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Vance M. Whitaker, Tomas Hasing, Craig K. Chandler, Anne Plotto and Elizabeth Baldwin

The University of Florida strawberry (Fragaria ×ananassa Duch. ex Rosier) breeding program has maintained a continuous breeding effort since 1968 to develop cultivars that are highly adapted to winter production in west-central Florida. To gain insight into breeding progress over time, two advanced selections (UF1 and UF2) and 10 released cultivars, from Florida Belle (1975) to Florida Radiance (2008), were compared for various fruit quality traits in a two-location field study during the 2009–2010 season. Fruit size varied dramatically from 30.8 g for ‘Elyana’ to 16.2 g for ‘Dover’ at Balm, FL, and from 28.3 g for UF2 to 16.6 g for ‘Dover’ at Dover, FL. A linear regression of fruit size on year of release revealed an average gain of 2.6 g per year since 1975 for the cultivars and selections tested (R 2 = 0.44). A similar analysis revealed a reduction over time in the proportion of cull fruit (R 2 = 0.30). Gains were apparent for the redness of the internal flesh, from a colorimeter a* value of 16.1 for ‘Florida Belle’ (1975) to 34.7 for ‘Carmine’ (2002) but were not sustained for later releases and selections. Although there were significant differences among genotypes for all chemical traits affecting flavor, there were no discernable patterns over time. There were wide month-to-month variations in individual sugars and organic acids, except for citric acid, which was stable across months and locations. The ratio of soluble solids content to titratable acidity ranged widely among genotypes, from a high of 15.7 for ‘Florida Belle’ in February at Dover, FL, to a low of 6.4 for ‘Winter Dawn’ in January at Balm, FL. The observed variability and trends in fruit quality traits will help guide future genetic studies and inform decisions about future breeding priorities and selection procedures.

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Steven J. MacKenzie, Craig K. Chandler, Tomas Hasing and Vance M. Whitaker

In west–central Florida, strawberries (Fragaria ×ananassa Duch.) are harvested from early December to late March. The peak harvest occurs at the end of the season and lasts ≈1 month, usually from late February to mid-March. As the peak harvest progresses and temperatures increase, fruit become smaller and the soluble solids content (SSC) of fruit declines. The main objective of this study was to determine whether the progression of peak harvest results in a decline in SSC independent of temperature. In 2007 and 2008, recently opened flowers were tagged in the field on the first week into the peak bloom (WPB) and for 3 additional weeks thereafter. Three days after tagging, plants were transplanted to one of two constant temperature environments (15 or 22 °C). At maturity, the weight, SSC, and fruit development period (FDP) of tagged fruit were recorded. Fruit SSC was lower at the higher temperature (5.2% at 22 °C versus 6.5% at 15 °C) in both years. In 2007, SSC was not correlated with WPB, and in 2008, SSC was positively correlated with WPB at constant temperatures. In addition, the coefficient of determination (r 2) for a regression of SSC on mean temperature over the period 8 days before harvest was 0.73 for fruit harvested from fields between 2003 and 2009. These results indicate that rising temperature is a major factor responsible for the late-season decline of SSC in strawberry fruit in a subtropical production system.

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Vance M. Whitaker, Craig K. Chandler, Natalia Peres, M. Cecilia do Nascimento Nunes, Anne Plotto and Charles A. Sims

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Emmanuel A. Torres-Quezada, Lincoln Zotarelli, Vance M. Whitaker, Rebecca L. Darnell, Bielinski M. Santos and Kelly T. Morgan

Earlier fall planting dates for strawberry (Fragaria ×ananassa) in west-central Florida tend to promote earlier onset of flowering and fruiting. However, warm air temperatures (>28 °C) can result in excessive growth and runner production. Sprinkler irrigation is a common practice to reduce air temperature in the first 10 to15 days after transplanting, requiring large volumes of irrigation water. An alternative to sprinkler irrigation is the application of crop protectants such as kaolin clay after transplanting. The objectives of this study were to determine the optimal planting dates and to assess the most appropriate establishment practices for strawberry bare-root transplants in Florida. Four establishment practices—10 days of sprinkler irrigation (DSI), 10 DSI + kaolin clay, 7 DSI, and 7 DSI + kaolin clay were evaluated for ‘Florida Radiance’ and Sweet Sensation® ‘Florida127’ transplanted in mid September, late September, and early October in consecutive seasons. For ‘Florida127’, September planting dates increased early yield compared with early-October traditional planting dates, with no difference in total yield. Seven DSI followed by the foliar application of kaolin clay at day 8 was also found to increase early yield compared with 10 DSI for strawberry establishment, with annual water savings of 108.7 mm.

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Vance M. Whitaker, Luis F. Osorio, Natalia A. Peres, Zhen Fan, Mark Herrington, M. Cecilia do Nascimento Nunes, Anne Plotto and Charles A. Sims

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Vance M. Whitaker, Craig K. Chandler, Bielinski M. Santos, Natalia Peres, M. Cecilia do Nascimento Nunes, Anne Plotto and Charles A. Sims

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Chengyan Yue, R. Karina Gallardo, James Luby, Alicia Rihn, James R. McFerson, Vicki McCracken, Vance M. Whitaker, Chad E. Finn, James F. Hancock, Cholani Weebadde, Audrey Sebolt and Amy Iezzoni

The primary goal of this research was to evaluate the relative importance of strawberry fruit quality and plant traits to strawberry producers. Previous studies focus on strawberry traits that impact postharvest quality and marketable yield; however, studies emphasizing the importance of these traits to strawberry producers are scarce. To investigate U.S. strawberry producer trait preferences, a series of audience surveys were conducted at four strawberry producer meetings across the United States. Results indicate that fruit firmness, fruit flavor, and fruit shelf life at retail were the most important fruit/plant traits to producers for a successful strawberry cultivar to possess. Growing state and producers’ years involved in the decision-making process of strawberry farms impacted the relative importance of the fruit/plant traits. This study directly contributes to a larger investigation of supply chain members’ trait preferences to improve the efficiency of Rosaceae fruit crop breeding programs and to increase the likelihood of new cultivar adoption. The overall project should result in a more efficient approach to new strawberry cultivar development and commercialization.