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ARS Home » Pacific West Area » Aberdeen, Idaho » Small Grains and Potato Germplasm Research » Research » Research Project #442841

Research Project: Genome-wide Association Mapping of Genes for Powdery Mildew Resistance in Oat

Location: Small Grains and Potato Germplasm Research

Project Number: 2050-21000-034-044-S
Project Type: Non-Assistance Cooperative Agreement

Start Date: Sep 1, 2022
End Date: Aug 31, 2023

Objective:
This project will characterize for reaction to powdery mildew disease a genetically diverse set of oat lines selected from the National Small Grains Collection. A dense set of molecular markers across the oat genome, already measured, will be used to map the locations of genes and quantitative trait loci (QTL) influencing powdery mildew resistance. This information may yield evidence of resistance not currently deployed in elite oat germplasm and molecular markers linked to known and novel resistance genes to aid in efficient oat breeding.

Approach:
Powdery mildew (caused by Blumeria graminis f. sp. avenae) can cause 5 to 40% yield loss under cool and humid growing conditions. Genetic resistance is the primary disease control strategy and new sources of resistance are in constant demand to counter adaptation of the fungal population. Twelve major powdery mildew resistance genes have been described, including 7 identified in cultivated oat (Avena sativa). In addition, powdery mildew resistance has been described in oat germplasm that is not currently attributable to a known gene. Thus, it is likely that at least some of the disease resistance in landraces and other older oat germplasm has not yet been deployed in cultivars developed for modern production. This untapped genetic variation has the potential to provide oat cultivars with new genetic resistance to powdery mildew. This project will identify resistance in 740 landraces and older cultivar accessions selected from the National Small Grains Collection (NSGC). Powdery mildew disease response will be scored by the Cooperator under controlled conditions at Lublin, Poland. The resistance of tested lines will be analyzed at the seedling stage using host-pathogen tests based on a set of 10 B. graminis f sp. avenae isolates with different levels of virulence. Leaf fragments will be placed on 12-well culture plates with agar medium supplemented with benzimidazole (6 g of agar per 1 L of water and 35 mg/L); and inoculated in an inoculation tower with approximately 500–700 spores per 1 cm2. Subsequently, the plates will be incubated in a growing chamber at 17 °C and an illuminance of 4 kLx. The leaf infection will be assessed ten days after inoculation according to a 5-point scale. The reactions to the isolates will be grouped into three classes: R (resistant)—from 0 to 20% affected leaf area, I (intermediate) from 20 to 50%, and S (susceptible)—more than 50% affected leaf area. Genome-wide association mapping using GBS-SNPS already obtained for this association mapping panel will be used in Mixed Linear Model genotype-phenotype association analyses to identify molecular markers for further validation and to place them in context of both the existing oat consensus linkage map and the anticipated physical genetic map. Markers highly associated with disease resistance will be converted to assay types suitable for high-throughput genotype screening. Crosses will be made for the purposes of validating linked markers and introgressing resistance onto elite germplasm adapted to U.S. oat production regions.