Systematics of pleurotoid Russulaceae from Guyana and Japan, with notes ontheir ectomycorrhizal status

Three species of pleurotoid, putatively lignicolous basidiomycetes previous ly described in the genus Lactarius sect Panuoidei were redescribed from fr esh material collected in Guyana andJapan. In Guyana, Lactarius panuoides a nd Lactarius campinensis were restricted to forests dominated by ectomycorr hizal Dicymbe species (Caesalpiniaceae) and basidiomata of both pleurotoid species were subtended by ectomycorrhizal rootlets. This suggested an ectom ycorrhizal nutritional mode for these fungi. Analysis of DNA sequences in t he nuclear large subunit region taken from basidiomata and co-occurring ect omycorrhizae of L. panuoides and L. campinensis confirmed that these fungi are ectomycorrhizal and that their fruiting habit on organic deposits and w ell rotted wood at elevated positions is not due to saprotrophy, as previou sly assumed. Lactarius uyedae was collected in Japan from mature temperate forests dominated by Fagaceae, yet ectomycorrhizal rootlets were not found in association with the basidiomata. Morphological features and analysis of DNA sequences suggested that L. panuoides and L. uyedae have affinities wi th established sections of the genus Lactarius, regardless of the pleurotoi d morphology of their basidiomata, and that L. campinensis should be transf erred to the genus Russula. Discussion is provided for the genus Pleurogala , which was erected to accomodate putatively lignicolous, pleurotoid specie s of Lactarius.