Surface coatings based on chitosan and tannins applied in the in vivo prevention of corn streak disease

The bacterial corn streak disease, caused by Xanthomonas vasicola pv. vasculorum (Xvv) has emerged as a threat to corn production due to its rapid spread and resistance to conventional agrochemicals. Therefore, this study proposes polymeric surface coatings based on chitosan (CS) and tannins (TN) as antimicrobial agents against Xvv. The coatings were formed via the layer-by-layer (LbL) approach on oxidized polystyrene (PS). The coatings increased the wettability and roughness of the surfaces. In vitro assays measuring the minimum inhibitory and minimum bactericidal concentrations (MIC and MBC) demonstrated the antimicrobial activity of CS and TN. Coatings deposited on PS exhibited in vitro anti-adhesive properties against Xvv. The in vitro antimicrobial results were compared with control assays performed with an ionic liquid (IL). The IL was also associated with the polymeric coatings. Polymeric coatings, with or without IL, were deposited on corn leaves for in vivo assays. The IL had no activity against Xvv, and its presence in the CS solution seemed to impair the coating deposition on the corn leaves. However, the in vivo assays confirmed the protective efficacy of the polymeric coatings against Xvv infection, acting as physical barriers. The surface coatings also significantly reduced the Xvv symptoms in infected plants even after the disease spread. These outcomes were attributed to the film-forming ability of CS and TN polymers, the coatings' antimicrobial action, and the LbL efficiency in depositing the coatings on the corn leaves. This study introduces a promising environmentally and economically viable strategy for combating bacterial corn streak disease using biodegradable, cytocompatible natural polymers. The surface coatings offer a sustainable method to address bacterial corn disease, overcoming the limitations of agrochemicals.