Genetic Diversity Analysis Of Ralstonia Solanacearum Using Mlst

Tobacco bacterial wilt caused by Ralstonia solanacearum is one of the most important diseases all over the world. Occurrence of Tobacco bacterial wilt in the Yangtze river basin and south of this area increasingly damaged and spread in recent years. However, the disease is hardly controlled for lack of efficient pesticide due to its rich variations. Therefore, to breed resistant varieties and develop new efficient pesticide, the study on genetic diversity of R. solanacearum should be carried out adequately.The study on genetic diversity of R. solanacearum in nationwide has not been carried out although some of the researches have been done in several provinces.167suspected samples from10main tobacco producing provinces were isolated, identified and typed by using MLST (Multilocus Sequence Typing) firstly to phylogenetic analysis. The results are as follows:(1)67strains isolated from167suspected infected samples that collected from Sichuan, Yunnan, Guizhou, Chongqing, Hunan, Hubei, Guangdong, Guangxi, Jiangxi and Anhui provinces, was compared to16SrDNA of R. solanacearum strain with results of identities up to99%by using NCBI to confirm the identification. All of the67strains in greenhouse were inoculated to tobacco seedlings by wounding and then showed symptoms although differ in period and severity.(2)The MLST analysis on seven housekeeping genes, rfbD, efp, pstSl, dnaQ, ureG, ppa, adk of R. solanacearum, showed that there was51sequence types (STs). All the strains were classified into4subgroups and4singletons:Subgroup1includes50stains with24STs; Subgroup2includes32stains with19STs; Subgroup3includes2stains with2STs; Subgroup4includes5stains with2STs. The4singletons include1strain isolated from Yunnan, Zhejiang, Zhejiang, Guangxi respectively. In geography, the ST1, which is the main ST in subgroup1, includes all the strains isolated from all provinces except Jiangxi, and strains in subgroup2were not closed to each other especially to ST40, which is their main ST, although2strains of ST40were from Anhui. This indicated that the MLST groups in this study are not related to geographical origin. In tobacco varieties, strains belonging to ST1in Subgroup1were isolated from7different tobacco species, and all strains in Subgroup1were from10different tobacco species;2strains of ST40in subgroup2were isolated from the same tobacco (Yunyan97), but all the strains in subgroup2were from6different tobaccos. From STs divisions, it is can be seen that the strains from different tobaccos could be divided into one ST, while strains isolated from same tobacco could be into different STs. It could not find out any law in relationship between tobaccos and STs. This result indicated that this pathogen was divided into subgroups irrespectively with tobacco varieties.