Assessment of resistance to bacterial wilt incited by Ralstonia solanacearum in tomato germplasm

Bacterial wilt incited by Ralstonia solanacearum has been found the most damaging and widespread diseases of tomato throughout the world and causes heavy yield losses. Management of the disease is mainly relied on chemicals, and their use is fraught with health risks. The hazardous effects of pesticides can be dispensed with using non-chemical strategies, and resistant cultivars can prove a promising alternative. In the present study, 30 tomato cultivars were assessed for their resistance to bacterial wilt. None of the cultivars was immune or highly resistant to R. solanacearum. Two cultivars Early King and Lerica were found resistant (R), and four viz. Red Hero, Giant Cluster, Red Ruby and Red Stone showed moderately resistant (MR) reaction. Eleven cultivars each appeared as moderately susceptible and susceptible, while two cultivars (Bonny Best and Roma VF) were assessed as highly susceptible (HS) to the bacterium. In HS cultivars, symptoms appeared 4 days after inoculation. The symptoms were first observed on leaves and then progressed toward other parts of plants resulting in complete wilting in susceptible cultivars within 14 days. Brown discoloration in vascular systems of transversely cut parts of HS plants was also observed. On the other hand, in R and MR cultivars, symptoms appeared on leaves followed by chlorosis and no wilting was observed even after 14 days of inoculation. The R and MR cultivars are therefore recommended for cultivation under integrated production systems and in developing new resistant tomato cultivars.