We tried to identify the genetic difference between cultivated and mutant strains of edible mushrooms such as Nameko (Pholiota nameko), Enokitake (Flammulina velutipes) and Shiitake (Lentinula edodes) by Random Amplified Polymorphic DNA (RAPD) analysis. The mutants exhibited characteristics of nondeveloping fruiting-bodies. Three mutant strains for Nameko, Enokitake and Shiitake were derived from respective cultivated strains. Several RAPD bands could be identified between cultivated and mutant strains. In the case of Nameko strains, a RAPD band specific using Y primer (5'CAAACGTGGG-3') was confirmed with the cultivated strain, whereas the mutant strain did not have the band. On the other hand, the mutant strain of Enokitake possessed a specific band using A primer (5'-TTCCGAACCC-3'), whereas the cultivated strain of that did not have the band. The molecular sizes of the specific bands of both Nameko and Enokitake were 750 bp and 937 bp, respectively. These results showed that the RAPD patterns are different between cultivated and mutant strains for Nameko and Enokitake. It is suggested that RAPD analysis is a useful tool for identifying of those strains of edible mushrooms.

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Effect of electric impulse was investigated on fruit body formation of Lentinula edodes in the sawdust-based substrate. Electric impulse of 15 kV was directly charged to the substrate at 3 different fruiting phases, 90- (1st flush), 130- (2nd flush), and 170- (3rd flush) day cultures, respectively. Ergosterol contents and water conditions of the substrate were examined at the 3 phases. The electric impulse was effective in fruit body formation of 4 strains for 3 different fruiting types, which occurred year-round, from autumn to winter. The effect of the electric impulse was more prominent as culture age proceeded (2nd and 3rd flushes).

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The antifungal activity of several chemicals against Cladobotryum varium was investigated. The inhibitive effect of Hibiten, Osuban and Mikurotoru H on the conidial germination was recognized in a 500 μg/ml concentration for a 5 min. treatment. However, these chemicals also inhibited the mycelial growth of Pleurotus eryngii, so it is suggested that these chemicals are able to only apply to the sterilization of growth houses. On the other hand, Benlate and Panmashu showed an inhibitive effect on mycelial growth of C.varium, but no effect was shown on the conidial germination. The treatment of the pinning cap with Benlate and Panmashu in primordia formation stage was useful in protecting the outbreak of Watakabibyo and their protective effect was continued until harvesting time. These results suggested that the chemicals used in this study are applicable in different cultivation stages of P. eryngii, that is, Hibiten, Osuban and Mikurotoru H are in cultivation house for cleaning and Benlate and Panmashu are in the primordia formation stage of P. eryngii.

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The effects of light exposures at different cultivation processes on fruit-body production in the colored strain of Flammulina velutipes were examined. The results were as follows: (1) Light exposure at 50 lux for over 2 weeks on the spawn running ("Baiyou" process) increased the yield of fruit-bodies. (2) When the cultures at the fruiting initiation stage ("Medashi" process) were conducted in the dark, primordia did not appear but aerial mycelium proliferated on the surface of the sawdust spawn. The optimum light intensity for the production of a maximum number of primordia was attained at a light intensity of 2-10 lux, but yield was produced by the light exposure at 2 lux. (3) When the "Narashi/Yokusei" process (for acclimating the mushroom to reduce water content, and for equalizing the size of fruit-bodies) was conducted in the dark, the fruit-bodies showed an irregular size. Stipe elongation was the longest in the dark, and the size of stipes were suppressed by increasing light intensity. On the other hand, the pileus development was promoted by increasing the light intensity up to 100 lux. The color development of fruit-bodies was strengthed by increasing light intensity. (4) The light exposure at the "Seiiku" process (growing up) also suppressed stipe elongation, but enhanced the color development. The pileus development was increased by the light exposure up to 100 lux, but it was suppressed by the light exposure at over 200 lux.

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