2012 Annual Report
1A. Identify molecular markers tightly linked to QTL controlling phenotypic variation in grape for environmental adaptation and fruit quality. 1B. Identify candidate genes for environmental adaptation through characterization of differences in gene content and global gene expression among wild grapes with divergent phenotypes.
2. Develop grape germplasm with novel phenotypes for fruit quality traits.
Grapevines grown in many regions of the Eastern United States are poorly adapted to low-temperature and frequently damaged by severe winters and fluctuating temperature during the spring and fall. There is tremendous variation among cultivated and wild grapes for tolerance to low-temperature stress, including some types that are substantially more tolerant to freezing than the primary cultivated species. In FY12 we assessed 32 wild and cultivated germplasm accessions for variation in the phenotypes of chilling hour requirement, dormancy fulfillment, and heating hour requirement. Variation in soluble carbohydrate levels, a trait hypothesized to be related to mid-winter freezing tolerance, was measured from over 2400 dormant buds, representing 40 different genotypes and two cold tolerance mapping populations. Finally, genetic variation was examined within a Vitis diversity panel of 190 wild and cultivated grapevine genotypes for 11 candidate cold tolerance genes.
Muscadine grapes are a regionally important fruit crop in the southern United States. Genetic information on the inheritance of economically important traits of muscadine grapes is minimal. In order to provide genetic information useful to muscadine grape breeders, a project was initiated to genetically map many fruit quality traits in two grapevine populations maintained by the University of Arkansas’s fruit breeding program. In FY12, genetic maps were constructed for these two populations and some initial phenotypic data was collected for flower type and berry color.
Grape aroma is a primary determinant of table grape, unfermented juice, and wine quality. In collaboration with the University of British Columbia a project was continued to conduct an association genetics screen for grape aroma in a subset of the USDA grape germplasm collection. In FY12 a genome-wide association analysis was completed to elucidate genetic components underlying variation in the content of several aromatic compounds from fruit samples collected in previous years from over 300 different grapevine varieties maintained by USDA.
Liang, Z., Zhao, S., Ma, A., Zhong, G., Li, S. 2011. Inheritance of sugar and acid contents in the ripe berries of a tetraploid x diploid grape cross population. Journal of Euphytica. 182:251-259.