Differential effect of chitosan on root rot fungal pathogens in forest nurseries

The effect of chitosan on the growth, morphology, and ultrastructure of Cylindrocladium floridanum Sobers & Seymour, Cylindrocarpon destructans (Zinss.) Scholten, Fusarium acuminatum Ellis & Everh., and Fusarium oxysporum Schlecht. was investigated in vitro. Chitosan was found to reduce the radial growth of all the fungi studied with some differences. Light microscope observations showed that chitosan induced morphological alterations to all fungi. Transmission electron microscope investigations revealed ultrastructural alterations such as increased vacuolation, retraction, and alteration of the plasma membrane, cell wall thickening, hyphal distortion, and cytoplasm aggregation. The possible modes of action of chitosan are discussed.