Feeding by Flea Beetles (Coleoptera: Chrysomelidae; Phyllotreta spp.) Is Decreased on Canola (Brassica napus) Seedlings With Increased Trichome Density

Abstract

Laboratory and Þeld studies were undertaken to determine the effects of increased numbers of trichomes on seedling stems, petioles, and Þrst true leaves of Brassica napus L., canola, on the feeding and behavior of the crucifer ßea beetle Phyllotreta cruciferae (Goeze) (Coleoptera: Chrysomelidae). Seedlings of ÔWestarÕ canola with genes inserted from Arabidopsis thaliana L. for increased trichome production, called Hairy1, were tested against Westar seedlings in no-choice and choice laboratory tests, and against parental plants and other cultivars grown from seed with and without insecticide in Þeld trials at Saskatoon and Lethbridge, Canada. Analyses of prefeeding and feeding behavior in no-choice tests of Þrst true leaves found that ßea beetles interacted with their host while off Hairy1 leaves more so than beetles presented with leaves of Westar. Beetles required twice as much time to reach satiation when feeding on leaves with increased pubescence than on Westar leaves. In laboratory choice tests, ßea beetles fed more on cotyledons and second true leaves of Westar than on comparable tissues of the transgenic line. In Þeld trials, variations in feeding patterns were seen over time on cotyledons of the line with elevated trichomes. However, all four young true leaves of Hairy1 seedlings were fed upon less than were the parental lines. Feeding on Hairy1 plants frequently occurred at levels equal to or less than on cultivars grown from insecticide-treated seed. This study highlights the Þrst host plant resistance trait developed in canola, dense pubescence, with a strong potential to deter feeding by crucifer ßea beetles.

Plant trichomes and a single geneGLABRA1contribute to insect community composition on field-grownArabidopsis thaliana

“…In Brassicaceae plants, evidence is accumulating to suggest that genetic variation within a plant species alters insect community composition and, in turn, exerts selection on plant defense [4, 79, 80]. Variation in the trichome density is also observed across Brassicaceae plants [71, 72, 73], where GL1 orthologs affect the trichome density [81]. In the context of community genetics, the present study on GL1 provides evidence of a key gene affecting the community composition of crucifer-feeding insects.…”

“…To date, several studies have reported associations between GL1 polymorphism and anti-herbivore functions in field populations of A. lyrata [9, 10] and A. halleri [11, 18]. Plant trichomes also prevent herbivory by sawflies [71] and flea beetles [72, 73] on Brassica cultivars. Together with these results, our present results indicate that plant trichomes and a single gene GL1 play a key role in physical defense against crucifer feeders.…”

Do plant trichomes cause more harm than good to predatory insects?

“…Glandular trichomes on crop and non‐crop plants can store and secrete exudates containing chemicals that repel, impede movement or even trap insects and mites, resulting in their death from desiccation or starvation . Plant breeding programs have successfully produced plant accessions and cultivars (or varieties) of crop plants that express increased trichome density, resulting in increased resistance to attack from some herbivores . Therefore, trichome‐based plant defense is an important mechanism of pest suppression for the agricultural community …”

Breeding for insect resistance in oilseed rape: Challenges, current knowledge and perspectives

“…This was achieved by transferring the AtGL3 trichome regulatory gene from Arabidopsis thaliana into the OSR genome, followed by the knock‐down of the BnTTG1 gene to ensure a similar plant growth as the original glabrous cultivar. In laboratory assays as well as in field trials, the resulting “hairy canola” (Gruber et al., ) was clearly more resistant to flea beetles ( Phyllotreta cruciferae and P. striolata ) and to the diamondback moth (Alahakoon, Adamson et al., ; Alahakoon, Taheri et al., ; Soroka, Holowachuk, Gruber, & Grenkow, ).…”

“…to the diamondback moth (Alahakoon, Adamson et al, 2016;Alahakoon, Taheri et al, 2016;Soroka, Holowachuk, Gruber, & Grenkow, 2011).…”