University
of Guelph plant scientists have shown for the first time how an ancient crop teams
up with beneficial bacteria to protect against a devastating fungal infection.
It’s
a discovery that may benefit millions of subsistence farmers and livestock in
developing countries. It’s soon going to be tested on corn and wheat.
Agriculture
professor Manish Raizada led the team that published its results this week in Nature
Microbiology.
The
team includes former PhD student Walaa Mousa, current graduate student Charles
Shearer, Ridgetown campus scientist Victor Limay-Rios and researchers in
California.
The
paper describes a novel defence mechanism allowing crop plants to work with bacteria
called endophytes living in their roots to ward off Fusarium graminearum.
This
fungus makes a toxin that can sicken livestock and people.
The
M6 microbe lives in the roots of finger millet, a cereal crop grown by
subsistence farmers in Africa and South Asia. Millions of people rely on the
crop, first domesticated in East Africa in about 5,000 BC.
The
crop has long been known to be resistant to fungal disease.
Through
microscope observations, Mousa learned how the mechanism works.
Sensing
the pathogen near the plant roots, the microbe enters the soil and multiplies
to millions of cells that form a protective barrier on the root surface.
Even
more striking, he said, the plant’s root hairs grow to many times their normal
length. Like layers in lasagna, the root hairs and the bacterial cells form a
dense mat that traps the fungus.
Mousas
found that natural products of these endophytic bacteria then kill the fungus.
Likening
the process to an animal’s immune system, Raizada said, “This appears to be a
new defence mechanism for plants.”
He
likens the mechanism to the human immune system, with immobile plant cells
“recruiting” mobile microbes to seek out and destroy pathogens.
The
researchers believe this mechanism evolved in a kind of evolutionary arms race
in the African ancestors of finger millet and Fusarium.
The
fungus can make an antibiotic against M6 for which the bacterium has developed
resistance in turn, Raizada said.
“We
think subsistence farmers in East Africa over generations may have selected for
this special microbe through breeding.”
He
said the findings may help agricultural companies develop seed treatments using
M6 to protect more susceptible and widely grown crops such as corn and wheat
against the fungus.
The
University of Guelph has licensed the lab’s results to an agricultural startup
company for potential use in those crops. The microbe is now being tested in
Canadian corn and wheat.
The
team found that M6 also protects against other fungi.
He
said the study shows the importance of indigenous farming knowledge and
practices. “These crops should be explored and valued.”
This
research was funded by Grain Farmers of Ontario, the Ontario Ministry of
Agriculture, Food and Rural Affairs, the Natural Sciences and Engineering
Research Council, and the International Development Research Centre and Global
Affairs Canada.
