Positive response of barley to an indigenous arbuscular mycorrhizal fungal (AMF) inoculant is modulated by genotype and environment through changes in AMF root abundance and community structure

In barley cultivation, high use of mineral fertilisers in combination with low crop nutrient use efficiency results in severe environmental and economic issues. In this context, inoculants with indigenous arbuscular mycorrhizal fungi (AMF) could represent an efficient solution where intensive agriculture negatively impacted soil AM fungal abundance and diversity. However, since crop breeding and environment can strongly affect plant mycorrhizal response, in this work, we tested the agro-ecological effect of field inoculation with a indifìgenous AM fungal consortium on three varieties of barley for two years. In 2020, when soil was clay loam with very low P availability and no drought stress, Atomo and Concerto varieties positively responded to inoculation in terms of AM fungal traits, whereas in 2021, with silty clay loam soil, low P availability and drough stress, only Concerto was responsive. In 2020, inoculation promoted grain yield by 64% and 37% in Atomo and Concerto, and in 2021 by 78% and 134% in Concerto and Atlante. Multivariate analysis highlighted a strong effect of environment on barley productivity and a third-order significant interaction AMF, genotype and environment (65% and 7% of explained variance). Inoculation slightly modified AM fungal composition, it strongly modified, together with plant growth stage, the AM fungal community structures. A significant relationship between root AM fungal abundance and barley productivity was highlighted, with arbuscules as best predictor. Accordingly, changes in AM fungal root community structure and not in composition drove barley response and the main players were Glomus sp. VTX00342 and Septoglomus sp. VTX00064, putative members of the local AM inoculum. The general positive barley productivity outcome supports the use of indigenous AMF for building efficient and ecologically safe inoculants and their inclusion in sustainable agriculture. Nevertheless, the selection of genotypes with stable AM fungal response in specific climatic conditions is crucial in biofertilization programmes.