Genetics and Improvement of Bacterial Blight Resistance of Hybrid Rice in China

Since 1980s,rice breeding for resistance to bacterial blight has been rapidly progressing in China. The gene Xa4 was mainly used in three-line indica hybrid and two-line hybrid rice. The disease has been ‘quiet’ for 20 years in China,yet in recent years it has gradually emerged and been prevalent in fields planted with newly released rice varieties in the Changjiang River valley. Under the circumstances,scientists inevitably raised several questions:what causes the resurgence and what should we do next? And/or is resistance breeding still one of the main objectives in rice improvement? Which approach do we take on resistance breeding so that the resistance will be more durable,and the resistance gene will be used more efficiently? A combined strategy involving traditional method,molecular marker-assisted selection,and transgenic technology should bring a new era to the bacterial blight resistance hybrid rice breeding program. This review also briefly discusses and deliberates on issues related to the broadening of bacterial blight resistance,and suitable utilization of resistance genes,alternate planting of available resistance genes;and understands the virulent populations of the bacterial pathogen in China even in Asia.