ANTIFUNGAL ACTIVITY OF AQUEOUS SOLUBLE CH ITOSAN DERIVATIVES ON FUSARIUM AND VERTICILLIUM

Three aqueous soluble chitosan derivatives, N-carboxymethylchitosan (= CM-1), N-(3-carboxypropyl)chitosan(= CM-2) and N,N,N-trimethylchitosa n (= CM-3) were synthesized to examine their antifungal activities on Fusarium solani f. sp. pisi(= F. solani) and Verticillium. CM-1, CM-2, and CM-3 were prepared by treating chitosan with monochloroacetic aci d, 4-chlorobutyric acid, and methyl iodide, respectively. CM-1 and CM- 2 are zwitter-ion type of chitosan derivatives, while CM-3 is a quater nized chitosan derivative having positive charges. The antifungal acti vities of them were quantitatively investigated by measuring the growt h rate and lag time of the fungal multipulication by means of a plate culture method. The growth rates decreased with an increase in the con centrations of chitosan derivatives. The lag time increased with incre asing concentrations of chitosan derivatives. The antifungal activity of chitosan derivatives on F. solani was about three times that of ori ginal chitosan. Their activities on Verticillium were about 1/10 of th ose on F. solani. The relative activity on F. solani of the chitosan d erivatives was in the following order: CM-3 greater than or equal to C M-2 greater than or equal to CM-1. That on Verticillium was as follows : CM-3 greater than or equal to CM-2>>CM-1. These results suggest that the cation charge of CM-3 and the hydrophobicity resulting from propy l chain and methyl groups of CM-2 and CM-3, respectively, would be eff ective for the growth inhibition of F. solani and Verticillium.