Interactions of heterologous mycelia colonized in the substrate govern fruit body production in the cultivated homobasidiomycete Pholiota nameko.

The spawn of cultivated mushrooms are generally produced, propagated, and distributed to growers as a mycelial culture without genetic purification, in which phenotypic variants frequently occur. We investigated how heterologous mycelia present in a spawn influence fruit body production in the cultivated basidiomycete Pholiota nameko. The 'di-mon' dual cultivation of protoplast clones produced mosaic fruit bodies, which could result from the 'di-mon' mating. In the 'di-di' dual cultivation of heterologous strains with different fruiting times, authentic fruit bodies of each dikaryon and chimera showing a feature combining characteristics of the two dikaryons emerged simultaneously. Mycelia isolated from the chimera produced all three types of fruit bodies, indicating unlikeliness of the occurrence of anastomosis. These results suggest that mycelia colonized in the substrate interact with each other and coordinately promote fruit body production in P. nameko. This phenomenon masks a clonal variability that may be surfaced through multiplication and distribution of the spawn, occasionally bringing about abnormal fruiting.