DNA Analysis of Ralstonia solanacearum Based on 270-bp PCR-amplified Fragment from the Lowlands and Highlands of Kenya

Aims: Bacterial wilt, caused by Ralstonia solanacearum, is a devastating disease resulting in tremendous losses of economic crops such as plants in the Solanaceae. Studies have shown that R. solanacearum is spreading from the lowlands to the highlands. This has seen increased need for understanding the genetic diversity of R. solanacerum strains common in these areas as a basis for better strategies in their control.

Methodology: Sixty-nine bacteria isolates obtained from various wilting plant hosts (Tomato, capsicum and potato) from 11 different sites in Nyeri, Nyahururu, Kirinyaga, Kiambu, Nakuru Murang’a and Embu were subjected to molecular analysis.

Results: All the bacteria isolates were confirmed to be R. solacearum following PCR amplification of about 270-bp fragment using specific primers OLI 1-F and Y2-R. Based on the targeted 16 S rDNA sequences using primers OLI 1 and Y2, the 69 bacteria isolates had 98 to 100% identity with other DNA sequences for R. solanacearum isolates deposited in the NCBI database. Analysis of genetic differentiation showed there were total of 26 haplotypes from the 11 studied populations. The total number of segregating sites in all populations was 225.

Conclusion: Through this study, it was realized that the main causative agent of bacterial wilt in potatoes, tomatoes and capsicum grown in the lowland and highland regions in Kenya is R. solanacearum. The isolates are in two main groups (Cluster A and B) that represent mainly the phylotypes I and II respectively.