1-Phenyl-3-pentanone, a volatile compound produced by the edible mushroom Mycoleptodonoides aitchisonii ("Bunaharitake" in Japanese) has antifungal activity against plant-pathogenic fungi. To determine its antifungal spectrum and effective concentration, we investigated the effects of 1-phenyl-3-pentanone on mycelial growth and spore germination of several plant-pathogenic fungi; Alternaria alternata Japanese pear pathotype, A. brassicicola, Bipolaris sorokiniana, Botrytis cinerea, Cladosporium cucumerinum, Colletotrichum orbiculare, Corynespora cassiicola, Magnaporthe oryzae, and Pasalora fulva. The compound inhibited significantly mycelial growth and spore germination of all pathogens tested at concentrations of 5-10 ppm (w/v) as vapor. When the compound was removed from spores of the pathogens, the spores began to germinate indicating the fungistatic activity of the compound. Lesion formation on detached leaves of cabbage and tomato inoculated with spores of A. brassicicola and C. cassiicola, respectively, was also significantly inhibited at 5-10 ppm. The compound did not cause injury at the concentrations used on either of the detached leaves. Since 1-phenyl-3-pentanone is a nontoxic product of an edible mushroom and has fungistatic activity against broad fungal pathogens, it may have great potential as a safe agent for controlling fungal diseases.

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The mushroom Pholiota microspora exhibited browning and decreased fresh weight by the second day of storage at room temperature (25℃). It was suggested that polyphenol oxidase (PPO), which is an index of browning in many edible mushrooms, played a role in the decline in P. microspora quality during storage. In this study, oxidase activity was assessed using L-tyrosine, L-DOPA, and catechol as substrates. It was shown that PPO activity for catechol as a diphenol increased rapidly in P. microspora during storage at 25℃. In contrast, the fruiting body stored at low temperature (5℃) maintained its freshness for more than one week. Also, the PPO showed minimal activity against substrates during storage at 5℃. These results suggested that a diphenol oxidase such as catecholase was increased predominantly in the mushrooms, negatively impacting product quality during storage. Further, low temperature storage effectively inhibited catecholase activity associated with the browning of edible mushrooms.

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The aim of this study was to establish a method for the bioremediation of forest dilapidation caused by the practice of leaving thinned woods and windfall trees in planted cedar forests. Specifically, the on-site degradation of wood logs by two species of wood-rot fungi was examined. The decay of cedar wood logs in a cedar forest was largely promoted by the inoculation of logs with Gloeophyllum trabeum or Trametes versicolor, which were selected due to their high degradation activity toward cedar wood flour and their universal distribution in nature. In addition, we confirmed that shiitake bed logs located next to rotting trees were not infected by G. trabeum. Our results suggest that the on-site biodegradation of thinned wood using these fungal strains will only have a small influence on the environment, and will promote the effective bioremediation of dilapidated forests.

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We studied the production of plant cell wall-degrading enzymes in Lentinula edodes grown on sawdust medium. A mycelial mat was spotted onto the center of a medium plate, which was then incubated at 23℃ for 31 days. Laccase (EC 1.10.3.2) activity was detected before that of other enzymes. Laccase activity increased along with mycelial growth until the leading edge of the mycelium reached the edge of the plate, and then decreased. Decrease of laccase activity was followed by increased activity of other enzymes. Sawdust treated with purified laccase (Lcc1) was more sensitive to degradation by crude enzymes from L. edodes. These results suggest that laccase plays an important role during early stages of solid-state cultivation of L. edodes.

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The Hyphozyma synanamorph of Eleutheromyces subulatus causes black spot disease of the shiitake (.Lentinula edodes) fruiting body. Characteristic symptoms are the blackening and superficial lysis of infected pileus surface tissues. As a result of examining pathogenicity of the Hyphozyma synanamorph toward shiitake and other cultivated mushrooms, inoculation with yeastlike cells of the Hyphozyma synanamorph caused browning lesions only on shiitake, but not on other cultivated mushrooms. The culture filtrate of the yeastlike cells also caused browning lesions only on shiitake. These results suggest that the Hyphozyma synanamorph produces host-specific substances that cause browning lesions only on shiitake. Therefore, isolation of browning-inducing substances from culture filtrate of the Hyphozyma synanamorph was attempted. The browning-inducing activity was detected in a high molecular weight fraction (>10kDa) and was inactivated by treatment with 40℃ for 30 minutes. Following SDS-PAGE of the fraction, 15-16kDa and 37kDa bands were detected and the sequence of the same 15 N-terminal amino acids was determined. Because a protein homology search by BLAST did not identify any significant homology, these were inferred to be unknown proteins. This is the first report to show that the mushroom pathogenic fungus produces browning-inducing substances with host-specific activity.

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