Isolation and Characterization of Ralstonia Solanacearum from Infected Tomato Plants of Soan Skesar Valley of Punjab

The most devastating disease of tomato is bacterial wilt (BW) caused by Ralstonia solanacearum which occur in hot and humid areas of Pakistan. Control of bacterial wilt is difficult, because the pathogen is soil-borne and has a wide host range. There is a need to establish resistance against this pathogen through biotechnological approaches. As a first step, infected tomato leaf samples were collected from various parts of soan skesar valley of Punjab, Pakistan. Isolations were performed on triphenyl tetrazolium salt (TTC) medium. Five samples, each of ten plants, from seven fields were used for isolation. Bacteria with similar characteristics were isolated from all positive samples which produced fluidal colonies that were either entirely white or white with red centre after incubation for 48 hours at 28C on TTC medium. They were found positive for gram staining, KOH test, Kovacs oxidase test, Catalase test, Oxidation/fermentation of glucose, Hydrolysis of tween 80 and negative for Arginine dihydrolase, Levan production, Salt tolerance, Lecithinase detection, Gelatin hydrolysis and production of Fluorescent pigment. Wilting and necrosis were observed for pathogenicity test and chlorosis/necrosis was observed for hypersensitivity. Isolates were identified as Ralstonia Solanacearum. . Out of 10 diseased plants, 7 were found positive and 3 were negative.