Allelopathic Effects of Selected Culinary Spices and their Preparation Methods on Wheat (Triticum aestivum L.) Seed Germination and Early Seedling Development

Abstract

Spices are widely recognised not only for their culinary and medicinal properties, but also for their bioactive compounds that can influence plant growth and development. Recent studies have highlighted the potential of certain spices to exhibit allelopathic or antifungal properties that may affect seed germination and seedling establishment. However, the specific effects of different spices and the influence of their preparation methods on cereal crops such as wheat remain underexplored. This study investigates the effects of selected culinary spices and their forms of preparation on wheat seed germination to assess their potential use in sustainable agriculture as natural seed treatments. This study aimed to evaluate the effects of selected culinary spices on germination and early seedling development of wheat (Triticum aestivum L.). Five commonly used spices – garlic (Allium sativum L.), ginger (Zingiber officinale Roscoe), cinnamon (Cinnamomum verum J.Presl), black pepper (Piper nigrum L.), and cayenne pepper (Capsicum annuum L.) – were tested in different preparation forms, including macerates, infusions, and decoctions. The results showed that black pepper had the most pronounced inhibitory effect on seed germination, with the infusion reducing germination by almost 68% compared to the control. Cinnamon also significantly suppressed germination, especially when applied as a macerate, reducing germination by approximately 39%. Granulated garlic macerate showed a dual effect, strongly inhibiting seedling development, while garlic decoction unexpectedly enhanced seed germination and seedling vigour. Ginger macerate had only a slight inhibitory effect, while chilli macerate slightly stimulated germination, but these effects were not statistically significant. Overall, none of the spice treatments significantly improved germination energy. Statistical analysis confirmed that the type of spice had a significant effect on germination rates (p = 0.030), while the method of preparation showed borderline significance (p = 0.055). Comparison of treatments showed that the effects of chilli and ginger were not statistically significant (p >0.05), while those of black pepper, garlic, and cinnamon were highly significant (p <0.05). These results confirm the allelopathic and antifungal potential of certain culinary spices, but also show that the biological activity of these spices is highly dependent on the extraction method used. The dual nature of garlic treatments and the pronounced inhibitory effects of black pepper and cinnamon suggest that their application in agriculture should be carefully optimised. The results highlight the potential for the development of environmentally friendly spice-based seed treatments, but also point to the need for further studies to determine appropriate concentrations and safe application methods that ensure both pathogen control and minimal phytotoxicity.