Imagine you’re a tiny wheat midge, buzzing around in search of the perfect place to lay your eggs. As you fly over a wheat field, you pick up scents with your delicate antennae. These scents, or volatile organic chemicals, tell you a lot about the wheat plants below.
Some wheat emits odours that just don’t appeal to you — they’re like a poorly mixed sound equalizer, with ratios of chemicals that don’t quite hit the mark. When the ratios are right, though, it’s like a perfect harmony to your senses. These plants smell inviting, and you’re drawn to lay your eggs there.
Scientists have discovered that some wheat varieties naturally deter you from laying eggs. It’s not about taste, but smell. These plants release volatiles that mimic those found in post-anthesis wheat, a stage wheat goes through that makes it hard for insect larvae to survive on them.
So, even if the wheat is at a pre-anthesis stage, optimal for your larvae’s survival, its smell tells you otherwise.
It’s like a clever trick — a plant defense strategy called oviposition deterrence. Just like any caring parent, you avoid wasting your eggs on plants that won’t support your offspring well.
Tyler Wist
“Understanding these volatile cues isn’t easy — it took scientists years of collecting air samples from wheat fields to decipher which chemicals deterred midge and which didn’t. Now, armed with this knowledge, we can better understand how plants defend themselves and how insects like wheat midge respond to their environment,” says Tyler Wist, entomologist with Agriculture and Agri-Food Canada (AAFC) in Saskatoon, Sask.
Wist’s team is uncovering new traits and genes that protect wheat from destructive pests like wheat midge. They’ve identified a specific region of DNA that enhances the efficacy of the Sm1 gene, along with other genetic regions altering wheat’s scent to make it less appealing to wheat midge.
It’s tools like this that represent a new weapon in the fight against pests and disease in crops.
As science reveals more about plant genetics, researchers are increasingly turning to plants’ own genes to help them defend against threats, often alongside chemistry and other products.
Wheat midge poses the greatest threat to wheat crops across Western Canada, noted James Harynuk, a professor from the University of Alberta’s Faculty of Science, in a document released by the university in 2022.
Harynuk said that in a typical year, wheat midge can inflict around $60 million in damage. During particularly severe seasons, that figure can soar to $300 million or more, and rising wheat prices may further escalate the total losses.
Like Wist, Harynuk focuses on identifying volatile organic compounds (VOCs) emitted by wheat.
The process involves drawing air samples through a tube filled with absorbent material to capture these tiny molecules. The team then uses comprehensive two-dimensional gas chromatography to separate the various molecules, followed by mass spectrometry to identify and quantify them.
By understanding how wheat plants naturally emit scents that deter wheat midge from laying eggs, scientists can now help breed wheat varieties that are less appealing to the pest.
For farmers, this means fewer crops lost to pest infestations and reduced reliance on chemical pesticides, leading to cost savings, improved yields, and more sustainable farming practices. Since wheat midge can cause millions of dollars in damage each year, incorporating wheat varieties with these natural defenses could dramatically reduce crop losses and help protect farmers’ livelihoods.
