Chitosan biogel effects on plant gas exchange, antioxidant enzymes, and citrus canker suppression

Citriculture holds significant economic importance but is threatened by diseases like citrus canker, suffering notable losses. Copper-based sprays are traditionally employed due to their bactericidal activity. However, their persistence in the environment may affect non-target organisms, leading to a selection of resistant strains, highlighting the need for safer alternatives. In this perspective, this study examined the effects of chitosan gel as a foliar spray on Citrus sinensis, assessing its effects on gas exchange, oxidative stress responses, foliar damage and activity against Xanthomonas citri. Antioxidant markers catalase, superoxide dismutase, and ascorbate peroxidase were quantified, and drying temperature influence on chitosan film properties was also evaluated. A transient increase in catalase activity was induced, which later normalized, while no long-term adverse effects on other antioxidant enzymes or gas exchange parameters were observed. Concentration C3 caused significant foliar damage, whereas C1 and C2 exerted minimal effects. In vitro assays demonstrated potential inhibitory effect of chitosan gel on Xanthomonas citri. Additionally, drying temperature affected film properties, decreasing elongation and rupture tension significantly. Those findings support chitosan as a sustainable and effective strategy in citrus, combining pathogen control, maintenance of plant physiological integrity, and prospective use as a carrier for bioactive compounds.