Flea beetles may be throwing a hairy fit in the not so distant future.
Unlike adding a gene that creates insecticidal properties in the plant, as is done in corn for the European corn borer, Agriculture Canada researchers at the University of Saskatchewan have found that a physical boundary can be added to canola that keeps the tiny, voracious beetles at bay.
Hair, more formally known as trichomes in plants, are already present in canola, but mustard has more of them. If a plant has enough hair, beetles can’t navigate their way to a site on which to feed.
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“We’re interested in seeing if we can stimulate the plants into producing more on the seedling leaves and stems,” said Margaret Gruber of Agriculture Canada.
Trichomes are usually a bumpy area that releases plant chemicals, but some plants, such as mint, possess trichomes that stick out further, providing a hair-like protuberance.
Branching out
Gruber and her colleagues are looking for the genetic source of this potentially valuable protective device.
“So far we haven’t got any trichomes with branches in canola, and that is important,” she said.
Branching is more common in arabidopsis, canola’s close cousin and research stand-in.
Gruber has already developed canola that has flea beetle resistance, but feels branching of the hairs will be necessary to beat the beetle.
She said the insect needs to go through a set of obsessive compulsive behaviours to test a plant’s surface before it can feed. The hairs interfere with this surface test and the bug moves on to a more vulnerable plant.
Trichomes in arabidopsis can have three or four branches each, making its surface tissues harder to reach and leaving the pests’ tactile testing unproductive. The insects are foiled without a bare spot in which to burrow.
Gruber has placed genes from arabidopsis in canola plants, causing the canola to overexpress the trichomes and creating a 1,000 times increase in the hair-like protuberances.
While this procedure placed the trichomes on the young leaves and stems, it didn’t put them on the cotyledons.
However, an unplanned effect of the gene is adding another form of protection to the plant that also leaves the cotyledons undesirable to flea beetles.
Researchers are now working to increase the number of trichomes to five or six from three in arabidopsis using mutation breeding techniques and isolating those genes for transfer to canola.
Gruber said she hopes that by observing why canola doesn’t naturally tend toward trichomes, she may be able to learn how to breed the hairy structures into plants using non-genetic modification techniques.
Breeding efforts have so far produced canola that has most of the positive agronomic factors farmers have come to expect, but the plants are taking about a week longer than average to reach maturity.
She expects it will take three years to produce genetic lines of canola that can be released to seed companies for development and distribution.
