Arbuscular mycorrhiza provides postanthesis benefits to maximize wheat grain yield and nitrogen concentration

Summary A trade‐off between high grain yield and high protein (or nitrogen, N) concentration is frequently observed for crop plants in agroecosystems and is difficult to resolve using conventional agricultural methods. Whether ecological strategies, such as exploring the interactions between plants and microbes, can be leveraged to tackle this problem remains unclear. Here, we used wheat as a model plant and focused on the interaction among plants, arbuscular mycorrhizal fungi (AMF) and hyphosphere bacteria. We conducted six independent but complementary experiments and demonstrated that AMF can enhance both wheat yield and grain N concentration, but only in specific varieties with high N conversion efficiency (grain yield per mean plant N at preanthesis). AMF can boost yield from increased grain weight via enhanced postanthesis photosynthetic carbon (C) assimilation through promoting plant phosphorus uptake, while elevating grain N concentration through stimulating postanthesis N uptake and assimilation. This dual effect arises from the enhanced postanthesis belowground C allocation, sustaining AMF hyphal network integrity and increasing soil nutrient availability via reshaping hyphosphere bacterial community structure. Our findings indicate that postanthesis plant–microbial interactions can potentially overcome an old dilemma between maximizing grain yield and N concentration in agricultural production.