Sodium Alginate–Based Coatings Safeguard Garlic Cloves and Provide Controlled Biostimulant Delivery to Improve Agronomic Performance

Abstract The application of biopolymers derived from natural sources as agricultural coating materials represents a promising strategy for improving propagation efficiency and seedling establishment. This approach can enhance moisture retention and mechanical protection while enabling the controlled release of bioactive compounds, such as biostimulants. The present study evaluated a sodium alginate–based polymeric matrix and its corresponding films, with and without the incorporation of tryptophol, for coating garlic cloves belonging to two distinct vigor classes. Physicochemical analyses revealed a predominance of mannuronic acid over guluronic acid in the polymeric matrix, suggesting that its structural characteristics may contribute to the protective properties of the coating. Furthermore, the incorporation of tryptophol, a biostimulatory compound, significantly influenced the physicochemical properties of the alginate films, particularly their water absorption and swelling behavior. Bioassays conducted with garlic propagules demonstrated that small cloves treated with the biopolymer–biostimulant combination exhibited reduced activation of oxidative defense mechanisms, whereas large cloves subjected to the same treatment showed improved yield and quality. Both vigor classes exhibited a lower incidence of physiological disorders following treatment with either the biopolymer–biostimulant combination or the biostimulant alone. Overall, this biotechnology-based approach is innovative, cost-effective, and readily adaptable to agricultural applications, offering a sustainable strategy for improving crop establishment and productivity.