Inhibitory Effect of Trichoderma harzianum Strain A3.1 Against Fusarium Species Causing Fig Root Rot

To identify the causal pathogen of fig root rot in Artux, Xinjiang, China and screen high-efficacy biocontrol agents, diseased fig root tissues were used as research materials. Pathogen isolation, morphological characterization, molecular identification and pathogenicity assays were sequentially performed to characterize the disease-causing fungus, followed by screening of antagonistic microorganisms. The results demonstrated that the pathogen responsible for fig root rot was Fusarium kazakhstanicum. To the best of our knowledge, this is the first report of F. kazakhstanicum causing fig root rot on Ficus carica in China. A highly effective antagonistic fungal strain designated A3.1 was isolated from the rhizosphere soil of healthy fig trees, and was identified as Trichoderma harzianum based on morphological traits and molecular phylogenetic evidence. Dual-culture assays revealed that T. harzianum A3.1 achieved a mycelial growth inhibition rate of 72.5% against F. kazakhstanicum. Light microscopic and scanning electron microscopy observations further illustrated that T. harzianum A3.1 severely disrupted the hyphal architecture of the pathogen, causing hyphal deformation and granular deposits at the contact sites. This strain possesses great application prospects for biocontrol against the pathogen causing fig root rot, and this research lays a foundation for developing environmentally sustainable control strategies of fig root rot in Xinjiang, China.