STUDIES OF GANODERMA LUCIDUM AND GANODERMA TSUGAE (DELIGNIFICATION, MATING SYSTEMS, ROOT ROT, CULTURAL MORPHOLOGY, TAXONOMY).

Ganoderma lucidum and G. tsugae are two members of the G. lucidum complex. The authenticity of the two wood-rotting species was demonstrated by comparative studies. Ganoderma lucidum is restricted to hardwoods. Its "smooth" walled basidiospores were characterized by narrow, numerous inter-wall pillars. Isolates of G. lucidum produced chlamydospores in culture and had an average growth of 7.8 mm/da at their optimum temperature range of 30-34 C. Ganoderma tsugae is restricted to conifers. Its basidiospores were "rough" walled and had broad inter-wall pillars. Isolates of G. tsugae did not produce chlamydospores in culture and had an average growth of 2.1 mm/da at the optimum temperature range of 20-25 C. Mating systems were determined for both species as heterothallic and tetrapolar. Interspecific matings of homokaryons were incompatible. Homokaryons of a European G. resinaceum isolate were interfertile with homokaryons from North American collections of G. lucidum. The ability of G. lucidum and G. tsugae to decay wood in vitro was studied using the following woods in agar block decay chambers: grape, oak, mesquite, white fir, and Douglas-fir. Grape wood lost the most weight while mesquite the least. G. lucidum isolates generally caused greater weight loss of all woods than did G. tsugae isolates. Both Ganoderma species caused simultaneous decay in all woods. However, chemical analyses of the decayed blocks indicated that selective delignification by both species also occurred in grape and white fir blocks but not in oak or Douglas-fir blocks. Scanning electron microscopy demonstrated various stages of selective delignification and simultaneous decay of all woods tested. Isolates of Ganoderma lucidum infected Dog Ridge variety grape plants, grown in the greenhouse, from below-ground wood block inoculations. Twenty-four plants were inoculated: one plant died and 4 other plants declined. After 24 months reisolations yielded only G. lucidum from the five declining plants, demonstrating pathogenicity. The fungus developed in the heartwood and, in later stages, invaded the sapwood. Infected plants developed water stress symptoms with leaves wilting, yellowing, and dying. Field grape plants inoculated with the fungus developed decay columns as large as 42 cm in 17 mons. Decay was limited to the heartwood; no foliar symptoms occurred