Kneubuhl, F. K. Line Shapes of Electron Paramagnetic Resonance Signals produced by powders, glasses, and viscous liquids. J.

Zingiberene was detected in foliage extracts of Lycopersicon hirsutum f. hirsutum. 2-Tridecanone was not present in L. hirsutum f. hirsutum but did occur in L. hirsutum f. glabratum. F2's of L. hirsutum f. glabratum X L. hirsutum f. hirsutum segregated for the presence of zingiberene and 2-tridecanone. The occurrence of zingiberene in L. hirsutum f. hirsutum coincided with the sporadic appearance of resistance to Colorado potato beetle (Leptinotarsa decemlineata) in this subspecies. Resistance to Colorado potato beetle in the F2's was correlated with zingiberene content and with 2-tridecanone content. Extracts of L. hirsutum f. hirsutum foliage were toxic to Colorado potato beetle larvae at zingiberene contents estimated at 12-25 gg/larva. Zingiberene content of L. hirsutum f. hirsutum leaflets was estimated to be from 160 to 250 µg/2-cm2 leaflet.

Resistance to Colorado potato beetle in a clone of Lycopersicon hirsutum f. hirsutum L. is attributed to the presence of the sesquiterpene zingiberene in the type VI leaf trichomes; however, both day/night temperature regimen and photoperiod affect zingiberene content and trichome density. In short days (SD), zingiberene content per trichome is more than 3-fold greater than in long days. In SD, trichome density per unit leaf surface is 2-fold greater at 25/20°C (day/night) than at either 30/25°C or 20/15°C, thus indirectly influencing zingiberene content per cm2. In long days, temperature regimen had little effect on either trichome density or zingiberene content, although trichome density was greater than or equal to that in SD.Glandular trichomes that accumulate large quantities of terpenes and other essential oils have been found to be associated with insect resistance in a number of species of tomato (6,11,13). Lycopersicon hirsutum f. hirsutum Humb. and Bonpl. is resistant to several arthropod pests, including the Colorado potato beetle (Leptinotarsa decemlineata Say), although the degree of resistance may vary in different environments and with different genetic backgrounds. Resistance to this pest has been associated with the presence of type VI trichomes, capitate glandular hairs, 0.2 to 0.5 mm long, which contain a four-celled head. The secretory head cells of the type VI trichomes from resistant genotypes contain high amounts of the sesquiterpene zingiberene (2, 9). Because L. esculentum contains type VI trichomes and can be successfully crossed with L. hirsutum, it may be possible to transfer this trait. To better understand the effect of environment on trichome density, zingiberene content, and insect resistance, the following research was undertaken to determine whether temperature and photoperiod modify the expression of the genes for type VI trichomes and zingiberene production.