Aggressiveness and genetic diversity of Ralstonia solanacearum strains from tomato in Vietnam

摘要

In Vietnam, bacterial wilt, caused by R. solanacearum , is a major threat to many important field crops. Disease management strategies suggested in the past have remained ineffective. Phylotype analysis and genetic diversity among Vietnamese R. solanacearum is unknown. The present study was conducted to investigate the relationship among isolates of R. solanacearum in the tomato production areas in Vietnam, to analyze genotypic characteristics, to characterize the phylotypes of the isolates and to determine their aggressiveness. All 207 R. solanacearum strains collected from tomato plants in 12 provinces in Vietnam belonged to Asian Phylotype I. All isolates belong to biovar 3, except for isolate Rs86 collected from Ninh Thuan, which belonged to biovar 4. A total of 52 isolates representing 12 origins (provinces) and two Taiwanese strains were selected to investigate genetic diversity and their genetic relationship by using RAPD markers. Based on the unweighted pair group method of arithmetic means endrogram and STRUCTURE results, 54 isolates were grouped into three main clusters. Cluster I includes 3 isolates obtained from Lam Dong province and 1 isolate collected from Tien Giang province. Cluster II had wide distribution from the northern to the southern part of Vietnam. This cluster could be divided into 3 sub-clusters and these sub-clusters were largely separated according to geographical distribution. Sub-cluster IIa consisted of five isolates from Lam Dong province. One isolate from Thai Binh and two isolates from Hai Duong grouped in sub-cluster IIb. Cluster IIc was found only in Hai Phong. Cluster III had highest variation with two sub-clusters. Eight isolates from Southern part, 5 isolates from Nghe An and 2 reference isolates from Taiwan were grouped in sub-cluster IIIa, while 14 isolates mainly from Northern part (Ha Noi, Nam Dinh, and Thai Binh) were grouped in sub-cluster IIIb. Isolates collected in Hai Duong, Hai Phong and Nam Dinh showed higher virulence than those on tomato. The results demonstrated that R. solanacearum isolates even though similar in genetic background do not necessarily cause similar virulence. This is the first report on genetic diversity and aggressiveness of Vietnamese R. solanacearum isolates in tomatoes.