Elicitation of Ethylene by Verticillium albo-atrum Phytotoxins in Potato

Petioles from a susceptible cultivar (De´ sire`e) of Solanum tuberosum treated with a low-molecular mass toxin, separated from culture fluid of Verticillium albo-atrum, produced greater quantities of ethylene than did petioles of a tolerant cultivar (Home Guard). Pretreatment of leaflets from cv. De´ sire`e with silver thiosulphite, which inhibits perception of ethylene, prevented the chlorosis and necrosis normally associated with exposure to the toxin. Similarly, application of aminoethoxyvinylglycine (AVG) an inhibitor of aminocyclopropane- 1-carboxylic acid (ACC) synthase, to petioles of cv. De´ sire`e reduced toxin-induced ethylene synthesis and symptom development. The data indicate that, in part, Verticillium-toxin acts through induction of ethylene biosynthesis in the host tissues, and different responses of susceptible and tolerant potato cultivars to V. albo-atrum are the result of differential production of ethylene.