Biotic and abiotic initiators for rishitin formation and accumulation in tomato

gamma-Ray irradiation of pre-sowing seeds of tomato did not trigger the formation of the phytoalexin `'rishitin'' in either leaves or fruits of tomato plants through different growth seasons. Application of copper sulfate initiated rishitin formation in both leaves and fruits. Increasing of gamma-ray dose was accompanied by decreasing rishitin accumulation in the presence of copper sulfate. Rishitin of tomato leaves was found to be reduced significantly, concomitant with increasing the disease incidence for late and early blight, and Fusarium wilt disease, after applying gamma-irradiation, in the case of biotic initiators Phytophthora infestans, Altenaria solani or Fusarium oxysporum alone or together with the abiotic inducer copper sulfate. Shelf-extending gamma-ray doses of 1.0, 1.5 and 2.0 kGy decreased rishitin amounts in tomato fruits treated with copper sulfate alone or infected with Phytophthora infestans. Also, the amount of formed rishitin was reduced by extending the storage period.