Molecular Characterization of Strawberry Mold and Antifungal Potential of Psidium guajava and Laurus nobilis Extracts for Post-Harvest Quality Preservation

Postharvest decay, especially gray mold caused by Botrytis cinerea, severely restricts the shelf life of strawberries (Fragaria × ananassa Duch) and causes significant economic losses. This study investigated the potential of Psidium guajava (Pg) and Laurus nobilis (Ln) leaf extracts as natural antifungal agents, both individually and within a gum arabic (GA) edible coating, to preserve strawberry quality. Phytochemical analysis showed that Pg extract was rich in phenolics (63.14 mg GAE/g), while Ln extract was higher in flavonoids (29.15 mg QE/g), both exhibiting significant antioxidant and antifungal characters against B. cinerea. In an in vivo trial, strawberries were treated and stored at 4°C for twelve days. The GA-Pg composite was the most effective. It reduced decay incidence (DI) to 42.22% and decay severity (DS) to 15.56%, a significant improvement over the control fruit, which reached 97.78% DI and 58.33% DS. Furthermore, these composite treatments excelled at preserving critical quality attributes, including total soluble solids (TSS), titratable acidity (TA), ascorbic acid, and phytochemical content (total phenolics, flavonoids, and anthocyanins), thereby maintaining higher antioxidant capacity. At a molecular level, the GA-Pg and GA-Ln treatments significantly tear down the relative expression of pectin-degrading genes, pectin lyase (PL) and pectin esterase (PE), which are responsible for fruit softening. These findings demonstrate that a composite edible coating of gum arabic with P. guajava or L. nobilis extract is a promising, eco-friendly postharvest strategy to control fungal decay, maintain quality of fruit, and extend the life span of strawberries.