The Single Base Mutation Of Avirulence Gene And Microsatellites Of Promoters In Magnaporthe Orvzae Isolates

Rice blast disease caused by the fungus pathogen Magnaporthe orzaye is the most serious threats to the yield and quality of rice,resulting in significant losses.Besides infecting rice, rice blast can also infect gramineae and cyperaceae and so on.The researchs have shown the fungus from grasses host pear spore have relationships with the occurrence of rice blast.After years of effort, the producer found the breeding of resistant varieties, and accumulates promotion is the most economic, effective and safety prevention rice blast fungus.Because of the rice blast fungus enrichment, high variability and the specific strain of the population succession quickly, the resistance of rice varieties can’t persist after the continuous use of 3-5 years. It has been reported there is a close relationship with resistance persisting and avirulent genes of rice blast. Avirulent gene in the rice blast fungus is a kind of elicitor, which can identify the host resistance genes.In the process of rice blast infection of rice, some elicitor priority at BIC accumulation, then move to the cytoplasm;Some elicitor accumulation at EIHM.Avirulent genes often mutates, the type of mutation have single base mutation,insert, deletion and so on. In order to ove rcome its variation, host plants would mutate, making the host plants and pathogens evolve and eventually reach equilibrium.Therefore, the study of rice blast fungus avirulent genes will help to understand the pathogenic mechanism of rice blast fungus, rice disease resistance mechanisms and rice to rice blast fungus interactions, the realization of ultimate resistance of persistence.The study collects and keeps 192 strains from 1978 to 2013, as the research material, making analysis of evolution, and study the way to detect single base mutation of avirulent genes.The results are showed as follows:(1)the isolates were divided into two groups,one is from rice, Eleusine indica and Setaria viridis, showing that there is a close genetic relationship. And the other is from Digitaria sanguinalis as a distinst phylogenetic group.(2) The mutant type of eight AVR genes is deletion, AVR-pii、AVR-pia、PWL1 in all strains showed a lot of loss phenomenon, and AVR- piks/km/KP, AVRPiz-t, PWL2, PWL3, PWL4 show the missing phenomenon in a small number of strains.Through statistical rate of expansion of avirulent genes in different host, found that none of the strains have all of the genes.The strains containing AVR- piks/km/KP, AVRPiz- t, PWL2, and had a rich rate.But there may be single-base mutation.(3) Through sequencing AVR- piks/km/KP, AVRPiz-t, PWL2 of rice blast, showing there is single-base mutation in piks/km/KP and PWL2 except AVRPiz-t.(4)Take AVRPiz-t as an example, to study a single-base mutation method about rice blast group, the results show that the method is feasible.In addition, the SSR is widely in the genomes, and SSR in the promoter region is associated with gene expression.There is an abundant of SSR existing in the genome of Magnaporthe grisea. It has been reported that SSR as molecular label study the rice blast fungus, but we have not known the rice blast fungus SSR in the promoter.This study carried out the SSR in the promoter by the statistical analysis: there is a lot of overlap in the group of rice blast and the distance between start codon is near. There is an obvious SSR enrichment phenomenon near the start codon, showing SSR in promoter regions have relationship to transcription.