National Center for Agricultural Research (CNRA), Vegetable and Protein, Research Program, Food Crops Research Station, 01 BP 633 Bouaké 01, Côte d’Ivoire
The watershed of the central lake system of the city of Yamoussoukro in Côte d’Ivoire is subject to various forms of pollution. Ralstonia solanacearum (R. solanacearum), responsible for bacterial wilt of tomato (Solanum lycopersicum; 2n=2X=24Chr.), persists in market garden environments and causes tomato yield losses of up to 100%. The aim of this study was to assess the genetic diversity of R. solanacearum, its impact on tomato cultivation in Yamoussoukro, and to obtain genotypes of Solanum lycopersicum resistant to R. solanacearum. Samples of water, soil and wilted tomato plants was collected from June 2022 to August 2023, at six growing sites around three selected lakes. R. solanacearum was isolated on SMSA medium and confirmed by PCR. Genetic diversity of strains was assessed by rep-PCR. Biovar, race and pathogenicity tests were used to assess the virulence levels of strains at each site studied, and to select tomato plants potentially resistant to R. solanacearum. The results showed a significant variation in the incidence and severity of bacterial wilt from one site to another. The 63 R. solanacearum strains isolated and confirmed by PCR belonged mainly to biovar 3 and race 1. Phylogenetic analysis of R. solanacearum showed three distinct groups with around 70% similarity. Two groups was made up solely of strains from Lake E. A single group included all strains from all lakes. Strains from the LacE-Ch2 site showed a particularly high aggressiveness of 88%. Of the 42 tomato cultivars tested in the greenhouse, three showed no symptoms of bacterial wilt.