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ARS Home » Pacific West Area » Davis, California » Crops Pathology and Genetics Research » Research » Research Project #439397

Research Project: Solutions to the Armillaria Root Rot Threat Affecting the U.S. Stone Fruit Industry

Location: Crops Pathology and Genetics Research

Project Number: 2032-21220-008-040-R
Project Type: Reimbursable Cooperative Agreement

Start Date: Oct 1, 2020
End Date: Aug 31, 2024

1) Identify and characterize sources of resistance to Armillaria. 2) Implement cultural practices and assess horticultural quality. 3) Discover genomics to enable breeding solutions. 4) Perform cost-benefit analysis of cultural practice adoption. 5) Conduct outreach and extension activities to facilitate the adoption of results.

Response to Armillaria infection will be evaluated on USDA-ARS germplasm repository accessions and hybrids, and on commercially available and newly collected Prunus germplasm using existing and newly developed screening techniques in this project. We propose to adopt a holistic approach to screen the resistance of cherry, peach, and almond germplasm to Armillaria solidipes, Armillaria tabescens, and Armillaria mellea by designing and implementing resistance screening pipeline. First, Prunus species material will be screened using an in vitro method for response to inoculation with the Armillaria species relevant to the species. Root sections of the material that exhibits tolerance in vitro will be analyzed under microscope to confirm absence of fungal penetration and tolerant accessions without fungal penetration in the root tissue will be multiplied in vitro and the tolerance will be confirmed using porous phenolic media. Aseptic, rooted micro-plants will be cultured for fifteen weeks in liquid medium infused Oasis IVE phenolic resin. At the same time, a second matched piece of phenolic resin will be culture-infused with selected Armillaria species. Co-culture is established during the latter 10 weeks of the 15-week period, when the rooted plant root block directly overlays the block that had been permeated with Armillaria. This subjects 12-18 rooted clonal plants of one or more genotypes, to uniform disease pressure in each vessel. Samples of infected root tissue and root exudates, free from contaminating organisms, will be available in time course for genetic and metabolomic analyses. Disease tolerance will be rated on a five-point scale. Tolerant material that passes these initial screens will be subjected to: in vitro wounded and intact root/shoot bioassay, and anti-Armillaria activity detection assay.