IDENTIFICATION AND BIOASSAY OF KAIROMONES FOR HELICOVERPA TEA

Hexane extracts of leaves of 307 accessions from 73 host plant species of Helicoverpa tea were analyzed by gas chromatography (GC) and used for H. tea oviposition and neonate larvae orientation bioassays. The g as chromatographic (GC) retention times of compounds statistically ass ociated with behavioral activity were identified by correlation of GC peak area with oviposition and larval orientation preferences. Althoug h taxonomically diverse in their origin, compounds for study were puri fied from extracts of species of the genus Lycopersicon, due to their relative abundance. The structures of eight long-chain alkanes associa ted with oviposition preference were assigned by mass spectrometry, an d the structures of five similarly associated organic acids and a terp enoid alkene were identified by H-1 and C-13 nuclear magnetic resonanc e spectroscopy. The structures of a number of other phytochemicals fro m the plant leaves were identified for comparative purposes, including a previously unknown terpene, 7-epizingiberene. Bioassays were perfor med on the isolated acids and on the alkane wax fractions of several L ycopersicon species, and significant differences were found in oviposi tion stimulation for both classes of compounds. Of the hundreds of com pounds found in the extracts, none were observed to act as oviposition deterrents. The results of these bioassays may be useful in explainin g the broad host range of H. tea, as well as the process and evolution of host plant selection for oviposition.