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    Within the past few years, the Rowland lab has extended its studies of cold acclimation to the deacclimation process. Deacclimation is an integral part of winter/early spring survival and reproductive success of blueberry as untimely winter or early spring thaws followed by hard freezes can cause severe injury to dehardened flower buds. Experiments have been undertaken to determine and compare the rate of deacclimation in several different blueberry genotypes with varying germplasm composition and mid-winter bud hardiness levels in response to an environmentally controlled temperature regime (constant 20ºC) and under field conditions. Levels of the three dehydrins of 65, 60 and 14 kDa, previously implicated in induction of cold acclimation in blueberry have also been monitored during deacclimation. Data indicate that differences in deacclimation rate are present among the genotypes studied under both environmentally controlled conditions and under field conditions. For example, of the genotypes analyzed under field conditions, the V. constablaei selection (collected from the mountains of western North Carolina) deacclimated the most slowly as temperatures began to warm, the northern highbush (V. corymbosum) cultivar ‘Bluecrop’ deacclimated at an intermediate rate, and the southern rabbiteye (V. ashei) cultivar ‘Tifblue’ deacclimated the most rapidly. Thus, rate of deacclimation of flower buds should be an important consideration in breeding to improve spring frost tolerance of blueberry. In addition, the blueberry dehydrins were found to progressively decrease in their abundance during deacclimation under environmentally controlled conditions in three cultivars studied. Downregulation of the 14 kDa dehydrin most closely mirrored the loss in cold hardiness during deacclimation, and, therefore, may be involved in regulation of bud dehardening.