Host range and potential distribution of ectomycorrhizal basidiomycete Suillus pictus in Japan

The host range and potential distribution of the ectomycorrhizal basidiomycete Suillus pictus was evaluated using both in vitro inoculation and bait experiments with sterilized pine seedlings. In both experiments, three pines were selected as host, i.e. Pinus parviflora of the subgen. Strobus, and Pinus densiflora and Pinus thunbergii of the subgen. Pinus which are widely distributed in Japan. The inoculation experiment revealed that fine roots of seedlings of all pine species were colonized by S. pictus and formed typical ectomycorrhizas. The bait experiment with intact soil of a P. parviflora forest, which included propagules of S. pictus, clarified that S. pictus could form ectomycorrhizas on the fine roots of P. parviflora seedlings, while it could not form them on the fine roots of P. densiflora and P. thunbergii. In the bait experiment with intact soil of P. densiflora or P. thunbergii forest, ectomycorrhizas of S. pictus were not observed on the fine roots of P. parviflora. These results demonstrate that the fungus has the potential to form ectomycorrhizas with Pinus subgen. Pinus, but in natural conditions it only lives symbiotically with Pinus subgen. Strobus in Japan. The fact that this fungus has ecological host specificity provides useful information to study the bio- and phylogeography of this fungus.