Location: Crop Germplasm Research
Project Number: 6202-21000-036-00
Start Date: Apr 18, 2013
End Date: Apr 17, 2018
In order to better elucidate patterns of genetic divergence and diversity in Carya (pecan and related taxa) and apply that knowledge to genetic resource management and to pecan improvement (Objective 1A), the ploidy level and genome size will be determined in selected accessions. Work will stress species whose ploidy level is not currently known and species whose subgeneric placement has been disputed. For more broadly represented species, accessions representing different areas of origin will be checked. Data on ploidy and genome size will be combined with genetic marker data being developed for routine profile determination of NCGR accessions (Objective 1B). Using sequence information generated in cooperative work, single nucleotide polymorphic sites (SNPs) will be selected to represent known genic regions that are well distributed across chromosomes in homologous species, as well as SNPs representing organelles. SNPs will be validated for information content using a panel of diverse species of Carya as well as geographically and phenotypically diverse pecan accessions. Validated SNPs will be used in analyses designed for cost efficiency. DNA will be extracted from remaining NCGR accessions to be profiled. The resulting datasets will contribute to effective ongoing management of ex-situ collections maintained at worksites in College Station and Brownwood, TX (Objective 2A) and will help in the identification of in situ reserves based on regional characterization of diversity (Objective 2B). Phenological records of the NCGR will be summarized and refined in consistency with uniform ontologies to facilitate cross-database queries and comparative analysis of gene expression and phenotype (Objective 3A). Based on previous observations of diversity, a phenotypic "core subset" will be established and used to monitor phenology (Objective 3B). Historical data will be examined to select a small group of cultivars that represent geographic diversity of origin and manifest broad diversity in phenology but which can be sampled at both the Brownwood and College Station worksites. Inventories of those accessions will be visited weekly to rate patterns of growth inception, flowering, nut development, nut quality, leaf condition, and leaf drop using revised descriptors (from sub-objective 3A). This will provide a framework onto which other Carya accessions will be integrated and their variability interpreted by comparison over a broad geographic range. The initial effort will be the aerial characterization of budbreak, which differs by over a month across accessions in provenance orchards. Observations of the progression of budbreak in the diverse phenotypic core cultivars at Burleson and Brown Counties in Texas will be entered into the budbreak protocol on Pecan ipmPIPE. In order to facilitate the transfer of pecan germplasm, genetic marker technology, and descriptive information and accelerate pecan research and genetic improvement (Objective 4), the historic origination records and all inventory-specific evaluation records will be made publicly available on GRIN-Global, with appropriate summaries on the Unit website.