A Wheat Stem Rust Resistance Gene Common to 12 Cultivars of the Fourth International Winter Wheat Performance Nursery1

Abstract

The wheat (Triticum aestivum L.) cultivar ‘McNair 701’ (CI 15288) was considered universally susceptible to wheat stem rust (Puccinia graminis Pers. f. sp. tritici) until tested with isolate SBC (72‐45‐1212B). With this isolate, an infection type 2= (IT2=) was produced. Twelve entries of the Fourth International Winter Wheat Performance Nursery gave a similar infection type with the same isolate. Crosses were made between some of these cultivars and three cultivars with no detectable genes for resistance. A cross was made between McNair 701 and an F3 progeny homozygous for IT2=. Genetic analysis using isolate SBC of F2 progenies showed that the gene tentatively designated SrMcN from McNair 701 for resistance to stem rust, was present in the 12 cultivars. These cultivars originated in 10 countries and appeared to have no common parentage. Although SrMcN was widespread, it has little value as a source of resistance against the stem rust population of North America.