DISTRIBUTION OF RESISTANCE TO COPPER, ZINC AND STREPTOMYCIN IN XANTHOMONAS-CAMPESTRIS PV VESICATORIA (DOIDGE) DYE IN INDIA AND ITS IMPACT ON CONTROL OF BACTERIAL SPOT OF TOMATO

Isolates of Xanthomonas campestris pv. vesicatoria, causal organism of Bacterial Spot of tomato, showed a widespread presence of resistance to copper and zinc. Isolates differed in their levels of resistance to these bactericides. Few isolates with high resistance to copper and z inc also showed resistance to streptomycin. An effort to control Bacte rial Spot on tomato incited by isolates with differing levels of resis tance showed copper oxychloride in combination with mancozeb, mancozeb alone or streptomycin sulphate to be effective in controlling X c. pv . vesicatoria isolates with lower levels of resistance. Isolates with higher levels of resistance could not be controlled with any of the ch emicals or their combinations used in the studies. A study on persiste nce of resistance to bactericides on storage in vitro revealed that lo wer levels of resistance were maintained over a long time, however the higher levels declined and stabilized at the lowest level of resistan ce in the absence of bactericides.