VOLATILE COMPOUNDS FROM MEDICAGO SPP AS POTENTIAL SIGNALS FOR ALFALFAWEEVIL RESPONSE

Alfalfa weevils (AW), Hypera postica (Gyllenhal), are important pests of alfalfa, Medicago sativa L. Although no resistant cultivars exist, certain wild Medicago species with erect glandular hairs impart repell ency to AW. It is felt that leaf and stem volatile compounds work in c onjunction with trichomes to produce antixenosis. Our study isolated a nd tentatively identified volatile compound differences among four alf alfa cultivars and three wild Medicago species using supercritical flu id extraction (SFE) followed by gas chromatography-mass spectrometry. Ninety-six volatile compounds present in the leaves and stems of at le ast one of the entries were observed. Of these, 17 were unique to the wild species. Three unique compounds, 1-methyl-4-(1-methylethyl)cycloh exanol, (Z)-geraniol, and hexahydrofarnesol are particularly interesti ng because of their similarity to known insect pheromones. Knowledge o f Medicago species volatile compounds should provide a nascent foundat ion for the pursuit of AW antixenosis.