GENES FOR RESISTANCE TO STRIPE RUST IN TRES WHEAT

The genetic basis of stripe rust (Puccinia striiformis Westend.) resistance in the club wheat (Triticum aestivum L.) 'Tres' was not previously known. This greenhouse, growth chamber, and field study was conducted to determine the inheritance of resistance in Tres and the relationship of genes for resistance in Tres to genes in other wheat cultivars. Tres was crossed with 20 wheat cultivars with genes Yr1, Yr2, Yr3a, Yr4a, Yr4b, Yr5 through Yr10, and 18 other genes for stripe rust resistance not officially named, and with 'Michigan Amber', which is susceptible to all identified stripe rust races in North America. Seedlings of parents and F1 and F2 progeny from all crosses, back-crosses of 'Chinese 166'/Tres, and F3 progeny from Tres/'Lemhi' were tested for response to selected races. Genetic analyses showed that Tres has two genes for stripe rust resistance; one was dominant, and the other either dominant or recessive depending on the cultivar crossed with Tres. The results indicate that epistasis is involved in genetic control of the resistance. The two genes for resistance in Tres are different from the 29 genes in the other cultivars. One of the resistance genes in Tres may be allelic or closely linked to a gene in 'Yamhill'.