AM fungus promotes wheat grain filling via improving rhizospheric water & nutrient availability under drought and low density

Arbuscular mycorrhizal fungi (AMF) are widely considered as ecosystem engineers to positively affect the adaptation of plants to adverse environments, but whether AMF can commonly promote root-soil relationships and reproductive allocation is unclear in dryland crops. It is crucial to reveal if AMF can promote grain filling via mediating rhizosphere interactions regardless of soil water regimes and planting densities in dryland crops for the application of AMF regarding more precise management. To address this issue, Funneliformis mosseae was inoculated in pot-cultured wheat to examine the inoculation effects on wheat growth, yield formation, rhizospheric moisture and nutrient status across four planting densities under the drought and well-watered conditions. As expected, under drought stress, wheat grain filling, shoot biomass, rhizospheric soil water content (SWC), water use efficiency (WUE), soil organic carbon (SOC) content and the ratio of SOC to soil total nitrogen (TN) contents were significantly lowered in the soils without AMF inoculation across four planting densities. Under well-watered conditions, the SWC ranged from 10.30 % to 16.64 %, while under water stress conditions, the values ranged from 5.77 % to 9.61 %. Soil mineralized nitrogen (NO3−-N and NH4+-N) contents were decreased with AMF regardless of soil water status and planting densities. Under drought stress, AMF inoculation increased wheat productivity, WUE, SWC, SOC content, the ratio of SOC to TN, and promoted the absorption of mineralized nitrogen. Particularly, AMF inoculation substantially promoted the soil easily oxidizable organic carbon (EOC) content by 58.5 % and 55.6 % in the two highest densities, respectively. The soil microbial biomass carbon (MBC) content was totally >50 mg kg−1, whereas that of the non-AMF group was