Do detoxification enzymes enable generalism by Japanese beetles Popillia japonica Newman?

Japanese beetle, Popillia japonica Newman (Scarabaeidae) is one of the most polyphagous herbivores feeding on > 300 host plant species of agricultural and horticultural importance. It has been demonstrated that plants are chemically defended against insect herbivores by means of allelochemicals, whereas, cytochrome P450s, carboxylesterases (CoE) and glutathione S-transferases (GST) are major detoxification enzyme systems that mediate host utilization in insects by metabolizing host plant allelochemicals via their induction. The goal of this study was to determine detoxification enzymes systems in Japanese beetle by characterizing changes in activities of these detoxification enzymes in response to the feeding of Japanese beetle adults on hosts that vary in preference. In the experiments, adult Japanese beetles were fed preferred and non-preferred host plants in laboratory bioassays. The preferred host plants were foliage of Virginia creeper, crape myrtle, sassafras and rose flowers. Foliage from non-preferred hosts; river birch, red oak and boxelder, were used for comparison. Microsomes and cytosols were prepared from the gut tissue of Japanese beetle adults and used to determine the activities of the detoxification enzymes (P450, GST and CoE) using multiple substrates. Induction of different detoxification enzymes systems was presented and the relationship of the detoxification enzyme systems to the ecology and management of Japanese beetle was discussed.