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Identification of RFLP Markers Linked to Crown Rust Resistance Genes Pc 91 and Pc in Oat

Rooney, William L., Rines, Howard W., Phillips, Ronald L.
Crop science 1994 v.34 no.4 pp. 940-944
Avena sativa, disease resistance, genetic resistance, Puccinia coronata, alleles, polyploidy, genetic markers, restriction fragment length polymorphism
Crown rust, caused by the fungal pathogen Puccinia coronata Cda. f. avenae (Eriks & E. Henn.), is recognized as a major diseasee of cultivated oat (Avena sativa L.). Control of the pathogen has relied on the identification of resistance genes (designated Pc genes) and their incorporation into oat cultivars. However, the limited durability of single genes conferring high levels of resistance to the disease has depleted the number of such resistance genes. New genes and ways to deploy them are needed to ensure adequate resistance in future oat cultivars. Our objectives were to characterize crown rust resistance from two unadapted Avena germplasms and to identify RFLP markers linked to the respective Pc genes. In this study, Pc 91 and Pc 92 were identified from the hexapioid germplasms Amagalon and Obee/ ‘Midsouth’, respectively. At each locus, crown rust resistance was conditioned by the presence of a single dominant allele. In backcross-derived lines, RFLP markers putatively linked to Pc 91 and Pc 92 were identified, and map distances were calculated using segregating F₂ populations for each gene. RFLP probe UMN 145 identified a sequence 4.5 cM from Pc 91 and RFLP probe OG 176 identified a sequence 13.6 cM from Pc 92. Using aneuploid stocks to map the location of RFLP markers, Pc 91 was localized to Chromosome 18, while Pc 92 could not be localized to a chromosome probably because of the lack of the corresponding aneuploid stock. The RFLP markers for these genes may be useful in pyramiding Pc genes in an effort to increase the durability of resistance. Journal Series no. 20,803 of the Minn. Agric. Res. Stn. Research supported in part by The Quaker Oats Co.