Submitted to: Phytopathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/6/2012
Publication Date: 6/12/2012
Publication URL: http://handle.nal.usda.gov/10113/57985
Citation: RoyChowdhury, M., Jia, Y., Jia, M.H., Fjellstrom, R.G., Cartwright, R. 2012. Identification of the rice blast resistance gene Pi-b in the national small grains collection. Phytopathology 102(7):700-706. Interpretive Summary: The rice blast resistance gene Pi-b confers resistance to a range of common races of blast fungus in the Southern US. In the present study, DNA markers and pathogenicity assays were used to identify rice accessions from the National Small Grains Collection that contain Pi-b. A total of 112 rice accessions were confirmed to contain Pi-b. These Pi-b containing accessions from diverse rice production areas are excellent resources for breeding for improved blast resistance using marker assisted selection. The remaining accessions where marker analysis disagreed with disease evaluation will require further analysis before their deployment for breeding for blast resistance. This study demonstrated the usefulness of DNA marker and pathogenicity assays for germplasm evaluation.
Technical Abstract: The Pi-b gene in rice confers resistance to a wide range of races of the rice blast pathogen, Magnaporthe oryzae, including race IE1k that overcomes Pi-ta. In this study, the presence of Pi-b in 164 rice germplasm accessions from the National Small Grains Collection was determined utilizing DNA markers and pathogenicity assays. The presence of Pi-b was evaluated with two simple sequence repeat markers (SSRs) and a dominant marker (Pib-dom) derived from the Pi-b gene sequence. Pathogenicity assays using two avirulent (AVR) races (IE1k and IB1) and a virulent (VIR) race (IB54) were performed to verify the resistance responses of accessions. Of the 164 accessions evaluated, 112 contained the Pi-b gene as determined using both SSR markers and pathogenicity assays, albeit different haplotypes were detected. The remaining 52 germplasm accessions were different in their responses to the blast races IB54, IE1k, and IB1, thus indicating the presence of R gene(s) other than Pi-b. The accessions characterized in this study could be used for marker-assisted breeding to improve blast resistance in indica and japonica cultivars worldwide.