Sustainable management of postharvest Fusarium rot in melon: A multi-target strategy based on bioactive extracts

Abstract

This study evaluated the efficacy of various bioactive extracts (BEs) as sustainable alternatives to synthetic fungicides for controlling postharvest peduncular rot caused by Fusarium falciforme and F. sulawesiense in ‘Yellow’ melon ( Cucumis melo L.). Under in vitro conditions, all tested extracts - eucalyptus extract (EUE), brown propolis extract (BPE), red propolis extract (RPE), green propolis extract (GPE), and pyroligneous extract (PYE) - demonstrated concentration-dependent inhibition of fungal growth, with the highest efficacy observed at 8% (v/v) concentration. Notably, PYE and RPE emerged as the most potent inhibitors, exhibiting statistically significant differences compared to the other treatments. This superior activity was likely due attributed to the high concentrations of acetic acid, phenols, and isoflavonoids, which are known to disrupt fungal membrane integrity and mitochondrial function. In in vivo assays, BEs application significantly reduced postharvest peduncular rot severity did not compromising the physicochemical quality of the fruits. Critical parameters, such as total soluble solids (TSS) and pH, remained stable across treatments, indicating that these bio-based solutions can successfully replace conventional fungicides (e.g., fludioxonil) without impacting the marketability of melon fruits. Biochemical analysis revealed that the extracts significantly increased the activities of oxidative defense enzymes, including catalase (CAT) and peroxidase (POX), alongside key phenylpropanoid pathway enzymes, namely phenylalanine ammonia-lyase (PAL) and polyphenol oxidase (PPO). This induction of the host’s defense system, coupled with a concomitant reduction in hydrogen peroxide (H 2 O 2 ) levels, suggests that BEs mitigate disease by promoting reactive oxygen species (ROS) detoxification and tissue lignification in postharvest melon fruit. Based on in vitro and in vivo data, bioactive extracts, particularly RPE and GPE, are highly effective at suppressing Fusarium species while preserving essential postharvest fruit quality. These findings offer a promising, eco-friendly strategy for managing postharvest decay in melon production systems destined for premium international markets.