Gas-chromatography and electroantennogram analysis of saturated hydrocarbons of cruciferous host plants and host larval body extracts of Plutella xylostella for behavioural manipulation of Cotesia plutellae

摘要

Saturated hydrocarbons (SHE) of five cruciferous host plants viz., cabbage, cauliflower, broccoli, knol khol and Brussels sprout and the larvae of diamondback moth (DBM), Plutella xylostella reared on these host plants were identified through gas-chromatography. The hydrocarbon profile of host plants and larval body extract of DBM reared on respective host plants revealed a wide variation in quantity as well as quality. Long chain hydrocarbons C-26-C-30 were detected in all the extracts. In electroantennogram (EAG) studies, SHCs at 10(-3)g dose elicited differential EAG response in the antennal receptors of gravid Cotesia plutellae females. Tricosane (C-23) and hexacosane (C-26) elicited 10-fold increased EAG response compared to control stimulus. Long chain hydrocarbons C-27, C-28 and C-29 elicited, 6-7 fold increased responses. The sensitivity of antenna was 4-5 folds for C-25, C-14, C-24, C-15 and C-30, while the short chain hydrocarbons elicited 2-3 fold increased EAG responses. Dual choice flight orientation experiments in a wind tunnel revealed that the gravid C. plutellae females preferred the odour of C-16, C-26, C-29, C-15, C-21, C-23, C-30, C-27, C-24 and C-22 as 60-70% females oriented and landed on SHC treated substrate compared to control odour, while the odour of eicosane (C-20), pentacosane (C-75) and octacosane (C-28) were not preferred by the females.