Changes in Microbial Diversity During Dictyophora indusiata Mycelium Regression Period

Dictyophora indusiata cultivation is severely impeded by premature hyphal regression. This study elucidates the spatiotemporal dynamics of mycelial regression and associated microbial succession in both substrate and soil matrices across progressive regression stages (CK: normal growth; S1: initial recession; S2: advanced recession; S3: complete recession). Microscopic analysis revealed preferential mycelial regression in the substrate, preceding soil regression by 1–2 stages. High-throughput sequencing demonstrated significant fungal community restructuring, characterized by a sharp decline in Phallus abundance (substrate: 99.7% → 7.0%; soil: 78.3% → 5.5%) and concomitant explosive proliferation of Trichoderma (substrate: 0% → 45.2%; soil: 0.1% → 55.3%). Soil fungal communities exhibited a higher richness (Chao1, p < 0.05) and stability, attributed to functional redundancy (e.g., Aspergillus, Conocybe) and physical protection by organic–mineral complexes. Conversely, substrate bacterial diversity dominated, driven by organic matter availability (e.g., the Burkholderia–Caballeronia–Paraburkholderia complex surged to 59%) and optimized porosity. Niche analysis confirmed intensified competition in post-regression soil (niche differentiation) versus substrate niche contraction under Trichoderma dominance. Critically, Trichoderma overgrowing was mechanistically linked to (1) nutrient competition via activated hydrolases (e.g., Chit42) and (2) pathogenic activity (e.g., T. koningii causing rot). We propose ecological control strategies: application of antagonistic Bacillus subtilis (reducing Trichoderma by 63%), substrate C/N ratio modulation via soybean meal amendment, and Sphingomonas–biochar soil remediation. This work provides the first integrated microbial niche model for D. indusiata regression, establishing a foundation for sustainable cultivation.