Bio-pesticidal Potential of Soapnut Saponins as a Sustainable Alternative for Managing Cowpea Web Blight: An in-vitro Evaluation

The present study examined the antifungal potential of saponin extracted from Sapindus species against the web blight pathogen of cowpea. The causal organism, identified as Rhizoctonia solani, was isolated from naturally infected cowpea plants exhibiting typical web blight symptoms. Comprehensive characterization of the pathogen was conducted through cultural, morphological, and molecular approaches and identified as R. solani. For the evaluation of soapnut saponins, the compounds were extracted from the fruit pericarp using two different solvents: ethanol and water, followed by lyophilisation. Ethanol proven to be the more efficient solvent in saponin extraction with an efficiency of 79.26%. The antifungal efficacy of the extracts was tested under in vitro conditions. The poisoned food technique was employed to determine their inhibitory effect on the mycelial growth of R. solani under different concentrations including 0.1%, 0.2%, 0.5%, 1.0% and 2.0%. The study demonstrated that Sapindus saponins exhibited significant antifungal activity, achieving up to 68.8% growth inhibition at 2%, indicating their potential as an eco-friendly alternative to conventional fungicides.