Complementary genes for reaction to Puccinia recondita tritici in Triticum aestivum. I. Genetic and linkage studies

Abstract

Although confirmed instances of complementary genes for rust resistance are rare, two such genes designated A and B for seedling leaf rust resistance were identified in 'Gatcher' and certain other wheats. The two complementary genes in 'Gatcher' were separated in susceptible lines which, when intercrossed, again produced resistant progenies with the specificity of 'Gatcher.' The substitution of a chromosome 3B pair from seedling susceptible 'Hope' into seedling susceptible 'Chinese Spring' resulted in lines displaying similar leaf rust responses to 'Gatcher.' Resistant segregates occurred in segregating populations from crosses of several Sr2-bearing leaf rust susceptible wheats with 'Chinese Spring.' Hence 'Chinese Spring' carried one (A) of the complementary genes, whereas the second gene (B) was very closely linked with Sr2 (r < 0.5%) and was present in a wide range of wheats possessing Sr2. Two wheats carrying gene B lacked Sr2.Key words: leaf rust, stem rust, specificity, wheat.