Soil pH and potassium drive root rot in Torreya grandis via direct modulation and microbial taxa-mediated pathways

Abstract

Root rot, a common soil-borne disease in Torreya grandis plantations, significantly reduces yields and causes economic losses. The occurrence and severity of plant root rot are influenced by climatic conditions and soil physicochemical properties at the planting sites. However, the specific relationships between T. grandis root rot and those factors remain poorly understood, and the key environmental driving factors have yet to be elucidated. In this study, we analyzed the differences in climatic conditions and soil physicochemical properties among six T. grandis planting sites across different regions. High-throughput sequencing was employed to analyze fungal community composition and co-occurrence network characteristics in healthy and diseased soils. Results indicated that root rot incidence was not significantly correlated with temperature, precipitation, or elevation. Compared to healthy soils, diseased soils exhibited lower organic matter, total nitrogen, and total potassium contents. Fungal community analysis revealed that the diversity and stability of fungal communities were decreased in the diseased soils. No significant difference was observed in the relative abundance of Fusarium between healthy and diseased soils. In diseased soils, the abundance of Exophiala and Gibellulopsis was positively correlated with Fusarium abundance. SEM further revealed that soil pH and total potassium were directly associated with root rot incidence (p < 0.05), while Fusarium, Gibellulopsis, and Aspergillus were indirectly related to root rot incidence. To summarize, effective management, particularly maintaining optimal soil pH and total potassium levels, is expected to influence the composition of the soil microbial community and reduce the incidence of T. grandis root rot.