Effect of Methanolic Extracts of Senna didymobotrya and Moringa oleifera on Growth of Ralstonia solanacearum

Tomato is one of the most important vegetables in the world. Ralstonia solanacearum causes a devastating bacterial wilt that is wide-spread throughout tropical environments that has been difficult to control with chemicals and African cultural practices in poor regions of the world. This study was initiated to determine the inhibitory effect of methanolic root extract of Senna didymobotrya and Moringa oleifera seed extracts on growth and development of R. solanacearum. The study was conducted both in the Laboratory and in the green house in Maseno from where S. didymobotrya and M. oleifera specimens used were collected from the University Botanic Garden, dried under shade for 30 days, before being ground into a fine powder. 1000 grams of the plant powder was later transferred into a conical flask and covered with 250mls of methanol. Filtration was done and the extracts concentrated. Ten diseased tomato plants showing bacterial wilt symptoms earlier collected from Maseno, Mariwa, Seme and Holo all within Kisumu county (Kenya) were cut to obtain plant sections (0.5–1cm) that were later plated onto Triphenyltetrazolium chloride media. Bacteriostatic activity of the extracts was determined by the disc diffusion method on Mueller Hinton agar. In vivo evaluations were conducted in a green house using tomato seedlings. Data collected was subjected to analysis of variance and means separated were compared using least significance difference (P≤ 0.05). Both plants extracts showed inhibitory activity against R. solanacearum pathogen (M. Oleifera; 8.5 and S. didymobotrya 9.2). Based on the outcome of this study, S. didymobotrya is recommended as a potential botanical agent suitable for future trials and use in the control of R. solanacerum by tomato farmers in Maseno region Kisumu county.