Biological Control Potential of Trichoderma virens Against Pythium ultimum Causing Damping-Off in Cucumber Seedlings

Abstract

Damping-off caused by Pythium ultimum is a serious soilborne disease of cucumber seedlings, resulting in poor crop establishment and significant economic losses in vegetable production systems. The present study evaluates the biological control potential of Trichoderma virens against P. ultimum under laboratory and greenhouse conditions. Antagonistic activity was assessed through dual culture assays, volatile and non-volatile metabolite tests, and seedling protection experiments. Results indicated that T. virens significantly inhibited mycelial growth of P. ultimum through rapid colonization, competition for nutrients, and production of antifungal metabolites. Microscopic observations revealed hyphal coiling, distortion, and lysis of P. ultimum hyphae in the presence of the antagonist, suggesting mycoparasitism as a key mechanism. Greenhouse experiments demonstrated a substantial reduction in damping-off incidence in cucumber seedlings treated with T. virens compared to untreated controls. Treated seedlings showed improved germination percentage, enhanced root and shoot growth, and increased overall vigor. Disease suppression was more pronounced under conditions favorable for both pathogen and antagonist activity, particularly in moist soils. The study also indicated that early application of T. virens provided better protection by establishing effective root colonization and competitive exclusion of the pathogen. These findings highlight the multifaceted biocontrol mechanisms of T. virens, including antibiosis, competition, and mycoparasitism, contributing to effective suppression of P. ultimum. Overall, the results demonstrate that T. virens has strong potential as a sustainable and eco-friendly biocontrol agent for managing damping-off disease in cucumber. Its integration into nursery management practices can reduce reliance on chemical fungicides and promote healthier seedling establishment in vegetable production systems.