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

Abstract

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.

Activities of cell‐wall‐degrading enzymes produced by Pestalotiopsis guepinii

“…The optimal pH for Cx, β‐glucosidase, and xylanase was determined to be 5.0, while PMG showed optimal activity at a pH range of 5.0–6.0. These findings suggest that all four CWDEs produced by Pestalotiopsis guepinii thrive in a weakly acidic environment (Gao & Tang, 2008; Valsangiacomo et al., 2010). Therefore, based on the study, it was found that selecting an environment with a temperature less than 30°C and a pH greater than 6.0 was conducive to avoiding the invasion of C. pitardii by pathogens.…”

“…The optimal pH for Cx, β-glucosidase, and xylanase was determined to be 5.0, while PMG showed optimal activity at a pH range of 5.0-6.0. These findings suggest that all four CWDEs produced by Pestalotiopsis guepinii thrive in a weakly acidic environment (Gao & Tang, 2008;Valsangiacomo et al, 2010).Therefore, based on the study, it was found that selecting an environment with a temperature less than 30°C and a pH greater than 6. is advisable to select cool and slightly acidic areas or consider the addition of organic pesticides to reduce pathogen proliferation (Jadhav et al, 2017;Köhl et al, 2019;Naher et al, 2014). Furthermore, the application of trace elements such as potassium, silicon, and calcium can enhance the ability of the host cell wall to resist degrading enzymes, thereby preventing diseases and increasing crop yield.…”

Detailed description of developmental growth stages of Diplocarpon rosae in Rosa: a core building block for efficient disease management

“…These electron‐opaque layers could be enzymes themselves that have been preserved by glutaraldehyde, as glutaraldehyde preserves protein such as fungal enzymes during fixation (Hayat, 1989 a , b ; Park et al , 2000). A third possibility is that the electron‐opaque layers are made up of a mixture of the enzymes and the degraded products (Valsangiacomo & Gessler, 1988; Valsangiacomo et al , 1992). This agrees with earlier suggestions of Aronescu (1934) that enzymes are involved in the development of D. rosae within the host tissue.…”

Vf scab resistance of Malus

“…This phenomenon may be somehow analogous to the ontogenic resistance (increased resistance to scab with the age of the leaf) present in all cultivars (Gessler and Stumm 1984) In a study of the interaction between V. inaequalis and apple, Maeda (1970) interpreted the ultra-structural changes in the plant's cell wall below the fungal stroma as the degradation of pectic substances by the fungus. However, in an experiment involving the 14 C-labelled cell walls of apple leaves, Valsangiacomo et al (1992) were able to exclude any correlation between Vf resistance and the absence of cell wall degradation. Similarly, inhibitors of fungal cellulase and polygaracturonase that were extracted from ''Florina'' (Vf) or ''Golden Delicious'' inhibited the corresponding two enzymes of V. inaequalis to the same extent (Koller et al 1992).…”