AMF symbiosis drives the rhizosphere microbiome to synergistically improve herbage growth in saline–alkaline soils

Abstract

Plant–microbe interactions are essential in shaping plant performance and overall ecosystem functioning. However, the regulatory mechanisms underlying plant–microbe interactions mediated by mycorrhizal symbiosis in saline–alkaline soils are still not fully understood. Here, we aimed to clarify the synergistic regulatory mechanism through which arbuscular mycorrhizal fungi (AMF) symbiosis drives the rhizosphere microbiome to improve perennial herbage growth in saline–alkaline soils and evaluate phytoremediation efficiency. This study revealed that Funneliformis mosseae inoculation (i) strongly promoted the growth of all three herbage species (with values ranging from 21.62% to 233.33%), Na⁺ accumulation in plants (with values ranging from 24.63% to 188.89%), and decreased soil electrical conductivity (with values ranging from 7.68% to 12.87%), potentially suggesting improved phytoremediation efficiency with AMF symbiosis; (ii) increased nutritional content and decreased C:P and N:P ratios (with values ranging from 27.20% to 92.87%) and improved K⁺/Na⁺ and P/Na⁺ ratios (with values ranging from 2.60% to 302.96%); (iii) increased the abundance of some beneficial bacterial taxa and strengthened the significant strong relationships among most of these bacteria and plant biomass, ion homeostasis as well as stoichiometric ratio constants, and AMF inoculation treatments also consisted the higher proportion of differential genera significantly correlated with these plant factors as well as plant nutrient contents, potentially reflecting that AMF mediated the enrichment process of beneficial bacterial taxa and may strength functional interaction between plant and bacterial taxa, which may be importance for the enhancement of saline–alkaline tolerance of plants; and (iv) enhanced stability of the rhizosphere bacterial community and complexity of interaction networks, and the related indictors also established significant correlations with plant/soil factors, suggesting that the improvement of stability and functional complexity driven by AMF may also be beneficial for enhancing phytoremediation efficiency. These findings indicate that AMF inoculation plays its own beneficial role by simultaneously activating the potential of beneficial rhizosphere bacterial taxa and that their synergistic interaction is more beneficial for enhancing plant growth in salt-affected soils and enhancing phytoremediation efficiency. This study helps to elucidate the underlying mechanisms through which AMF-mediated rhizosphere bacterial community improve plant growth and tolerance to saline–alkaline stresses, and provides evidence that effective ecological restoration of saline–alkaline degraded grasslands can be achieved via the use of mycorrhizal symbiosis herbage.