The Use Of Pi-ta And Pi-b Gene For Rice Panicle Blast Resistance Breeding In Rice

Rice is one of the major food crops in the world, and rice blast as a important worldwide rice disease caused by Magnaporthe grisea (Hebert) Barr, threating to the world food security. Jiangsu is the main rice producing province in our country, rice cultivation area was about3400mu, and planting area for the japonica rice reached85%. Rice blast especially rice panicle blast is one of the major diseases in Jiangsu. Therefore, it is of important theoretical and practical significance to understand the relationship of panicle blast resistance genes and resistance to blast fungus races for the development of new rice varieties resistant to panicle blast. In this study,618new japonica lines bred by Institute of Food Crops, Jiangsu Academy of Agricultural Sciences were identified for panicle blast resistance by artificial inoculation method using6physiological races of ZB29, ZC15, ZD1, ZE3, ZF1and ZG1represented in Jiangsu at the booting stage of rice in2011and2012. Resistant genes of Pi-ta and Pi-b of618new japonica lines were detected by molecular methods. And the relationship of the two genes and their resistance to6physiological races were analyzed. The main results obtained were as follows:1. The results of resistance identification showed that60%of the japonica lines identified in the study were resistant to6panicle blast physiological races. Even more,75%-80%of the identified lines were resistant to ZB29, ZG1and ZE3races.2. The resistance genotype analysis of618japonica lines showed that the ratio of lines with genotype pi-ta/Pi-b was the highest, accounting for more than60%. And the ratio of other lines with Pi-talPi-b, pi-talpi-b and Pi-talpi-b were32%,6%and2%, respectively. The distribution frequency of resistance gene Pi-b was significantly higher than Pi-ta.3. The lines containing both Pi-ta and Pi-b possessed the highest resistance percentage and the lines without Pi-ta and Pi-b have the lowest resistance percentage, combined with the fact that the lines with only Pi-ta showed better resistance than thoes with only Pi-b indicated that Pi-ta was more effective than Pi-b in resisting to the6panicle blast physiological races.4. Some new japonica lines without resistant gene Pi-ta and Pi-b were also resistant to6panicle blast physiological races to some extent, which concluded that there probablely exist other resistant genes. So the new genes should be used in improving the resistance of rice panicle blast.