GANODERMA ON TREES—DIFFERENTIATION OF SPECIES AND STUDIES OF INVASIVENESS

Abstract

Summary The relative abilities ofGanoderma applanatum, G. resinaceum and G. adspersum to overcome the reaction zone (R-zone) of Platanus x acerifolia were assessed under controlled conditions using wood blocks containing naturally induced R-zones. Also, the effect of physically damaging the R-zone on fungal spread was examined. During incubation, fungal entry into each block was controlled by coating it with paraffin wax, so as to leave only one side available for colonisation. The results were examined mainly in the context of the different colonisation strategies and wood-degrading mechanisms of these fungi. In order to allow for possible intra-specific differences, two isolates of each fungus were used. There were clear differences between the fungi, on the basis of both histological criteria and drilling resistance measurements, as determined after four and eight weeks' incubation. Both G. adspersum and G. resinaceum breached the R-zone, but the G. adspersum was more aggressive in this respect (Figure 11). On the other hand, G. applanatum did not breach the R-zone, due to an inability to modify the defensive compounds in this region. When wood blocks were drilled before incubation, so as to breach the R-zones physically, G. applanatum was able to colonise and degrade the adjacent sapwood. This pre-treatment also enhanced the ability of G. resinaceum and G. adspersum to enter the sapwood. Ganoderma resinaceum preferentially exploited the sapwood before starting to degrade the polyphenolic barrier of the R-zone, whereas G. adspersum began to degrade this barrier at an early stage. Within control blocks, containing no R-zones, G. applanatum caused the most rapid loss of cell wall structure, followed by G. resinaceum and G. adspersum. These results were confirmed by weight loss data.