Bioprospecting of wild botanicals against alternaria leaf blight of radish and their phytochemical profiling by GC–MS

Radish, considered a globally important crop, faces a severe threat from Alternaria blight. This pervasive and highly damaging disease causes black spots and blight on leaves in field conditions, resulting in reduced yield and seed quality. The study aimed to evaluate the antifungal potential of different wild botanicals against the Alternaria leaf blight pathogen through in vitro and in vivo studies and to analyze the phytochemicals using Gas Chromatography-Mass Spectrometry (GC–MS).

Among the fifty botanicals screened at 10% concentration against the pathogen, the aqueous extracts of Hemidesmus indicus, Lippia alba, Chromolaena odorata, and Solanum violaceum displayed the highest mycelial inhibition. Further in vitro evaluations of these four botanicals at different concentrations (2.5%, 5.0%, 7.5%, 10.0%, and 12.5%) revealed that at a 12.5% plant extract concentration H. indicus and L. alba exhibited the most effective inhibition of 82.96% and 76.60%, respectively, followed by C. odorata (71.93%) and S. violaceum (63.53%). Based on the promising in vitro results, these botanicals were assessed in pot experiments at 12.5% concentration. Among the four botanicals, the highest percentage of disease reduction was observed with H. indicus and L. alba, with 69.79% and 60.44%, respectively. Overall, the botanicals effectively reduced disease severity while increasing radish yield. GC–MS analysis of the phytochemicals revealed that the botanicals are composed of various bioactive compounds such as phenolics, flavonoids, saponins, and volatile compounds, which are known to exhibit antimicrobial activities.

This study emphasizes the potential of botanicals as a natural alternative for managing fungal diseases, offering resilient and sustainable approaches to safeguard crops from destructive fungal infections.