Multifaceted evaluation of onion bio-actives against Fusarium oxysporum f.sp. Cubense: Bio-efficacy assay, LC-MS metabolomics and in-silico validation.
Panama wilt is a devastating disease caused by the soilborne fungus Fusarium oxysporum f. sp. cubense (Foc) and poses a serious threat to the global banana industry, including the expanding plantations of Jharkhand, India. In this study, the antifungal potential of onion (Allium cepa L.) bulb extract against Foc was evaluated in a multifaceted way, including field surveys,in vitroassays, LC-MS metabolomics and molecular docking. Field surveys in East and West Singhbhum districts showed disease incidence rates ranging from 15.7% to 53.4%. In vitro evaluation using the poisoned-food technique revealed concentration-dependent inhibition of mycelial growth, with the highest reduction of 62.65% observed at a 20% extract concentration. The greenhouse study showed that the 20% extract concentration was the most effective. It had the lowest wilt incidence (25%) and the highest disease reduction (73.68%) compared to the untreated control (95%). Ethanolic onion extract was profiled by LC-MS, resulting in the identification of a wide variety of bioactive compounds, mainly alkaloids and isoquinoline derivatives, with 2-methoxy-5-dehydro-scoulerine as the most abundant metabolite. We conducted molecular docking studies on the SGE1 protein, a key regulator of Foc pathogenicity. Our results indicated that several identified compounds exhibited high binding affinities, particularly dihydronitidine (-8.1 kcal/mol) and fagaronine (-7.4 kcal/mol), which formed stable interactions within the enzyme's catalytic pocket via hydrogen bonding and aromatic Pi interactions. These results suggest that onion bio-actives can effectively suppress Foc virulence by targeting key pathogenicity factors. Our study demonstrates the efficacy of onion bulb extract as a botanical alternative for managing Panama wilt, offering a sustainable solution for smallholder farmers.