Effect of the Essential Oils of Bursera morelensis and Lippia graveolens and Five Pure Compounds on the Mycelium, Spore Production, and Germination of Species of Fusarium

Essential oils of thyme (Thymus vulgaris) and oregano (Origanum vulgare) as an alternative for the control of pesticide-resistant Fusarium spp. in quinoa seeds

BACKGROUND

The phytopathogenic genus Fusarium can cause damage such as root and stem rot in economically important crops, with significant implications. To seek a sustainable method for controlling this phytopathogen in seeds, the antifungal activity of essential oils (EOs) from thyme (Thymus vulgaris) and oregano (Origanum vulgare) was evaluated against isolates of F. graminearum, F. equiseti, F. culmorum and F. oxysporum originating from quinoa (Chenopodium quinoa) crops in the Boyacá (Colombia).

RESULTS

Initially, the effectiveness of commercial fungicides against the mentioned phytopathogenic fungi was evaluated. Upon verifying that these isolates exhibited high resistance to these compounds, the EOs were assessed as a potential control alternative. A disk diffusion assay demonstrated complete in vitro inhibition of the growth of the evaluated phytopathogens when undiluted EOs were used. Subsequently, the minimum inhibitory concentration (MIC) of these oils was determined using the agar well diffusion technique, revealing a MIC of 10 and 1 μL mL-1 for thyme and oregano oil, respectively. Following this, the antifungal activity of the EOs applied to quinoa seeds was evaluated, and germination indices were measured as an indirect indicator of their toxicity.

CONCLUSION

Despite both EOs successfully inhibiting microbial growth in the seeds, it was also found that thyme EO at 100 μL mL-1 and oregano EO at 10 μL mL-1 inhibited seed emergence and germination. However, lower concentrations exhibited a reduction in fungal population without affecting these germination indices. Therefore, it is suggested that the use of these compounds has potential in the treatment and disinfection of quinoa seeds. © 2024 Society of Chemical Industry.

Enhancement of Strawberry Shelf Life via a Multisystem Coating Based on Lippia graveolens Essential Oil Loaded in Polymeric Nanocapsules

Strawberries (Fragaria xannanasa) are susceptible to mechanical, physical, and physiological damage, which increases their incidence of rot during storage. Therefore, a method of protection is necessary in order to minimize quality losses. One way to achieve this is by applying polymer coatings. In this study, multisystem coatings were created based on polymer nanocapsules loaded with Lippia graveolens essential oil, and it was found to have excellent optical, mechanical, and water vapor barrier properties compared to the control (coating formed with alginate and with nanoparticles without the essential oil). As for the strawberries coated with the multisystem formed from the polymer nanocapsules loaded with the essential oil of Lippia graveolens, these did not present microbial growth and only had a loss of firmness of 17.02% after 10 days of storage compared to their initial value. This study demonstrated that the multisystem coating formed from the polymer nanocapsules loaded with the essential oil of Lippia graveolens could be a viable alternative to preserve horticultural products for longer storage periods.

Essential oil from Sabina chinensis leaves: A promising green control agent against Fusarium sp

Sabina chinensis is a woody plant with important ecological functions in different regions of China, but its essential oils (EO) against plant pathogenic fungi remain largely undetermined. The purpose of our study was to assess the chemical composition and antifungal activity of S. chinensis EO based on optimization of the extraction process. In this study, an actionable and effective model with the experimental results and identified optimum conditions (crushing degree of 20 mesh, liquid-solid ratio of 10.1:1, immersion time of 9.1 h) was established successfully to achieve an extraction yield of 0.54%, which was basically consistent with the theoretical value. A total of 26 compounds were identified using headspace gas chromatography-mass spectrometry (GC-MS) and showed that the major constituent was β-phellandrene (26.64-39.26%), followed by terpinen-4-ol (6.53-11.89%), bornyl acetate (6.13-10.53%), etc. For Petri plate assays, our experiments found for the first time that S. chinensis EO revealed high and long-term antifungal activity against the tested strains, including Fusarium oxysporum and Fusarium incarnatum, at EC₅₀ values of 1.42 and 1.15 µL/mL, which especially reached approximately 76% and 90% growth inhibition at a dose of 0.2 µL/mL, respectively. Furthermore, the antifungal activity of EO from different harvest periods showed remarkable variation. The orthogonal partial least-squares discriminant analysis (OPLS-DA) method revealed 11 metabolites with chemical marker components, and 5 of its potential antifungal activities, terpinen-4-ol, α-terpineol, α-elemol, γ-eudesmol, and bornyl acetate, were strongly correlated with the mycelial inhibition rate. In total, this study explored the antifungal activity of EO against root rot fungus as a potential fungicide and provided valuable information into developing potential products from natural agents.