Abstract: Aims The accumulation of nutritional components in plants is critically linked to their survival capacity and productivity. Investigating how arbuscular mycorrhizal fungi (AMF) inoculation regulates drought tolerance in plants through nutrient component changes in various organ will establish a theoretical framework for applying AMF to improve crop resilience under water-limited conditions. Methods A controlled pot experiment employing two water regimes (75% vs.55% field capacity) with AMF inoculation was conducted using oat (Avena sativa) cultivar Bayou 1. Mycorrhizal colonization rates were quantified at jointing and filling stages, followed by analysis of non-structural carbohydrates (NSC), C, N, P in root, stem, and leaf. Grain yield was recorded at the maturity stage. Important findings In oat plants inoculated with AMF under drought stress, the AMF colonization rate, plant height, and root-to-shoot ratio were significantly enhanced, resulting in 13.31% increase in grain yield. Notably, these improvements in growth parameters and yield exceeded those observed in AMF-inoculated plants under well-watered conditions. Furthermore, AMF inoculation under drought stress increased soluble sugar accumulation in stem and leaf. Concurrently, the contents of C, N, P in root, stem, leaf, as well as the leaf C:N significantly increased, especially the contents of P in leaf. In contrast, the leaf N:P significantly declined. Redundancy analysis revealed that the contents of leaf soluble sugars, and stem C, root N content served as key indicators explaining variations in growth traits and grain yield under drought stress and AMF inoculation, respectively. Overall, AMF inoculation under drought conditions enhanced oat drought tolerance and hence improved grain yield, primarily attributed to increase AMF colonization rate, which facilitated synergistically the accumulation of soluble sugar and C, N, P in organs, and modulated the leaf stoichiometric ratios (C:N and N:P).

Key words: oat, drought stress, AMF, NSC, C,, N and P, grain yield