| Rhizoctonia solani Kühn is a kind of soil-borne fungal disease, ang the Rhizoctonia disease complex is common and occurs in potato production areas throughout the world. And it has become one of the main effective factors in limiting high yield and quality of potato production. In this study, we carried out the systematic studies on the anastomosis groups identification of R.solani collected from 17 counties of Inner Mongolia and Hebei. And did further investigation on the genetic diversity and sensitivity to fungicides of isolates. The main results are summarized as follows:1. One hundred and sinety Rhizoctonia solani isolates were obtained from stems and tubers of infected potato plants in Inner Mongolia and Hebei. Anastomosis group (AG) identification showed that the isolates belonged to nine kinds of Anastomosis group, which is AG1-IB、AG2-1、AG3、AG4 HG-I、AG4 HG-II、AG4 HG-III、AG-5、AG9 and AG A. Most isolates collected belonged to AG 3 (77.37% of total isolates), but 7.37% and 6.84% of the isolates were AG2-1 and AG4 HG-II.2. Phylogenetic analysis among isolates belonged to different anastomosis groups was studied based upon ITS sequence, and four standard strains of different groups were determination. The standard strains JGY-17, JWC-11, JWC-13 and MYK-18 belonged to four kinds of Anastomosis group, which is AG2-1, AG4 HG-I, AG4 HG-III, AG A. The results revealed that the isolates of the same anastomosis groups (or sub-group) had the highest genetic relationship than the different groups. We could easily identify the anastomosis groups of unknown isolate and analyzing the genetics relationship.3. Hyphal anastomosis reactions, ITS sequences, and sensitivity to fungicides were integrated to evaluate the genetic diversity of isolates R. solani AG2-1 and AG3 from potato. Anastomosis reactions indicated that the complete fusion reaction occurred between the different isolates of AG3. Either the complete or incomplete fusion reaction occurred among the traditionally defined isolates of AG2-1, and so we grouped AG2-1 into two sub-groups by incomplete fusion reaction. Phylogenetic tree constructed by ITS sequences showed AG3 formed a separated clade, whereas AG2-1 clustered into the two differnet sub-clades, which were consistent with the two sub-groups based on the incomplete anastomosis reaction. Horizontal lengths of the branches indicate that AG2-1 has been appearing obvious genetic differentiation because the relative genetic diversity of the AG2-1 two subgroups were higher than AG3. Moreover fungicide sensitivity of hymexazol and thiophanate-methyl showed remarkable difference between two sub-group AG2-1-1 and AG2-1-2. Incomplete fusion reaction can be used as a referent character for genetic differentiation within an anastomosis group of R. solani.4. Sensitivity to fungicides were integrated to evaluate the sensitivity difference of isolates R. solani AG2-1 and AG3 from potato. Five fungicides were selected among the fungicides tested gave consistently strong inhibition against all two anastomosis groups of R. solani. The results showed that the isolates were sensitive to fludioxonil, azoxystrobin, thifluzamide, tolclofos-methyl and iprodione, the EC50 values of which ranged from 0.0079、0.019、0.046、0.11、0.42μg/mL. And Sensitivity test show that different fungicides sensitivity among different anastomosis groups.5. SSR genotypes revealed a high diversity of R. solani collected from potato and every isolate had a specific SSR genotype. SSR genotype of isolates was closely related to anastomosis groups and the part of infected potato plants, however, not correlative with the geographic origin. |
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