In vivo Antiphytoviral Activity of Essential Oils and Hydrosols From Origanum vulgare, Thymus vulgaris, and Rosmarinus officinalis to Control Zucchini Yellow Mosaic Virus and Tomato Leaf Curl New Delhi Virus in Cucurbita pepo L.

Abstract

In the last decades, the interest in biological activity of natural compounds has been growing. In plant protection, essential oils have been reported to exhibit antiviral, antimycotic, and antiparasitic activities, and are regarded as promising for the formulation of safe antimicrobial agents. Attention has also been focused on hydrosols, the by-products of hydro-distillation of essential oils. Their production is easy, fast, and cheap, and they seem to arise less concern for human health than essential oils. Plant viruses represent a major concern for agricultural crops since no treatment compound is available for virus control. This work was aimed at evaluating the antiphytoviral effectiveness of treatments with three essential oils and corresponding hydrosols extracted from Origanum vulgare, Thymus vulgaris, and Rosmarinus officinalis on Cucurbita pepo plants infected by zucchini yellow mosaic virus or tomato leaf curl New Delhi virus. Treatments were applied either concurrently or after virus inoculation to ascertain an inhibition or curative activity, respectively. Symptoms were observed and samplings were performed weekly. Virus titer and expression levels of phenylalanine ammonia lyase gene (PAL) were measured on treated and untreated infected plants by real-time PCR. PAL gene plays an important role in plant defense response as it is involved in tolerance/resistance to phytopathogens. Results indicated that treatments were effective against tomato leaf curl New Delhi virus whether applied simultaneously with the inoculation or after. A major inhibition was observed with O. vulgare essential oil and hydrosol, resulting in 10–4-fold decrease of virus titer 3 weeks after treatment. Curative activity gave maximum results with all three essential oils and T. vulgaris and R. officinalis hydrosols, recording from 10–2-fold decrease to virus not detected 4 weeks after treatment. An induction of PAL gene expression was recorded at 12 d.p.i. and then was restored to the levels of untreated control. This allows to hypothesize an early plant defense response to virus infection, possibly boosted by treatments. Plant extracts’ composition was characterized by gas chromatography-mass spectrometry. Phenols were largely main components of O. vulgare and T. vulgaris extracts (carvacrol and thymol, respectively), while extracts from R. officinalis were based on monoterpene hydrocarbons (essential oil) and oxygenated monoterpenes (hydrosol).

Pinus mugo Essential Oil Impairs STAT3 Activation through Oxidative Stress and Induces Apoptosis in Prostate Cancer Cells

“…Essential oils (EOs) are complex mixtures of volatile, lipophilic and aromatic low-molecular-mass secondary plant metabolites, usually obtained through steam distillation, that are usually associated with an important role in plant protection [ 14 , 15 ]. The bulk of EOs are composed of terpenes, but they also include non-terpene components such as phenols and alcohols.…”

Antiviral Activity of Selected Essential Oils against Cucumber Mosaic Virus

“…However, effective crop protection with this method is possible only for a limited number of viruses. Additionally, it is possible to eliminate viruses in vitro, which is accomplished with different techniques (e.g., thermotherapy or meristem culture) which are all expensive, time-consuming, and are not suitable for all plant/virus pathosystems [ 1 , 2 ]. Thus, the search for alternative methods of crop protection against plant viruses is of great significance.…”

“…The detailed mechanism of such activity is yet to be fully explored. It has been hypothesized that EO components could either directly inactivate viral particles or induce resistance/tolerance response in the host [ 2 ]. The mechanisms of action of EOs are versatile due to the complexity of composition and synergism of bioactive compounds compared with synthetic antiviral substances (e.g., acyclovir) that act in a manner specific to a particular type of virus.…”

“…Plant cultivation in the proximity of CMV host plants should be avoided. Diseased plants with a considerably reduced yield should be removed from the plantation [ 1 , 2 ]. Recently, essential oils extracted from different plants and their constituents have been studied for their antiviral properties against CMV in Europe, Asia, Africa, and South America.…”

“…RI1 -experimental retention index on polar column, RI2 -range of retention indices on polar column reported by Babushok et al[30].…”