Submitted to: Acta Horticulture Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 5/9/2003
Publication Date: 9/20/2003
Citation: Rowland, L.J., Mehra, S., Dhanaraj, A., Ogden, E.L., Arora, R. 2003. Identification of molecular markers associated with cold tolerance in blueberry. Acta Horticulture Proceedings. 625:59-69. Interpretive Summary: Because the development of more cold hardy varieties is an important need to the blueberry industry, our laboratory has been working on identifying, isolating, and mapping genes that control cold hardiness (CH) in blueberry. Previously, we have identified three abundant proteins that are induced during cold acclimation and levels are closely associated with CH levels. These proteins, known as dehydrins, are good candidates for controlling CH in blueberry. Progress has been made to construct genetic maps utilizing populations comprised of individuals that have a range of CH levels, study inheritance of cold hardiness, map cold hardiness genes, and isolate and map the dehydrin genes of blueberry. Results include addition of more markers to the genetic maps of the blueberry populations, determination of CH levels for a portion of the blueberry mapping populations, identification of one site on the chromosomes that controls cold hardiness, isolation of a clone for the gene encoding the smallest, but most abundant, of the 3 major blueberry dehydrins, and use of the sequence of another of the dehydrins to map a dehydrin gene in the population. Identification and mapping of genes associated with CH will help scientists develop more effective strategies for increasing CH of existing varieties or develop new, more cold hardy varieties of blueberry.
Technical Abstract: 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 use genetics 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. corymbosum-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 use systematic molecular genetics 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 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.