Identification Of Avirulence Genes And Genetic Diversity Analysis Of Magnaporthe Oryzae In Hunan Based On SSR Markers

Rice blast, caused by Magnaporthe oryzae, is one of the most widespread and destructive diseases in rice. Although the most effective and economical way of controlling blast disease is breeding and plantting the various resistant cultivars rationally, newly released varieties planted in large areas frequently lose their resistance within3-5years because of shifts in strains of the M. oryzae population. Therefore, it is important value for the breeding blast resistance and deployment of resistant cultivars in Hunan.The avirulent genes of103M.oryzae isolates in Hunan were analyzed by30near-isogenic lines (NILs) which contained single resistance gene to blast. The results showed that the above103isolates hold30avirulent genes relative to NILs, among which30avirulence genes, frequency of Avr-Pi-a(1), Avr-Pi-a(2), Avr-Pi-Ks (1), Avr-Pi-z and Avr-Pi-ta (2) was less than20%, whill frequency of avirulence genes Avr-Pi-kh, Avr-Pi-9, Pi-b(c), Pi-ta2, Avr-Pi-k1, Avr-Pi-1, Avr-Pi-5and Avr-1-Pi-sh was more than70%. Therefore, the above results sugest the resistance genes, Pi-a (1), Pi-a (2), Pi-Ks (1), Pi-z and Pi-ta (2), may be nearly not used, but Pi-Kh, Pi-9, Pi-b(c), Pi-ta2, Pi-k’, Pi-1, Pi-5and Pi-sh (1) have good to be utilized in blast resistance breeding in Hunan.103isolates were divided into7groups24races by7Chinese national differential varieties, the results showed that the population structure of M. oryzae in Hunan were complex, ZB was the dominant group of Hunan M.oryzae groups, the frequency was33.10%, ZB, ZC and ZA groups had been greatly differentiated, respectively contained7,6and5races. And ZG1was the dominant race, the frequency was16.50%, secondly for ZC15and ZB31. Although ZG1was the dominant race, the occurrence frequency of indica races higher than Japonica race, therefore, speed up breeding or introduce new broad-spectrum resistant varieties has become a pressing matter of the moment.Genetic diversity of169blast fungus isolates collected from rice susceptible cultivars in Hunan was analyzed by using13pairs of SSR markers. The results showed that these isolates were classified into8genetic lineages at0.8similar level, among which01was the dominant lineage and its isolates accounted for69.7%of the total ones. Most genetic lineages contained isolates from several source areas and many rice cultivars. Genetic relationship between the lineages and the origin and cultivars of isolates was complex, in which isolates from the same location were ascribed to the several different lineages, but the isolates from the same area or cultivar had relatively close genetic relationship. Furthermore, the results also indicated that the more planting cultivars in a certain area, the more genetic diversity of M.oryzae in the area was. Genetic diversity of192blast fungus isolates collected from Li Jiang was analyzed by using13pairs of SSR markers. The results showed that these isolates were classified into9genetic lineages at0.8similar level, among which01was the dominant lineage and its isolates accounted for71.9%of the total ones. And the the Population Genetic Structure of M.oryzae from Li Jiang are more representative than from rice cultivars.