Antifungal Activity of Aqueous Soluble Chitosan Derivatives on Fusarium and Verticillium

Abstract

Three aqueous soluble chitosan derivatives, N-carboxymethylchitosan (= CM-1), N- (3-carboxypropyl)chitosan (= CM-2) and N, N, N-trimethylchitosan (= CM-3) were synthesized to examine their antifungal activities on Fusarium solani f.sp. pisi(=F. solani) and Verticillium. CM-1, CM-2, and CM3 were prepared by treating chitosan with monochloroacetic acid, 4-chlorobutyric acid, and methyl iodide, respectively. CM-1 and CM-2 are zwitter-ion type of chitosan derivatives, while CM-3 is a quaternized chitosan derivative having positive charges. The antifungal activities of them were quantitatively investigated by measuring the growth rate and lag time of the fungal multipulication by means of a plate culture method. The growth rates decreased with an increase in the concentrations of chitosan derivatives. The lag time increased with increasing concentrations of chitosan derivatives. The antifungal activity of chitosan derivatives on F. solani was about three times that of original chitosan. Their activities on Verticillium were about 1/10 of those on F. solani. The relative activity on F. solani of the chitosan derivatives was in the following order: CM-3≥CM-2≥CM-1. That on Verticillium was as follows: CM-3≥CM-2>>CM-1. These results suggest that the cation charge of CM-3 and the hydrophobicity resulting from propyl chain and methyl groups of CM-2 and CM-3, respectively, would b e effective for the growth inhibition of F. solani and Verticillium.