METHYL JASMONATE EXPOSURE INDUCES INSECT RESISTANCE IN CABBAGE AND TOBACCO

The effect of methyl jasmonate treatment of 2 plant species (cabbage a nd tobacco) on the feeding of their corresponding lepidopteran pests w as studied. Treatment of cabbage and tobacco plants with methyl jasmon ate increased lipoxygenase activity in the leaf tissues. Reduced feedi ng of lepidopteran larvae was observed in choice test experiments with cabbage loopers and tobacco hornworms. Similar results were obtained for the feeding of both pests on detached methyl jasmonate-treated lea ves. Treatment of tobacco plants with methyl jasmonate had no effect o n hatching of hornworm eggs but inhibited larval development after hat ching. Application of methyl jasmonate to detached leaves in petri fee ding of tobacco hornworms. Methyl jasmonate is known to increase lipox ygenase activity in several plant species and cause elevated productio n of volatile aldehydes that increased after treatment of plants with methyl jasmonate (hexanal and E-2-hexenal) inhibited feeding of tobacc o hornworms on detached tobacco leaves. No effect was observed on larv al development and pupation of either cabbage loopers or tobacco hornw orms when methyl jasmonate was applied to artificial diet. Cabbage loo per larvae whose feeding was inhibited on leaves from methyl jasmonate -treated plants were transferred to an artificial diet along with larv ae that fed on the leaves from control plants, There was no effect obs erved on the subsequent development of either larval group. This study demonstrates that inhibition of lepidopteran larval feeding is not ca used by the direct effect of methyl jasmonate, but rather to altered m etabolism in the plant tissues.