Repellency to two-spotted spider mite,Tetranychus urticae Koch, as related to leaf surface chemistry ofLycopersicon hirsutum accessions

Abstract

Bioassays employingTetranychus urticae Koch were used to examine repellency of leaves and trichome secretions of one cultivar of tomato,Lycopersicon esculentum, and 11 accessions ofL. hirsutum consisting of seven accessions ofL. hirsutum f.typicum and four accessions ofL. hirsutum f.glabratum. Leaves of f.typicum were more repellent to mites than were those of f.glabratum orL. esculentum. Removal of trichomes and their secretions by wiping leaves of f.typicum accessions with 95% ethanol rendered them less repellent, indicating that trichomes or their secretions were potentially responsible for repellency. Gas and thin-layer chromatography of leaflet washes obtained by steeping leaflets in hexane indicated that the chemical composition of the washes differed among accessions. The main difference between botanical forms was the presence in leaflet washes from f.typicum accessions of compounds eluting late on the gas Chromatograph and migrating further on reverse-phase thin-layer chromatography; compounds having these characteristics were absent in washes of f.glabratum andL. esculentum. The compositions of secretions taken directly from type I, type IV, and type VI trichomes were similar to that of the leaflet wash obtained from the same f.typicum plant, indicating that leaflet washes contained mainly compounds of trichomal origin. Leaflet washes from f.typicum plants were generally more repellent toT. urticae than were washes from f.glabratum when tested by choice and nonchoice bioassays. Taken together, the data indicate that trichome secretions of f.typicum are likely responsible for potent repellency to two-spotted spider mites observed in this taxon; the likely active compounds are sesquiterpene acids or other polar constituents of trichome secretions.

Resistance to the two-spotted spider mite (Tetranychus urticae) by acylsucroses of wild tomato (Solanum pimpinellifolium) trichomes studied in a recombinant inbred line population

“…Lycopersicon hirsutum Dunal) and S. pennellii Correll], allelochemicals produced by glandular trichomes are known to severely hamper feeding and reproduction of many arthropod pests. Type IV and VI glandular trichomes of some accessions of S. habrochaites produce the sesquiterpene zingiberene that confers resistance to the tobacco spider mite (Tetranychus evansi Baker and Pritchard) (Maluf et al 2001), the two-spotted spider mite (Guo et al 1993), the cotton whiteXy [Bemisia tabaci (Gennadius)] (Freitas et al 2002), and the South American tomato pinworm [Tuta absoluta (Meyrick)] (de Azevedo et al 2003). Type VI trichomes of S. habrochaites f. glabratum C.H.…”

Genetic mapping of two QTL from the wild tomato Solanum pimpinellifolium L. controlling resistance against two-spotted spider mite (Tetranychus urticae Koch)

“…(Carter and Snyder 1985;Chatzivasileiadis and Sabelis 1997). The density of type IV and VI glandular trichomes and the presence of volatile compounds in trichome gland secretions have been described as factors mediating this resistance in some accessions of S. habrochaites (Guo et al 1993) and S. pennellii (Blauth et al 1998;Maluf et al 2010;Saeidi et al 2007). Unfortunately, crosses between cultivated tomato and these wild relatives often result in a progeny bearing many undesirable traits inherited from the wild parent, such as small and hairy-green fruits and the presence of trichomes other than those conferring resistance.…”

Assays for the effects of volatile compounds from artificially damaged cotyledons of subterranean clover on the redlegged earth mite, Halotydeus destructor

“…Methods for testing volatile compounds released from non-damaged plant tissues or from surfaces of plant tissues resistant to tetranychid mites have been described (Guo et al, 1994). The volatile compounds in these cases are present as a vapour and mainly affect the olfactory systems of the mites.…”