Mixed inoculation of dark septate endophytic and ericoid mycorrhizal fungi in different proportions improves the growth and nutrient content of blueberry seedlings

Despite extensive studies on the interaction between dark septate endophytes (DSE) and host plants, little is known about the effects of mixed inoculation of DSE and ericoid mycorrhizal fungi (ERMF) on plants. We assessed the effects of mixed inoculation of five species of ERMF and five species of DSE on soil factors and growth and physiological functions of blueberry (Vaccinium corymbosum L. 'O'Neal') seedlings. The strains were isolated from blueberries in several regions of Guizhou Province. The fungi suspension root irrigation method was used to inoculate the seedlings. Six inoculation treatments, i.e. D (Cladosporium cladosporioides), N (Oidiodendron citrinum), D1N1 (D : N, 1:1), D1N2 (D : N, 1:2), D2N1 (D : N, 2:1) and CK (not inoculated) were conducted. Samples were collected two months after inoculation. The mixed inoculation of DSE and ERMF significantly promoted the height, stem diameter, shoot dry weight, total biomass, root activity and total chlorophyll content of the blueberry seedlings and enhanced their absorption capacity to mineral nutrients. The mixed inoculation also improved the activities of soil enzymes such as urease and acid phosphatase. The effect of mixed inoculation was better than that of single inoculation or CK. Combining the analysis results of the membership function, we concluded that D1N2 and D2N1 most significantly promoted the growth of blueberry seedlings. These data provide a basis for the potential application of DSE and ERMF mixed inoculation for promoting the growth of seedlings.