Tomato Biostimulation with Nanochitosan–Iodine Complexes: Enhancing Antioxidant Metabolism

Biostimulants are currently essential for agriculture as they increase crop productivity and quality sustainably. The aim of this work was to evaluate the effects of biostimulation on the application of nanochitosan-iodine complexes (nCS-I) on tomato plants. Leaf samples were taken for analysis of total protein content, photosynthetic pigments, antioxidant enzymatic activity, mineral and iodine contents, gene expression, and shelf life in tomato fruit. The catalase (CAT), glutathione peroxidase (GPX), ascorbate peroxidase (APX), and superoxide dismutase (SOD) activities increased significantly with the application of nanochitosan (nCS) and nanochitosan-potassium iodate (nCS-KIO₃) and nanochitosan-potassium iodide (nCS-KI) complexes and the iodine salts potassium iodate (KIO₃) and potassium iodide (KI). The total protein content and photosynthetic pigments also increased significantly with the application of the treatments. The mineral and iodine contents did not change with the application of the treatments. Similarly, overexpression of the <i>SOD</i>, <i>GPX</i>, and <i>CAT</i> genes was observed. Finally, in the shelf life test, an increase in the total phenols and antioxidant capacity was observed with the application of the treatments. This study shows that the use of nCS-I complexes can modulate different transcriptional and post-translational processes with possible synergistic effects on the antioxidant metabolism of tomato plants.