Methyl jasmonate exposure induces insect resistance in cabbage and tobacco

The effect of methyl jasmonate treatment of 2 plant species (cabbage and tobacco) on the feeding of their corresponding lepidopteran pests was studied. Treatment of cabbage and tobacco plants with methyl jasmonate increased lipoxygenase activity in the leaf tissues. Reduced feeding 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 leaves. Treatment of tobacco plants with methyl jasmonate had no effect on hatching of hornworm eggs but inhibited larval development after hatching. Application of methyl jasmonate to detached leaves in petri feeding of tobacco hornworms. Methyl jasmonate is known to increase lipoxygenase activity in several plant species and cause elevated production of volatile aldehydes that increased after treatment of plants with methyl jasmonate (hexanal and E-2-hexenal) inhibited feeding of tobacco hornworms on detached tobacco leaves. No effect was observed on larval development and pupation of either cabbage loopers or tobacco hornworms when methyl jasmonate was applied to artificial diet. Cabbage looper larvae whose feeding was inhibited on leaves from methyl jasmonate-treated plants were transferred to an artificial diet along with larvae that fed on the leaves from control plants, There was no effect observed on the subsequent development of either larval group. This study demonstrates that inhibition of lepidopteran larval feeding is not caused by the direct effect of methyl jasmonate, but rather to altered metabolism in the plant tissues.