Objective  Isolating and identifying Ralstonia solanacearum strains from tomato plants in the Southern of Jiangxi Province, and clarifying the bacterial differentiation can lay the foundation for local tomato bacterial wilt resistance breeding and disease control.

Method  The diseased tomato plants were collected from the south of Jiangxi Province, R. solanacearum strains with different geographical origins were isolated by selective plate, purificated and identificated by PCR. The test of physiology and biochemistry and inoculation on tomato plants were conducted for the determination of biovar and virulence difference. The endoglucanase gene (egl) fragments were amplified by PCR to determine the phylotype and sequevar of R. solanacearum.

Result  A total of 44 R. solanacearum strains were obtained from nine cities (counties) in the south of Jiangxi Province, among which 41 strains were identified as biovar III and three strains were identified as biovar IV. According to the results of virulence difference, 44 strains were clustered into three groups, namely group I (high virulence), group II (moderate virulence) and group III (weak virulence), of which group I (high virulence) strains accounted for 65.9%. All strains were belonged to the phylotype I and further divided into eight sequevars, namely Sequevar 13, 14, 15, 17, 18, 34, 44 and 48 respeclively. Most R. solanacearum strains were sensitive to the eight tested bacteriophages.

Conclusion  The strains of R. solanacearum from tomato in the south of Jiangxi Province are mainly biovar III and high virulence, sensitive to bacteriophages, have eight sequevars, and have obvious differentiation and genetic diversity.