Biocontrol of Agroathelia rolfsii: Harnessing plant extracts and beneficial microbes to induce host resistance in vitro

Cluster bean (Cyanopsis tetragonoloba L. Taub) is a significant leguminous crop cultivated in the dry and semi-arid regions of India during the Kharif season. In recent years, stem rot caused by the soil-borne pathogen Agroathelia rolfsii has emerged as a severe disease, leading to substantial yield losses ranging from 50 to 70%. The reliance on broad-spectrum chemical pesticides for disease management raises concerns regarding food safety, soil health, and environmental sustainability. Due to concerns over the environmental and health impacts of continuous chemical pesticide use, this study investigated alternative management strategies. An in vitro assay was conducted to evaluate the efficacy of biological control agents and plant extracts against the pathogen. Among the bioagents, Trichoderma harzianum and Pseudomonas fluorescens demonstrated the highest mycelial growth inhibition, at 70.78% and 50.78%, respectively. Evaluating plant extracts at various concentrations (5%, 10%, 15%, and 20%) revealed the 20% concentration to be most effective. At this concentration, extracts of Citrullus colocynthis (60.50% inhibition), Azadirachta indica (53.77%), and Datura stramonium (52.29%) were the most effective in suppressing fungal growth. The results indicate that these biocontrol agents and plant extracts represent a potent and eco-friendly strategy for the integrated management of stem rot in cluster bean, offering an effective alternative to chemical pesticides.