Vaccinium corymbosum interact with mycorrhizal fungi to affect nitrogen metabolism and alleviate soil nutrient limitation

By helping their hosts access soil nitrogen (N), ericoid mycorrhizal fungi (EMF) perform a crucial role in ecosystem processes. However, how plants sense and take up N during EMF symbiosis and the integration of EMF in the soil N cycle with the analysis of N balance and symbiotic dynamics is still far from being well understood. In this study, the experimental system of EMF Oidiodendron maius 143 inoculated and non-inoculated blueberry plants under three N levels were established. Results showed that EMF inoculation significantly improved plants soluble protein content, chlorophyll content, total N, NO₃⁻ and NH₄⁺ contents, and mediated changed in root configuration under low N treatments. EMF-inoculated plants significantly increased the activities of N-related enzymes and up-regulated N metabolism genes. However, as the N level rose, these effects eventually disappeared and the rate of EMF colonization significantly decreased. Congruently, EMF inoculation also significantly alleviated microbial N limitation under low N conditions. EMF inoculation and soil organic carbon were the main causes of microbial P limitation by influencing soil available P, and N levels directly regulated P limitation. Microbial C limitation was mainly mediated by N levels, pH and soil N:P ratios, where N levels mediate soil acidification. In conclusion, our results suggested that low N levels favored blueberry symbiosis with EMF, and N levels influenced C, P, and N limitation of soil microbial communities, where mycorrhizal fungi may play an important role in balancing nutrient stoichiometry.