The Co-Application of Piriformospora Indica and Vermicompost Enhances the Drought Resistance of Apple

Climate change has increased drought frequency in Loess Plateau apple-producing regions. Vermicompost (Vc) and Piriformospora indica (Pi) have been reported to improve plant drought resistance. However, the effects of their combined application on apple growth, soil environment and soil microbial community under drought remains unexplored. Here, we investigated these effects through a 90 days pot experiment with four treatments (control, Vc, Pi, Pi+Vc) under well-watered (WW) and drought stress (DS). The results indicated DS inhibited plant growth and nutrient uptake, and also increased the levels of H2O2 and MDA. However, Pi+Vc treatment significantly increased relative growth rate (RGR), and enhanced antioxidant enzyme activities and nutrient absorption under DS, but did not significantly affect biomass accumulation. Vc and Pi+Vc improved soil nutrients and enzyme activities under both WW and DS, whereas Pi alone showed no significant benefit. Although the treatments differentially affected bacterial and fungal diversity, the co-application of Pi and Vc enhanced microbial diversity under DS. Individual or combined Pi and Vc altered the structure and composition of microbial communities, and increased microbial co-occurrence network modularity. PLS-SEM analysis further demonstrated that the co-application of Pi and Vc promote the plant growth were closely related to bacterial community restructuring under DS. Collectively, this study suggests that combined Pi and Vc application hold potential for improving apple seedling drought tolerance, providing a foundation for future field-based validation on the Loess Plateau.