Identification And Genetic Diversity Of Rhizoctonia Solani From Black Scurf Of Potato In Northern China

Potato is the fourth largest crops in the world followed rice, wheat and maize,it can beused as food, vegetables, feed and processing.The potato black scurf is one of the maindiseases of potato. In this paper,the Rhizoctonia solani anastomosis groups were identificationand pathogenicity identification from black scurf of potato in northern China.,and using themethod of SSR to analyze the genetic diversity of AG3group that from different regions.,Follows are the main conclusion:1. A total of251isolates of Rhizoctonia solani were obtained from stem canker lesions,stolon and root lesions, or black scurf on tubers of300potato (Solanum tuberosum) plants innorthern China (Shandong, Gansu, Qinghai, Inner Mongolia, Harbin and Heilongjiangprovinces). The nuclear phase observation identify that all isolates of Rhizoctonia are allmultinucleate.Anastomosis group (AG) identification showed that the isolates belonged tomultinucleate Rhizoctonia AG-3, AG1-IB, AG4-HG-I, AG4-HG-Ⅱ, AG4-HG-III, AG-5andAG-11groups. Of these, AG-3was the major anastomosis group (AG)(71.31%of totalisolates), followed by AG4-HG-I (15.14%). AG-11was isolated for the first time from potatoblack scurf diseased plants in China.2. Phylogenetic analysis among isolates belonging to different AGs was studied basedupon5.8S rDNA-internal transcribed spacer (ITS) sequence. Conclusion,five anastomosisgroups belong to R. solani were divided into two major branches.The26isolates whichbelong to3different AGs(AG3, AG11and AG-5) constituted the first branch, account for thatthe AG11who was isolated for the first time from China with AG3、AG5have close geneticrelationship;The second branch made up of3different sub-Ags(AG1-IB、AG4-HG-I、AG4-HG-II�'�AG4-HG-III), account for that theAG1-IB with AG4-HG-I、AG4-HG-II andAG4-HG-III have close genetic relationship.3. Used the methods of soil inoculation for pathogenicity identification,the56isolates ofRhizoctonia solani AG3and several representative strains of AG1-IB、 AG4-HG-I、AG4-HG-II、AG4-HG-III、AG-5and AG-11were be test in the Seedling stage of potato.All AG3isolates had strong pathogenicity in general,56isolates of R. solani AG3was divided in3groups: Strong pathogenic strains、Secondary pathogenic strains and Weakpathogenic strains by disease index. The AG1-IB、AG4-HG-I、AG4-HG-II and AG-5groupshad strong pathogenicity too and the average disease index was about78.9to86.33, while theAG4-HG-III and AG11have the lower pathogenicity and the average disease index was about69.33and64.4. The66strains belong to AG3what come from Shandong、Gansu、Inner Mongolia、Qinghai、Hebei and Heilongjiang was analyzed by SSR enlargement reaction technique. Tenoligonucleotide primers were used. The observed number of alleles were35,the effectivenumber of alleles were22, the shannon’s index numbe（rI）between1.22and0.42.The isolatescome from Inner Mongolia and Qinghai had higher values in I and Nei’s, instructions thatthe R. solani AG3Collected from there With high genotype.The dendrogram derived fromSSR data by UPGMA suggested that the five Geographical populations were divided intotwo groups in the value of Genetic consistency was0.70, The isolates which belong to3different Geographical populations (Heilongjiang、Gansu and Shandong) constituted the firstbranch meanwhile the value was0.87. The second branch make up of Inner Mongolia andQinghai, the value was0.88. The conclusion is that the Genetic distance and the geographicaldistance of Rhizoctonia solani AG3had Significant associate.