Rpg7: A New Gene for Stem Rust Resistance from Hordeum vulgare ssp. spontaneum.

Wheat stem rust (causal organism: Pitccinia graminis f. sp. tritici) is an important fungal disease that causes significant yield losses in harley. The deployment of resistant cultivars is the most effective means of controlling this disease. Stem rust evaluations of a diverse collection of wild bat·ley Hordeum vulgare ssp. spontaneum) identified two Joi·danian accessions WBDC094 and WBDC238) with resistance to a vimlent pathotype P graminis f. sp tritici HKHJC) from the United States. To elucidate the genetics of stem rust resistance, both accessions were crossed to the susceptible landrace Hiproly. Segregation ratios of F- and Fi progeny indicated that a single dominant gene confers resistance to P graminis f. Rp tritici HKHJC. Molecular mapping of the resistance locus was performed in the Hiproly/WBDC238 Fj population based on 3,329 single-nucleotide polymorphism markers generated by genotyping-by-sequencing. Quantitative trait locus analysis positioned the resistance gene to the long arm of chromosome 3H between the physical/genetic positions of 683.8 Mbp/172.9 cM and 693.7 Mbp/176.0 cM. Because this resistance gene is novel. it wasi assigned the new gene locus symbol of Rpg7 with a corresponding allele symbol of RpgZ i. At the seedling stage, Rpg7 confers resistance against a number of other important R gm,nmis f. sp. truici pathotypes from the United States (MCCFC. QCCJB, and TITTF) and Africa (TrKSK) as well as an isolate (92-MN-90) of the rye stem rust pathogen (P. graminis f. sp. seca/is) from Minnesota. The resistance conferred by Rm:7 can be readily transferred into breeding programs because of its simple inheritance and clear phenotypic expression. [ABSTRACT FROM AUTHOR]