Chemical Composition of Fir, Pine and Thyme Essential Oils and Their Effect on Onion (Allium cepa L.) Seed Quality

Abstract

Botrytis allii and B. cinerea are important seed-transmitted pathogens of onion. The aim of this study was to determine the chemical compositions of fir, pine and thyme essential oils and evaluate their effects on the germination, vigour and health of onion seeds. Gas Chromatography/Mass Spectroscopy was used for the analysis of the oils’ chemical compositions. Seed germination, vigour and health tests were performed on untreated seeds and on seeds treated with volatile compounds of the oils applied at a concentration of 0.2 µL cm−3 for 6, 12, 24, 48 and 72 h or at a concentration of 0.4 µL cm−3 for 3, 6 and 12 h. The main components of fir oil were bornyl acetate (55.5%) and α-pinene (15.6%), pine oil contained mostly α-pinene (35.5%) and β-pinene (18.6%), and thymol (34.2%) and p-cymene (26.2%) prevailed in thyme oil. Almost all treatments significantly reduced seed infestation with Alternaria alternata and Fusarium spp., and some effectively controlled Botrytis spp., however, seed health improvement was usually associated with deterioration of seed germination and vigour. Only treatment with fir oil at a concentration of 0.2 µL cm−3 for 6 h effectively controlled seed-borne pathogens and positively affected seed germination. Considering the beneficial effect of the oils on seed health, further studies are necessary in order to establish the optimal conditions for onion seed treatment.

Basic Substances and Potential Basic Substances: Key Compounds for a Sustainable Management of Seedborne Pathogens

“…on the onion seeds and frequently reduced their infestation with Botrytis spp. The lowest dose tested with antifungal activity and without phytotoxic effects was 0.2 µL cm −3 , while increasing the dose led to increased phytotoxicity [59].…”

Evaluation of the Use of Oregano and Coconut Hydrolates to Improve Onion Seed Quality

“…These methods could significantly improve seed quality, reduce pathogen development and be harmless to the environment and human health. There have been reports on the use of essential oils for seed treatment, e.g., basil, fir, lemongrass, pine, sage and thyme on onion seed quality [7,8]. It has been shown that they can improve germination and seed vigour parameters and effectively inhibit pathogen development.…”

“…It has been shown that they can improve germination and seed vigour parameters and effectively inhibit pathogen development. Dorna et al [7] reported that treating seeds with fir oil at the concentration of 0.2 µL cm −3 for 6 h effectively controlled Botrytis aliii, B. cinerea and Fusarium spp. and improved seed germination.…”