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ARS Home » Pacific West Area » Davis, California » Nat'l Clonal Germplasm Rep - Tree Fruit & Nut Crops & Grapes » Research » Research Project #438270

Research Project: Characterization of Molecular and Phenotypic Diversity in the USDA-NCGR Pistacia Collection

Location: Nat'l Clonal Germplasm Rep - Tree Fruit & Nut Crops & Grapes

Project Number: 2032-21000-026-003-S
Project Type: Non-Assistance Cooperative Agreement

Start Date: Jun 1, 2020
End Date: Oct 15, 2022

(1) To characterize the genetic and phenotypic diversity of National pistachio collection at the National Clonal Germplasm Repository. (2) To connect this information with pistachio breeding activities that will culminate in the release of additional female and male cultivars with lower chill requirements.

All 184 total accessions of Pistacia in the USDA-NCGR will be phenotyped and genotyped over two years. Annual phenotyping will focus on (a) sex and leafing date data collection for each individual tree; and (b) harvest date, nut harvest and nut quality assessment of all of the 119 Pistacia vera accessions for which they can obtain sufficient nuts (nut size, % splits, and pest/disease incidence will be evaluated); and (c) estimation of chilling requirement for a subset of P. vera accessions (~20%, or ~24 accessions). To estimate the chilling requirement of a tree, they will cut budwood at the onset of winter (December 15th- January 1st); store budwood wrapped in plastic in a walk-in cold room at 5C in the dark; move budwood sticks at 4 week intervals to a growth chamber with optimal light, heat, and water; and collect quantitative data on bud break of sticks in the growth chamber. Bud break on sticks of a given tree will be indicative that this tree’s chilling requirement has been met. Genotyping will consist of two phases. First, two sets of young leaf tissue will be harvested from all trees of all 184 total accessions. One set of tissue will be stored at -80C as backup, and the other set will be used for DNA extraction. Principal component analysis (PCA) and FastStructure analysis of genotype data will be used along with phenotype data to verify species identity of the collection, relationships between taxa, and to select a subset of taxa for a Pistacia core collection that will be prioritized for further phenotypic and molecular characterization.