VIRULENCE TO TOMATO OF IRANIAN ISOLATES OF RALSTONIA SOLANACEARUM
A. Safaie Farahani, S.M. Taghavi, M. Djavaheri
Four strains belonging to biovars 2A and 2T (N2) of Ralstonia solanacearum and two mutants impaired in extracellular polysaccharide (EPS) production were studied for their virulence to tomato, colonization of host tissue and survival in the soil. Mutants impaired in EPS biosynthesis were generated using a plasmid containing Tn5. Results showed that whereas biovar 2A is more virulent than 2T, they did not differ in the ability to survive in the soil. Susceptibility of various tomato cultivars to R. solanacearum strains was evaluated. Results showed that besides the bacterial biovar, the host cultivar is effective in determining disease severity. However, no significant differences were observed in bacterial populations from tomato cultivars with different susceptibility. Mutants defective for EPS production were less virulent than the wilde-type strain, highlighting the role of EPS in pathogenicity. No difference was observed in the colonization of tomato stems by either mutant impaired in EPS production and the wild-type.