Genetic Diversity Of Magnaporthe Oryzae Form Lijiangxintuanheigu And Identification Of Pathogenic Avirulence Genes And Blast Resistance Genotypes Of Rice Cultivars

Rice blast, caused by the rice blast fungus (sexual Magnaporthe oryzae, anamorph Pyricularia oryzae) is one of the important fungal diseases in rice, and it seriously restrictes the world grain security production. Currently, one of the most safe, economical and effective measure to control the disease is breeding and utilization blast resistant cultivars. However, a new resistant cultivar planted in a large area for several years will often become susceptible because of the pathogenicity variation of rice blast fungus. Therefore, it is very important to understand the genetic structure and avirulent genes types of M. oryzae and resistant genotypes of rice cultivars for breeding and layout resistant cultivars.The genetic diversity of 120 monoconidial isolates of M. oryzae collected from rice susceptible cultivars (LTH) in Hunan Taojiang nurseries was analyzed by 14 pairs SSR primers in 2014.The results showed that all texted isolates were classified into 32 genetic lineages at 0.75 similar coefficient.The lineages L1 and L7 were dominant lineage, including 20 and 16 isolates respectively, accounting for 16.67% and 13.33% in the total isolates; L03, L04 and L02 with 11,11 and 13 isolates which separately hold 9.17%,9.17% and 10.83%of the total isolates; and the other 27 lineages contained either 1?6 isolates accounting for 40.83% of the total isolates.According to the thory of "gene for gene" for Flor, the avirulent genes of above 120 isolates with 24 NILS, each line holding a blast resistance gene were analyzed by the acupuncture vitro leaf inoculation. The results showed that the above 120 isolates hold 24 avirulent genes relative to NILS, among which 24 avirulent genes, frequency of Avr-pita and Avr-pish was more than 40%; while frequency of Avr-Piz, Avr-Piz5, Avr-Pi3 and Avr-Pi9 was between 30% to 40%; frequency of the rest avirulent genes were low, especially Avr-Piks, Avr-Pikp, Avr-Pib, Avr-Pil2 and Avr-Pill, its frequency were less than 10%.To determine the performance of blast resistance and utility values of the 24 NILS in Hunan, thrie blast resistance was identified and evaluated in the blast nursery. Based on leaf and panicle blast integrated index, moderate resistance and moderate susceptible lines were 3 and 8, respectively; most of the others were susceptible or highly susceptible.Blast resistance genotypes of 50 rice cultivars planted in Hunan with 20 isolates known avirulence genes were identified by the acupuncture vitro leaf inoculation. The results showed that the anti-isolates frequencys of tested cultivars were between 0 to 70%, among which the highest frequency of Longliang 608 was 70%, and the lowest was Nongxiang 18 with 0%; while the frequencys of 23 rice cultivars ranged from 40% to 65%, accounting for 46%, and anti-isolates frequency of 20 rice varieties between 20% to 39%, accounting for 40%. The results of cluster analysis showed that 50 tested cultivars could be divided into 32 groups at the 0.75 similarity, and presumed the major blast resistance genotypes.