2010 Annual Report
1a.Objectives (from AD-416)
1. Determine some of the key genetic factors controlling environmental adaptation and fruit quality differences among cultivated grapes and between cultivated and wild grapes.
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.
1b.Approach (from AD-416)
The objectives will be accomplished by applying genetic and genomic tools and research strategies, including populations and marker development, dissection of complex phenotypes, QTL mapping, gene expression analysis, and mutagenesis. Genetic linkage maps will be contructed from populations segregating for economically important traits. Genetic dissection of traits will be conducted in populations derived from bi-parental crosses as well as diverse cultivated and wild grape germplasm.
Berry size and seedlessness are two critical traits for table grape industry. We phenotyped about 200 progeny of two populations segregating for berry and seed sizes for two years and genotyped most of the progeny with SNP makers. QTLs controlling berry and seed sizes will be identified and used in table grape breeding programs.
Phenolics are an important group of secondary metabolites which have significant benefits to human nutrition and health and, to a large extent, determine the quality of grape berry, juice and wine. The profiles of 36 such metabolites were analyzed through HPLC for 344 USDA grape collections (Vitis vinifera). We identified numbers of collections which had much higher contents of various phenolic compounds than currently cultivated grape cultivars. This work provided a comprehensive assessment of the range of variation of these important grape quality traits in the USDA grape germplasm, which in turn will accelerate the utilization of the germplasm for improving grape quality
Grapevines grown in many regions of the Eastern United States are poorly adapted to low-temperature and frequently are 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 freezing tolerant than the primary cultivated species. In FY’10 studies were continued to genetically map regions of the grape genome responsible for controlling differences in freezing tolerance.
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. For FY ’10 fruit tissue was collected for 374 accessions. Profiles of aromatic compounds was continued in FY-10.
Somatic embryogenesis has been used in many species for generating somaclonal variation for trait improvement. This technology, if successfully adapted, can provide an important tool for developing new traits and testing gene functions in grapevines. Towards this goal, we successfully established EMS-treated cell suspension cultures of Vitis vinifera cv. Chardonnay. Mutant plants generated from the EMS-treated cell suspensions will be screened for fruit quality traits.
Localizing genes for cold hardiness in grape: Grapevines grown in many regions of the Eastern United States are poorly adapted to low-temperature and frequently are 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 can survive -40 F. To understand the genetic control of freezing tolerance, the locations of genes controlling freezing-tolerance were identified by ARS Researchers in Geneva, New York, in the grape genome based on the analysis of offspring of parents that differ dramatically in their cold hardiness. This experiment was conducted in a population of 190 individuals and utilized over 400 molecular markers to help identify regions of the genome that are important for freezing tolerance. The mapping of this trait is the first step in developing an assay that will improve the selection efficiency within grape breeding programs for this trait and generating improved cultivars of grape for cold climates.