Submitted to: Phytopathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/13/2004
Publication Date: 4/30/2005
Citation: Pahalawatta, V., Chen, X. Genetic analysis and molecular mapping of wheat genes conferring resistance to the wheat stripe rust and barley stripe rust pathogens. Phytopathology. 45:427-432. Interpretive Summary: Stripe rust is one of the most important diseases on both wheat and barley worldwide. Stripe rust of wheat and stripe rust of barley are caused by two different specialized forms of the fungal species. Most wheat varieties are resistant to the barley form and most barley varieties are resistant to the wheat form. To determine genetics of wheat resistance to the barley stripe rust pathogen, identify the resistance gene(s), and determine its relationships to wheat genes for resistance to the wheat stripe rust pathogen, wheat crosses were made between wheat genotypes Lemhi (resistant to the barley form and only one of the races of the wheat form) and PI 478214 (susceptible to both the wheat and barley forms). Genetic studies were conducted in the controlled greenhouse conditions by testing the parents and various generations of progeny of the cross with two races of the barley form and one race of the wheat form. Our resistance gene analog polymorphism (RGAP) technique also was used to map genes for resistance to the two different forms of the pathogen. The results showed that the Lemhi wheat has a dominant gene for resistance to the barley form, and the gene is closely linked to a previously reported gene in Lemhi for resistance to the wheat form. A linkage group consisting of 11 RGAP markers was constructed for the genes and the genes were mapped on wheat chromosome 1B. The genetic information obtained from this study is useful in understanding interactions between inappropriate hosts and pathogens. This study provides genetic basis for using wheat genes in barley for controlling barley stripe rust. The molecular markers identified in this study will be useful for incorporating the gene from wheat into barley for controlling the appropriate form of the pathogen, barley stripe rust.
Technical Abstract: Stripe rust is one of the most important diseases on both wheat and barley worldwide. Stripe rust of wheat is caused by Puccinia striiformis f. sp. tritici (P. s. tritici) and stripe rust of barley is caused by P. striiformis f. sp. hordei (P. s. hordei). Most wheat genotypes are resistant to P. s. hordei and most barley genotypes are resistant to P. s. tritici. To determine genetics of wheat resistance to the P. s. hordei inappropriate pathogen, crosses were made between wheat genotypes Lemhi (resistant to P. s. hordei) and PI 478214 (susceptible to P. s. hordei). The seedling test of 150 F2 progeny from the Lemhi X PI 478214 cross inoculated with race PSH-14 of P. s. hordei under controlled greenhouse conditions indicated that Lemhi has a dominant gene for resistance to PSH-14. The single dominant gene was confirmed by testing seedlings of the F1, backcrosses to the two parents, and 150 F3 lines from the F2 plants with the same race. The tests of the F1, BC1, and F3 progeny with race PSH-48 of P. s. hordei and PST-21 of P. s. tritici also showed a dominant gene for resistance to these races. Co-segregating analyses of the F3 data from the tests with the two races of P. s. hordei and one race of P. s. tritici suggest that the same gene confers the resistance to the two races of P. s. hordei and that gene is different but closely linked to Yr21, a previously reported gene in Lemhi conferring resistance to race PST-21 of P. s. tritici. A linkage group consisting of 11 resistance gene analog polymorphism (RGAP) markers was established for the genes. The gene was confirmed to be on chromosome 1B by amplification of a set of nulli-tetrasomic Chinese Spring lines with an RGAP marker linked in repulsion with the resistance allele. The genetic information obtained from this study is useful in understanding interactions between inappropriate hosts and pathogens. The genes identified in this study should provide resistance to stripe rust when introgressed into appropriate host cultivars.