Effects of chitosan and its derivatives on Aureobasidium pullulans and plant pathogenic fungi.

The hyphomycetes Phoeomoniella chlamydospora (Pch) and Phaeoacremonium aleophilum (Pal) cause the "brown-wood streaking" of branches and trunk of grapevines. The ascomycete Cryphonectria parasitica (Cpa) is the causal agent of chestnut blight. Leaf surfaces are among the many substrata colonised by the deuteromycete Aureobasidium pullulans (Apu). All these fungi produce phytotoxic exopolysaccharides. Chitosan and four derivatives N-dicarboxymethyl-chitosan, N-carboxymethyl-chitosan, 5-methylpyrrolidone-chitosan, N-methyl-pirrolydone-chitosan) were used as carbon sources for growing each species. Chitosan concentration up 0.2 mg ml-1 inhibits the growth of all the fungi tested. Pal showed the highest growth rate when it was growing on each chitosan derivative as sole carbon source. Data indicate that the four fungal species can be depressed or inhibited by chitosan or its derivatives even in the presence of a medium as malt-agar. The inhibitory effect of chitosan and its derivatives was also observed in grapevine tissues inoculated with Pch and Pal. Growth on the solid medium on in planta was indicative of biodegradation or fungistatic activity.