Cytogenetical studies in wheat. IX. Monosomic analyses, telocentric mapping and linkage relationships of genes sr21, pm4 and mle

Abstract

Gene Sr21 for resistance to Puccinia graminis tritici in five hexaploid derivatives of the diploid Triticum monococcum was located in chromosome 2A. Since only one chromosome was involved in resistance, abnormal ratios found in some diploid wheat crosses and in one hexaploid derivative were attributed to differential transmission of gametes rather than to gene duplication in the diploid wheat sources. By using 2AS and an unknown telocentric presumed to be 2AL in telocentric mapping, Sr21 was placed 2·4±0·9 recombination units from the centromere in 2AL. Genes Pm4 and Mle for resistance to Erysiphe graminis trifici were also located in chromosome 2A. Attempted telocentric mapping of Pm4 with the 2AS telosome suggested that Pm4 was situated either very close to the centromere in 2AS, or somewhere in 2AL. The latter possibility was confirmed when Pm4 showed 37.5±1.7% recombination with Sr21. Mle was located in chromosome 2AL and segregated independently of the centromere. Pm4 and Mle behaved as alleles. Consequently, Pm4 was redesignated Pm4a and Mle was designated as Pm4b. © 1979 ASEG.