Red root rot alters root-zone microbial communities and enzyme activities in Hevea brasiliensis

Abstract

Rubber tree (Hevea brasiliensis) is an important industrial raw material and strategic resource in China, and red root rot caused by the pathogenic fungus Ganoderma pseudoferreum is its most severe root disease. However, the differences in rhizosphere microbial communities between healthy and diseased rubber trees remain unclear. This study employed Illumina Mi-Seq sequencing to investigateanalyzed the rhizosphere microbial communities in healthy and diseased trees, analyzing the relationships among soil properties, enzyme activities, and disease incidence. The occurrence of red root rot increased the richness and diversity of both bacterial and fungal populations in the rhizosphere soil. Principal Coordinates Analysis indicated that while overall community structures were not significantly different, fungal composition played a more critical role in disease development than bacterial composition. At the phylum level, Acidobacteria, Proteobacteria, Actinobacteria, and Firmicutes dominated bacterial communities, with Actinobacteria was significantly reduced in diseased soils. For fungi, Basidiomycota, Ascomycota, and Mortierellomycota were predominant, diseased plant root-zone exhibited a significantly higher abundance of Ascomycota but a markedly reduced abundance of Basidiomycota (P p < 0.05). Notable genus-level changes revealed a dramatic fungal community shift. The beneficial genus Termitomyces plummeted from 37.50% in healthy soils to 0.026% in diseased soils. Concurrently, Hygrocybe, Peniophora, unclassified Archaeorhizomycetes, and Ganoderma increased substantially (82.13%, 98.59%, 69.74%, and 97.87%, respectively), indicating a transition from mutualistic to pathogenic taxa. These genus-level changes may be closely associated with red root rot development. Diseased soils exhibited significantly higher pH, soil water content, total nitrogen, sucrase, and catalase activities, but lower nitrate nitrogen and acid phosphatase. Correlation analysis showed that soil pH, total nitrogen, water content, available phosphorus, catalase, and sucrase were positively correlated with Ganoderma and Archaeorhizomyces, while nitrate nitrogen and acid phosphatase correlated positively with Termitomyces. This study elucidates the interrelationships among rhizosphere microbiota, soil properties, and red root rot, providing a scientific basis for developing ecological disease management strategies in rubber plantations.