Volume 19 Part 1 Article 67
Title: Establishment of a crossbreeding system for the ectomycorrhizal mushroom Rhizopogon roseolus
Author: Norihiro Shimomura, Shota Nakano, Qi Gao and Tadanori Aimi
Rhizopogon roseolus, known as “shoro” in Japanese, is an edible ectomycorrhizal mushroom. Research aiming at elucidating the steps in the life cycle of mushrooms, such as basidiospore germination, subsequent hyphal elongation, and heterokaryosis between compatible mycelia, is fundamental in developing a crossbreeding system. Variability in the germination ability of the basidiospores was observed among the fruiting bodies, implying that selection of the fruiting body is an important step for efficient isolation of germlings. The highest germination ratio was observed in the spore suspension in which spores showed three types of wall, viz., two-layer spore wall, three-layer spore wall and four-layer spore wall. No significant difference in colony morphology was evident between the basidiospore isolates and the hybrid strains obtained from crosses between the isolates. Variability in nuclear number was observed in not only the basidiospore isolates but also in the hybrid strains. Binucleate cells were frequently observed in both, the basidiospore isolates and the hybrid strains, indicating that nuclear number is not a key characteristic that can be used to distinguish between primary mycelia and secondary mycelia. Clamp connections were occasionally observed in the hybrid strains. When the hybrid strains were cultured on a specific medium, clamp connections were consistently observed in the hybrid strains, but never in the basidiospore isolates, indicating that the specific medium is useful to distinguish between primary mycelia and secondary mycelia in R. roseolus. These results will contribute to the establishment of a crossbreeding system for shoro mushrooms.