Technical Abstract: Although development of cold hardiness (CH) is an integral part of the life cycle of woody perennial plants, studies on its genetic control are scarce. A better understanding of the genetic control of CH would be valuable for developing more effective strategies to increase CH and, hence, climatic adaptation of woody perennial crops. In blueberry, three major dehydrins of 65, 60, and 14 kDa have been found to increase with cold acclimation and decrease with deacclimation. Efforts are underway to isolate and map the dehydrin genes of blueberry utilizing blueberry populations that segregate for CH in order to determine if the dehydrin genes map to QTLs controlling CH. CH levels were determined for a portion of the blueberry mapping populations (derived from interspecific hybrids of Vaccinium darrowi Camp and V. caesariense Mackenz.) using a laboratory controlled freeze-thaw regime, followed by visual assessment of injury to floral buds. As expected, the V. darrowi and V. caesariense parents were found to differ significantly in terms of CH levels (LT50s of -13C and -20C, respectively). Mean CH level of F1s (-14.7) was skewed more toward the V. darrowi parent and was significantly different from the V. caesariense parent, suggesting that CH is a partially recessive trait. The sequence of a 2.0 kb cDNA clone, which encodes the 60 kDa blueberry dehydrin, was used to map a dehydrin-related gene to current linkage group 12 of the V. caesariense testcross population.