Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/17/2011
Publication Date: 5/27/2011
Citation: Jia, L., Yan, W., Agrama, H.A., Yeater, K.M., Li, X., Hu, B., Moldenhauer, K., McClung, A.M., Wu, D. 2011. Searching for germplasm resistant to sheath blight from the USDA Rice Core Collection. Crop Science. 51(4):1507-1517. Interpretive Summary: Rice (Oryza sativa L.) sheath blight (ShB) caused by the soilborne fungal pathogen Rhizoctonia solani is one of the most devastating diseases that threaten rice production worldwide. Reduction of rice grain yield from ShB can be up to 50%. Identifying germplasm that is resistant to ShB is a first and essential step for developing cultivars resistant to ShB. Using the micro-chamber method, our objectives in this study were to characterize the USDA rice core collection for ShB resistance, search for germplasm with greater resistance than Jasmine 85, the best resistant germplasm used most commonly in studies of ShB, and agronomically and genetically describe resistant germplasms for breeders to use in their cultivar improvement programs. After screening the USDA rice core collection of 1794 accessions and verifying initially resistant accessions, we are introducing 52 accessions to rice community worldwide for breeding and genomic research. Among them, 17 were more resistant at 1% probability and the rest more resistant at 5% probability than Jasmine 85. These resistant accessions with vast variation in morphological traits and genetic background would provide breeders and geneticists much greater flexibility for their purposes than ever before.
Technical Abstract: Sheath blight, caused by the fungal pathogen Rhizoctonia solani, is one of the most important and widely distributed diseases capable of infesting numerous crops including rice. Resistant germplasm with wide variation is essential for controlling this disease via breeding efforts, and genetic background helps design breeding strategies. We used the micro-chamber method to evaluate the USDA rice core collection, including 1794 accessions from 114 countries for sheath blight resistance. Seventy-two molecular markers were used for genotyping. Compared with Jasmine 85 which has been recognized as one of the most resistant germplasm accessions, 52 accessions were significantly more resistant at the 5% level of probability, and of these 17 were more resistant at the 1% level of probability. The resistant accessions originated from 26 countries in nine geographic regions, and are diversified for 13 phenotypic characteristics. The resistant accessions all belonged to the cultivated species O. sativa. Genetic analysis using 72 molecular markers revealed that 45 resistant accessions (87%) were indica type that were further classified in two groups. Three accessions were identified as AUS, two as aromatic and one each as temperate japonica and tropical japonica. Breeders could use these findings to choose sheath blight resistant accessions for cultivar improvement.