Genetic And Pathogenic Diversity Of Magnaporthe Grisea In Different Indica And Japonica Cultivation Areas

Asian cultivated rice(Oryza sativa L.)is an important crop,which is a staple food for more than half of the worldwide populations.As one of the three devastating diseases in rice,rice blast has occurred in almost all the rice-growing areas with different degree every year.Taking advantage of disease resistant varieties may be the most effective and economical way in rice production,the variation of population structure in rice blast fungus,however,is so complex that the resistant varieties just can be maintained by 2-3 years.Therefore,investigating the population structure and the dynamic of variation in rice blast fungus,grasping its changing rule and finding the corresponding disease resistance genes is one of the most urgent problems in rice production.China is one of the oldest rice-growing countries,which is also the only country that largely cultivated indica and japonica this two subspecies of rice.Indica and japonica showed obvious difference in morphological and physical characteristics and exhibited relatively independent geographic distribution.In order to get knowledge of whether there’s difference in the genetic structure of rice blast fungus found between Indica and Japonica,we collected 57 rice blast strains from 10 provinces or regions widely planting rice and analyzed their DNA fingerprints by the means of Pot2-Rep-PCR.The results from the clustering analysis of DNA fingerprints suggested that all the rice blast strains can be divided into 21 groups by the 78%similarity,the blast strains in 2 of the 15 groups all came from the japonica regions and that in the other 13 groups came from indica areas.The rice blast strains from japonica and indica areas showed obvious genetic differentiation for they are located in distinct groups.Besides,the structure of rice blast strains from japonica regions is much simple than that from indica regions and some strains from the same province distributed in different branches,this observations may be explained by the humid climate in southern,which suited for the growth of rice blast and lead to the much more abundant genetic diversity in indica regions.According to the results from the fingerprints analysis of the pathogens,we selected 29 rice blast strains exhibited substantial genetic differentiation and tested the pathogenicity in the two parents indica ZYQ8 and japonica JX17 from a double haploid(Double Haploid,DH)population.The results showed that 12 strains of rice blast have significant differences in pathogenicity between the two parents,9 strains(6 and 3 from indica and japonica regions respectively)are resistant to ZYQ8 and susceptible to JX17 and 3 strains from indica regions are susceptible to ZYQ8 and resistant to JX17.The test results suggested that ther resistance to rice blast in ZYQ8 is better than that in JX17,but there also exist some unique resistance locus in JX17.This finding provide basis for screening corresponding blast resistance genes in DH population by exploiting 12 strains.