Managing the functional diversity of arbuscular mycorrhizal fungi for the sustainable intensification of crop production

Societal Impact Statement The need to increase food production with reduced use of resources and environmental impact demands innovative rethinking and evolution of cropping systems. The essential changes required are consistent with sustaining arbuscular mycorrhiza, which, together with their associated microorganisms, could be managed to play an important role, especially in the protection of crops against abiotic and biotic stresses. Mycorrhiza should be included in agronomic decision processes, where chemical options to protect crops are limited or require the use of large applications. Defining rotational plant sequence or using cover crops and adopting reduced or no‐till techniques are key components of a strategy for a consistent and predictable way of manipulating the native inoculum to capitalize on the manifold benefits potentially provided by arbuscular mycorrhizal fungi through their functional diversity. Summary Despite the wide range of benefits arbuscular mycorrhiza can confer, they are not usually considered in large‐scale farming systems because the potential improvements in crop yields through the enhanced uptake of nutrients is a matter of debate and the advantages from the bio‐protection afforded against biotic and abiotic stresses have not been adequately recognised. Research carried out by our group over the last 20 years has allowed the development of a strategy based on the intentional use of selected host plants (Developer plants), to develop an extensive extraradical mycelium which, when kept intact by the adoption of appropriate tillage techniques, acts as preferential source of inoculum for the following crop, leading to earlier and faster colonization by AM fungi. Depending on the particular host plant chosen as Developer, this strategy can also be used as a tool to manage AMF functional diversity. Using this approach, we have achieved effective protection against abiotic (Mn soil toxicity) and biotic (Fusarium oxysporum and Magnaporthiopsis maydis) stresses in different crops. The strategy can easily be applied at field scale, both in low and high input cropping systems. It only requires small changes to the cropping system, such as employing no‐till and altered crop rotation or cover crops, that are simple to adopt and can realistically be implemented at the field level. This represents an important breakthrough as it allows intentional and predictable manipulation of the native soil mycorrhizal population over a range of dif