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Cold-hardiness, acclimation, and deacclimation among diverse blueberry (Vaccinium spp.) genotypes

Ehlenfeldt, Mark K., Rowland, Lisa J., Ogden, Elizabeth L., Vinyard, Bryan T.
Journal of the American Society for Horticultural Science 2012 v.137 no.1 pp. 31
Vaccinium, acclimation, breeding, buds, climate change, cold tolerance, genotype, germplasm, temperature, United States
Until recently, only limited evaluations have been done on the acclimation and deacclimation process in blueberry, even though it is an integral part of flower bud survival and, thus, reproductive success. In this study we have measured the timing and rate of acclimation and deacclimation in seven blueberry genotypes with different amounts of diverse species germplasm in their backgrounds. Primary differences observed among the seven genotypes were differences in maximum acclimation/hardiness levels and the date at which they were reached, and differences in the date at which maximum acclimation levels were no longer sustained and deacclimation commenced. ‘Bluecrop’, ‘Legacy’, ‘Tifblue’, and two rabbiteye-hybrid derivatives, US 1043 and US 1056, all reached maximum or near maximum cold acclimation by late December with LT50 temperatures in a range from -22 to -27 °C. ‘Northsky’ and ‘Little Giant’ both achieved cold acclimation of -28° C or below (the lowest value we could measure) by the end of November. After reaching their maximum acclimation in late December, ‘Legacy’, ‘Tifblue’, and US 1043 began a sustained and relatively linear deacclimation, whereas US 1056, ‘Bluecrop’, ‘Northsky’ and ‘Little Giant’ sustained their acclimation for longer intervals. ‘Bluecrop’ and US 1056 did not begin to deacclimate until early March, and ‘Little Giant’ and ‘Northsky’ had no LT50 values higher (warmer) than -25° C until late March. As concerns of climate change increase, knowledge of the ability of breeding germplasm to tolerate greater extremes and greater fluctuations will prove increasingly valuable.