Strawberry foliage headspace vapor components at periods of susceptibility and resistance toTetranychus urticae Koch

Abstract

Headspace components from strawberry foliage have been isolated by nitrogen entrainment and Tenax trapping. Traps were eluted with hexane, and components were analyzed by gas chromatography-mass spectrometry. Fifteen compounds were identified by comparison with authentic standards,trans-2-hexenal, 1-hexanol,trans-2-hexen-1-ol,cis-3-hexen-1-ol, hexyl acetate,cis-3-hexenyl acetate, 6-methyl-5-hepten-2-ol, 1-octanol, 1-octen-3-ol, linalool, α-terpineol, methyl salicylate, ethyl saiicylate, benzyl alcohol, and 2-phenylethanol. The relative amounts of these components were compared at flowering and after fruit harvest when plants were more resistant to the two-spotted spider mite,Tetranychus urticae Koch. The predominant components,cis-3-hexen-1-ol and its acetate, did not change markedly between the sampling periods, but methyl salicylate increased approximately 10-fold after fruit harvest. Methyl salicylate at low concentrations under bioassay conditions did not affect mite behavior. The biosynthetic relationship of this compound to other phenols which have been implicated in plant resistance is discussed.