Establishment Of Inoculation Technique And Rating System In Researching Rice Sheath Blight Resistance And Genetic Diversity Analysis Of Rhizoctonia Solani Populations From Fujian

Sheath blight, caused by Rhizoctonia solani is an important disease of rice around the word,but the research about it is relative lag. To establish the standard methods to evaluate the pathogenicity of the pathogen isolates and the resistance of rice cultivars, this research first cooperate with other internal labs to put up inoculation method of Rhizoctonia solani on seedling, select identification isolates and identification cultivars. Use paddy's inoculation method, make seedling cause sheath blight in glasshouse. 29 isolates of R. solani AG-1 IA, which collected from several provinces including Fujian, Yunnan, Guangdong, Hunan, Hainan, Jiangsu and Guangxi was studied by testing their pathogenicity to a set of candidate identification rice cultivars. Five identification isolates and 5 identification cultivars were screened out after considering our results combining with the results from other two labs. The 5 identification isolates were C30, GD118, E67, YN7 and YN3 respectively, and the 5 identification cultivars were Lemont, Wu Yujing 3, jasmine85, C418 and 91SP respectively. The results indicated that the different rice variety showed obviously different resistance level to R. solani. Among them, 91SP was resistance variety, and ZH-5, Shanyou 63, Guofu 6, Jasmin85, Nongken57, Teqing and C418 were middle resistance varieties, and while, Wu Yujing3, Lemont were the susceptible varieties. The pathogenicity tests indicated that the most virulence isolate was D60, which from Pingguo of Guangxi province, with the average of 7.08 disease level.To understand the genetic diversity of Rhizoctonia solani, genetic diversity of one hundred rice sheath blight isolates (R. solani) from ten counties in Fujian province, were investigated by the Inter-Simple Sequence Repeat (ISSR) technique, using three specific and stable primers selected from 16 primers. A total of 41 sites were generated, among which 90.2% were polymorphic. The data were analyzed by PopGene. The average percentage of polymorphic loci of populations was 55.14% and demonstrated high genetic diversity (the average value of Shannon index (I)) was 0.2953). And the genetic variation was very significant among populations (average Nei's index was 0.1991, and average Gst was 0.6423). The tested isolates could be classified into 5 ISSR groups. At the same time, the growth rate and pathogenicity of the isolates were surveyed. The ISSR clustering groups had obvious correlation with geographical origin of the isolates, but had no significant correlation with growth rate and pathogenicity variation. Our results will contribute to further study the population of R. solani and control of the disease.