Antifungal Activity and Chemical Composition of Seven Essential Oils to Control the Main Seedborne Fungi of Cucurbits.

Marwa Moumni,Mohamed Bechir Allagui,Basma Najar,Olfa Karous,Ikbal Chaieb,Gianfranco Romanazzi,Luisa Pistelli,Kaies Mezrioui,Hajer Ben Amara

doi:10.3390/antibiotics10020104

Abstract

Essential oils represent novel alternatives to application of synthetic fungicides to control against seedborne pathogens. This study investigated seven essential oils for in vitro growth inhibition of the main seedborne pathogens of cucurbits. Cymbopogon citratus essential oil completely inhibited mycelial growth of Stagonosporopsis cucurbitacearum and Alternaria alternata at 0.6 and 0.9 mg/mL, respectively. At 1 mg/mL, Lavandula dentata, Lavandula hybrida, Melaleuca alternifolia, Laurus nobilis, and two Origanum majorana essential oils inhibited mycelia growth of A. alternata by 54%, 71%, 68%, 36%, 90%, and 74%, respectively. S. cucurbitacearum mycelia growth was more sensitive to Lavandula essential oils, with inhibition of ~74% at 1 mg/mL. To determine the main compounds in these essential oils that might be responsible for this antifungal activity, they were analyzed by gas chromatography–mass spectrometry (GC-MS). C. citratus essential oil showed cirtal as its main constituent, while L. dentata and L. nobilis essential oils showed eucalyptol. The M. alternifolia and two O. majorana essential oils had terpinen-4-ol as the major constituent, while for L. hybrida essential oil, this was linalool. Thus, in vitro, these essential oils can inhibit the main seedborne fungi of cucurbits, with future in vivo studies now needed to confirm these activities.

Highlights

Cucurbits are an important source of income for countries in the Mediterranean basin, with a total production of nearly 3,356,669 tonnes in 2018 [1]
This study investigated seven essential oils for in vitro growth inhibition of the main seedborne pathogens of cucurbits
The effects of increasing concentrations of seven essential oils on mycelial growth of the fungi A. alternata and S. cucurbitacearum were investigated. These essential oils were from various sources, and are defined as: C.cit, Cymbopogon citratus; L.dent, Lavandula dentata; L.hyb, Lavandula hybrida; M.alt, Melaleuca alternifoglia; L.nob, Laurus nobilis; O.maj1/2, Origanum majorana 1/2

Summary

Introduction

Cucurbits are an important source of income for countries in the Mediterranean basin, with a total production of nearly 3,356,669 tonnes in 2018 [1]. Cucurbita spp. can be affected by a number of fungal pathogens, which can cause major economic losses [2]. The majority of these fungi are seedborne, such as gummy stem blight (with foliar symptoms) and black rot (with fruit symptoms), which are caused by Stagonosporopsis cucurbitacearum (Fr.) Aveskamp, Gruyter & Verkley (anamorph: Phoma cucurbitacearum (Fr.) Sacc.), synonym Didymella bryoniae (Fuckel) Rehm, and which represent serious diseases that are a major constraint to cucurbit production worldwide [2,3,4]. Yield losses of 50% and more can occur under weather conditions that are conducive to leaf spot, and in particular temperatures of 25 to 32 ◦C associated with 40% relative humidity during the day and 95% at night [6]. Many other pathogens have been detected on cucurbits seeds, such as Fusarium solani [7,8], Alternaria cucumerina [9], Paramyrothecium roridum, and Albifimbria verrucaria [10,11]

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