Genetic Diversity and Pathogenicity of Ralstonia solanacearum Causing Tobacco Bacterial Wilt in China

Abstract

Bacterial wilt caused by Ralstonia solanacearum is the most serious soilborne disease of tobacco (Nicotiana tabacum) in China. In this study, 89 strains were collected in 2012 to 2014 from across the four major tobacco-growing areas in China. The strains were identified as phylotype I by multiplex polymerase chain reaction and further divided into seven sequevars based on polymorphisms in the endoglucanase (egl) gene. Among the seven sequevars, four (15, 17, 34, and 44) have been previously described as pathogens of tobacco and two (13 and 14), which are reported here on tobacco, were previously found only on other plants. In addition, a new sequevar named 54 was identified. Strains from tobacco from different regions showed different levels of genetic diversity based on partial egl gene sequences. The farther north the distribution, the lower the gene diversity found. Pathogenicity of 27 representative strains was assessed by inoculation onto three tobacco cultivars of varying susceptibility. Through cluster analysis of area under the disease progress curve values, the 27 strains were classified into different pathotypes based on virulence; however, no obvious associations were found between sequevar and pathotype. These results will assist in determining geographical distribution of strains, and provide the foundation for breeding and integrated management programs in China.

The sequevar distribution of Ralstonia solanacearum in tobacco-growing zones of China is structured by elevation

“…contained sequevar 17, 44, 54 and 55. It was surprising that the sequevar 54 (reported on tobacco R. solanacearum strains recently) (Li et al 2016) and the new sequevar 55 were only found in areas with moderate to high elevations. The new sequevar may gather R.solanacearum strains evolving to adapt to the high elevations environment.…”

“…1). Among the eight sequevars, sequevar 13,14,15,17,34,44, and 54 had been reported in Chinese tobacco R. solanacearum strains by Li et al (2016), and sequevar 55, the new one, has not been previously described. The new sequevar may be an evidence that verified the ongoing evolutionary of phylotype I.…”

“…Sequevar 44 (group F), with reference strain Bd11 (Xu et al 2009), was distributed in Z1, Z2, and Z3. Sequevar 54 (group G), containing reference strain HBJS1 (Li et al 2016), was identified in Z1 and Z2. Sequevar 34 (group E), with reference strain PSS219 (Xu et al 2009), was found in Z1 and Z3.…”

“…Based on this information, Chinese R. solanacearum strains isolated from Nicotiana tabacum are suitable candidates for studying the relationship between the elevation and genetic structures of R. solanacearum. Li et al (2016) have reported the genetic diversity of Chinese tobacco R. solanacearum, but they did not explain the relationship between genetic structure and elevation. The aims of this study were to analyze: i) genetic diversity of R. solanacearum strains collected from all tobacco-growing zones in China, and ii) whether elevation affects phylogenetic diversity in China.…”

Técnicas para el aislamiento, identificación y caracterización molecular de cepas de Ralstonia solanacearum relacionadas a Moko del plátano

“…Los filotipos se subdividen en secuevares, los cuales están basados en la secuencia nucleotídica del gen Egl, que codifica para una endoglucanasa (Fegan y Prior, 2005). Hasta el momento, se han identificado 54 secuevares en el complejo de R. solanacearum (Li et al, 2016); los secuevares causantes de la enfermedad Moko en plátano son el 3, 4, 6, 24, 25, 41 y 53. En el continente americano la enfermedad Moko está presente desde Brasil hasta Estado Unidos (Sanchez-Perez et al, 2008;Norman et al, 2009;Hong et al, 2012;Albuquerque et al, 2014).…”