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Societal Impact Statement: Sorghum is an important cereal crop that provides calories and nutrients for much of the world's population, and it is often grown with low fertiliser input. Optimising the yield, nutritive content and bioavailability of sorghum grain with minimal input is of importance for human nutrition, and arbuscular mycorrhizal (AM) fungi have previously shown potential to assist in this. Across sorghum genetic diversity, AM fungi improved the yield, nutrition and zinc and iron bioavailability of grain in a low phosphorus soil. Thus, food production systems that effectively manage AM fungi may improve consumer outcomes. Summary: Sorghum is a C4 cereal crop that is an important source of calories and nutrition across the world, predominantly cultivated and consumed in low‐ and middle‐income countries. Sorghum can be highly colonised by arbuscular mycorrhizal (AM) fungi, and the plant‐fungal association can lead to improvements in biomass and nutrient uptake. High‐throughput phenotyping allows us to non‐destructively interrogate the 'hidden' effects of AM fungi on sorghum growth and phenology.Eight genetically diverse sorghum genotypes were grown in a soil amended with 2 or 20 mg P kg−1 and inoculated with an AM fungal culture of Rhizophagus irregularis. High‐throughput phenotyping uncovered the 'hidden' effects of AM fungi on growth and phenology, while grain biomass, nutrition, Zn and Fe bioavailability and root AM colonisation was determined after destructive harvest.Sorghum plants colonised by AM fungi generally performed better than non‐AM control plants, with greater yield, harvest indices, and grain P, Zn and Fe contents. During the early growth stages, AM colonisation led to temporary growth depressions. There were also AM fungal and P fertilisation effects on sorghum time‐of‐flowering. The sorghum genotype with the highest AM colonisation could barely produce grain when non‐inoculated.The two genotypes that failed to mature had very low AM colonisation. Generally, the genetically diverse sorghum genotypes were highly responsive to AM colonisation and produced more grain of greater nutritive quality when colonised, without adverse consequences for micronutrient bioavailability. [ABSTRACT FROM AUTHOR]

Societal Impact Statement: Cereal crops such as wheat and barley provide key nutritional elements to the human diet. However, the distribution of nutrients within the cereal grain itself is critically important, as nutrients can be lost during the grain milling process. Mycorrhizal fungi can take up nutrients from the soil and deliver them to plants, and consequently, grain nutrient content can be modified by inoculation of the soil with mycorrhizal fungi. Here we show at the microscopic level how mycorrhizal fungi modify the concentration and distribution of nutrients within wheat and barley grain, and consider the impact of this for human nutrition. SummaryThe concentration and distribution of nutrients in cereal grains are critically important for human nutrition. Mycorrhizal fungi affect the yield and nutrition of cereal crops, but there has been little focus on the effects on the grain, particularly at the microscopic level. Although arbuscular mycorrhizal fungi (AMF) can modify grain nutrient concentrations relative to mock‐inoculated plants, it is not known whether this contributes to modifications to the distribution of nutrients within the grain.Barley and bread wheat plants were grown to maturity with or without AMF (Rhizophagus irregularis) inoculation in soil amended with 20 mg added zinc kg−1. The resulting grain from matured plants was dried, fixed and sectioned to the root primordia level, then subjected to laser ablation ICP‐MS to analyse the distribution and concentration of 12 elements.Elemental concentration and localisation in the grain samples was highly influenced by plant species, and for some elements, AMF inoculation. Heavy metals (zinc, iron, manganese, copper, cobalt and nickel) were the most highly influenced by AMF inoculation, particularly in wheat; macronutrients including phosphorus, magnesium, potassium and sulphur were also affected by AMF, particularly in barley.Elemental concentrations, particularly of macronutrients, tended to be greater in mycorrhizal barley grain than non‐mycorrhizal, but the reverse was observed in wheat grain. Mycorrhizal plants of both species had reduced accumulation of manganese, nickel and cobalt in the grain. [ABSTRACT FROM AUTHOR]

Societal Impact Statement: Micronutrients such as zinc and iron are critical for human health. For the world's population that relies on cereal products to obtain micronutrients, the bioavailability (absorption of nutrients in the gut) can be hindered by an anti‐nutritional compound, phytate. Phytate accumulation in grain is affected by soil properties including phosphorus availability and arbuscular mycorrhizal (AM) fungi. Here, we investigated the effects of AM fungi and soil phosphorus fertilization on micronutrient bioavailability in durum wheat and found that fertilization greatly decreased the bioavailability of micronutrients, but AM fungi can take up more micronutrients, which can lead to improved bioavailability when the soil is not fertilized. Summary: The bioavailability of micronutrients (zinc [Zn] and iron [Fe]) in cereal crops such as durum wheat is critically important for human nutrition. Bioavailability is a product of complex interactions between plant phosphorus (P) uptake and storage in grain (as phytate), and plant micronutrient uptake. The bioavailability of Zn and Fe in cereal grain is affected by soil nutrient concentrations and associations with arbuscular mycorrhizal (AM) fungi, but has been scarcely studied.A geographically diverse collection of 101 durum wheat genotypes was surveyed for grain bioavailability of Zn and Fe. Ten genotypes were then selected and grown with and without AM fungal inoculation and soil P fertilization to understand the effects of manipulating soil P availability and uptake on micronutrient bioavailability.The strongest negative effect on grain micronutrient bioavailability was soil P fertilization, however, it also led to increased grain weight. Crop variety selection had the greatest variation in the P‐fertilized soil, but AM fungal inoculation had a positive effect on bioavailability in one variety in the non‐fertilized soil.In order to grow more nutritious durum wheat crops, variety selection and AM fungal inoculation are important considerations. In general, there is a trade‐off between grain weight (yield) and micronutrient bioavailability in grain that could be addressed through breeding P‐deficiency tolerant varieties. [ABSTRACT FROM AUTHOR]

Societal Impact Statement: Arbuscular mycorrhizal fungi (AMF) may contribute to enhanced yield and nutrition of host plants for the purpose of sustainable agriculture. However, the growth response of the host plant to mycorrhizal colonization is generally only measured at harvest, and thus management decisions regarding AMF are made using only a single time point. This study highlights that AMF can provide growth benefits to the host plant over its life. Greater knowledge of how plants respond to AMF over time will improve understanding of how the association functions and ultimately lead to improved management decisions regarding AMF in an agricultural context. SummaryColonization by arbuscular mycorrhizal fungi (AMF) can result in variable responses in the growth and mineral nutrition of host plants, and is highly dependent on soil nutrient condition; limited studies have addressed the effects of AMF on plant growth over time. The aim of this study was to investigate the AMF effects on plant growth over the life of the plant, and interactions with soil phosphorus (P) and zinc (Zn) availability.We used a high‐throughput shoot phenotyping system to examine the temporal growth responses to AMF and soil P and Zn availabilities in the pasture legume Medicago truncatula. Plants were either inoculated with Rhizophagus irregularis or mock‐inoculated, and were examined under two soil P and five soil Zn availability treatments. Plants were then destructively harvested to obtain final biomass and shoot nutrition data.The growth of M. truncatula plants over time responded very differently to AMF depending on the soil P availability. At low P, projected shoot area and absolute growth rate (AGR) became increasingly greater in the mycorrhizal plants over the course of the experiment. At high P, there was a positive growth response to AMF until approximately 40 days after planting, after which the AGR of the non‐mycorrhizal plants increased and the response to AMF became neutral. Zinc availability was highly interactive with P availability, but not with AMF inoculation.This research demonstrates that growth responses to mycorrhizal fungi change over the plant's life, and are highly dependent on soil P availability. [ABSTRACT FROM AUTHOR]