How can crops reliably benefit from applied mycorrhizal fungi?

Find when and where applied mycorrhizal fungi really raise crop yields, and how to predict success and check products before sowing.

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State the question, from One hundred important questions facing plant science

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	1	+# How can crops reliably benefit from applied mycorrhizal fungi?
	2	+
	3	+Most crops form partnerships with arbuscular mycorrhizal fungi, which help them take up nutrients and water, and companies sell these fungi as inoculants. But results in the field are unpredictable, and many products fail to colonise roots at all.
	4	+
	5	+## Question
	6	+
	7	+How can we ensure that plants actually benefit when arbuscular mycorrhizal fungi are applied in agriculture? This covers whether inoculants establish, when they raise yield, how to predict success before sowing, and the risks to native soil communities.
	8	+
	9	+## Background
	10	+
	11	+The question is in the category "Plant–Environment Interactions" of the 2023 list of 100 important questions facing plant science, chosen by four regional panels from 616 submitted questions [1]. Reliable inoculation could reduce fertiliser use, but only if its benefits can be predicted and the products trusted.
	12	+
	13	+## What is known
	14	+
	15	+- A meta-analysis of seven cereals found that field inoculation raised grain yield by 16% on average, with 77% of trials positive; the effect was crop-specific, smaller in cultivars released after 1950 and modulated by soil pH [2].
	16	+- Of 28 commercial inoculants, 84% failed to colonise roots in controlled greenhouse trials, and only two raised yields [3]. In 23 products tested under organic-farming conventions, colonisation was often poor, some carried plant pathogens such as Olpidium, and growth benefits often vanished once added fertilisers were controlled for [4].
	17	+- In on-farm trials in 54 Swiss maize fields, growth responses ranged from −12% to +40%; soil microbiome indicators and a few soil properties predicted 86% of the variation, with the abundance of pathogenic fungi the best single predictor [5].
	18	+- Inoculants are difficult to monitor in the field, and their unintended consequences for soil and plant biodiversity, should they become invasive, are unknown [6].
	19	+
	20	+## What would count as progress
	21	+
	22	+No single result settles a question like this; contributions like these would move it forward:
	23	+
	24	+- An independent, open testing scheme for commercial inoculants that reports viable propagules, root colonisation and contaminants, so that products can be checked before use.
	25	+- Multi-site field trials that test whether soil microbiome indicators predict inoculation success, with predictions made before sowing.
	26	+- Tracking studies that follow introduced strains in the field over several seasons, to measure establishment, persistence and effects on native fungal communities.
	27	+
	28	+## References
	29	+
	30	+1. Armstrong, E. M. et al. (2023). [One hundred important questions facing plant science: an international perspective](https://doi.org/10.1111/nph.18771). New Phytologist 238(2), 470–481.
	31	+2. Zhang, S. et al. (2019). [Arbuscular mycorrhizal fungi increase grain yields: a meta-analysis](https://doi.org/10.1111/nph.15570). New Phytologist 222(1), 543–555.
	32	+3. Salomon, M. J. et al. (2022). [Global evaluation of commercial arbuscular mycorrhizal inoculants under greenhouse and field conditions](https://doi.org/10.1016/j.apsoil.2021.104225). Applied Soil Ecology 169, 104225.
	33	+4. Koziol, L., Lubin, T. & Bever, J. D. (2024). [An assessment of twenty-three mycorrhizal inoculants reveals limited viability of AM fungi, pathogen contamination, and negative microbial effect on crop growth for commercial products](https://doi.org/10.1016/j.apsoil.2024.105559). Applied Soil Ecology 202, 105559.
	34	+5. Lutz, S. et al. (2023). [Soil microbiome indicators can predict crop growth response to large-scale inoculation with arbuscular mycorrhizal fungi](https://doi.org/10.1038/s41564-023-01520-w). Nature Microbiology 8(12), 2277–2289.
	35	+6. Hart, M. M. et al. (2018). [Fungal inoculants in the field: is the reward greater than the risk?](https://doi.org/10.1111/1365-2435.12976) Functional Ecology 32(1), 126–135.
	36	+
	37	+## Source
	38	+
	39	+Imported from [One hundred important questions facing plant science, question 74](https://doi.org/10.1111/nph.18771), curated by Armstrong et al. Listed as open in the source (2023) and still an active research question as of 2026-10-20. The statement above is written in our own words; see the source for the original wording, history and discussion.