Effect of soil moisture content on the survival of Ganoderma species and other wood-inhabiting fungi

The survival of mycelia of Ganoderma australe, G. boninense, G. lucidum, and G. weberianum in colonized wood was measured in soils with different soil matrix potentials. Survival of mycelia of G. australe and G. boninense, which do not produce chlamydospores, buried in plots subjected to different soil moisture treatments, declined rapidly, and the fungi could not be recovered after 9 to 12 weeks. Survival of mycelia of G. lucidum and G. weberianum, which produce chlamydospores, rapidly declined from 0 to 15 weeks of incubation but consistently ranged from 35 to 50% after 15 weeks of incubation. In regression analyses for each of the four Ganoderma species, there was no difference in the rate of change of mycelial survival over time among different soil moisture treatments. However, when data from only the -0.20 MPa treatment were used, the rates of change of mycelia survival over time of G. australe and G. boninense significantly differed from those of G. lucidum and G. weberianum. G. australe and G. boninense were not recovered from pieces of infested wood subjected to 3 and I months of flooding, respectively. In treatments with lower soil moisture, the survival of these two fungi ranged from 80 to 90% over 2 years. In all soil moisture treatments, survival of G. lucidum and G. weberianum ranged from 80% to more than 90% over 2 years. Similarly, seven species of other wood-inhabiting fungi that do not produce chlamydospores were not recovered from pieces of infested wood subjected to 1 or 5 months of flooding, but chlamydospore-producing species were recovered. These results indicate that, regardless of chlamydospore formation, woody debris in soils harboring wood-decay fungi may be important for long-term survival, and chlamydospores of Ganoderma in woody debris enhance the resistance of the fungi to environmental stresses such as flooding. Flooding infested fields may help control those woodinhabiting fungi such as G. australe and G. boninense that do not produce chlamydospores.