Interactions between arbuscular mycorrhizal fungi and phosphate-solubilizing fungus (Mortierella sp.) and their effects on Kostelelzkya virginica growth and enzyme activities of rhizosphere and bulk soils at different salinities

This study investigated the interactions between two arbuscular mycorrhizal fungi (AMF) (Glomus aggregatum and Glomus mosseae) and a P-solubilizing fungus (Mortierella sp.), with respect to their effects on growth of Kostelelzkya virginica and urease, invertase, neutral phosphatase, alkaline phosphatase, and catalase activities of rhizosphere and bulk soils at different salinity levels (i.e., 0, 100, 200, and 300 mM NaCl). Percentage of AMF colonization, Mortierella sp. populations, pH, electrical conductivity, and available P concentration in soil were also determined. Combined inoculation of AMF and Mortierella sp. increased the percentage of AMF colonization and Mortierella sp. populations under salt stress (i.e., 100, 200, and 300 mM NaCl). The dual inoculation of Mortierella sp. with AMF (G. aggregatum or G. mosseae) had significant effects on shoot and root dry weights and available P concentrations, pH values, and electrical conductivities of rhizosphere and bulk soils under salt stress. The inoculation of Mortierella sp. significantly enhanced the positive effects of AMF on some enzyme activities (i.e., neutral phosphatase, alkaline phosphatase, and catalase in bulk soil; neutral phosphatase and urease in rhizosphere soil); on the contrary, it produced negative effects on urease activities in bulk soil and invertase activities in bulk and rhizosphere soils. The results indicated that the most effective co-inoculation was the dual inoculation with Mortierella sp. and G. mosseae, which may help in alleviating the deleterious effects of salt on plants growth and soil enzyme activities.