The genetic composition of the A-mating locus in bipolar mushrooms such as “nameko” mushrooms has not been known for a long time. In this paper, I present our findings on the mating system of bipolar basidiomycetes. The A-mating locus of the bipolar mushroom, Pholiota maicrospore, contains a pair of homeodomain protein genes [<i>hox1 (HD1), hox2 (HD2)</i>], a mitochondrial intermediate peptidase gene (<i>mip</i>), a methylmalonic acid semialdehyde dehydrogenase gene (<i>mmsd</i>), a low molecular weight phosphotyrosine protein phosphatase gene (<i>lmwppp</i>), an ammonium transport protein gene (amtp), and a glycine dehydrogenase gene (<i>glydh</i>). In order to determine whether only the homeodomain protein gene can drive clamp formation, I introduced a homeodomain protein gene derived from an <i>A4</i> homokaryon strain into an <i>A3</i> homokaryon strain of the mushroom, and examined whether clamp cells were formed. I concluded that sufficient expression of the homeodomain protein gene is required to induce true clamp cell formation in bipolar mushrooms, since two nuclei per cell are present, as in heterokaryons. Fruiting body development and the formation of true clamp cells are also observed in the homokaryon strain of <i>Mycoleptodonoides aitchisonii</i>. These results strongly suggest that heterokaryotization of mushrooms is not essential for fruiting body formation and clamp cell formation; however, heterokaryotization may be necessary for the "efficient" or "high frequency" formation of fruiting body and true clamp cells.

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In this study, we crossed 31 basidiospore isolates from the fruit bodies of dikaryotic strain <i>Grifola frondosa </i> IM-BM21 to analyze mating compatibility groupings. Two incompatibility groups ( <i>A1 </i> and <i>A2 </i>) were identified, identifying <i>G. frondosa </i> as a bipolar mushroom. Based on nucleotide sequences of whole genomic DNA of <i>G. frondosa </i> WM1-25 from next-generation sequencing, we designed oligonucleotide primers to amplify the homeodomain protein gene located on the <i>A </i> locus ( <i>A1hox2 </i>) and pheromone genes ( <i>A1phb1 </i>) located on the <i>B </i> locus in the tetrapolar mushroom. The DNA fragment of the <i>A1hox2 </i> gene was amplified only from <i>A1 </i> monokaryotic strains and the <i>A1phb1 </i> gene was amplified in all <i>A1 </i> and <i>A2 </i> monokaryotic strains. Therefore, the linkage groups of the analyzed genes were defined as <i>A1hox2 </i> in linkage group I, which is closely linked to <i>A </i> mating-type locus, and <i>A1phb1 <i>, which has no relationship with mating type.

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Turkeytail mushrooms (<i>Trametes versicolor</i>) are used in to prepare tea Chinese medicine. Fermented mushroom products include sake and miso made from mushroom koji. However, fermented foods made from a fermentation starter of mushroom koji do not exist. We therefore fermented tofu with mushroom koji using <i>Trametes versicolor</i> mycelium. Fermenting tofu at a fermentation temperature of 10°C for 1 day resulted in an increase in glutamic acid and alanine, and consequently, umami. Furthermore, the tofu tasted and smelled like shimeji mushrooms and antioxidant activity increased. In summary, we developed a new type of fermented tofu with increased nutritional value, palatability and functional properties.

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<i>Lentinula edodes</i> (Berkeley) Pegler (i.e., shiitake mushroom) is one of the most widely produced mushrooms, especially in Asia. However, even though the species’ genome and transcriptome have been analyzed extensively, breeding of the species has continued to rely on traditional mating. Accordingly, the aim of the present study was to apply marker-assisted selection, based on genetic and genomic information, to <i>L. edodes</i> breeding. An L. edodes strain (Mu789) with a glucanase-encoding gene (<i>exg2</i>) mutation was identified using targeting-induced local lesions in genomes (TILLING). The strain produced fruiting bodies with sustained post-harvest gill whiteness and reduced post-harvest glucanase activity, and the <i>exg2</i> mutation-associated phenotype was inherited by the progeny of a cross between Mu789 and the commercial strain, HS715. Backcrossing of the progenies with HS715 yielded strains that exhibited both desirable post-harvest and cultivation traits. When compared to strain HS715, the fruiting bodies of two strains in particular (2520DA and 5624DA) exhibited both maintained post-harvest gill whiteness and reduced post-harvest glucanase activity. Furthermore, the strains had higher agronomic traits, such browning of the mycelial block and cap shape, than strain Mu789. The findings of the present study demonstrate the usefulness of Mu789 as a parent strain in marker-assisted selection-based shiitake breeding programs.

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To shorten the cultivation period and decrease the space required for screening <i>Hypsizygus marmoreus</i> (Bunashimeji mushroom) strains, we investigated several cultural traits of strains using ‘miniature beds’, which were 15% the size of conventional beds (control). Earlier fructification was observed when spawn runs were carried out on Japanese cedar (sugi) sawdust-based media or at 25℃ compared to on corn cob meal-based media or at 20℃, respectively. When spawn runs of 18 to 22 strains were compared under suitable conditions using ‘miniature beds’ and under conventional conditions and beds, significant positive correlations (<i>r</i> = 0.73 and 0.79) were observed in the miniature beds for days to harvest after scratching and in fruit body yield per bottle, respectively. In all strains, the pilei of fruit bodies that formed in the ‘miniature beds’ were morphologically similar to those that formed in the conventional beds. Further, other characteristics were completely consistent with the characteristics of each strain. The optimized methods together with the use of miniature beds reduced the time required to form fruit bodies by more than one month compared to conventional culture methods. The findings suggest that the use of miniature beds will accelerate the estimation for cultural traits of strains in Bunashimeji mushroom breeding.

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