EFFECT OF SESAME LEAF DIET ONDETOXIFICATION ACTIVITIES OFINSECTS WITH DIFFERENT FEEDINGBEHAVIOR

摘要

Three diverse insects, a polyphagous “leaf chewer” (Atractomorpha lata), apolyphagous “sap feeder” (Myzus persicae), and a “restrictive feeder”(Plutella xylostella) responded differently when fed with eight cultivars ofsesame either as whole leaf or via artificial diet. There was limited or nocorrelation in induction between detoxifying enzyme substrates (esterase,glutathione s-transferase [GST], and mixed function oxidase [MFO]activities) when activity toward various substrates α-naphthyl acetate,1-chloro-2,4-dinitrobenzene, 1,2-dichloro-4-nitrobenzene, andp-nitroanisole (pNA), were compared although they were generally elevatedin the tissues from insects on sesame than a reference fed with radishseedlings. In A. lata, esterase activity for the cultivar 11Pusan and 45Laoswere three-fold higher compared to the reference, while other cultivars,24Nanbu-twasaki and 56S-radiatum were—two- to three-fold lower thanthe reference. In M. persicae, the esterase activity was as much as five-foldhigher than the reference in one test cultivar. GST activities of the sesamecultivars were generally higher (≈two-fold) than the reference in all insectsand at variable ratios among the cultivars. The MFO activity toward pNAin grasshoppers feeding on these sesame cultivars was either highlyexpressed or nonexistent. These results indicate that although the cultivarsbelong to the same species, they might have undergone changes in secondary phytochemicals in response to varying biogeographical distribution. Eachinsect species is suspected to target a specific plant chemicalburden that it tries to overcome in each cultivar through enzyme activation.