ABSTRACT
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.
ABSTRACT
The present study aimed at investigating the susceptibility of the microorganisms Pseudomonas aeruginosa, Salmonella typhi, Escherichia coli, Staphylococcus aureus, and Bacillus subtilis to ethanolic extracts of propolis (EEP) from three regions of Kenya (Taita, Tana and Samburu). Propolis was extracted using four different concentrations of ethanol: pure, 70 percent, 50 percent, and 30 percent. Ethanol (70 percent) and Streptomycin were used as controls. The agar diffusion method using filter paper disks was employed. Antibacterial activity was determined as an equivalent of the inhibition zones diameters (in millimeters) after incubation at 37°C for 24h. Significant differences in the antibacterial activities of propolis were observed among the three regions, depending on the test microorganisms and on the procedure used for the preparation of propolis extract. Bacillus subtilis and Staphylococcus aureus were the most susceptible bacteria and 70 percent EEP had the best antibacterial effect.(AU)