Number of Genes Controlling High-Temperature, Adult-Plant Resistance to Stripe Rust in Wheat

Abstract

Winter wheat cultivars Gaines, Nugaines, and Luke have durable adult-plant, temperature-sensitive resistance to Puccinia strifformis. Parental, F1, F2, and backcross populations from reciprocal crosses between these resistant cultivars and reciprocal crosses between each resistant cultivar and a susceptible line (PS-279) were evaluated in the field for rust intensity in 1982. F4 rows were evaluated for resistance as measured by rust intensity at three locations in 1984. Estimations based on three quantitative formulas indicated that rust intensity was controlled by two or three genes in Nugaines and Luke. A qualitative analysis based on the proportion of resistance F2 progeny indicated that resistance in Gaines, Nugaines, and Luke was determined by two genes, and that Gaines and Nugaines have one locus in common. Gaines and Nugaines probably have different alleles at the second locus, since there was no transgressive segregation in the Nugaines .times. Gaines cross. Because of the assumptions in these formulas, these estimates are for the minimum number of genes involved. Based on the very low estimates of the number of resistance genes in the Luke .times. Nugaines and Luke .times. Gaines crosses and on transgressive segregation for both resistance and susceptibility in the F4 generation, the genes in Luke differ from those in Gaines and Nugaines. Progeny with enhanced levels of resistance should be useful sources of durable resistance for breeding programs.