Genotypic diversity in a localized population of Ralstonia solanacearum as revealed by random amplified polymorphic DNA markers

To assess genotypic diversity within Ralstonia solanacearum isolates of a single field. A total of 44 field isolates and 22 in vitro generated clones of R. solanacearum were studied for genotypic diversity by random amplified polymorphic DNA (RAPD) technique. Genomic DNA of these isolates and clones was extracted by proteinase-K-SDS lysis mini-prep method. RAPD analysis was done with 30 decamer primers. The data were analysed using NTSYSpc 2·02h software. Forty-two out of 44 field isolates and all the clonal isolates were identified as distict genotypes at 70% similarity level. Very high level of genome variability was observed within the field and clonal isolates of R. solanacearum. This might be a reason for the wide host range of this bacterium and for quick breakdown of wilt resistance in host plants. The results suggest that it would be difficult to design specific diagnostic protocol for R. solanacearum even for a localized population and to breed cultivars with broad-spectrum resistance.