Chitosan as a Component of Pea-<i>Fusarium solani</i> Interactions

Abstract

Chitosan, a polymer of beta-1,4-linked glucosamine residues with a strong affinity for DNA, was implicated in the pea pod-Fusarium solani interaction as an elicitor of phytoalexin production, an inhibitor of fungal growth and a chemical which can protect pea tissue from infection by F. solani f. sp. pisi. Purified Fusarium fungal cell walls can elicit phytoalexin production in pea pod tissue. Enzymes from acetone powders of pea tissue release eliciting components from the F. solani f. sp. phaseoli cell walls. Hydrochloric acid-hydrolyzed F. solani cell walls are about 20% glucosamine. The actual chitosan content of F. solani cell walls is about 1%. However, chitosan assays and histochemical observations indicate that chitosan content of F. solani spores and adjacent pea cells increases following inoculation. Dormant F. solani spores also accumulate chitosan. Concentrations of nitrous acid-cleaved chitosan as low as 0.9 microgram per milliliter and 3 micrograms per milliliter elicit phytoalexin induction and inhibit germination of F. solani macroconidia, respectively. When chitosan is applied to pea pod tissue with or prior to F. solani f. sp. pisi, the tissue is protected from infection.