Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Abstract Only
Publication Acceptance Date: 1/9/1997
Publication Date: N/A
Technical Abstract: Phytoalexins are an essential component in the disease response of cotton to fungal wilt pathogens. The speed of response and the potency of the phytoalexins are critical elements that determine the success of the resistance response. Modern Acala cottons have reached a level of resistance comparable to the most resistant Gossypium barbadense variety. Significant improvements in resistance can probably be achieved only by introducing more potent phytoalexins from other plants. Kenaf, a species in the Malvaceae, could provide such compounds. It exhibits a very high level of resistance to Verticillium wilt, and produces a phytoalexin, hibiscanone (3,8-Dimethyl-1,2- naphthoquinone), which is several times more toxic to the wilt pathogens than any of the phytoalexins produced by cotton. We found Verticillium dahliae reduces hibiscanone to the hydroquinone (1,2-dihydroxy-3,8-dimethylnaphthalene). Under our bioassay conditions, the hydroquinone at a concentration of 40 ug/ml did not kill V. dahliae conidia, whereas hibiscanone kills all conidia.