Olfactory Responses of Gravid Melon Fly Females and Bactrocera cucurbitae (Coquillett) to Selected Cucurbitaceous Fruit Volatiles

摘要

The present study investigates olfactory responses of gravid females to selected cucurbitaceous host fruit volatiles viz., ridge gourd (Luffa acutangula L.), cucumber (Cucumis sativus L.), bitter gourd (Momordica charantia L.) and snake gourd {Trichosanthes cucumerina L.) at different phenological fruiting stages viz., mature (10 days prior to harvest) and immature (10 days after fruit set) fruits. Olfactometer assays revealed that mature fruit volatiles elicited positive behavioural responses compared to immature fruit volatiles across the hosts. Further, multiple choice assays with mature fruit volatiles revealed significant (P < 0.0001) positive behavioural response by female flies to ridge gourd followed by snake gourd, cucumber and bitter gourd. The gas chromatography coupled mass spectrometry (GCMS) analysis of host fruit volatile samples showed varied volatile organic compounds across the host fruits and also between fruit phenological stages. Principal Component Analysis of volatile compounds revealed that chemical cues like beta-cis-ocimene, ethyl-benzaldehyde, ethanone, l-(4-ethyl phenyl), p-diacetylbenzene and 2,4-dimethylacetophenone were responsible for the major variation among the volatile profiles of host fruits. Further, electroantennogram (EAG) studies indicated significant (P< 0.0001) antennal response to ridge gourd fruit volatiles followed by snake gourd, cucumber and bitter gourd.