Isolation and Characterisation of Ralstonia Solanacearum Strains of Tomato Wilt Disease from Maseno, Kenya

Ralstonia solanacearum (E.F. Smith) Yabuuchi, is the cause of bacterial wilt of tomato and one of the most severe pathogens of solanaceous crops with a very wide host range. There is little information on R. solanacearum strains in Maseno region in Kenya despite the fact that bacterial wilt of tomato is of economic importance. The objective of this study was to isolate the strains of R. solanacearum of tomato and characterize morphologically and biochemically Ralstonia solanacearum races and biovars from infected tomato plants in Maseno region. This study was conducted at Maseno University in the Department of Botany at Microbiology Laboratory. Ten diseased tomato plants from Maseno, Mariwa, Seme and Hollo were collected and cut into small sections (0.5–1cm). The plant sections were then plated onto Triphenyl tetrazolium chloride (TZC) media. Profiling of the pathogen was done morphologicaly using culture techniques; biochemical tests included Gram staining test, Potassium hydroxide test, Catalase oxidase test, Gas production test, Starch hydrolysis test and sugar utilization test. The races were then identified by pathogenicity test on wide host range. All the isolates had fluidal pinkish red centered colonies on TZC 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 race 3 biovar 1 and race 3 biovar 3. All isolates were pathogenic on tomato plants.