Mapping And Cloning Of A Novel Avirulence Gene AvrPi11 Responsible To Rice Blast Resistance Gene Pi11

Rice blast is a worldwide rice disease which caused by Magnaporthe oryzae(Pyricularia oryzae Cavara).Currently,in order to control the disease,the most economical,environmentally-friendly and effective measure is to cultivate and use resistant cultivars.However,due to high variability of rice blast fungus,the resistance of resistant varieties is often overcome in a short time.According to the gene-for-gene theory,the host will show resistance when a specific interaction occurs between the host's resistance gene and the avirulence gene of Magnaporthe oryzae.Therefore,the study of the avirulence genes will contribute to understand the molecular mechanism of resistance reactions.Meantime,it's greatly significant to overcome the harmness of rice blast.In order to develop a novel avirulence gene AvrPi11 from Magnaporthe oryzae,the following work was carried out in this study: 1.Genetic analysis and primary mapping of AvrPi11In order to identify a new rice blast fungus avirulence gene,two field strains CHL42,CHL357 and their sexually hybridized 219 ascospores were inoculated on IRBL11-Zh carrying the rice blast resistance gene Pi11 for pathogenicity analysis.The results showed that the ratio of pathogenic and non-pathogenic strains was 1:1,so the avirulent parent CHL42 was considered to carry an avirulence gene AvrPi11.Therefore,using the bulked segregant assay(BSA)analyses the 121 SSR markers developed in our laboratory on the reference sequence of M.oryzae 70-15,five linkage markers located on chromosome 6 were screened for further study.The progeny population was further used for linkage analysis to quickly locate the avirulence gene AvrPi11.2.Fine mapping of AvrPi11 and construction of physical mapFor fine-scale mapping of the AvrPi11 locus,we use the reference sequence of 70-15 to further develop new markers for linkage analysis.Finally,AvrPi11 was located at an area of approximately 50 kb between LSM6-8 and CAG11-14.The molecular markers closely linked to the target gene were anchored to reference strain 70-15,and the physical map of AvrPi11 was constructed.3.Prediction and sequence analysis of the candidate gene of AvrPi11Gene prediction software was used to predict candidate genes for the reference strains 70-15,KJ201 and parental strains.The results showed that there were 15 candidate genes in the target area.Subsequently,sequence analysis was performed on the candidate genes.As a result,11A4,11A5,AvrPib,11A10 and 11A11 were identified as the most likely candidate genes.