Effect of 11 essential oils on seed germination, radicle development, and seedling growth in wheat and barley

Wheat and barley are the two most important small-grain crops globally. A persistent challenge in their cultivation is pre-harvest sprouting (PHS), which occurs when seeds begin to germinate on the spike due to rainfall before harvest. Despite ongoing efforts, effective and environmentally friendly solutions for PHS control are limited. This study presents a novel approach by exploring the use of essential oils (EOs) as natural germination suppressants. This study hypothesized that essential oils (EOs) could suppress seed germination in wheat and barley, offering a potential avenue for developing products to mitigate PHS. The objective of the study was to evaluate the effects of 11 EOs on the germination rate (%), number of seminal roots, root length (mm), and seedling height (mm) of two grain crops: wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.). The EOs tested included Eucalyptus polybractea (blue mallee), Eucalyptus globulus (southern blue gum), Cinnamomum cassia (Chinese cassia), Abies sabirinensis (fir needle), Artemisia vulgaris (mugwort), Citrus paradisi (grapefruit), Commiphora myrrha (myrrh), Melaleuca viridiflora (Niaouli), Pinus strobus (Eastern white pine), Citrus reticulata (tangerine), and Cymbopogon martini (palmarosa). Essential oils were applied at rates of (0, 10, 30, and 90 μL/Petri dish) to study their inhibitory effect on seeds. The application of Cymbopogon martini and Cinnamomum cassia EOs reduced wheat and barley seed germination rate (%), number of seminal roots, root length (mm), and seedling height (mm) at 10 μL. Therefore, they were further evaluated at reduced amounts (0, 1, 3, and 9 μL/Petri dish). Barley and wheat seed germination was suppressed by applying Cymbopogon martini and Cinnamomum cassia EOs at 1, 3 and 9 μL; these EO significantly decreased all response variables relative to the non-treated control. Due to the effectiveness of the EOs, even at low amounts, a tetrazolium test (TZ) was conducted to test the viability of the seeds after they were exposed to EOs. The results of the TZ test showed that EOs had significant effects on seed viability. When the amount of EOs increased, the viability of the seed decreased. More research is necessary to confirm the findings in field conditions. This study was the first report to demonstrate that Cymbopogon martini and Cinnamomum cassia EO have promising potential as natural agents for controlling preharvest sprouting (PHS) in wheat and barley, offering a sustainable alternative to synthetic chemicals in grain production and storage systems.