Trichome Secretion Composition, Trichome Densities, and Spider Mite Resistance of Ten Accessions of Lycopersicon hirsutum

Trichome secretion composition, glandular trichome densities, and spider mite resistance were measured for 10 accessions of Lycopersicon hirsutum Humb. & Bonpl., a wild, South American relative of tomato exhibiting high arthropod resistance. The sesquiterpene hydrocarbons zingiberene and γ-elemene were identified as major volatile components of Type VI trichome secretions from L. hirsutum f. typicum (hir) plant introduction (PI) 251303. These compounds predominated trichome secretions from five other hir accessions, whereas the methyl ketones 2-undecanone and 2-tridecanone predominated trichome secretions from five accessions of L. hirsutum f. glabratum (gla) . Type IV trichome densities were greater on gla than on hir accessions, whereas Type VI trichome densities were greater on hir than on gla. Type VI trichome densities were greater on plants cultured under a 14- to 15-hr photoperiod (LD) than on plants cultured under an 8-hr photoperiod (SD) for gla , but not hir , accessions. Type IV trichome densities were greater under SD than under LD conditions for all accessions. In general, hir accessions were more resistant to mites ( Tetranychus urticae Koch) than gla accessions. Spider mite resistance was correlated with Type IV trichome density on hir , but not on gla , accessions. Differences in Type IV trichome densities alone between hir and gla do not explain the greater mite resistance of hir accessions.