Profiling And Pathogenicity Of Ralstonia Solanacearum Disease Of Tomato And It’s Control Using Senna Didymobotrya And Moringa Oleifera Plant Extracts In Maseno (Kenya)

ABSTRACT

Tomato (Lycopersicon esculentum Mill) is one of the most popular vegetables in the world.Tomato and its products are rich in antioxidants and vitamins C, E and carotenoids. The world consumption of tomato has increased significantly. Despite its importance, its production is below full potential due to the effect of pests and diseases such as bacterial wilt. Bacterial wilt, caused by Ralstonia solanacearum is one of the most devastating, and wide-spread bacterial diseases of crops in tropical environments. The disease has limited both commercial and domestic level production of tomato in Maseno region. The disease is one leading cause of great annual losses of tomato globally. It has been difficult to control R. solanacearum with chemicals and cultural practices.There is lack of information on R. solanacearum strains in Maseno region, it’s pathogenicity on tomato plants and use of Botanicals for its management. Senna didymobotrya and Moringa oleifera plants were chosen because of their wide antimicrobial properties.The objectives the study were; To profile morphologically and biochemically Ralstonia solanacearum landraces and biovars from infected tomato plants in Maseno region; to determine the pathogenecity of R. solanacearum strains on tomato plants and to determine the inhibitory effect of Senna didymobotrya, root extract and Moringa oleifera seed extracts on the growth and development of R. solanacearum.These study was conducted at MasenoUniversity in the Department of Botany Laboratory and green house. Botanical specimens were collected from Maseno University Botanic Garden and dried under shade for 30 days. They were ground using a heavy duty laboratory mill into a fine powder. 1000 grams of the plant powder was transferred into a conical flask and 250mls methanol was added. Filtration was done and the extracts concentrated. Ten diseased tomato plants from Maseno, Mariwa, Seme and Hollo were collected. The plant sections (0.5–1cm) were then plated onto Triphenyl tetrazolium chloride media. Profilling of the pathogen was done morphologicaly, biochemically and races were determined by pathogenicity test on wide host range. Bacterialstatic 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. The experimental design was completely randomized design. The data collected was subjected to analysis of variance. All the isolates had fluidal pinkish red centered colonies on Triphenyl tetrazolium chloride media, they were Gram negative, potassium hydroxide solubility positive, produced gas from glucose, ooze test positive and did not hydrolyse starch which is typical of R. solanacerum. R. solanacearum strains from infected tomato plants in Maseno region were Maseno, Seme and Holo isolates belonged to race3 bioviar III while Mariwa isolate belonged to race 3 biovar 1. All isolates were pathogenic on tomato plants. Both plants extracts had inhibitory activity against R. solanacearum pathogen but they had significant difference for the mean widths of clear zones (M. Oleifera; Maseno-8.8, Mariwa-7.9, Seme-7.8, Hollo-9.55 and S. didymobotrya; Maseno-8.7, Mariwa-8.8, Seme-8.5, Hollo-10.8). Virulence of an isolate can be determined on the basis of colony colour on TZC media. Production of gas may be attributed to the presence of enzyme systems in bacteria. Variation in restricting disease progression between S. didymobotria and M.oleifera might be due to difference in chemical compositions of the extracts, membrane permeability of the target pathogen, difference in efficacy and durability of extracts in the soil. Botanicals decrease the negative impact of the pathogen.The two plant extracts suppressed bacteria wilt incidence at 15% and had evident control activity against R. solanacearum but S. didymobotrya which performed better than M. oleifera was recommended for further studies inorder to determine cost benefit analysis before actual production as potential botanical agent for control of R. solanacerum by tomato farmers in Maseno region.