Stem rust resistance genetics in tall fescue germplasm screening and mapping

Overview

Stem rust, caused by Puccinia graminis subsp. graminicola, is the most damaging rust disease of cool-season grasses including tall fescue, reducing forage quality and turf aesthetic value. While host resistance has been used successfully in wheat and other crops, the genetic basis of stem rust resistance in tall fescue remains largely unexplored. This research program addresses that gap by systematically screening tall fescue germplasm, generating bi-parental populations, and applying modern genomic tools to dissect the genetics of stem rust resistance. The outcomes will support the development of resistant cultivars, reduce fungicide dependence, and lower production costs for forage and turf growers.

Technical specifications

Research approach:

• Screening of a diversity collection of approximately 500 tall fescue lines sourced from USDA, UGA, and industry breeders, planted at the UGA Griffin campus
• Field phenotyping for stem rust reaction under natural infection with at least three replicates and two years of data
• Generation of new bi-parental crosses from confirmed resistant and susceptible lines identified in preliminary screenings
• Genotyping using genotype-by-sequencing (GBS) for both the diversity panel and bi-parental populations
• Genome-wide association studies (GWAS) and quantitative trait loci (QTL) mapping to identify genomic regions and candidate genes conferring stem rust resistance
• Confirmation of F1 hybrid origin using SSR markers with strong parental polymorphism before phenotyping and mapping

Key features:

• Integration of association mapping and bi-parental QTL approaches to improve detection power and resolution
• Use of multiple replicates and multi-year field data to ensure robust phenotype calls
• Access to diverse germplasm pools spanning public and industry breeding lines

Technology readiness level

The program is at an early-to-mid stage of development. Preliminary germplasm screening at UGA Griffin has identified resistant and susceptible tall fescue lines, and F1 populations from crosses performed in 2020 have been germinated, with SSR marker confirmation underway. Future work will expand the diversity collection to 500 lines, conduct multi-year field phenotyping, and complete GBS-based genotyping followed by GWAS and QTL analyses to pinpoint resistance loci. The research is positioned to deliver validated genetic markers and candidate genes that breeders can use to develop stem rust resistant tall fescue varieties.