Abstract
Resistance to stem rust (Puccinia graminis Pers. f. sp. tritici Eriks. and and E. Henn.) was transferred from diploid wheat, Triticum monococcum L. cv. RL 5244, to Stewart tetraploid and Marquis hexaploid cultivars by interspecific hybridization. Genetic studies at the diploid, tetraploid and hexaploid levels indicated that a dominant gene gave resistance to the seven races of rust tested. Differential transmission of this gene was noted in some of the intradiploid and intrahexaploid crosses. The degree of resistance, as indicated by infection type, decreased with increasing levels of ploidy. This newly identified gene, designated Sr22, is located on chromosome 7A and is different from resistance genes Sr8, Sr13 and Sr15, which are also on chromosomes of the A genome.