Ganoderma basidiospore germination responses as affected by spore density, temperature and nutrient media

The present study investigated the axenic basidiospore germination of Ganoderma australe, G. mastoporum and G. philippii at three spore densities in five nutrient media encompassing a range of carbohydrate complexity, in combination with sawdust and/or ethanol as medium additives. Five incubation temperatures ranging from 10 to 35 °C were used, totalling 300 treatment combinations. AWeibull model, with the asymptote occurring at 50 to 75 h, provided good fit to percentage spore germination data at each treatment combination for all three Ganoderma species. Ganoderma australe and G. mastoporum basidiospores germinated on all media, whereas G. philippii basidiospores required media that contained 2% ethanol. The best medium for G. australe and G. mastoporum basidiospore germination was rice dextrose agar with amixture of Eucalyptus and Acacia sawdust, whereas for G. philippii it was 1% malt extract agar plus ethanol, with or without sawdust. Spore density was also critical to achieving the best germination rate, with ~400 spores/cm² optimal for all three species. As Ganoderma root rot disease affects commercial Acacia mangium and Eucalyptus pellita plantations, the greater understanding of basidiospore germination gained from the current study should assist in developing strategies to contain the dispersal and spread of root rot in Indonesia and other southeast Asian countries where these species have been planted.