Herbicide-induced resistance of cotton to Verticillium wilt disease and activation of host cells to produce the phytoalexin gossypol

Abstract

Pretreating cotton seeds with selected herbicide markedly increased cotton resistance to vascular wilt caused by Verticillium albo-atrum. The present investigation studied the mechanism of resistance to V. albo-atrum induced by some herbicides in susceptible cotton plants. The three herbicides tested repressed mycelial growth. Prometryn and dalapon caused a marked reduction in the appearance of Verticillium wilt disease and were the most effective in controlling the disease. Phytoalexin (gossypol) production was greatly increased in herbicide-treated inoculated cotton plants. The level of gossypol was higher in the root than stem. Maximum production of gossypol was achieved in cotton plants treated with the herbicides prometryn and dalapon and inoculated with fungal spores but it was not present in uninoculated control plants. Key words: cotton, Verticillium albo-atrum, herbicides, phytoalexin, disease resistance.