Effects of herbal hydrolates on germination and health of onion seeds

Introduction: Hydrolates, the by-products of essential oils distillation, have antioxidant and antimicrobial properties and can be used in food, cosmetic and pharmaceutical industries. Sage, common yarrow, blue tansy and nettle are common herbs used in traditional medicine for their properties. Objective: The aim of the experiment was to evaluate the effect of four herbal hydrolates on the onion seed gemination and health. Methods: Two seed samples were used. The seeds were soaked for 30 minutes in 20, 50 and 100% hydrolate solutions of sage, blue tansy, common yarrow and nettle. Germination was determined according to ISTA requirements. Germination was calculated at the first count after 6 days and other germination parameters after 12 days. The agar plate method was used to assess seed health. Results: Common yarrow and nettle hydrolate solutions, regardless of concentration, significantly improved germination at the first count, compared to all controls. Nettle hydrolate solutions also improved the germination capacity at the final count of seeds of sample II. In general, hydrolate solutions reduced the incidence of Alternaria alternata, Botrytis allii, B. cinerea, Cladosporium spp., Fusarium spp. and Stemphylium botryosum. The least effective in limiting the occurrence of fungi on onion seeds was blue tansy hydrolate. More seeds free of fungi were observed after soaking seeds in hydrolate solutions. Conclusion: The use of herbal hydrolates can be as effective as fungicides in improving seed quality. Due to their antifungal properties and interactions between the effects of the hydrolate components, they can be effective bioagents. However, their efficacy depends on their concentration and the initial colonisation of the seed by individual fungi. Further research is needed to assess the long-term effects of these treatments on the seed health and the control of seed-borne pathogens.