Essential Oils and Hydrolates: Potential Tools for Defense against Bacterial Plant Pathogens

Abstract

The essential oils (EOs) of Origanum compactum and Satureja montana chemotyped (CT) at carvacrol, two Thymus vulgaris CT at thujanol and thymol, and Hydrolates (Hys) of S. montana and Citrus aurantium var. amara were chosen for studying their bactericidal efficacy against few phytobacterial pathogens. The Minimal Inhibitory Concentration (MIC) and Bactericidal Concentration (MBC) were found by microdilution assay. The essential oils of O. compactum (MBC 0.06% v/v), T. vulgaris CT thymol (MBC 0.06% v/v), and Hy of C. aurantium (MBC 6.25% v/v) resulted in being the most effective against Erwinia amylovora; thus, they were used as starting concentrations for ex vivo assays. Despite the great in vitro effectiveness, the disease incidence and the population dynamic ex vivo assays showed no significant results. On the other hand, EO of O. compactum and Hy of C. aurantium (at 0.03% and 4.5% v/v, respectively) showed resistance induction in tomato plants against Xanthomonas vesicatoria infections; both treatments resulted in approximately 50% protection. In conclusion, EOs and Hys could be promising tools for agricultural defense, but further studies will be necessary to stabilize the EOs emulsions, while Hys application could be an effective method to prevent bacterial diseases when used as resistance inducer by pre-transplantation treatment at roots.

A New Potential Resource in the Fight against Candida auris: the Cinnamomum zeylanicum Essential Oil in Synergy with Antifungal Drug

“…In this scenario, discovery and development of new drugs is urgently needed to combat the increase of fungal azole resistance. Nowadays, essential oils (EOs), alone or in combination with conventional drugs, are used to fight human pathogens, including multidrug-resistant ones ( 16 to 19 ). EOs are mixtures of natural substances obtained from the distillation or pressing of aromatic plants with a known antimicrobial activity ( 20 ).…”

Essential Oils: An Ecofriendly Approach for Plant Pest and Disease Management

“…Furthermore, they play a defensive role against predators and diseases. This role is related to their antifungal [20], antiviral [21] and antibacterial [22] activity thus ensuring plant protection [2].…”

“…manihotis in vitro and in vivo conditions [44]. Proto et al [22] found that the essential oil of Origanum compactum (at 0.03% v/v) showed resistance induction in tomato plants against Xanthomonas vesicatoria infections. The same authors noted that the essential oils of Origanum compactum and Thymus vulgaris resulted in being the most effective against Erwinia amylovora under in laboratory conditions.…”

Disclosing the potential of Cupressus leylandii A.B. Jacks & Dallim, Eucalyptus globulus Labill., Aloysia citrodora Paláu, and Melissa officinalis L. hydrosols as eco-friendly antimicrobial agents

“…Hydrosols have recently started to receive a lot of credit in a variety of areas, such as food (e.g., flavouring, preservatives, and sanitisers) [ 18 , 19 ], cosmetic and perfumery [ 20 ], aromatherapy [ 21 ], agriculture (e.g., biopesticides and repellents) [ 22 ], pharmaceutical (e.g., natural antibiotics, antioxidants and anti-inflammatory agents) [ 17 , 23 ], and medical (e.g., antimicrobial and antitumor agents) [ 24 ]. According to circular economy principles, using industrial by-products can be a sustainable way to address the environmental problems caused by waste discharging.…”