INHERITANCE AND MOLECULAR MAPPING OF BARLEY GENES CONFERRING RESISTANCE TO WHEAT STRIPE RUST

Authors: Chen, Xianming; PAHALAWATTA, VIHANGA - WASHINGTON STATE UNIV

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2005
Publication Date: 8/1/2005
Citation: Chen, X., Pahalawatta, V. 2005. Inheritance and molecular mapping of barley genes conferring resistance to wheat stripe rust. Phytopathology. 95:884-889.

Interpretive Summary: Most barley cultivars are resistant to wheat stripe rust and most wheat cultivars are resistant to barley stripe rust. The barley cultivar Steptoe is susceptible to all races of the barley stripe rust pathogen identified so far in the United States, but is resistant to most races of the wheat stripe rust pathogen. To determine genetics of resistance in Steptoe to the wheat stripe rust pathogen, a cross was made between Steptoe and a susceptible barley cultivar, Russell. Various progeny generations derived from the cross were evaluated in the greenhouse for their reactions to selected races of the wheat stripe rust pathogen. The results of the genetic studies show that Steptoe has two genes, one dominant and one recessive, for resistance to the wheat stripe rust races. Using our resistance gene analog polymorphism (RGAP) technique and chromosome-specific microsatellite markers, we constructed a molecular map for the dominant gene and mapped the gene on barley chromosome 4H. The results show that resistance in barley to the wheat stripe rust pathogen is qualitatively inherited. Therefore, it is feasible to incorporate the resistance from barley to wheat for control of wheat stripe rust. This is the first study of genetics and molecular mapping of genes in an unfavorable plant host, barley, conferring resistance to the wheat form of the stripe rust pathogen. The identified genes might provide useful resistance against wheat stripe rust when incorporated into wheat from barley through chromosome manipulation or transformation.

Technical Abstract: Most barley cultivars are resistant to stripe rust of wheat that is caused by Puccinia striiformis f. sp. tritici (PST). The barley cultivar Steptoe is susceptible to all identified races of P. striiformis f. sp. hordei (PSH), the barley stripe rust pathogen, but is resistant to most PST races. To determine inheritance of the Steptoe resistance to PST, a cross was made between Steptoe and Russell, a barley variety susceptible to some PST races and all tested PSH races. Seedlings of parents and F1, BC1, F2, and F3 progeny from the barley cross were tested with races PST-41 and PST-45 under controlled greenhouse conditions. Genetic analyses of infection type data showed that Steptoe had one dominant gene and one recessive gene (provisionally designated as RpstS1 and rpstS2, respectively) for resistance to races PST-41 and PST-45. Genomic DNA was extracted from the parents and 150 F2 plants that were tested for rust reaction and grown for seed of F3 lines. The infection type data and polymorphic markers identified using the resistance gene analog polymorphism (RGAP) technique were analyzed with the Mapmaker computer program to map the resistance genes. The dominant resistance gene in Steptoe for resistance to PST races was mapped on barley chromosome 4H using a linked microsatellite marker, HVM68. A linkage group for the dominant gene was constructed with 12 RGAP markers and the microsatellite marker. The results show that resistance in barley to the wheat stripe rust pathogen is qualitatively inherited. These genes might provide useful resistance against wheat stripe rust when introgressed into wheat from barley.