نامه انجمن حشرهشناسی ایران (Feb 2012)
Entrapment of two-spotted spider mite, Tetranychus urticae (Acari: Prostigmata: Tetranychidae), by type IV glandular trichomes of Lycopersicon species
Abstract
Two-spotted spider mite (TSSM) is becoming resistant to many of the pesticides used in the tomatofields. A potential alternative method of control is host plant resistance, which may be mediated byglandular trichomes. In this experiment, level of entrapment and mortality of the pest by type IVglandular trichomes were studied on accessions of Lycopersicon hirsutum Humb & Bonpl, L. pennellii(Cor.) DÂArcy and L. esculentum Mill on leaflets with trichomes intact or with exudates removed. Threeaccessions of L. hirsutum (LA1740, LA1777 and LA2860), two accessions of L. pennellii (LA2963 andLA2580) and one susceptible variety (Sankranthi) of L. esculentum were used. Leaflets from the terminalpair of the third-last fully expanded leaves were excised and leaf disks prepared. Ten female mites ofTetranychus orticae Koch were placed on the adaxial leaflet surface of each disk and after 2 h, thenumber of mites trapped, untrapped and moved into water were recorded. Again after 24 and 48 h, miteswere recorded either dead, morbid or moved into water. Results indicated that the highest number ofentrapment was on L. hirsutum LA1777, followed by L. pennellii accessions. None of the mites wasentrapped on L. esculentum. Moreover, L. hirsutum (LA1777 and LA1740) and L. pennellii accessionshad greater number of dead mites than L. esculentum after 48 h. Lycopersicon esculentum did not possesstype IV glandular trichomes. The highest density of type IV glandular trichomes was recorded on abaxialand adaxial leaf surfaces of L. hirsutum LA1777 (86.72 and 34.44 trichomes/mm², respectively). Removalof trichome exudates has significantly increased the mite survival in resistant accessions. Correlationbetween the density of type IV glandular trichomes and entrapment rate of TSSM was significantlypositive.
