Capability of the European and North American race of Gremmeniella abietina to hydrolyse polygalacturonic acid in vitro

Polygalacturonase was found to be one of the first enzymes secreted by a pathogen during infection. The polygalacturonic-acid hydrolysing activity was compared between the North American and the European race of Gremmeniella abietina in vitro. Isolates were grown in pure pectin media from which the enzyme activity was analysed. Altogether, 29 isolates were tested in five experiments (experimental runs in a growing chamber). The data were analysed using variance-component models that included fixed-race effects and random-experiment, isolate, flask and measurement effects. The European race secreted more polygalacturonic-acid hydrolysing enzyme than the North American race and the mycelial dry weight produced was smaller for the European race. The differences between races were of the same order of magnitude as the variation between isolates within races; variance components relating to experimental errors were quite large. No correlation was found between the activity and mycelial dry-matter production within the races. Logarithmic transformation removed the apparent racial differences in the variability of the activity and mycelial dry weight. Results from the additionally tested A- and B-type of Finnish isolates indicated differences in dry-matter production.