The effects of different CO_2 concentrations on morphogenesis in three strains, MH19910, MH19912 and MH19915, of Isaria japonica Yasuda under artificial cultivation were investigated. CO_2 concentrations were designated at three levels: 1, 4 and 9 ml/L. Proliferation of vegetative hyphae under various CO_2 concentrations in artificial cultivation was inhibited in strain MH19910 at 9 ml/L, unaffected in strain MH19912 at any concentration, and slightly promoted in strain MH19915 at 4 ml/L CO2. However, the effects of CO_2 concentration in subsequent growth processes were multifaceted: proliferation of vegetative hyphae proportional to CO_2 concentration in MH19915 indicated reduced yields, while proliferation suppression due to enhanced CO2 concentration in MH19910 demonstrated tendency towards increased yields. The effects of CO_2 concentration on flushing and growth were uniform in the three strains tested: decreases in yields and number of synnemata, and variation in branching rate were observed as CO_2 concentration increased. In contrast, although the three strains displayed different patterns of synnema elongation, only MH19910 demonstrated elongation with elevation of CO_2 concentration.

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The effect of light on the fruit-body production of Pleurotus ostreatus, strain (MH00608) was examined. 1) Light exposure at 50 lux during the spawn running stage ("Baiyou" process), produced primordia in almost all bottles tested, while no primordia formed in the dark. Under the dark condition, the yield of fruit-bodies at harvest was much higher than that of the cultures exposed to light during spawn running. 2) When fruit-body initiation ("Medashi" process) was conducted in the dark, primordia did not appear, but aerial hyphae proliferated on the surface of the solid substrate. The 2 lux light intensity was optimal for increasing both the number of primordia and the yield of fruit-bodies at harvest. 3)When the fruit-body development stage ("Seiiku" process) was conducted in the dark, the stipes bulged and pileus developed only slightly. The optimal light intensity was estimated to.be 30 lux for stipe elongation, while that for the yield of fruit-bodies was 200-500 lux. The largest pileus diameter was observed in cultivation under 200 lux. The color of fruit-bodies was bluish-brown at 2-100 lux, whereas it became grayish-brown at intensities above 500 lux.

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A monokaryon which showed a phenotypic character to form a flat colony was obtained by the monokaryotization of the parental dikaryon to become an inferior fruiting stock of Pholiota nameko after successive subcultures. This monokaryon lost the capability to be a recipient cells against different mating types of monokaryon in redikaryotization due to the defect of the nucleus migration capability. The genetic analysis was carried on the loss of this capability and on the character to form a flat colony to cross the defect monokaryon with a normal stock and to back cross between them. The appearance of the defective trait on the redikaryotization of the basidiospre derived monokayons from the dikaryons crossed the abnormal monokaryon with a normal one was assumed to be followed statistically by the mutation hypothesis of two genetic factors. However, the segregation ratio in progenies of the back cross products did not show the expected ratio of the hypothesis. Furthermore, the characteristic of the abnormal monokaryon to form a flat colony did not show any linkage to the characteristic of an abnormal redikaryotization capability in the spore progenies. On the other hand, it was found that 2-6 monokaryons among 45 basidiospre derived monokaryons did not cross any of one parental monokaryons. Therefore, it is concluded that those monokaryons might lose the capability to form dikaryons with any monokaryons carrying different mating types by an undesirable recombination of the incompatibility genes in the meiotic process of a basidiospore formation in this mushroom.

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In order to develop the spawns of Tricholoma matsutake for the inoculation in forests, which are tolerant for Trichoderma spp. living in the soil, the cultivation of the mycelia of T. matsutake on the vermiculite substrate saturated with the nutrient solution with fungicides was examined. The concentration of fungicides in a nutrient solution, which inhibited the growth of Trichoderma spp. and did not inhibit the mycelial growth of T. matsutake, were nearly lOppm on benomyl and 15-30ppm on thiabendazole. Then the spawns of T. matsutake for the inoculation in forests were made from the nutrient solution with lO ppm benomyl or 15 ppm thiabendazole. When the mycelia of Trichoderma spp. inoculated on these spawns, the mycelia did not grow on the spawns.

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