Pathotypes And SSR Analysis Of Magnaporthe Grisea In Hunan

In order to understand dynamic of genetic diversity and the genetic structure of Magnaporthe grisea, provide the theory basis of interaction between rice cultivars and its isolates, and further effectively serves rice blast resistance breeding,we obtained the 230 monoconidial isolates from samples of Magnaporthe grisea which were collected from 17 counties such as Taojiang, Anhua, xinhua,et al. in Hunan. The population construction and the genetic diversity of these isolates were firstly analysed with SSR (simple sequence repeats) makers.Some representative isolates were characterized for pathotypes (physiological race). The relationship between SSR and pathotypes results were compared.The main results of this study are as follows.1. The genetic diversity of 230 monoconidial isolates of Magnaporthe grisea was analysed using 8 pair of SSR markers. All isolates tested were classified into seven genetic lineages at 0.23 lever of the genetic dissimilarity through the clustering analysis of unweighted pair-group method with arithemetic average (UPGMA). The lineages I,V,VI were the predominant lineages with the ratio 23.9%,23.5%,23.0% respectively. Only one isolate located in the lineage IV and five isolates belonged to the lineage VII.2. 77 isolates selected from above monoconidial isolates were characterized with 7 Chinese differential varieties.We demonstrated they were distributed in the 7 groups (ZA, ZB, ZC, ZD, ZE, ZF, ZG) and 30 pathotypes . There was great differentiation in ZA, ZB and ZC groups. ZG₁ was the predominant race, and its frequency in the total blast fungus population was as high as 26.5%.3. Compared with the results of SSR analysis and pathotypes, there wasn't obviously corresponding relationship between genetic lineages and pathotypes.We found that the same genetic lineage was grouped into several pathotypes, and the isolates of the same pathotype were also attributed to different genetic lineage.