The basidiomycete Fomitiporia torreyae (Cha-anatake-modoki) causes a severe trunk rot disease called “Hi-akagare-sei-mizogusare-byo” on the cultivar “Sanbu-sugi” of Cryptomeria japonica in Japan. For a long time, this disease had been reported from limited areas in Chiba Prefecture. In recent years, however, this fungus was also reported to cause disease on another C. japonica cultivar and some other economically important tree species such as Chamaecyparis obtusa and Pyrus pyrifolia var. culta. This fungus is believed to invade trees through dead branches, destroy the cambium layer, and prevent outward growth of the invaded parts. The reason why the Sanbu-sugi cultivar was frequently targeted by the fungus, however, had not been well described. Laboratory studies clarified that this fungus utilizes carbohydrates, which are components of tree tissues, and could grow in a medium with a high glucose/yeast extract ratio and low water potential. Compared to bark in living branches and xylem in dead branches, bark in dead branches and xylem in living branches contain a higher amount of glucose, which might give suitable nutrition for the fungus to grow. The characteristics of this cultivar, in which trunks keep dying branches long-term, might establish adequate conditions for the fungus to invade them. The invaded trunks contained a lower amount of polyphenols, which are supposedly an effective defensive substance.

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Effects of adding polysaccharide-degrading enzymes to the substrate during medium preparation on the fruiting body formation of Hericium erinaceus and Pholiota microspora were evaluated by the free glucose and a- and b-glucan content in the medium. The fruiting body yield of H. erinaceus was 1.4 times higher after addition of an amylase, mesophilic amylase (MPA) or heat-resistant amylase (HRA), than the control. After addition of b-1,3-glucanase (GLU), the fruiting body yield of H. erinaceus was similarly 1.5 times higher than the control, while a mixture of HRA and GLU (HRA+GLU) did not show any additional effect. In the case of P. microspora, yields of fruiting body were 10－20% higher after addition of MPA or HRA from 50 ppm to 500 ppm to the substrate than in the control without enzyme. Moreover, the weight of each fruiting body was also higher in medium containing MPA or HRA. Although the addition of GLU had no effect, higher fruiting body yield was observed after the addition of HRA+GLU than HRA alone, suggesting a complementary effect of the enzyme mixture. The content of free glucose and low molecular weight a- and b-glucan were all increased by the addition of MPA or HRA in both H. erinaceus and P. microspora cultures. In P. microspora, however, there was no change in glucose or a- or b-glucan after GLU addition, while the addition of GLU had a similar effect to the addition of amylase in the H. erinaceus culture. These results reflect well the yield of fruiting bodies of both mushrooms. The addition of polysaccharide-degrading enzymes during medium preparation is an effective way to increase fruiting body yield if the appropriate combination of mushroom and enzymes is carefully evaluated.

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The taste characteristics of a fruit body of the novel strain IC1, belonging to the genus Pleurotus, were compared with those of P. ostreatus and P. eryngii using a combination of quantitative analysis of taste compounds and sensory evaluation. The Glu and 5’-GMP contents of the IC1 fruit body were similar to those of P. ostreatus, while the trehalose content was significantly higher. Sensory evaluation showed that the IC1 broth was less bitter and sweeter than the P. ostreatus broth, with higher umami than the P. eryngii broth. The palatability score of the IC1 broth was significantly higher than that of the P. ostreatus and P. eryngii broths. Principal component analysis revealed that the taste characteristics of IC1 were clearly differentiated from the others in terms of a stronger taste and higher palatability. The higher contents of Ala, Gly and 5’-IMP suggested that these compounds contributed to the taste characteristics of IC1. Overall, IC1 is a superior strain with favorable taste characteristics originating from both P. ostreatus and P. eryngii. In addition, the techniques of quantitative analysis and sensory evaluation complement each other to provide an effective method for evaluating the taste characteristics of foods.

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Pathogenic bacteria were isolated from yellow-browning and rotting fruiting bodies of oyster mushroom (Pleurotus ostreatus), king oyster mushroom (Pleurotus. eryngii), lion’s mane mushroom (Hericium erinaceus) and winter mushroom (Flammulina velutipes) individually cultivated on sawdust medium using A-D3 selective medium. The bacteria isolated were all identified as Ewingella americana based on bacteriological characteristics and 16S rRNA gene analysis. Yellow-browning symptoms on pileus of oyster mushrooms were observed after inoculation by spraying the obtained bacterial isolate into culture bottle after removal of surface mycelia (called the Kinkaki treatment). Discolored fruiting bodies with signs of rot were detected in the culture bottles 4 days after Kinkaki treatment followed by incubation at 20℃ for 3days. The causative bacterium from the discolored fruiting bodies was re-isolated using A-D3 selective medium, thus fulfilling Koch's postulates. These results suggested that E. americana is widely distributed and causes discoloration and rotting of cultivated mushrooms in Japan. Spray inoculation with Pseudomonas tolaasii into culture bottles of oyster mushrooms induced brown spots on the pileus of fruiting bodies that differed from symptoms caused by E. americana. This is the first report confirming yellow-browning and rotting symptoms on oyster mushrooms in culture bottles by inoculation of E. americana or P. tolaasii prior to primordium formation.

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