Clove Essential Oil as an Alternative Approach to Control Postharvest Blue Mold Caused by Penicillium italicum in Citrus Fruit

Abstract

Penicillium italicum causes blue mold disease and leads to huge economic losses in citrus production. As a natural antifungal agent, clove essential oil (CEO), which is a generally recognized as safe (GRAS) substance, shows strong in vitro activity against fungal pathogens. However, few studies on CEO for controlling postharvest blue mold disease caused by P. italicum in citrus fruit have been reported. Our aims were to investigate the control efficacy and possible mechanisms involved of CEO against P. italicum. In the present study, CEO treatment inhibited the disease development of blue mold when applied at 0.05% to 0.8% (v/v), and with the effective concentration being obtained as 0.4% (v/v). Besides its direct antifungal activity, CEO treatment also spurred a rapid accumulation of H2O2 compared with untreated fruits, which might contribute to enhancing an increase in the activities of defense-related enzymes, such as β-1,3-glucanase (β-Glu), chitinase (CHI), phenylalanine ammonia-lyase (PAL), peroxidase (POD), polyphenol oxidase (PPO), and lipoxygenase (LOX) in citrus fruit. Results of real time-quantitative polymerase chain reaction (RT-qPCR) showed that the gene expressions of β-Glu, CHI, PAL, POD and PPO were up-regulated in CEO-treated fruits. At the same time, CEO treatment led to down-regulated expression of the LOX gene in citrus fruit. Clove essential oil effectively control the disease incidence of blue mold decay in citrus fruit by motivating the host-defense responses, suppressing the malondialdehyde (MDA) accumulation while enhancing the activities and gene expressions of defense-related enzymes. Our study provides an alternative preservative applying CEO to reduce postharvest fungal decay in citrus fruit.

Physiological and Proteomic Analysis of Penicillium digitatum in Response to X33 Antifungal Extract Treatment

“…The current knowledge suggested that the ZOI of P. digitatum increased in a dose-dependent manner, indicating significant inhibition of the growth of P. digitatum by the X33 antifungal extract. In addition to the antifungal agents thymol ( Perezalfonso et al, 2012 ), chitosan oligomers ( Lu et al, 2014 ), clove essential oil ( Chen et al, 2019a ), and trans-cinnamaldehyde ( Huang et al, 2019 ), this study suggests a novel fungicide to control citrus postharvest green mold. Compared to other antifungal agents, the X33 antifungal extract, a poly-L-lysine analog derived from S. lavendulae , exhibited excellent antifungal activity.…”

Pinocembrin-7-Glucoside (P7G) Reduced Postharvest Blue Mold of Navel Orange by Suppressing Penicillium italicum Growth

“…Medicinal plant extracts and their bioactivators are being paid increasing attention by researchers due to their potential to control fungal growth as well as their preservative effects [3,21,25,30,37,38]. Among plant extracts, Ficus hirta Vahl.…”

“…The effects of P7G on lesion diameter and disease severity in navel oranges were determined following the method previously described with slight modifications [30,31]. The sterilized navel oranges were wounded (4 mm diameter and 2-mm deep) using a sterile puncher at the equatorial side on each fruit, and then divided in five randomized groups for various P7G treatment levels (0, 1, 2, 4, and 8 g/L).…”

“…The lesion diameter was measured by the cross method using a Vernier caliper. The disease severity was evaluated and expressed as a percentage following a previously described method [30].…”

“…The activities of chitinase (CHI) and β-1,3-glucanase (β-Glu) were determined by our previously described method [30]. One unit of the above two activities was equal to the amount of enzyme that catalyzed the production of 1.0 nM N-acetyl-d-glucosamine (GlcNAc) and 1 µg of reducing sugar per min of 1 g fresh weight mycelia.…”