Abstract
In the search for new strains of edible mushrooms in the Brazilian Amazon Forest, we found Lentinula specimens different from Lentinula raphanica. These were described morphologically and evaluated phylogenetically within the Lentinula clade. The mating system was determined, and interbreeding compatibility with L. raphanica was verified. The basidiomata have a cinnamon or deep orange to fulvous brown, moist to dry pileus, occasionally with whitish scales; crowded whitish cream lamellae; and an eccentric to lateral stipe. The typical, predominant basidiospores are 4.4-7.2 µm in length. Endogenous, elongate (7.8-14 µm) basidiospores were also found in some specimens. The long spores seem rare and occasional, but nonetheless a novelty for the group. Basidia are homogeneous in size, cheilocystidia are pyriform or bulboid, and caulocystidia are long and spheropedunculate. The hyphae of the pileipellis are pigment-encrusted. The characteristics match those of Agaricus ixodes originally described from Guyana, currently a synonym of Lentinula boryana. In the phylogenetic trees, such taxon appears distinct from L. boryana and sister to L. raphanica with strong support. This unique lineage was confirmed to be reproductively isolated from sympatric L. raphanica strains. Lentinula ixodes comb. nov. is the second species of the genus reported in the Amazon Forest.