Rhizophagus irregularis combined with biochar can improve the saline-alkali tolerance and energy quality of switchgrass through osmoregulation and salt- tolerance gene expression

Abstract Arbuscular mycorrhizal fungi (AMF) and biochar have potential applications in agriculture and ecological restoration. However, the effects of AMF combined with biochar on saline-alkali tolerance and bioenergy quality of plants under saline-alkali stress have yet to be thoroughly studied. In this study, we investigated the effects of Rhizophagus irregularis (Ri) and biochar application alone or in combination on growth, osmoregulation, ion uptake, expression of genes related to saline-alkali tolerance, and energy quality of switchgrass under saline-alkali stress. The results showed as follows: (1) The biomass of switchgrass in Ri combined with biochar treatment group was significantly higher than that in single treatment group (P < 0.05); (2) Ri combined with biochar increased the activity of antioxidant enzymes and the accumulation of osmoregulatory substances, and affected the synthesis of plant hormones; (3) Combined treatment significantly increased the contents of K+, Ca2+ and Mg2+ in leaves and roots, decreased the contents of Na+, and maintained high K+/Na+, Ca2+/Na+ and Mg2+/Na+; (4) Combined treatment could significantly induce stress response, active oxygen scavenging, ion transport and overexpression of cellulose biosynthesis genes in switchgrass leaves and roots; (5) Ri combined with biochar increased cellulose, hemicellulose and calorific value of switchgrass, and decreased lignin and ash content. Our research results prove that Ri combined with biochar can further enhance the saline-alkali tolerance of switchgrass, improve the quality of plant energy, and provide a new idea for increasing the planting area and improving the quality of energy plants.