Genetic Diversity Of Magnaporthe Oryzae In Hunan And Identification Of Pathogenic Arirulence Genes And Resistance Blast Genotypes For Hunan Rice Cultivars

Rice blast, caused by Magnaporthe oryzae, is one of the most destructive fungal diseases in rice. Breeding and plantting the resistant cultivars are an economical, effective, and environmentally responsible way to control the disease. Thus, it is highly importance to study the genetic diversity of M. oryzae and compose of avirulent genes and blast resistance genes.In order to know the genetic diversity of M oryzae in the rice blast nursery in Taojiang, Hunan.100isolates from the disease lesions on leaves of a highly broad susceptibe variety Lijiangxintuanheigu(LTH) in Taojiang in2012were isolated. The genetic diversity of the isolates was analyzed by13pairs of SSR markers. The results showed that these isolates were classified into24genetic lineages at0.76similar level,among which L04and L16, including13and10isolates respectively, were the dominant lineage, accounting for13%and10%in the total isolates.The avirulent genes of above100M. oryzae isolates were analyzed by24near-isogenic lines (NILs) which contained single resistance gene to blast. According to the gene-for-gene hypothesis, the100isolates hold24avirulent genes relative to NILs. Frequency of Avr-Pizt in24avirulence genes, was44%, while Avr-Pita, Avr-Pi5and Avr-Pita2were32%,36%and31%, respectively, and yet Avr-Pil9was just8%.Identification data in the blast nursery and the room artificial inoculation with20representative strains for24NILs was compared. The results revealed that leaf blast score and the frequency against M. oryzae isolates showed significant negative correlation, while neck blast score and the anti-isolate frequency presented low negative related, their correlation coefficient are0.64and0.39, respectively.The resistant genotypes of the50rice cultivars from Hunan were identified by20M.oryzae isolates known avirulence genes. The result showed that there were4cultivars with the anti-isolate frequency reaching60%, accounting for8%of the total. According to Nei&Li, the50rice cultivars can be classified into29groups at the index similarity0.7and the major resistance gene in these cultivars were presumed based on theory of’gene for gene’.