Genistein: A promising botanical fungicide candidate for enhancing tomato yield and quality by controlling Alternaria solani.

The overreliance on traditional chemical fungicides, combined with the emergence of resistance, poses significant challenges for food safety. Early blight, caused by the fungal pathogen Alternaria solani (A. solani), is among the most significant contributors to pre- and postharvest yield losses in tomato cultivation. To address this challenge, through evaluation of the antifungal activity of 52 commercially available natural products against A. solani, we revealed for the first time that the naturally occurring compound genistein exhibited potent fungicidal activity against A. solani, with an EC50 value of 6.53 μg/mL, surpassing that of chlorothalonil (EC50 = 8.35 μg/mL). In vivo assays demonstrated that genistein exhibited strong protective (48.1 %) and therapeutic (42.5 %) efficacy, effectively safeguarding tomatoes from fungal infection. Mechanistic investigations, including transcriptomic analysis, scanning electron microscopy, fluorescence imaging, and measurements of malondialdehyde and ATP levels, collectively indicated that genistein disrupted energy metabolism, leading to reactive oxygen species (ROS) accumulation. This oxidative stress cascade triggered both apoptotic-like responses and membrane lipid peroxidation, ultimately inhibiting the growth of A. solani. Interestingly, genistein showed enhanced anti-A. solani activity when used in combination with either chlorothalonil or tebuconazole. Additionally, genistein displayed low phytotoxicity and favorable drug-likeness properties. Taken together, these findings elucidate the mechanisms underlying genistein's antifungal activity against A. solani, underscoring its promise as a natural antifungal agent for enhancing food safety and improving tomato yield and quality. Furthermore, this study provides valuable insights for the rational design of flavonoid-based antifungal agents.