PHOTO: UNIVERSITY OF GUELPH
PHOTO: UNIVERSITY OF GUELPH
PHOTO: UNIVERSITY OF GUELPH
PHOTO: MARK PASVEER
CROP PROTECTION ▶▶▶ Probiotics for tougher plants BY MATT MCINTOSH A
ncestral varieties of modern corn and wheat might hold a key to non-chemical mycotoxin preven- tion. More specifically, some of the
bacteria strains which naturally developed alongside those varieties have been shown by Canadian researchers to be highly effective against fusarium head blight and gibberella ear rot. Now, those same researchers are work- ing with the private sector to bring a practical product to grain growers.
Finding the right bacteria Manish Raizada is a long-time professor of plant agriculture at the University of Guelph. After elevated levels of mycotoxins spurred prominent grain marketing issues in recent years (most notably in 2018), Raizada was asked to head a team of researchers charged with developing a more effective biological control for grain growers. To do so, they turned to much older, apparently more-resistant vari- eties of each crop. They looked at microbial en- dophytes: bacteria that live between plant cells. These were isolated from ancient and landrace corn varieties, as well as finger millet (a very old African crop with natural fusarium resistance). These microbes are numerous in
Canadian researchers combine modern tech with ancient organisms to find solutions to mycotoxin-producing fungus. Naturally occurring bacteria called endocytes are promising soldiers to battle diseases like head blight and ear rot in wheat and corn.
the natural world and often have a mutual- ly-beneficial relationship with the host plant. Some strains can, for example, enhance root growth and nitrogen absorption. Raizada also reiterates the ability of fungi to rapidly develop resistance to commonly-used fungicides, which continues to be a growing concern. But because probiotic microbes can evolve with the pathogen, the right endophyte could provide farmers with a longer-term mycotoxin management tool.
Enormous success in the lab Out of approximately 200 microbial strains screened, five anti-fusarium bacteria strains were isolated and used in greenhouse trials. Each one dramatically suppressed mycotoxin DON accumulation (up to 97% in corn and 85% in wheat). Applying the endophytes via seed coating was less effective then direct fo- liar applications, but the results overall were startlingly positive. “It’s the best fusarium
control in a study ever reported in corn,” says Raizada. Some endophyte strains almost elimi- nated the ear rot pathogen. The results for wheat were lower, but three of the tested strains still managed to reduce pathogen levels by 60%. Why some of the endophytes were so success- ful in suppressing fusarium and ear rot, has to do with mobility. In particular, Raizada says, they observed one strain (M6, derived from finger millet) respond to infection by leaving the root system to coat the exterior of the plant. It also promoted root hair growth. Both factors combined, says Raizada, create an ideal habitat within which the endophyte can cap- ture and kill the pathogen. “It’s actually mobile; some of these microbes have little tails they use to seek and destroy pathogens.”
From left to right: untreated corn infested with fusarium (head blight), corn treated by spraying fungicides, and treated with the promising M6 endocytes. The effectivi- ty in the field still has to be confirmed.
22 ▶ FUTURE FARMING | 22 May 2020
Barriers to commercialisation The overall goal of this research was to devel- op an in-season spray or a seed coating with the microbes that could prevent and suppress the establishment and spread of mycotoxins. If commercialised, such a tool would also have greater longevity than standard fungicides. Grain growers could also employ it in conjunc- tion with chemical solutions for a mul- ti-pronged attack strategy. Currently the uni- versity is working with the private sector to make this happen. There are some notable barriers to commer- cialisation, though. Delivering endophytes via seed coating – the theoretically ideal system – is inherently less effective than in-season ap- plications made directly to corn ear silks and wheat heads. Indeed, bacteria delivered through seed coating did not appear to effec- tively colonise the plant in the field. The re- searchers are not entirely sure why this is the case, though suspect it’s due to a combination
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