Submitted to: Frontiers of Agriculture in China
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/11/2009
Publication Date: 9/1/2009
Publication URL: http://handle.nal.usda.gov/10113/58053
Citation: Jia, Y., Liu, G., Costanzo, S., Lee, S., Dai, Y. 2009. Current progress on genetic interactions of rice with rice blast and sheath blight fungi. Frontiers of Agriculture in China. 3(3):231-239. Interpretive Summary: Blast disease caused by the filamentous ascomycete fungus Magnaporthe oryzae (formerly known as M. grisea) and sheath blight disease caused by the necrotrophic soil-borne fungus Rhizoctonia solani are the two major rice diseases that threaten the global stability of rice production. Both diseases have been managed by the utilization of major and minor resistance genes integrated with cultural practices including the use of fungicides. For blast disease, over 80 major resistance genes have been described and some of them, including the Pi-ta gene, have been effectively deployed for blast control. For sheath blight disease a major quantitative resistance locus qSB9-2 has been identified and recently verified. Research progress on molecular and genetic interactions of rice with both fungi was reviewed. Consequently, new knowledge will lead to the development of environmentally benign strategies to manage both rice blast and sheath blight diseases worldwide.
Technical Abstract: Analysis of genetic interactions between rice and its pathogenic fungi Magnaporthe oryzae and Rhizoctonia solani should lead to a better understanding of molecular mechanisms of host resistance, and the improvement of strategies to manage rice blast and sheath blight diseases. Presently dozens of rice resistance (R) genes against specific races of the blast fungus have been described. Among them, ten were molecularly characterized and some were widely used for breeding for genetic resistance. The Pi-ta gene was one of the best characterized rice R genes. Following the elucidation of its molecular structure, interaction, distribution, and evolution, user friendly DNA markers were developed from portions of the cloned genes to facilitate the incorporations of the Pi-ta mediated resistance into improved rice varieties using marker assisted selection (MAS). However, rice blast is still a major threat for stable rice production because of race change mutations occurring in rice fields, which often overcome added resistance based on single R genes and these virulent races of M. oryzae pose a continued challenge for blast control. For sheath blight, progress has been made on the exploration of novel sources of resistance from wild rice relatives and indica rice cultivars. A major quantitative trait locus (QTL), named qSB9-2, was recently verified in several mapping populations with different phenotyping methods, including greenhouse methods. The ability to identify qSB9-2 using greenhouse methods should accelerate the efforts on the qSB9-2 fine mapping and positional cloning.