The influence of covering methods on the microbial community, physicochemical properties and enzyme activities of Grifola frondosa cultivation substrate
Grifola frondosa is a rare and valuable edible and medicinal fungus, whose growth and development highly depend on the microenvironment of the cultivation substrate. Casing is a key cultivation practice for regulating the substrate microenvironment and inducing primordia formation. However, the mechanisms by which different casing materials comprehensively regulate the physicochemical properties, microbial community, and enzyme activities of the substrate to influence the growth microenvironment of G. frondosa remain unclear. This study aimed to investigate the comprehensive effects of five different casing methods (Bamboo Leaves, Soil Mulching, Pine Needles, Organic Fertilizer, Straw) on the microbial community structure, physicochemical properties, and enzyme activities of the G. frondosa cultivation substrate, with no casing as the control (CK). A randomized block design was adopted, and rhizosphere substrate samples were collected at 116 days after casing. High-throughput sequencing, conventional biochemical analysis, and enzyme-linked immunoassays were employed for determination. The results showed that different casing treatments had significant and differentiated regulatory effects on the substrate microenvironment. The Organic Fertilizer treatment significantly increased the contents of total nitrogen, available nitrogen, available phosphorus, and organic matter in the substrate. The Straw treatment showed the highest available potassium content. Regarding microbial biomass, the Organic Fertilizer treatment resulted in the highest microbial biomass carbon and microbial biomass phosphorus, while the Soil Mulching treatment significantly reduced microbial biomass nitrogen. Concerning enzyme activities, the Organic Fertilizer treatment significantly enhanced dehydrogenase and acid protease activities; the Bamboo Leaves treatment specifically stimulated urease activity; whereas the control group maintained higher beta-glucosidase and catalase activities. The fungal community responded more sensitively to casing treatments; Bamboo Leaves casing significantly increased the richness and diversity of the fungal community and possessed the most unique OTUs. This study systematically reveals the mechanisms through which different casing materials reshape the microecology of the G. frondosa cultivation substrate via differentiated pathways: Organic Fertilizer acts as an efficient nutrient source and microbial metabolism activator; Bamboo Leaves serves as an excellent fungal diversity promoter and urease-specific inducer; Straw is an effective potassium activator. These findings elucidate the mechanism of casing management from a microecological perspective, providing a solid theoretical basis and data support for developing green and efficient cultivation techniques for G. frondosa based on microecological regulation.