Analysis of the primary sources of quantitative, adult plant resistance to stripe rust in U.S. soft red winter wheat germplasm

Authors: Ward, Brian; MERRILL, KEITH - North Carolina State University; BULLI, PETER - Washington State University; PUMPHREY, MIKE - Washington State University; MASON, RICHARD - University Of Arkansas; MERGOUM, MOHAMED - University Of Georgia; JOHNSON, JERRY - University Of Georgia; SAPKOTA, SURAJ - University Of Georgia; Brown-Guedira, Gina

Submitted to: The Plant Genome
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/10/2021
Publication Date: 2/17/2021
Citation: Ward, B.P., Merrill, K., Bulli, P., Pumphrey, M., Mason, R.E., Mergoum, M., Johnson, J., Sapkota, S., Brown Guedira, G.L. 2021. Analysis of the primary sources of quantitative, adult plant resistance to stripe rust in U.S. soft red winter wheat germplasm. The Plant Genome. 14:e20082. https://doi.org/10.1002/tpg2.20082.
DOI: https://doi.org/10.1002/tpg2.20082

Interpretive Summary: Stripe rust, or yellow rust is a disease of wheat historically causing significant economic losses in cooler growing regions. Novel isolates of stripe rust with increased tolerance for high temperatures were detected in the United States circa 2000. This increased heat tolerance puts geographic regions such as the soft red winter wheat (SRWW) growing region of the Southeastern United States at greater risk of stripe rust induced losses. In order to identify sources of stripe rust resistance in contemporary wheat lines, we conducted genome-wide association studies on stripe rust severity measured in two panels: the first consisted of 273 older varieties, landraces, and some modern elite breeding lines, and was evaluated in environments in the Pacific Northwestern and the Southeastern United States. The second panel consisted of 588 modern, elite SRWW breeding lines and was evaluated in four environments in Arkansas and Georgia. The analyses identified three major resistance loci on three different chromosomes – one on 2AS, presumably the 2NS:2AS alien introgression from Aegilops ventricosa Tausch, one on 3BS, and one on 4BL. Although lines containing all three resistance genes tended to exhibit the highest disease resistance in both panels, the 4BL locus explained a greater portion of variance in resistance than either the 2AS or 3BS genes in Southeastern environments. Relatively few lines carry resistance alleles at all three loci, suggesting that there is a pre-existing reservoir of enhanced stripe rust resistance which may be further exploited by regional breeding programs.

Technical Abstract: Stripe rust, or yellow rust (Puccinia striiformis Westend), is a disease of wheat (Triticum aestivum L.) historically causing significant economic losses in cooler growing regions. Novel isolates of stripe rust with increased tolerance for high temperatures were detected in the United States circa 2000. This increased heat tolerance puts geographic regions such as the soft red winter wheat (SRWW) growing region of the Southeastern United States at greater risk of stripe rust induced losses. In order to identify sources of stripe rust resistance in contemporary germplasm, we conducted genome-wide association studies on stripe rust severity measured in two panels: the first consisted of 273 older varieties, landraces, and some modern elite breeding lines, and was evaluated in environments in the Pacific Northwestern and the Southeastern United States. The second panel consisted of 588 modern, elite SRWW breeding lines and was evaluated in four environments in Arkansas and Georgia. The analyses identified three major resistance loci on three different chromosomes – one on 2AS, presumably the 2NS:2AS alien introgression from Aegilops ventricosa Tausch, one on 3BS, and one on 4BL. Although lines containing resistance alleles at all three loci tended to exhibit the highest disease resistance in both panels, the 4BL locus explained a greater portion of variance in resistance than either the 2AS or 3BS loci in Southeastern environments. Relatively few lines carry resistance alleles at all three loci, suggesting that there is a pre-existing reservoir of enhanced stripe rust resistance which may be further exploited by regional breeding programs.