Variation of antifungal activities of chitosans on plant pathogens

Abstract

The effect of chitosan on the growth of plant pathogenic fungi was investigated. Chitosan solubilized in acetic acid showed much higher and more consistent antifungal activity than that solubilized in HCl. The antifungal activity was not significantly affected within a DA (degree of deacetylation) range of 57.3-99.2% tested. Water-soluble and low molecular weight chitosan (57.3% DA) against 6 plant pathogens showed that Monosporascus canonballus and Pythium irregulare were the most susceptible to the chitosan, while Fusarium oxysporum and F graminearum were the most resistant. At a concentration of 2.5 mg/ml, the growth of pathogens was completely inhibited except for F oxysporum. The MIC 50 values varied depending on both the DA of the chitosan and the plant pathogens. A chitosan with 57.3% DA exhibited the lowest MIC 50 (ranging <0.1-1.8 mg/ml) and that with 84.7% DA the highest MIC 50 (ranging <0.4-4.0 mg/ml) depending on the pathogen.