In vitro antifungal activity of chitosan and its Schiff bases against Fusarium oxysporum f. sp. cubense Tropical Race 4 (TR4)

The lack of effective and eco-friendly alternatives against Fusarium oxysporum f. sp. cubense Tropical Race 4 (Foc TR4), the causal agent of Fusarium wilt in Musaceae, makes the development of new control tools imperative; therefore, this research aimed to synthesize and evaluate in vitro the antifungal potential of two chitosan-derived Schiff bases through reaction with vanillin and p-dimethylaminobenzaldehyde. The compounds were characterized by FTIR, confirming the formation of the imine group, and were tested using a completely randomized factorial experimental design evaluating compound type and concentration (1, 1.5, and 2% w/v) across 10 treatments with 5 replicates each. Mycelial growth inhibition (MGI) and sporulation inhibition (SI) data were analyzed via ANOVA and Tukey’s test (P<0.05), revealing that the 2% vanillin-Schiff base achieved the highest sporulation inhibition (85.1%), significantly surpassing unmodified chitosan (77.9%), while the 2% concentrations of native chitosan and the p-dimethylaminobenzaldehyde-Schiff base were most effective for MGI at 56.6 and 56.3%, respectively. It is concluded that the chemical modification of chitosan, particularly with 2% vanillin, enhances its in vitro antifungal activity by drastically inhibiting Foc TR4 sporulation, acting as a key reproductive blocker that halts micro/macroconidia and chlamydospore production. This interrupts the primary pathway for pathogen dispersion and survival in the soil, targeting the most critical point for its epidemiological control toward sustainable disease management, although in vivo validation remains necessary to confirm its agronomic efficacy as a biofungicide.