Use of Substitution‐Monosomics to Determine the Chromosomal Location of Genes Conditioning Stem Rust‐Resistance in Langdon Durum1

Abstract

All of the available D‐genome substitution‐monosomics of ‘Langdon’ durum wheat (Triticum turgidum L.) were corssed with the stem rust susceptible cv. ‘Marruecos‐9623,’ and the chromosomal locations of some of the genes for stem rust (Puccinia gramminis f. sp. tritici Ericks and E. Henn) resistance in Langdon were determined. Substitution‐monosomics (13”+2’) and normal (14”) F1 plants were identified by microscope examination of pollen mother cells. Critical crosses were detected by differences between the segregation of F2 progenies from 13” + 2’ and 14” F1 plants. Landgon has one gene for resistance to culture Or9e on chromosome 7A, and three genes for resistance to culture 111‐SS2 located on chromosomes 2B, 3B, and 7A. The gene for resistance to culture Or9e on chromosome 7A is linked to one of the genes for resistance to 111‐SS2 with a recombination value of 8.5%. A gene for resistance to culture GB121 was located on chromosome 4A. The Landgon substitution‐monosomics were used for the first time in this study, and their usefulness for locating genes on chromosomes was demonstrated. They were more fertile, more vigorous, and had higher frequencies of substitution‐monosomics in their progenies than durum monosomics lacking a compensating homoeologous chromosome from the D‐genome.