Quality control strategy for postharvest fragrant pears: pathogenesis of brown rot caused by Monilinia fructicola and protective mechanism of carvacrol.

Background: Brown rot, triggered by Monilinia fructicola, causes substantial postharvest losses. However, the widespread application of chemical fungicides has triggered the development of resistance in pathogenic fungi and the accumulation of hazardous residues. Plant-derived fungicides offer an eco-friendly alternative to chemical fungicides owing to their low toxicity and broad-spectrum activity.

Results: Monilinia fructicola secreted acidic substances that reduced pH while increasing pectinase (PG) and cellulase (Cx) activities by 230.6% and 59.8%, respectively, leading to an increase of 85.9% in hydrogen peroxide (HO), slight increases in superoxide dismutase (SOD; 15.1%), catalase (CAT; 5.8%) and peroxidase (POD; 9.2%), and elevations in malondialdehyde (MDA content and conductivity by 48.8% and 49.4%. Meanwhile, it reduced defense enzyme activity [phenylalanine ammonialyase (PAL), β-1,3-glucanase (GLU), Chitinase (CHI)] and secondary metabolite secretion (lignin, total phenol, flavonoids). By contrast, carvacrol treatment inhibited M. fructicola in vitro [median effective concentration (EC) of 24.2 mg L] and lesion diameter expansion in vivo. Additionally, it controls pH values and decreases Cx and PG activity, and reduces reduced HO, MDA and conductivity accumulation by enhancing antioxidant enzymes. Meanwhile, CVR treatment restores the defense system by promoting the activity of defense enzymes and secondary metabolite secretion, thus achieving a protective effect against M. fructicola invasion.

Conclusion: This study demonstrated that carvacrol can increase the resistance of pears to M. fructicola and protect them from pathogens, thus prolonging the storage period. This research provides a novel approach to controlling brown rot in fruit caused by M. fructicola, which has profound implications for the global fruit industry and is of great economic and environmental significance. © 2025 Society of Chemical Industry.