Abstract
(1) Background: The use of natural products based on essential oils (EO) is nowadays arousing great interest as an alternative method to control plant pathogens and weeds. However, EO possess low bioavailability and are highly volatile, and their encapsulation in hydroxypropyl-ß-cyclodextrin (HP-β-CD) could be a means to enhance their stability and maintain their bioactivity. Thus, the current study aims at investigating, in the presence and the absence of HP-β-CD, the antifungal and phytotoxic activities of nine EO, distilled from plant species belonging to Alliaceae, Apiaceae, and Cupressaceae families, with considerations for their chemical composition. (2) Methods: EO antifungal activity was assessed by direct contact and volatility assays against Fusarium culmorum, a major phytopathogenic fungi, while phytotoxic effects were evaluated against lettuce (Lactuca sativa L.) and rye-grass (Lolium perenne L.), by seedling’s emergence and growth assays. (3) Results: These EO inhibit fungal growth in both direct contact and volatility assays, with half-maximal inhibitory concentrations (IC50) ranging from 0.01 to 4.2 g L−1, and from 0.08 up to 25.6 g L−1, respectively. Concerning phytotoxicity, these EO have shown great potential in inhibiting lettuce (IC50 ranging from 0.0008 up to 0.3 g L−1) and rye-grass (IC50 ranging from 0.01 to 0.8 g L−1) seedlings’ emergence and growth. However, the EO encapsulation in HP-β-CD has not shown a significant improvement in EO biological properties in our experimental conditions. (4) Conclusion: All tested EO present antifungal and phytotoxic activities, with diverse efficacy regarding their chemical composition, whilst no increase of their biological effects was observed with HP-β-CD.
Highlights
In recent years, there has been a clear tendency towards the utilization of alternative methods in agriculture for pest and disease control, food preservation, and weed control that are less damaging to the environment and human health
The results presented based on in vitro antifungal activity against F. culmorum, by both direct contact and volatility assays, have shown that all tested essential oils (EO) are able to inhibit the growth of this phytopathogenic fungus, with higher efficiency for the direct contact method
The inhibitory concentrations obtained by direct contact assay were significantly lower in comparison with those obtained with the volatility assay: the half-maximal inhibitory concentrations (IC50) obtained by volatility assay ranged from 1.2 up to 23–fold higher than those obtained by direct contact assay
Summary
There has been a clear tendency towards the utilization of alternative methods in agriculture for pest and disease control, food preservation, and weed control that are less damaging to the environment and human health. EO are complex oily volatile liquids characterized by a strong odor and synthetized by all aromatic plant organs (flowers, buds, seeds, leaves, twigs, bark, herbs, wood, fruits, and root) as secondary metabolites and stored in secretory cells, cavities, canals, epidermic cells or glandular trichomes They can contain 20 to 60 active compounds, responsible for their biological activities [3]. Food safety from spoilers and pathogens is an important worldwide public health concern, and microbial contamination is a vital factor causing food deterioration and shelf life reduction, and resulting in economic losses and diseases [4,5] Weeds are another major biological constraint in agriculture. The inappropriate or overuse of pesticides is known to result in environmental issues (groundwater and soil contamination, presence of toxic residues in agricultural products), noxious effects on human health, as well as leading to the development of herbicide resistance in weeds [6,7,8]
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