Study On The Relationship Between Genetic Lineage And Pathogenicity Of Magnaporthe Grisea In Chongqing

1. DNA fingerprinting of Magnaporthe grisea isolates collected from Chongqing area was determinated using the rep-PCR technique. The results showed 2 - 15 DNA bands among 546bp-23kb for each isolate were amplified. All isolates tested were classfied into nine genetic lineages at 0.8 genetic similarity through the clustering analysis of unweighted pair-group method using arithmetic average (UPGMA). L3, L6, L9 were the predominant lineage. It was obviously related among the genetic lineage and the hosts, collecting places. L3, L6, L9 were the major lineage of Shanyou 63, Nuogu, Gangyou22, respectively, and they were the major one of ShiZhu, WanZhou, ZhongXian rice growing area, respectively.This provides useful genetic information for the rice resistant breeding and the resonable arrangement of the rice varieties.2. The types of physiological races of 40 M. grisea isolates distributed in each of the genetic lineage were tested, by the traditional means of identifying physiological races via the differential varieties resistant or susceptible reaction to the isolates. The 40 isolates were divided into 5 groups, 15 races. ZA and ZB belonged to the dominant groups. ZA1, ZA3 and ZB1 were the major races. The result also showed there have no certain corresponding relationships between genetic lineage and physiological race. The same lineage could be composed of several diffent physiological races, and the same physiological race could belong to different lineage.3. The pathogenicity of 10 isolates from the same or different lineage was alsotested. It showed there was close relationship among the pathogenicity of the blast isolates and their genetic lineage, type of races, host and the site of collection. The isolates from the same genetic lineage and isolated from the same host with close related race types showed highest similarity in pathogenicity. Isolates separated from the different hosts, but fell into the same genetic lineage and collected from the same site also presented higher rate of similarity. The pathogenicity of isolates tested as different lineage and collected from different hosts varied greatly. It not only ensures that selecteing representative isolates of rice blast for exploring and breeding resistant cultivars can realy standy for the character of the pathogen group in the field; and also facilitate evaluating the new cultivar, germplasm resistance and conducting the rice resistant breeding.