Chitosan Combined with Methanolic Plants Extracts: Antifungal Activity, Phytotoxicity and Acute Toxicity

Anthracnose is a disease caused by phytopathogenic fungi such as Colletotrichum siamense that attacks plants and fruits causing great postharvest losses. Different alternatives for the control of this fungus have been studied, and in the present study we evaluated the in vitro antifungal activity of chitosan mixed with methanolic extracts of Baccharis glutinosa and Jacquinia macrocarpa as well as toxicity in different models. Using the radial growth technique, it was observed that the mycelial development of C. siamense was altered and reduced during exposure to the different treatments evaluated during the first hours of incubation, indicating a fungistatic effect. While the cell viability, by colorimetric assay using the XTT salt, showed alteration since the chitosan reduced proliferation by 50 %, while the plant extracts and their mixtures with chitosan reduced approximately 40 % indicating cell damage, which was confirmed by fluorescence microscopy. In addition, toxicity tests showed that the extract of J. macrocapra affected the germination percentage of Lactuca sativa seeds while radicle length was reduced in all treatments, except with chitosan alone. The larval survival test for Artemia salina with the extracts indicated their potential toxicity by causing up to 60% mortality. The results indicate that the extracts of B. glutinosa and J. macrocarpa mixed with chitosan are a good option for the control of C. siamense, but at the concentrations used they show a toxic effect in the models evaluated.