The Florida strawberry industry, valued at $362 million during the 2009–2010 season, is concentrated in subtropical west–central Florida on ≈3600 ha (U.S. Department of Agriculture, 2011). During a typical season, transplants are set in the field in early October and fruit is harvested from the beginning of December to late March. Total fruit yield as well as the average size and the SSC of fruit, which impact perception of fruit quality (Jouquand et al., 2008), fluctuate over the course of the season (MacKenzie and Chandler, 2009). There are typically two or three cycles in which yields rise and then fall (Chandler et al., 1994). Larger primary fruit predominate at the beginning of cycles, whereas smaller fruit predominate later in the cycles (MacKenzie and Chandler, 2009). Fruit size is largely dependent on the predominant order of fruit ripening at any one time (Dana, 1980; Janick and Eggert, 1968). The period lasting from late February to mid-March usually corresponds to the highest yielding cycle and is often described as the peak harvest (Legard et al., 2005). The fruit from the peak harvest result from flowers produced during the period from late January to mid-February, and this period is usually described as the peak bloom.
Soluble solids content is the collective concentration of sugars, acids, and other substances dissolved in the cell sap. In strawberry, sugars comprise 80% to 90% of the SSC (Perkins-Veazie, 1995). Fruit SSC is usually satisfactory for consumers until a point during the month of March when low SSC decreases fruit quality and contributes to growers’ decisions to quit harvesting. Rising temperatures may explain the decline in fruit SSC at the end of the season (Wang and Camp, 2000). However, other factors such as the age of plants, the predominant order of harvested fruit, and increasing yield correlate with the progression of the peak harvest and could affect fruit SSC independently. The ratio of fruit weight to leaf weight has been shown to increase over time, and an increased sink:source ratio could help explain the decline in fruit SSC (Olsen et al., 1985). Although fruit SSC was positively correlated with the incidence of solar radiation in other production systems (Hoppula and Karhu, 2006; Watson et al., 2002), fluctuations in photosynthetically active radiation (PAR) are not likely to have a major effect on fruit SSC in Florida because plant exposure to PAR is increasing late in the season when fruit SSC is declining.
The primary objective of this study was to test the hypothesis that the progression of the peak harvest results in a decline of fruit SSC independent of temperature. This hypothesis was tested over two seasons by moving plants from the field to constant temperature and light environments at different times during the peak bloom period that precedes the peak harvest. Trends in fruit weight and fruit development period over time under the controlled environments were also determined. A second objective was to determine the potential for predicting fruit SSC from atmospheric temperature alone using temperature and fruit SSC data collected during six seasons in Florida.
Chandler, C.K., Crocker, T.E., Price, J.F. & Albregts, E.E. 1994 Growing strawberries in the Florida garden Proc. Fla. State Hort. Soc 107 397 399
Dana, M.N. 1980 The strawberry plant and its environment 33 44 Childers N.F. The strawberry: Varieties, culture, pests and control, storage, marketing Horticultural Publications Gainesville, FL
Del Pozo-Insfran, D., Duncan, C.E., Yu, K.C., Talcott, S.T. & Chandler, C.K. 2006 Polyphenolics, ascorbic acid, and soluble solids concentrations of strawberry cultivars and selections grown in a winter annual hill production system J. Amer. Soc. Hort. Sci. 131 89 96
Ferree, D.C. & Stang, E.J. 1988 Seasonal plant shading, growth, and fruiting in ‘Earliglow’ strawberry J. Amer. Soc. Hort. Sci. 113 322 327
Haller, M.H., Rose, D.H. & Harding, P.L. 1941 Studies on the respiration of strawberry and raspberry fruit U.S. Dept. Agr. Circ. 613 1 13
Hoppula, K.B. & Karhu, S.T. 2006 Strawberry fruit quality responses to the production environment Intl. J. Food Agr. Environ. 4 166 170
Hortyński, J.A., Liniewicz, K. & Hulewicz, T. 1994 Influence of some atmospheric factors affecting yield and single fruit weight in strawberry J. Hort. Sci. 69 89 95
Jouquand, C., Chandler, C., Plotto, A. & Goodner, K. 2008 A sensory and chemical analysis of fresh strawberries over harvest dates and seasons reveals factors that affect eating quality J. Amer. Soc. Hort. Sci. 133 859 867
Legard, D.E., MacKenzie, S.J., Mertely, J.C., Chandler, C.K. & Peres, N.A. 2005 Development of a reduced use fungicide program for control of Botrytis fruit rot on annual winter strawberry Plant Dis. 89 1353 1358
Le Mière, P., Hadley, P., Darby, J. & Battey, N.H. 1998 The effect of thermal environment, planting date and crown size on growth, development and yield of Fragaria × ananassa Duch. cv. Elsanta J. Hort. Sci. Biotechnol. 73 786 795
Macías-Rodríguez, L., Quero, E. & López, M.G. 2002 Carbohydrate differences in strawberry crowns and fruit (Fragaria × ananassa) during plant development J. Agr. Food Chem. 50 3317 3321
MacKenzie, S.J. & Chandler, C.K. 2009 A method to predict weekly strawberry fruit yields from extended season production systems Agron. J. 101 278 287
Olsen, J.L., Martin, L.W., Pelofske, P.J., Breen, P.J. & Forney, C.F. 1985 Functional growth analysis of field grown strawberry J. Amer. Soc. Hort. Sci. 110 89 93
Schaffer, B., Barden, J.A. & Williams, J.M. 1986 Whole plant photosynthesis and dry-matter partitioning in fruiting and deblossomed day-neutral strawberry plants J. Amer. Soc. Hort. Sci. 111 430 433
U.S. Department of Agriculture 2011 Noncitrus fruits and nuts 2010 summary 23 Aug. 2011. <http://usda.mannlib.cornell.edu/usda/current/NoncFruiNu/NoncFruiNu-07-07-2011.pdf>.
University of Florida 2009 Florida Automated Weather Network: Report generator 10 July 2009. <http://fawn.ifas.ufl.edu/data/reports/>.
Watson, R., Wright, C.J., McBourney, T., Taylor, A.J. & Linforth, R.S.T. 2002 Influence of harvest date and light integral on the development of strawberry flavor compounds J. Exp. Biol. 53 2121 2129
Yoshida, Y. & Morimoto, Y. 1997 Measurement, modeling and seasonal changes of canopy photosynthesis in ‘Nyoho’ strawberry Acta Hort. 439 575 582