Management of postharvest blue mold of apple caused by Penicillium fuscoglaucum using a gel formulation containing Monarda citriodora essential oil and linalool.

Abstract

This study aimed to develop essential oil-containing biopolymer-based vapor gel formulations for the postharvest management of blue mold of apples. Apples are one of the widely cultivated fruits. They are susceptible to a wide range of fungus leading to high losses in overall production. Many research articles have highlighted the applications of essential oil-biopolymer coatings in the postharvest storage of fruits. However, no studies have yet tried to explore the potential of a vapour gel formulation for postharvest applications. Contaminated apples were collected from the local market. The causative fungus was isolated and identified. Minimum fungicidal concentrations of Monarda citriodora essential oil (MEO) and hexanal/linalool in the vapour phase were determined in vitro. In vitro and in vivo, checkerboard assays were used to demonstrate the synergistic activity between MEO and hexanal/linalool vapours against the isolated pathogen. MEO and linalool (M+L) combinatorial treatment indicated synergy in vivo and in vitro. In vivo treatment of M+L on apples by direct fumigation showed phytotoxicity. Gel formulations (carrageenan-guar gum, carbopol gel, and soft gel) were developed and evaluated to address phytotoxicity. M+L combination synergistically remediated the phytotoxicity in both carbopol (FICI=0.625) and soft gels (FICI=0.5625). The physicochemical parameters (pH, weight loss, TSS, and ascorbic acid (AsAC) of the treated apples were analysed. Reduction in weight loss and increase in AsAC were observed for treated fruits when compared to control, and no change in pH and TSS was observed. Biopolymer vapor gel formulations containing M+L vapours effectively protect apples from the postharvest blue mold for extended storage.