Pathogenicity Variation And Genetic Diversity Of Different Rice Rhizoctonia Solani In Jiangsu Province

Rice sheath blight is one of the three major destructive diseases of rice worldwide. Its pathogen Rhizoctonia solani Kuhn is an imperfect fungi. The fungi has a wide host range and is pretty adaptable, so it is very difficult to control. The disease has become one of the major constraints for rice productivity and yield stability of rice in recent years. It is even more difficult to control the disease for the diversity and variability of the Pathogen.In order to clarify the genetic mutations and diversity of the pathogens causing rice sheath blight in Jiangsu,86pathogenic isolates derived from typical leaf lesions were analyzed for classification and genetic differentiation.The researches try to find the relationship between the DNA polymorphism and growth rate and virulence of the strains, meanwhile, to understand the phylogenetic relationship of genetic structure and virulence differentiation among strains of different geographical origins.80strains were collected from samples with typical symptoms of rice sheath blight in field of six cities (six ecological zones) in Jiangsu province in2009to2010. Six from the field collection of Xiamen, in Fujian province. With the addition of one Rhizoctonia, stored in our lab, R.h-2, there were a total of87strains.The87strains were respectively studied on the observation about the nuclear fusion number, the anastomosis groups and morphological classification. The87strains were compared in several biological characteristics of the pathogen. The results show that different strains show differences in the characteristics of their growth rate, colony morphology, aerial mycelium and sclerotia amount.The pathogenicity of the87strains was examined in three different ways. The results of the inoculation method in vitro (inoculated broad bean leaves, rice leaves and leaf sheaths) were that four strains show low pathogenicity, and have not been detected pathogenicity on the rice sheaths; The rest of strains represent high pathogenicity in vitro. And we find that the same strain inoculate three different materials in vitro, the pathogenicity appraisal result diversity is not big.In the results of embedded inoculation method in greenhouse, it showed that significant differences exist between these strains. Except four strains were non-pathogenic in vivo rice, the remaining83strains could infect rice, two strains show the strongest pathogenicity. It exists obvious pathogenicity differentiation among these strains. In the research for the pathogenicity differentiation base on the interaction between rice varieties and pathogen, using the embedded inoculation method in field, six varieties of rice were inoculated with87strains. The significant differences and genetic variation potential show in the pathogenicity of different strains with different rice varieties.Finally, using both ISSR and RAPD molecular fingerprinting techniques, the writer has analysed genetic diversity of the87strains. UPGMA cluster tree of the genetic relationship between individuals with the NTSYS software seven geographic populations strains amplified polymorphic build. The genetic similarity coefficient of molecular markers revealed seven different geographic populations of rice with Rhizoctonia solani and for cluster analysis of genetic relationship between geographic populations. The ISSR molecular markers cluster analysis results show that at the similarity coefficient of about0.70,87strains can be divided into seven categories. ISSR phenotypic data matrix input PopGene software for analysis of seven geographic populations. Statistics of the parameters, the reaction of different populations.Growth rate and virulence of87strains analyzed, the correlation coefficient is0.507, two moderate-intensity correlation. Growth rate and virulence between strains of individual no significant correlation between growth rate and virulence, but the overall level of positive correlation, that is, the faster growth rate groups more virulence.Comparison of RAPD and ISSR fingerprinting result, phylogenetic tree was constructed. ISSR-PCR fingerprinting strains within the same strain is similar to the very obvious differences between different strains, each strain are the respective characteristic bands can be specific as to identify different strains of Rhizoctonia markers.