Identification of molecular markers associated with cold tolerance in blueberry

A survey of blueberry (Vaccinium spp.) research and extension scientists in the United States has identified lack of cold hardiness as one of the most important genetic limitations of current blueberry cultivars. Therefore, the development of more cold hardy cultivars is an important need to the blueberry industry. To address this need, our laboratory has been using two distinct but related approaches to identify molecular markers/genes associated with cold tolerance in blueberry. One approach has been to map quantitative trait loci (QTLs) controlling cold hardiness in the cold acclimated state. Progress toward mapping QTLs is presented here including: (1) construction of initial, low density genetic linkage maps for two diploid (V darrowi x V. caesariense-derived) blueberry populations segregating for cold hardiness; (2) use of randomly amplified polymorphic DNA (RAPD) and expressed sequence tag-polymerase chain reaction (EST-PCR) markers for mapping purposes; (3) evaluation of the mapping populations for cold hardiness; and (4) genetic analyses of the cold hardiness data. The other approach has been to identify, isolate, and characterize cold-responsive genes from blueberry and to map these genes to determine if any map to QTLs that control cold hardiness. Levels of a group of dehydrin proteins (proteins induced by dehydration stress such as freezing and drought) of 65, 60, and 14 kDa increase during cold acclimation such that they become the most abundant proteins in blueberry floral buds during the winter. Progress in characterizing this gene family is presented including: (1) characterization of expression of the dehydrins, (2) cloning members of the dehydrin gene family, (3) mapping members of the dehydrin gene family and (4) segregation of the dehydrin genes with the cold hardiness trait. Finally, preliminary results using a new genomic approach to characterize cold-responsive genes from blueberry is presented.