A team of Canadian researchers led by University of Saskatchewan chemistry professor Soledade Pedras is hoping to develop new non-toxic chemical compounds that can limit crop losses caused by blackleg.
Pedras, a Canada research chair in bio-organic and agricultural chemistry at the university, has developed a process that uses synthetically produced chemical compounds called paldoxins to limit the damage caused by blackleg and other crop diseases.
If successful, the research could reduce dependence on commercial fungicides and would save farmers billions of dollars each year in lost production.
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Unlike commercial fungicides now available, paldoxins would not kill fungi but would inhibit the production of harmful enzymes produced by the fungi.
Pedras says the development of a non-toxic control agent would reduce concerns over the emergence of resistant strains of fungi and provide farmers with a greener, more sustainable method of disease control.
“For the future, for sustainability, I would like to have chemicals that don’t have any anti-fungal activity.”
Developing a paldoxin to control blackleg has been a challenging and time-consuming task, with Pedras trying to eliminate crop damage caused by fungi without killing the fungus itself.
The work is progressing and the university is already seeking patent approval on several promising paldoxins.
The idea of developing a non-toxic chemical control agent has intrigued Pedras since her days at the National Research Council’s Plant Biotechnology Institute.
Pedras studied plant pathogens, particularly those that affected the crucifer family, which includes canola, rapeseed, mustard, cauliflower, Brussels sprouts, turnips and broccoli.
At the time, many plant researchers were focusing on plant microbiology and genetics as the most promising method of controlling plant disease.
Pedras felt plant chemistry was being overlooked.
When she later joined the U of S chemistry department, she began studying the natural defence mechanisms of plants in greater detail.
She determined that some crucifer plants developed minute amounts of chemicals that served as a natural defence mechanism.
In response, fungi in the crop produced enzymes that disabled the plant’s defensive chemicals.
By disabling the plant’s defences, the enzymes allowed the pathogen to spread throughout the plant, causing irreparable damage.
Pedras theorized that if researchers could produce synthetic chemicals that inhibited the production of the fungal enzymes, then the plant’s natural defences could continue to work, suppressing the pathogen’s ability to spread.
“The pathogen is still there but the plant has a signalling system that senses the pathogen and it continues producing more defences, to the point that the pathogen is choked out. It cannot grow any more,” Pedras explained.
“If production of the fungal enzymes can be inhibited, then the plant should be able to survive on its own defences. The chemical (paldoxin) will only have to work when the pathogen is infecting the plant.”
Though much work remains to be done, Pedras’s research is generating considerable interest among plant researchers and chemical companies around the world.
Her team of researchers has already developed and tested roughly 200 prototype paldoxins, many of which show promise in controlling blackleg.
The paldoxins are produced in a lab by combining different molecules such as simple sugars, acetic acids or amino acids.
“It’s like building a puzzle but with chemical elements,” said Pedras.
“We have gotten to a point now where we have a very high inhibition level in many of the compounds we’ve produced.
“The part that I’m still not happy with is that we still have antifungal activity in everything we’ve tested. I want something that is much more innocuous.”
Pedras’s goal is to develop paldoxins that are simple to build, using substances that are readily available.
This will keep production costs low and make paldoxins more accessible to farmers who have little money to spend on crop inputs.
Pedras and her colleagues now have about 40 paldoxins that offer varying levels of enzyme inhibition, but the search for the perfect compound.
“For the first several years, it was like banging my head against the wall,” said Pedras.
“If you go down a road that no one else has travelled, how do you know if there’s going to be somewhere to turn,” she said.
“How do you know if you’ll reach your destination?”
Pedras could not predict when the first paldoxins would become commercially available but said interest among major chemical manufacturers is growing.
“There is still a lot of work to be done but I can say that we are finally on the right track,” she said. “We have to be very perseverant and we can’t accept negative results as our failure.”
