Field growth traits and insect-host plant interactions of two transgenic canola (Brassicaceae) lines with elevated trichome numbers

Plant growth and insect resistance characteristics were determined for two Brassica napus Linnaeus (Brassicaceae) lines, AtGL3+ and K-5-8, developed for enhanced trichome densities relative to their parental cultivar Westar. In the field, both transgenic lines had glabrous cotyledons that curled upwards at emergence but flattened with time, and young leaves with elevated trichome density. Flea beetle (Phyllotreta cruciferae (Goeze) and Phyllotreta striolata (Fabricius); Coleoptera: Chrysomelidae) feeding was reduced on true leaves of both lines by 30-50% compared with insecticide-free Westar. Flea beetle feeding levels on cotyledons of the two hairy-leaved lines were lower than on unprotected Westar and similar to those seen on insecticide-treated Westar. Antixenosis and antibiosis resistance was observed when diamondback moths (Plutella xylostella (Linnaeus); Lepidoptera: Plutellidae) interacted with the hairy AtGL3+ and K-5-8 lines in the laboratory. Although the numbers of eggs laid by female diamondback moths on the transformed lines were similar to or higher than on Westar, in feeding bioassays larvae moved off AtGL3+ plants and larval feeding injury decreased on the transformed lines compared with Westar leaves. No agronomic or seed yield penalties were found for plants of K-5-8. These data highlight the utility of manipulating trichome regulatory genes to increase plant resistance against brassicaceous insect pests.