The Phylotype And Sequevar Of Ralstonia Solanacearum Ana Characteristics Of Bacterial Wilt Pathogen Isolated From Cucurbitaceae Plants In Guangxi

Bacterial wilt,caused by Ralstonia solanacearum,is a soil-borne disease,and widely distributes in tropical,subtropical,and temperate regions of the world.Meanwhile,it is gradually spreading from the lowlands to the highlands cold areas.R.solanacearum present a very wide plant host range,and new host plants are continuously being discovered.In this study,basis of the investigation on the occurrence and damage of bacterial wilt in Guangxi,the disease plants were collected from different hosts and the phylotype and sequevar of strain isolated from disease plant were identified by multiplex PCR and phylogenetic relationships.Meanwhile,the characteristics of bacterial wilt pathogen isolated from Cucurbitaceae plants were analysized.The results were shown as follows:1.Bacterial wilt was widespread throughout Guangxi.Nanning was the most serious areas suffered bacterial wilt damage,followed by southeastern Baise.Bacterial wilt occured more lower in areas of Longlin,Tianlin,Fangchenggang,Chongzuo and Hezhou.The occurrences of bacterial wilt in different hosts were different.Peanut bacterial wilt was widely distributed and seriously occurred in Guangxi.Bacterial wilt of tobacco and eggplant occurred mainly in Jingxi and Yulin,respectively,Pepper bacterial wilt seriously occurred in north Guangxi,and tomato bacterial wilt was a common disease in Tianyang and Tiandong,Baise.2.One hundred and ninety-five R.solanacearum strains were collected from twenty hosts in different geographic regions of Guangxi.Two strains(Pt07and Pt08,collected from potato)were identified as phylotype II by multiplex PCR,and the other 193 strains were identified as phylotype I.Based on the analysis of partial sequence of egl gene and mutS gene of R.solanacearum,the 195 isolates were divided into fifteen different sequevars(1,12,13,14,15,16,17,18,34,44,48,54,62,63 and 64),among which,sequevar 62,63 and 64 were new sequevars,sequevar 44 was the dominant sequevar.3.R.solanacearum strains were obtained from grafting chiehqua,towel gourd and balsam pear plants with bacterial wilt in Guangxi.The colonial,morphological,physiological and biochemical characteristics of these isolates were consistent with previous descriptions of R.solanacearum.Based on their pathogenicity to different hosts,the tested strains were determined to be race 1 and to infect many Cucurbitaceae plants.According to their carbohydrate utilization patterns,two strains from balsam pear belonged to biovar IV,other strains belonged to biovar Ⅲ.The results of this research indicated that bacterial wilt was widespread throughout Guangxi.Local R.solanacearum strains were almost phylotype I except that 2 strains isolated from potato were Phylotype Ⅱ.Sequevar 44 was the dominant sequevar in Guangxi.All of tested strains from Cucurbit plant belonged to race 1,and biovar Ⅲ was the dominant biovar.