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High-resolution mapping of Rsn1, a locus controlling sensitivity of rice to a necrosis-inducing phytotoxin from Rhizoctonia solani AG1-IA
Rhizoctonia solani is a necrotrophic fungal pathogen that causes disease on many crop-plant species. Anastomosis group 1-IA is the causal agent of sheath blight of rice (Oryza sativa L.), one of the most important rice diseases worldwide. R. solani AG1-IA produces a necrosisinducing phytotoxin and rice cultivar’s sensitivity to the toxin correlates with disease susceptibility. Unlike genetic analyses of sheath blight resistance where resistance loci have been reported as quantitative trait loci, phytotoxin sensitivity is inherited as a Mendelian trait that permits high-resolution mapping of the sensitivity genes. An F2 mapping population derived from parent cultivars ‘Cypress’ (toxin sensitive) and ‘Jasmine 85’ (toxin insensitive) was used to map Rsn1, the necrosis-inducing locus. Initial mapping based on 176 F2 progeny and 69 simple sequence repeat (SSR) markers located Rsn1 on the long arm of chromosome 7, with tight linkage to SSR marker RM418. A highresolution genetic map of the region was subsequently developed using a total of 1,043 F2 progeny, and Rsn1 was mapped to a 0.7 cM interval Xanked by markers NM590 and RM418. Analysis of the corresponding 29 Kb genomic sequences from reference cultivars ‘Nipponbare’ and ‘93- 11’ revealed the presence of four putative genes within the interval. Two are expressed cytokinin-O-glucosyltransferases, which Wt an apoptotic pathway model of toxin activity, and are individually being investigated further as potential candidates for Rsn1.
quantitative trait loci
Theoretical and applied genetics 2011 3 19 v.123
Journal Articles, USDA Authors, Peer-Reviewed
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Agricultural Research Service
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