Biocontrol of Fusarium solani: Antifungal Activity of Chitosan and Induction of Defence Enzymes

In this work, the efficiency of chitosan as a biocontrol agent against <i>Fusarium solani</i> on tomato plants was determined and the antifungal activity and the induction of defence enzymes were evaluated. Treatments were carried out with different concentrations of chitosan (1, 2 and 3 g L^-1) combined with a synthetic fungicide (carbendazim). The results showed that all chitosan treatments significantly inhibited the mycelial growth and biomass of <i>F. solani</i>, with the most effective results obtained with the 3 g L^-1 treatment. Scanning electron microscopy revealed that chitosan causes severe structural damage to <i>F. solani</i>, including cell lysis and the deformation of mycelium and spores. In addition, plants treated with chitosan showed significant improvements in height, stem diameter, root dry biomass and root length compared to those treated with synthetic fungicide and the control (no chitosan application). Enzyme assays showed that chitosan significantly increased superoxide dismutase, catalase, peroxidase and phenylalanine ammonia-lyase activity, indicating an increased defensive response. These results suggest that chitosan is a viable and less toxic alternative for the management of disease caused by <i>F. solani</i> in tomato plants, promoting both plant health and growth.