In vitro screening of bioantagonistic agents and plant extracts to control bacterial wilt (Ralstonia solanacearum) of tomato (Lycopersicon esculentum).

Field survey was undertaken in major tomato growing districts of the Karnataka and other states in Southern Part of India to isolate bacterial wilt pathogen Ralstonia solanacearum from wilted tomato plants and soil samples. A total of 100 isolates named as RS1-RS100 were subjected to cultural, morphological, biochemical and pathogenicity studies. Significant variations existed among the isolates with respect to rate, type of growth and colony colour. According to the pathogenicity tests conducted, around 57% of the isolates were found to be highly virulent. The population build up of the pathogen on the root system was found to have played an important role in relation to the pattern of occurrence of pathological wilting among tomato plants in the field. Bacteria with the same characteristics as those inoculated were re isolated from the infected plants, uninoculated plants remained healthy.