Pathogenicity Avirulent Gene Detection And Genetic Diversity Analysis Of Magnaporthe Oryzae In Heilongjiang Province

In this study,panicle blast markers of rice blast fungus were collected from 30 cities(counties)in Heilongjiang Province in 2014 and 2015 to obtain one strain of rice blast fungus,the pathogenicity of main cultivar,the distribution situation and population structure of avirulence genes in different regions were studied,for clarifying the diversity of rice blast fungus population and the complexity of variability in Heilongjiang Province.These results provided the theoretical basis for the proper redistribution of rice planting、the selection and breeding of resistant germ plasm resources in Heilongjiang Province.Through the pathogenicity rate,virulence frequence and pathogenicity association coefficient to analyst the pathogenicity of 171 rice blast fungus to 18 main cultivated rice varieties by the method of inoculation of pathogens at seedling stage.The results showed that the pathogenicity of different rice blast fungus strains was different to the main cultivated rice varieties,the pathogenicity range is 0~78%;And the pathogenicity of the tested strains was obviously different to the all tested varieties,the virulence frequency of Longjing31 is lowest,only 1.17%;Taking the pathogenicity association coefficient as index to explore the interaction between different varieties combination and rice blast fungus,Longyang16+Longjing31 、Longjing31+Longjing43、Longjing31+Songjing20 are combinations of highly resistance,their RAC is greater than 0.8,VAC is 0,so it can be used in production and promotion.A method of designing specific primers was used to amplify 288 strains of rice blast fungus by PCR,to detect the existence situation of avirulence genes AVRPiz-t and AVR-Pita in rice blast fungus,and partial strains were sequenced and analyzed.The results showed that the frequency of occurencesof avirulence genes AVRPiz-t and AVR-Pita in Heilongjiang Province were 56.6% and 22.9%.The frequency of occurrencesof avirulence genes AVRPiz-t and AVR-Pita were 37.0% and 23.0% in 2014,were 95.8% and 22.9% in 2015.The avirulence genes of the tested strains were obviously different between years,regions and genes.The sequencing analysis of partial strains showed that two avirulence genes were variation in the population of rice blast fungus in Heilongjiang Province,especially AVR-Pita has multiple variation loci and types,these changes may also lead to loss of gene function and loss of non toxicity.The results showed that the strains variation of rice blast fungus in Heilongjiang province is universal,and genetic diversity.To research the genetic diversity of strains in Heilongjiang Province,a method of Pot2-rep-PCR fingerprint identification method was used to amplify 227 strains of rice blast fungus.The results showed that the tested strains were amplified to 2~13 DNA bands and the size were between 500~6000bp.By UPGMA cluster analysis,162 strains in 2014 were divided into 10 genetic lineages at 0.73 genetic distances.65 strains in 2015 were divided into 8 genetic lineages at 0.77 genetic distances.A total of 227 strains of rice blast fungus in 2014 and 2015 were divided into 12 genetic lineages at the similarity level of 0.75.The genetic lineages of rice blast fungus in Heilongjiang Province varied greatly between regions and years,indicating the highly variable and abundant genetic diversity of rice blast fungus in Heilongjiang Province.