigation system. The no-Ca2+ source provided nitrogen as urea ammonium nitrate and potassium nitrate. Calcium supplementation was implemented using CaS2O3 supplement ( 0-0-0-6Ca-10S ThioCal, Best Sulfur Products Fresno, CA) at the rate of 46.7 Lha-1wk-1. Fertilization regime for N-P-K, irrigation, and all other crop maintenance were managed in accordance to University of Florida, Institute of Food and Agriculture (UF-IFAS) recommendations (Simonne et al., 2003). Marketable yield were collected from a twelve plant harvest plot. All twelve plants were adjacent to each other within an experimental plot. Fruits were harvested when they were at least U.S. Number one grade (Mitcham, 2003). Quantification of harvest was measured by total yield (kgha-1), total number of fruits, and fruit quality (marketable or unmarketable). Marketable fruit were greater than 10 g in weight and free of visible defects as described by Mitcham (2003) for U.S. number one grade fruits. Unmarketable fruits were determined on visual inspection and separated based on pathological infection, size, malformation, or water damage. Ten marketable sized and U.S. number one grade fruits (Mitcham, 2003) were randomly collected from each experimental plot on 94, 149, and 164 DAT (days after transplant) for Ca2+ content. Calyces were collected from the ten fruits and replications combined to create a tissue sample as done by Albregts and Howard (1978). All samples were dried at 70C in an air dryer, ground using a standard household electric coffee grinder, calyx samples were ground using a Foss Tecator Cyclotec Sample Mill (Sweden). All Ca2+ concentrations were expressed in mgkg-1 based on Ca2+ percent dry weight. Total moisture content values were recorded simultaneously with Ca2+

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101 content procedures. Fresh weight on the day of harvest and dry weight of strawberry fruits were collected to calculate total moisture content. Soil samples were collected on 149 DAT at depths of 15.2 and 30.4 cm for each experimental plot. Samples were air dried at GCREC-Dover and sent for analysis to the Analytical Research Laboratory in Gainesville, FL for soil Ca2+ and pH determination (EPA Method 200.7, Mehlich-1 extraction) (Mylavarapu, R.S., and E.D. Kennelley. UF/IFAS extension soil testing laboratory analytical procedures and training manual. University of Florida Extension Publication. http://edis.ifas.ufl.edu/SS312. October 2004.). Fruits selected for destructive firmness analysis by deformation to the bioyield point were U.S. number one grade (Mitcham, 2003), and greater than 10 g in weight. On 160 DAT, fruits were harvested from each experimental plot and placed into 0.9 kg hinged clamshell containers and transported to the Postharvest Horticulture Laboratory, University of Florida, Gainesville, FL for measurements. Each sample consisted of ten fruits selected from each plot. Samples were stored in at 1°C for a maximum time interval of 2 h until the destructive test was performed. Samples were placed into storage at 1°C to slow respiration during the time allotment necessary to test the previous sample. Fruits were warmed to room temperature (approximately 22°C) before being sliced into an 11 mm equatorial section. Each slice was oriented proximal end up for mechanical resistance. The fruit tissue puncture measurements were taken using a penetrometer (Instron Universal Testing Instrument, Model 4411) with a 5 kg load cell fitted with a 4 mm convex probe with a crosshead speed of 0.83 mm·s-1 to an endpoint of 7 mm. Two measurements were taken within the cortex tissue of each fruit slice.

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102 Measurements in which the tissue pushed out the side of the epidermis during deformation were removed from the data set. Measurements of bioyield points were used to determine fruit firmness of each sample and expressed in N (Newtons) Postharvest quality measurements of pH, titratable acidity and soluble-solids content were conducted on frozen fruits. Ten U.S. number one grade fruits (Mitcham, 2003) were collected on 154 and 169 DAT from each plot and frozen for a later postharvest analysis. Samples were thawed at room temperature (approximately 22C) before homogenization, in a Waring blender, centrifuged at a force of 2,576 gn for 40 min and filtered through cheesecloth. The filtered supernatant was used for all postharvest quality measurements. The pH was directly measured from the sample of supernatant using a Corning 140 pH meter, standardized with pH 4.0 and 7.0 buffer solutions. Titratable acidity represents the buffering capacity of the fruit, and is generally expressed as milli-equivalents of organic acid per 100 g juice (Perkins-Veazie and Collins, 1995). Total titratable acidity measurements were taken using a sub-sample of 6 g of supernatant plus 50 mL of de-ionized water. The measurements were performed using an electrode meter, using a burette/dispenser and a titrate demand using 0.1 N (Normal) solution of NaOH (sodium hydroxide) to an endpoint pH of 8.2. Titratable acidity measurements were recorded as milliliters of NaOH dispensed. Milliliters of NaOH dispensed were used to calculate total titratable acidity by using the initial volume of the sample, normality of the base, and the milli-equilivant for citric acid (0.064). Total titratable acidity was reported as percent citric acid.

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103 Soluble-solids content were measured using an ABBE Mark II Digital Refractometer using the refractive index range of degree Brix for sucrose. Two drops of supernatant were placed on the prism at room temperature (approximately 22°C) to determine soluble-solids content. Soluble-solids content measurements were recorded as the concentration percentage of soluble-solids (sucrose) within a solution (sample). Between each sample, the prism was rinsed with de-ionized water and dried with a laboratory wipe. Marketable and unmarketable yield, Botrytis fruit rot affected fruit, Ca2+ content, total moisture content, firmness, titratable acidity, soluble-solids content, pH, soil Ca2+ content, and soil pH were subjected to ANOVA with a general linear model in SAS (SAS, 2003, Version 9.0) with Fischer's least significant difference for mean separation. Variables were considered significant at a significance level of 5% or P<0.05. The coefficient of variation (CV) was calculated as one hundred times the ration between the standard deviation and the mean and reported for each variable. Results and Discussion The interaction between fertilizer and CaS2O3 supplementation was not significant for every variable measured. Total yield and monthly totals for yield were not significantly different among treatments (Table 5-2). These results were similar to previous studies measuring yield as affected by additional Ca2+ (Erincik et al., 1998; Wojcik and Lewandowski, 2003). The mean yield for the season was 20,221 kg·ha-1 with 47% of this produced during February. Percent unmarketable fruits were not significantly reduced by CaS2O3 treatments (Table 5-3). For this variable, CV values greater than 50% can be interpreted as a relatively high variability. Previous studies focused on certain aspects of unmarketable fruits either Botrytis fruit rot infection or

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104 malformation at harvest (Cheour et al., 1990; 1991; Wojcik and Lewandowski, 2003). Of all harvested fruits, 22% were unmarketable. The percent of unmarketable fruits affected by visible Botrytis fruit rot development were not significantly affected by CaS2O3 application for the season or monthly totals. For this variable, CV values greater than 60% can be interpreted as a relatively high variability. Visible Botrytis fruit rot development, however, was significantly reduced by Ca(NO3)2 treatment for the month of March (Table 5-4). These results confirm previous studies results conducted in Arkansas, Canada, and Poland that found a reduction in Botrytis fruit rot formation during storage and at harvest (Makus and Morris, 1989; Cheour et al., 1990; Wojcik and Lewandowski, 2003). Calcium thiosulfate did not significantly affect postharvest quality measurements of total titratable acidity, soluble-solids content and pH of fruit juice (Table 5-5). The means for these measurements were 6.09% citric acid, 5.4% percent soluble-solids content, and 3.62, respectively. Firmness measurements were not significantly increased with CaS2O3 treatments (Table 5-5). The mean bioyield point for strawberry fruits on 160 DAT was 0.52 N. The postharvest quality results are consistent with previous studies with foliar, soil and injected supplemental applications of Ca2+ (Erincik et al, 1998; Markus and Morris, 1989). Total moisture content was not significantly affected by CaS2O3 applications (Table 5-6). Despite that, this variable was not significant, on 149 DAT; fruit moisture content was the highest at 93% compared to 80% on 94 DAT. Later season fruits were consistently greater in size regardless of treatment compared to earlier season fruits. Previous studies did not measure this postharvest quality parameter.

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105 Calcium concentration within fruit was not significantly increased by Ca2+ fertilizer source or supplemental Ca2+ (Table 5-7). The same pattern for moisture content occurs for Ca2+ of strawberry fruits. The influx of Ca2+ with water into the fruits would explain these results. The insignificant results for fruit Ca2+ content are consistent with the previous studies on increasing Ca2+ distribution within fruit tissues with supplemental Ca2+ (Markus and Morris, 1989; 1998). Soil samples taken in late February showed no significant increase in Ca2+ content or pH for any treatments (Table 5-8). An increase in soil Ca2+ without a change in pH is a favorable response for gypsum applications, but most other Ca2+ soil amendments are used to adjust pH as well. Calcium thiosulfate did not increase soil Ca2+ level or soil pH; therefore, it was not beneficial to apply it. Conclusions Applying supplemental Ca2+ as CaS2O3 had no benefits in improving quality strawberry fruits. Marketable yield, fruit firmness and postharvest quality were not significantly increased by calcium source. Unmarketable fruits were not decreased by calcium source. The lack of added benefit from CaS2O3 to both no Ca2+ and standard growers fertilizer further implicates that the standard fertilizer, Ca (NO3)2, should remain as the dominate fertilizer source of Ca2+ for strawberry growers.

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Table 5-1. Calcium fertilizer and calcium supplemental source treatment combination on 'Sweet Charlie' strawberry ( Fragariaananassa Duch.) grown at GCREC-Dover 2003-04 season bNo-Ca2+ and calcium nitrate fertilizers were injected separately through irrigation system aCalcium thiosulfate was injected separately from fertilizer treatment Calcium Fertilizer Treatment b Supplemental Calcium Fertilizer Sourcea No Calcium nitrate Calcium thiosulfate No Calcium nitrate No Calcium thiosulfate Calcium nitrate No Calcium thiosulfate Calcium nitrate Calcium thiosulfate

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Table 5-2. Marketable yield (monthly and season total) of ‘Sweet Charlie’ strawberry fruits ( Fragariaananassa Duch.) grown at GCREC-Dover 2003-04 season with and without recommended calcium fertilizer source Nov. Dec. Jan. Feb. Mar. Season (kgha-1)c Fertilizer No Ca2+ 965 2627 673 10293 7105 21660 Ca (NO3)2 905 2382 291 9062 6142 18780 P-value 0.75 0.50 0.05 0.40 0.15 0.51 Supplement No CaS2O3 973 2472 566 9158 9160 19360 CaS2O3 896 2538 398 10196 7058 21085 P-value 0.68 0.85 0.35 0.47 0.19 0.69 LSDb 418 796 392 3183 1391 8750 Mean 934 2504 482 9677 7366 20221 CV(%)a 39 28 71 29 18 97 cValues in columns are means for each treatment bMean separation by Fischer's Least Significant Difference aCoefficient of variation

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Table 5-3. Percent unmarketable fruits (monthly and season total) of ‘Sweet Charlie’ strawberry fruits ( Fragariaananassa Duch.) grown at GCREC-Dover 2003-04 season with and without recommended calcium fertilizer source Nov. Dec. Jan. Feb. Mar. Season Percentd,c Fertilizer No Ca2+ 14.6 14.8 33.0 25.2 21.5 23.2 Ca (NO3)2 20.9 9.2 32.6 20.7 23.7 21.0 P-value 0.47 0.09 0.40 0.83 0.52 0.88 Supplement No CaS2O3 27.1 a 10.3 28.5 23.4 23.1 21.4 CaS2O3 8.4 b 13.6 37.0 22.5 22.1 22.7 P-value 0.01 0.30 0.24 0.73 0.85 0.86 LSDb 14.3 6.2 14.1 11.7 7.4 5.0 Mean 17.7 11.9 32.7 22.9 22.6 22.0 CV(%)a 138 158 131 145 45 142 dPresented as untransformed means cValues in columns are means for each treatment bMean separation by Fischer's Least Significant Difference aCoefficient of variation

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Table 5-4. Percent Botrytis fruit rot (caused by Botrytis cinerea Pers. ex Fr.) incidence occurring on unmarketable fruits (monthly and season total) ‘Sweet Charlie’ strawberry ( Fragariaananassa Duch.) at GCREC-Dover 2003-04 season with and without recommended calcium fertilizer source Nov. Dec. Jan. Feb. Mar. Season Fertilizer Percent Botrytis fruit rotd,c No Ca2+ 0 0 0 6.0 32.0 a 3.6 Ca (NO3)2 2.0 0 0 7.8 13.1 b 3.0 P-value 0.32 ----0.96 <0.01 0.83 Supplement No CaS2O3 0 0 0 5.2 20.0 2.6 CaS2O3 2.0 0 0 8.5 25.1 4.0 P-value 0.32 ----0.45 0.30 0.22 LSDb 4.2 0 0 7.3 13.7 2.3 Mean 1.0 0 0 6.8 22.5 3.3 CV(%)a 692 ----301 59 400 dPresented as untransformed means cValues in columns are means for each treatment bM ean separation by Fischer's Least Significant Difference aCoefficient of variation

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Table 5-5. Postharvest quality of ‘Sweet Charlie’ strawberry fruits ( Fragariaananassa Duch.) grown at GCREC-Dover 2003-04 season with and without recommended calcium fertilizer source Total titratable acidity Soluble-solids Contentd pH Bioyield point 154 & 169 DATc 160 DAT Percent citric acid Percent Newton Fertilizer No Ca2+ 6.05 5.4 3.62 0.53 Ca (NO3)2 6.14 5.6 3.63 0.51 P-value 0.07 0.35 0.70 0.43 Supplement No CaS2O3 5.93 5.3 3.63 0.51 CaS2O3 6.25 5.6 3.62 0.53 P-value 0.54 0.81 0.94 0.30 LSDb 0.34 0.57 0.04 0.03 Mean 6.09 5.4 3.62 0.52 CV(%)a 7 14 1 16 dSoluble-solids content measured using the Brix refractive index range cValues in columns are means for each treatment bM ean separation by Fischer's Least Significant Difference aCoefficient of variation

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Table 5-6. Moisture content of fruits of ‘Sweet Charlie’ strawberry ( Fragariaananassa Duch.) at GCREC-Dover 2003-04 season with and without recommended calcium fertilizer source 94 DAT 149 DAT 164 DAT Percent moisturee,d,c Fertilizer No Ca2+ 80.8 93.6 91.8 Ca (NO3)2 80.3 93.3 91.8 P-value 0.88 0.43 0.88 Supplement No CaS2O3 80.5 93.3 91.8 CaS2O3 80.6 93.6 91.8 P-value 0.99 0.43 0.94 LSDb 9 1 0.8 Mean 80 93 91 CV(%)a 9 1 1 eValues in columns are means for each treatment dPresented as untransformed percentages cAverage of ten fruits bM ean separation by Fischer's Least Significant Difference aCoefficient of variation

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Table 5-7. Calcium concentration within fruit on dry weight basis of ‘Sweet Charlie’ strawberry ( Fragariaananassa Duch.) grown at GCREC-Dover 2003-04 season with and without recommended calcium fertilizer source 94 DATc 149 DAT 164 DAT (mgkg-1) Fertilizer No Ca2+ 2095 2683 2395 Ca (NO3)2 2145 2682 2370 P-value 0.54 0.12 0.79 Supplement No CaS2O3 2135 2591 2286 CaS2O3 2106 2574 2479 P-value 0.72 0.89 0.07 LSDb 180 268 212 Mean 2120 2632 2382 CV(%)a 7 9 7 cValues in columns are means for each treatment bMean separation by Fischer's Least Significant Difference aCoefficient of variation

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Table 5-8. Soil test (Mehlich-1 extraction method for calcium) at the end of the season within area grown with ‘Sweet Charlie’ strawberry ( Fragariaananassa Duch.) at GCREC-Dover 2003-04 season with and without recommended calcium fertilizer source Calcium contente (mgkg-1) Soil pHd 151 DAT c Fertilizer No Ca2+ 956 5.86 Ca (NO3)2 953 5.88 P-value 0.93 0.84 Supplement No CaS2O3 953 5.86 CaS2O3 956 5.88 P-value 0.92 0.68 LSDb 69 0.1 Mean 954 5.87 CV(%)a 10 2 e> 400 mgkg-1 soil Ca2+ interpreted as very high by Simonne and Hochmuth (2003) dTarget pH 6.5 for strawberries grown on mineral soils cValues in columns are means for each treatment bM ean separation by Fischer's Least Significant Difference aCoefficient of variation

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114 CHAPTER 6 CONCLUSIONS The purpose of our study was to probe and further our understanding of Ca2+ and its relationship to quality and yield of strawberry ( Fragaria × ananassa Duch.). This was accomplished by determining the influence of cultivar on firmness and Ca2+ content, examining the influence of supplemental Ca2+ on postharvest quality of strawberry under Florida conditions, and determining if the current fertilizer source for strawberry supplies the necessary Ca2+ for development and quality of strawberry. Each individual cultivar determined the relationship of Ca2+ content and firmness. No consistent patterns of correlations developed for any breeding program in terms of higher frequency of positive association between these two variables. Calcium of fruits and leaves were not a reliable predictor of fruit firmness in strawberry. The development of firmer fruit will have to come from the development of new cultivars. Other factors must influence texture not just Ca2+. Soil and water levels of Ca2+ are sufficient in Florida to supply the necessary amount of Ca2+ for growth and development. Adjusting the current fertilization of strawberries to include more Ca2+ did not increase quality or yield of strawberry. Marketable yield, the incidence of Botrytis fruit rot at harvest, fruit firmness, total titratable acidity, and soluble-solids content were not increased with soil and foliar supplementation (Table 6-1). The practice of applying additional Ca2+ as a foliar spray, decreases quality of U.S. grade one strawberry fruits at harvest.

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115 When soil and water Ca2+ are high, preharvest Ca2+ applications, offer no benefit to the strawberry. The potential cost savings per hectare of production by not using supplemental Ca2+ are dramatic (Table 6-2). The addition of Ca2+ is does not lead to any increase in yield, or postharvest quality of strawberry fruit. These results support the recommendation that current soil, water and fertilizer sources of Ca2+ are sufficient and adequate for strawberry nutrition and fruit quality.

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116 Table 6-1. Summary of strawberry ( Fragaria ananassa Duch.) responses to additional calcium applied as foliar, soil amendment, or injection Attributes Benefits Soil Ca2+ Foliar Ca2+ Injected Ca2+ Yield None None None Unmarketable fruits None None None Botrytis cinerea incidence None None Positivec Ca2+ Content Leaves Not practicalb None N/Aa Fruit None None None Calyces None None N/A Achenes None None --Firmness Deformation at: 2 mm None Positive N/A 3 mm Positive None N/A Bioyield None None None Total titratable acidity None None None Soluble-solids content None None None pH of extracted juice Positive None None Storage Negative Negative N/A Moisture content None None None Soil Ca2+ Positive None None Soil pH Negative Positive None Overall Some but not practical None None cFo r fertilizer source as Ca(NO3)2 bNo practical application use to increasing leaf Ca2+ content aNot applicable

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117 Table 6-2. Current prices (in US$) for calcium products on the market at recommended rates by the hectare Calcium sources available Price (in US$) by ha Foliar applied DynaGold $13.03 Cal-Serve (CaCl2)c 1097 mgL-1 $57.19 2214 mgL-1 $115.42 3999 mgL-1 $208.48 5261 mgL-1 $274.27 Soil or Drip applied Gypsum (Ca2+) 224.5 kgha-1 $344.63 449 kgha-1 $689.26 ThioCal $12.88 Calcium nitrateb,a First 2 weeks $0.01 Nov. Jan. $0.02 Feb. Mar. $0.03 cRate at 935 Lha-1 bBased on the increasing kgha-1d-1 injection rate recommended for strawberry for different months aPrice based on the rates recommended fertilizer applications by Simonne et al. (2003)

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128 BIOGRAPHICAL SKETCH Camille grew up in New Hampshire (in the heart of scenic New England), surrounded by the majestic White Mountains National Forest, the historic Robert Frost Farm, and the quaint colonial New England sea coast. She developed an appreciation for nature and the outdoors from both of her parents. Her father (Curtis R. Esmel, Sr.) is an avid outdoorsman. Her mother (Lydia E. Fortier) is a gardener and naturalist. Camille attended Pinkerton Academy in Derry, New Hampshire, where she studied horticulture through high school vocational classes and participated in the National FFA organization. Camille remained active in the National FFA organization while attending the University of New Hampshire. She graduated from the University of New Hampshire in May 2002 with a Bachelor of Science degree in environmental horticulture.