Project Number: 5306-22000-015-10
Project Type: Reimbursable

Start Date: Sep 01, 2012
End Date: Aug 31, 2014

Objective:
1) Assempble germplasm and generate mapping populations for discovery and mapping of novel genetic loci that mediate resistance to major soil-borne diseases of walnut. 2)Characterize Juglans species half-sib and interspecific hybrids for resistance to the soil-borne pathogens; Agrobacterium tumefaciens (Crown Gall Disease, CG), Phytophthora spp. (crown and root rot, PHY), Armillaria mellea (Armillaria root disease, ARD), Pratylenchus vulnus (Root-lesion nematode, NEM); and threatening rootstock pathogens Geosmithis morbida (Thousand canker disease, TCD) and the walnut strain of cherry leaf roll virus (walnut blackline disease, WBD). 3)Develop and map SNP markers associated with disease resistance. 4)Quantify economic impact of disease-resistant rootstocks on US walnut industry. 5)Conduct bi-directional extension efforts that: a)deliver disease-resistant rootstocks to stakeholders, and b)assess emerging threats to walnut rootstocks.

Approach:
Our multi-disciplinary team will build on a conventional breeding approach with pathogen screening techniques, novel plant propagation technology and modern genomic tools for marker-assisted selection, in combination with educational outreach, to develop, characterize, and demonstrate walnut rootstocks with resistance to all major walnut rootstock pathogens. We will identify genetic markers associated with the resistant phenotypes, and these markers will be the first of their kind for Juglans. Integrated bi-directional extension efforts will insure that emerging diseases and other issues affecting adoption of new walnut rootstocks are identified and marketable products of the research are deployed and evaluated in commercial orchards.