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United States Department of Agriculture

Agricultural Research Service

Research Project: Generation and evaluation of Juglans Microcarpa hybrids and paradox stock selections for crown gall resistance
2011 Annual Report


1a.Objectives (from AD-416)
1. Identify and characterize a novel source of crown gall (CG) resistance in the species Juglans microcarpa germplasm and associated hybrids maintained in the USDA/ARS National Clonal Germplasm Repository in Davis, CA. 2. Characterize crown gall resistant phenotypes of clonally propagated cuttings from genotypes exhibiting crown gall resistance. 3. Produce clonal copies of promising hybrids and conduct "large scale" greenhouse and field evaluation to identify promising genotypes.


1b.Approach (from AD-416)
Open pollinated seeds will be stratified, germinated and grown under glasshouse conditions. Once the seedlings reach a trunk diameter of at least 0.5cm the crown of the tree will be inoculated with A. tumefaciens strain EC1. Observations on tumor development will be recorded at monthly intervals by noting first-appearance and then percent trunk/crown girdled.


3.Progress Report

The agreement was established in support of objective #1 of parent project, the goal being to improve management strategies for key soil borne diseases of tree fruit and nut crops, sub-objective #1B – identify and characterize available walnut and almond rootstock germplasm for resistance to key soil borne pathogens. The goal of this project is the generation and evaluation of Juglans microcarpa hybrids and paradox root stock selections for crown gall resistance in walnut. In the first few months of this project recruitment and hiring has been accomplished for support staff and purchases for necessary lab and field supplies to date have been processed. Preliminary field work has been accomplished. During the course of the year we plan to stratify, germinate and grow open pollinated seeds under glasshouse conditions. Once the seedlings reach a trunk diameter of at least 0.5cm the crown of the tree will be inoculated with the Agrobacterium tumefaciens strain EC1. Observations on tumor development will be recorded at monthly intervals by noting first-appearance and then percent trunk/crown girdled. Next year’s annual report will reflect all of the accomplishments under this research project.


Last Modified: 11/27/2014
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