Submitted to: Molecular Plant Breeding of China
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/15/2012
Publication Date: 4/24/2012
Citation: Zhao, G., Yan, Z., Jia, Y., Deren, C.W., Dai, L. 2012. Analysis of rice blast resistance in rice breeding parents from USA using molecular markers and pathogenicity assays. Molecular Plant Breeding of China. 10:207-213. Interpretive Summary: Breeding for rice blast resistance is a major objective for breeding programs around the world. DNA markers for the rice blast resistance gene Pi-ta have been effectively used for the identification of this gene in breeding parents and for use in marker assisted selection in rice breeding programs. In the present study, two sets of dominant markers derived from portions of Pi-ta were used to examine the existence of Pi-ta in 39 breeding parents. Although most breeding parents determined to carry Pi-ta were shown to be resistant to a mixture of avirulent blast races under greenhouse conditions, a few exceptions were found. This study demonstrated that DNA markers in conjunction with pathogenicity assays can significantly improve the accuracy of breeding for blast resistance.
Technical Abstract: Rice blast disease is caused by the fungal pathogen Magnaporthe oryzae. The Pi-ta gene in rice is effective in preventing infections by strains of M. oryzae that carry AVR-Pita1 in a gene for gene specificity. In the present study, two dominant markers YL153/YL154 and YL155/YL87 derived from different regions of the Pi-ta gene were used to examine the existence of Pi-ta in 39 breeding parents. A mixture of avirulent races IC-17, IB-49, IB-1, IE-1, G-1, and IH-1 of M. oryzae was used to inoculate each rice genotype. Using molecular markers YL153/YL154 and YL155/YL87, 26 breeding parents possessed the Pi-ta gene, 21 of which were resistant, and 5 were susceptible to mixed races of M. oryzae. Eleven breeding parents were determined to lack Pi-ta by molecular markers, 4 of which were susceptible and 7 of which were resistant, suggesting the presence of other blast resistance genes. For two breeding parents, recombination between the two molecular markers YL153/YL154 and YL155/YL87, where one marker indicates the presence of Pi-ta and other marker indicates the absence of Pi-ta, while their blast reaction was susceptible. These apparent recombinants may be useful for further studies on gene function. These findings also demonstrated the importance of using molecular markers in conjunction with pathogenicity assays for selecting breeding parents in rice breeding.