Molecular Mapping of Two Genes for Stripe Rust Resistance in Durum Wheat Germplasm Accessions PI 331260 and PI 480016.

New genes for effective resistance to stripe rust are needed for diversifying genes deployed in wheat cultivars. Durum wheat germplasm has excellent resistance to stripe rust, but not many genes for stripe rust resistance had been identified from this resource. Durum wheat accessions PI 331260 and PI 480016, originally from Ethiopia, have shown excellent stripe rust resistance.  To study the genetics of their resistance and transfer the resistance into common wheat, both accessions were crossed with ‘Avocet Susceptible’ (AvS). F₃ plants with 42 chromosomes and stripe rust resistance were selected by counting Feulgen stained root tip cells and tested with PST-100 in the seedling stage under controlled greenhouse conditions.  The 3:1 segregation obtained in the F₄ lines derived from a single F₃ plant in each of the crosses indicated that a single dominant gene was transferred into the common wheat lines from each of the accessions. To develop an adequate mapping population, 146 F₆ plants of AvS/PI 331260 and 172 F₆ plants of AvS/PI 480016 derived from a single F₅ plant for each cross were used as an “F₂” segregating population for mapping the resistance gene and the F₆ single-seed descent F₇ lines (treated as “F₃” lines) were used to determine the stripe rust resistance genotype for each F₆ plant. A total of 576 simple sequence repeat (SSR) markers were screened for markers linked to the resistance locus in each cross.  Ten markers were identified for each of the resistance genes and these markers mapped both YrPI331260 and YrPI480016 on chromosome 1BS. YrPI331260 was flanked by Xbarc119 and Xgwm413 at a genetic distance of 3.0 cM and 3.5 cM, respectively; and YrPI480016 was flanked by Xgwm18 and Xgwm273 at 1.2 cM and 2.1 cM, respectively. Based on the chromosomal locations and reactions to various races of the pathogen, the two genes are different from all previously designated genes for stripe rust resistance and should be useful for developing resistant cultivars.