Formation of atypical fruiting structures inGanoderma lucidum isolates on a nutrient agar medium

Effects of light and ventilation on the formation of atypical fruiting structures (AFSs) and fruit body primordia (FBPs) ofGanoderma lucidum on nutrient agar media were investigated. Although the mycelial growth was inhibited by illumination and ventilation, brown AFSs appeared on the white mycelial colony, and basidia and basidiospores were produced on the AFSs. On the other hand, FBPs were induced by illumination alone, regardless of ventilation. However, the primordia could not develop to mature fruit bodies. In the dark, only vegetative growth of the fungus progressed. Twenty-three isolates ofG. lucidum collected from four countries were tested for the formation of AFSs and FBPs under light and ventilation. Thirteen isolates formed AFSs, and another five isolates produced FBPs. Of the remaining five isolates, one formed callus-like structures without elaborating basidiospores, and the other four did not induce AFSs or FBPs. Microscopical observation showed that the basidia were formed directly from generative hyphae on the surface of AFSs. Basidiospores formed on the basidia were brown and ellipsoid with an eccentric hilar appendix on the rounded spore base. They had a double wall and mostly contained one or two large vacuoles. The surface of basidiospores was smooth or wrinkled and had shallow holes. The spore size was (4.5–)6.4–9.6(–10.3) × (2.6–)3.2–5.1(–6.4), 7.3 × 4.2 µm on average.