In vitro Degradation of Cell Walls of Apple Leaves by Pectinolytic Enzymes of the Scab Fungus, Venturia inaequalis, and by Commercial Pectinolytic and Cellulolytic Enzyme Preparations

A new method involving ¹⁴C-labelled cell walls of apple leaves was developed in order to study the process of cell wall degradation in vitro and its role in pathogenesis and host-resistance. ¹⁴C-labelled cell walls were efficiently digested by commercial enzyme preparations and less efficiently by the polygalacturonase of Venturia inaequalis, the causal agent of apple scab. Further, degradability of cell walls from a susceptible and a resistant variety were compared, but there was no evidence for a correlation of reduced degradability with resistance. The method presented here can be regarded as a useful tool for investigations where enzymatic processes of polymerization or depolymerization of plant material is involved.