Genetic Diversity Of 24 Good Quality Rice Germplasm Resources Resistant To Rice Blast

Rice blast, caused by Magnaporthe grisea(Hebert)Barr., is a destructive diease around the world. The practice proved that planting blast resistance cultivars is an economical and effective way to control the disease. However, the blast resistance cultivars would easily lose resistance in the field due to the frequent aberrance of pathogenicity of Magnaporthe grisea. It is a vital part of the rice breeding research in the coming a few years, to keep working on the new (combine) cultivars to improve the rice productivity, quality, adaptability and wide-resistant spectrum. Studying on resistance germplasm resources and using it in practice played an important role in rice resistance breeding. We got 24 good quantity resistance germplasms based on agronomic characters in Sichuan Provience. Furthermore, we studied the genetic diversity of the 24 resistance germplasms based on random amplified microsatellite polymorphism (RAMP). In addition, the optimal conditions and the relationships between cell wall degrading enzyme (CWDE) and pathogenicity of Magnaporthe grisea were studied too.The genetic diversity of 24 good quality rice germplasm resources resistant to rice blast was evaluated by using RAMP. The result showed that 22 out of 80 RAMP primers, which could amplify polymorphic bands clearly, were selected for the PCR amplification of genomic DNA. A total of 108 bands were amplified from 22 primers, while 80 bands (about 74.1%) were polyrnorphic. One to 9 polymorphic bands could be amplified from each primer, with an average of 3.6 bands. The RAMP-based genetic similarity (GS) among 24 rice germplasm resources ranged from 0.138 to 0.900. Based on the GS matrix, a dendrogram was constructed using the unweighted pair group method with arithmetic average (UPDMA). All the 24 rice germplasm resources could be distinguished by RAMP makers. Clustering analysis showed that the 24 tested resources could be classified into 6 groups at 0.462 similarity coefficient. It indicated that these 24 rice germplasm resources had abundance genetic diversity. It had important value for breeding new high-yield and good quality varieties or hybrid rice combinations resistant to blast.Magnaporthe grisea were collected from neck-tissue of rice, 40 isolates were obtained by tissue isolation, and were inoculated with spray method during 3～4 leafs stage to determine the pathogenicity in the field. 40 isolates showed huge different pathogenicity to rice cultivar Q253, from 1 to 9 band. It is showed that different isolates had different pathogenicity at the same host.The results showed that Magnaporthe grisea could produced CWDE at manual condition, including pectin methylgalacturonase (PMG),β-1, 4-glucosidase (β-G), 1, 4-β-D-glucan cellobiohydrolase (CBH), polygalacturonase (PG). The activity of PG was the highest, then PMG,β-G, and CBH was the lowest. The optimal manul culture conditions is to be cultured in improved Czapek' S medium (pHS) at 28℃shaking for seven days.The activities of CWDE markedly increased with increasing pathogenicity of the isol- ate, especially PG. It was indicated that the CWDE played an important role during fungal infected host cell wall.