“Hairy” canola bred to resist flea beetles

A new type of canola plant, with tiny “hairs” on its leaves and stem to disrupt flea beetles’ feeding patterns, may allow growers to skip an insecticide application.

Researchers led by Margie Gruber at Agriculture and Agri-Food Canada’s Saskatoon Research Centre inserted genes from a “hairy” model plant, Arabidopsis, into canola.

“The trait we were looking at is trichomes, which are plant hairs,” Gruber said in a release Wednesday from the Western Grains Research Foundation, which through its endowment fund is one of several groups funding this work.

“Lots of plants have trichomes. Canola has a few, but related species like mustards have a lot more. We’re interested in seeing if we can stimulate the plant to produce more on the seedling leaves and stems.”

Two types of trichomes are commonly found on plants: a bumpy protuberance on the plant surface that often releases various plant chemicals, like in the mint family, and another that “sticks out a bit farther,” the WGRF said.

The latter are found in various species related to canola, as well as in Arabidopsis, Gruber said.

“Series of behaviours”

A flea beetle, she said, is “a specialized insect, with specific behaviours it undergoes when testing a plant surface before eating it. If a full series of behaviours are not completed, it starts over or moves off the plant.”

Gruber already has lines developed with significantly reduced flea beetle feeding damage — but the “hairy” canola trichomes, unlike those on Arabidopsis, don’t yet have any branches on them.

“We’re currently testing genes that would make branches on the trichomes. In Arabidopsis, they can have three to four branches depending on where they grow. In canola there are no branched trichomes at all,” she said.

“We feel branching will increase the density of the trichome mat, so flea beetles that can find a little bare spot and can burrow down wouldn’t be able to do that nearly as well. The average is three branches, but we can make mutants with six or seven.”

Gruber’s team sought to put the hairs on any and all parts of the seedlings. “What we achieved was to put them on the young leaves and stems. The cotyledons were still smooth, but they seemed to be more flea beetle-resistant, even without the trichomes. So the genes that we used also modified the plants in some way to be more resistant.”

However, it will still take time to develop canola plants that are worthy of going into a plant breeding program. Current breeding lines with the hairy characteristics mature about a week later than commercial canola varieties, Gruber said.

“When the agronomics of those lines are close to the agronomics of current varieties, then we’ll provide that material to plant breeding companies. That might be in three years.”

The type of insect resistance developed here would be a “more robust” resistance that won’t break down or have resistant flea beetles develope. Because it’s a physical resistance rather than a biological system, it will be more difficult for the insects to adapt to.

When the final developments of hairy canola are complete and the trichomes have branches, farmers shouldn’t have to use any chemical flea beetle control at all, Gruber said.

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