In Vitro and In Vivo Antifungal Activities of Nine Commercial Essential Oils against Brown Rot in Apples

Assia El Khetabi,Zineb Belabess,Othmane Merah,Lahsen El Ghadraoui,Abdessalem Tahiri,Said Ezrari,Lhoussain Ait Haddou,Rachid Lahlali

doi:10.3390/horticulturae7120545

Abstract

After harvest, numerous plant pathogenic fungi can infect fresh fruits during transit and storage. Although synthetic fungicides are often used to manage postharvest fruit diseases, their application may lead to problems such as the development of fungicide resistance and residues on fruits. In the present study, the antifungal potential of nine commercial essential oils (EOs) extracted from Eucalyptus radiata ssp. radiata, Mentha pulegium, Rosmarinus officinalis, Origanum compactum, Lavandula angustifolia, Syzygium aromaticum, Thymus vulgaris, Citrus aurantium, and Citrus sinensis were tested against the apple brown rot fungi Monilinia laxa and Monilinia fructigena at different concentrations in vitro (against mycelial growth and spore germination) and in vivo (on detached apple fruit and in semi-commercial postharvest conditions). In addition, fruit quality parameters were evaluated and the composition of the EOs was characterized by Fourier transform infrared (FT-IR) spectroscopy. In vitro results showed significant antifungal activity of all tested EOs on both fungal species. EOs from S. aromaticum were the most effective, whereby inhibition percentages ranged from 64.0 to 94.7% against M. laxa and from 63.9 to 94.4% against M. fructigena for the concentrations 12.5 and 100 µL/mL, respectively, with an EC50 of 6.74 µL/mL for M. laxa and 10.1 µL/mL for M. fructigena. The higher concentrations tested of S. aromaticum, T. vulgaris, C. aurantium, and C. sinensis EOs significantly reduced spore germination, brown rot incidence, and lesion diameter. Evaluation of the treatments during storage for 20 days at 4 °C on apple fruit quality parameters demonstrated the preservation of the fruit quality characteristics studied (weight loss, total soluble solids, titratable acidity, firmness, and maturity index). FT-IR spectra obtained from all tested EO samples presented characteristic peaks and a high diversity of functional groups such as O–H groups, C–H bonds, and C–C stretching. The EOs examined here may have the potential for controlling postharvest fungal diseases of fruit such as brown rot.

Highlights

The Fourier transform infrared (FT-IR) spectrum was used to determine functional groups of active compounds of the essential oils (EOs) based on the peak level in the infrared radiation area
Our findings revealed that T. vulgaris has a significant impact on apple fruit brown rot, which is similar to the findings of other researchers who examined
The results obtained through in vitro spore germination, in vivo fruit quality parameters, and FT-IR characterization highlighted that most examined EOs can be used to inhibit or reduce infections produced by M. laxa, and M. fructigena with small differences between both fungi at any concentration

Summary

Introduction

Borkh) are a member of the Rosaceae family and Spiraoideae subfamily. It is a major cultivated fruit grown widely in temperate regions around the world [1]. Horticulturae 2021, 7, 545 major production areas are situated in the High and Middle Atlas, in the two regions of Daraa-Tafilalt and Fez-Meknes. These locations account for more than half of the country’s apple-cultured area [2]. Part of this production is held in cold storage for prolonged marketing, when large quantities of fruit are harvested over a short period of time [3]

Methods

Results

Discussion

Conclusion