Biochemical and cytochemical aspects of the interactions of chitosan and Botrytis cinerea in bell pepper fruit

The effect of chitosan on the necrotrophic growth of Botrytis cinerea in bell pepper fruit was investigated. In control tissue, massive fungal colonization was followed by extensive degradation of the pectin component of host walls and middle lamella. Reduction of pectin labelling was also observed in walls distant from invading hyphae. In contrast, cellulose breakdown was limited to small wall areas closely appressed against the pathogen. The disruption of host walls and the reduction of pectin labelling appeared to parallel levels of cell-wall-macerating enzymes isolated from B. cinerea-infected tissue. High levels of polygalacturonase and trace amounts of cellulase were detected in B. cinerea-infected tissue. In chitosan-treated tissue, the preservation of pectin binding sites and the intense and regular cellulose distribution over host walls, suggested that chitosan might have prevented the maceration of host tissue by B. cinerea. Chitosan not only was effective in reducing the production of polygalacturonases by B. cinerea, but also caused seven cytological damage to invading hyphae. This may, in part, explain the limited ability of the pathogen to colonize tissues in the presence of chitosan. (C) 1997 Elsevier Science B.V.