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United States Department of Agriculture

Agricultural Research Service

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Research Project: Development of Disease-Resistance Walnut Rootstocks: Integration of Conventional and Genomic Approaches

Location: Crops Pathology and Genetics Research

Project Number: 5306-22000-015-28
Project Type: Reimbursable

Start Date: Apr 01, 2013
End Date: May 31, 2014

Objective:
1)Identify and characterize Juglans germplasm resistant to key soil-borne pathogens. 2)Identify and develop SNP markers and the associated SNP genotyping platform. 3)Quanitfy economic impact of disease-resistant rootstocks on US walnut industry. 4)Conduct extension efforts that: a)deliver disease-resistant rootstocks to stakeholders, and b)assess emerging threats to walnut rootstocks.

Approach:
Based on extensive preliminary disease resistance screening data, a diverse and promising panel of wild Juglans spp. germplasm selections has been assembled to provide novel sources of resistance to the major soil-borne diseases. Mother trees (MTs) will be selected from this panel based on progeny evaluation of resistance conducted in objective 1. Mother trees segregating for resistance to one or more disease will be used to produce biparental interspecific hybrid mapping populations for the construction of genetic maps used to map resistance genes relative to molecular markers, and to select the best hybrid genotypes for field testing (objective 2). To broaden the search for resistance genes in the germplasm collection, open-pollinated progeny of several MT's from each species that have been genotyped and evaluated for resistance, will be used in linkage disequilibrium analysis as explained in objective 2 to find association between molecular markers and resistance. Integrated extension efforts will reach and receive input from more than 4,800 walnut producers and nursery operators.Outreach efforts will promote informed adoption and refinement of targeted rootstocks and associated genomic technologies. This involves testing and demonstrating rootstocks in orchard trials and educating and engaging stakeholders through county-based grower meetings, extension newsletter, webcasts, trade magazines and websites.

Last Modified: 9/20/2014
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