The global market for arbuscular mycorrhizal (AM) inoculants, touted as a cornerstone of sustainable agriculture, is valued at nearly $995 million. Yet, a recent meta-analysis published in New Phytologist reveals a glaring disparity between the promise of these products and their actual performance in the field. Conducted by researchers Liz Koziol, Thomas P. McKenna, and James D. Bever, the study underscores critical issues of quality, efficacy, and transparency within the AM inoculant industry.
The Results Are In: Most Products Miss the Mark
The analysis spans 302 trials assessing commercial AM inoculants from around the world. Findings are sobering: fewer than 12% of these products demonstrated both significant crop growth benefits and viable fungal colonisation. By contrast, laboratory-grown inoculants—produced under rigorous scientific controls—achieved these outcomes in 63% of trials.
Over 80% of commercial products failed to facilitate even minimal root colonisation, calling into question their value to farmers. The study highlights a significant flaw in the market: many commercial inoculants rely on nutrient additives or fertilisers for any perceived benefits rather than genuine fungal activity.
"The benefits of many commercial inoculants may not stem from mycorrhizal fungi at all," the authors write, pointing to a lack of viable propagules as a recurring issue.
Courtesy of Mycorrhizal Applications
Why Are Commercial Inoculants Failing?
The crux of the problem lies in propagule viability—the ability of fungal spores, hyphae, and root fragments to establish symbiotic relationships with crops. Commercial products often feature insufficient or non-viable propagules due to poor storage and production practices.
Notably, the analysis reveals that the number of propagules listed on a product’s label is not a reliable indicator of effectiveness. Even products with high propagule counts often fail to establish meaningful root colonisation. The study also flags contamination by fungal pathogens in some commercial inoculants, further complicating their use.
Regulatory gaps exacerbate these challenges. In the United States, which accounts for 25% of the global AM inoculant market, there are no federal regulations governing the quality or import/export of these products. The lack of oversight means farmers and agronomists are left navigating a largely unregulated industry.
A Costly Problem for Sustainable Agriculture
The economic implications are staggering. Of the $995 million spent annually on AM inoculants, the study estimates that $876 million is effectively wasted on products that lack fungal viability or efficacy.
For farmers adopting mycorrhizal inoculants to boost crop yields, reduce chemical inputs, or improve soil health, these findings represent more than financial loss—they threaten trust in mycorrhizal biotechnology as a sustainable solution.
Despite the bleak outlook, the study provides a glimmer of hope. Laboratory-grown inoculants, produced with meticulous attention to quality, consistently deliver higher colonisation rates and agronomic benefits. This demonstrates the untapped potential of AM fungi when quality control is prioritised.
Courtsey of Dr.Christine Jones
What Needs to Change?
For mycorrhizal inoculants to fulfil their promise, the industry must embrace transparency and accountability. The authors advocate for:
Independent product testing: Regular assessments of fungal viability and purity.
Stricter labelling standards: Clear reporting on propagule type, quantity, and quality.
Regulatory oversight: Establishing global standards for inoculant production and distribution.
Adopting these measures would not only safeguard farmers’ investments but also unlock the full potential of mycorrhizal fungi in agriculture.
"With proper quality control, AM fungi could be transformative for sustainable agriculture," the researchers suggest. "But the current industry must address its shortcomings."
Looking Ahead
The findings from this meta-analysis come at a critical juncture as agriculture faces mounting challenges, from soil degradation to climate change. Mycorrhizal fungi offer a proven pathway to improving crop resilience, nutrient uptake, and soil health—but only if the industry ensures its products work as intended.
As the AM inoculant market continues to grow, farmers, researchers, and policymakers must push for higher standards. It’s clear: the future of mycorrhizal biotechnology depends on building trust, one viable propagule at a time.