Diversity of Ralstonia solanacerum Strains in Solanaceous Crops Production Regions of Central Kenya

Aims: Bacterial wilt disease is a very serious yield limiting problem in crops in the solanaceae family grown in regions of Kenya. The very much encouraged field sanitation and use of clean planting materials have been inadequate in combating this challenge. This has seen increased need for understanding the genetic and biochemical diversity of Rastonia solanacerum stains common to these areas as a basis for better strategies in their control.

Methodology: A field survey accompanied by samples collection was conducted covering: Nyeri, Nyahururu, Kirinyaga, Kiambu, Nakuru Murang’a and Embu Counties exclusively for solanaceae crop farms. Purposeful sampling was employed.

Results: A total of 160 samples of bacterial wilt symptomatic plants were collected, 120 isolates were confirmed as R. solanacearum using biochemical tests. They were further subjected to biovar tests using sugars and alcohols, (Cellobiose, Lactose, Maltose, D-Ribose, Salacin, Dulcitol, Mannitol, Trehalose and Sorbitol). Dextrose and Salacin were used as positive controls while sterile distilled water was used as negative control respectively. The results enabled mapping of R. solanacearum biovar in these regions. Biovar 2 was the most prevalent in the study area with biovar 2T showing high prevalence in both highlands and lowlands; biovar 2A was common in lowlands. Other biovars identified were 1 and 3.

Conclusion: This survey findings indicated that R. solanacerum, biovars present in Kenyan Highlands and Lowlands included biovars 1, 2 and 3. These biovars are highly pathogenic on solanaceae crops throughout the world. The findings of the present study will be useful for designing the study of the population structures of R. solanacearum using the molecular approaches with special emphasis on its integrated management.