A new species of Obba (Polyporales, Basidiomycota) from Thailand

Obba thailandica sp. nov. is described and illustrated from northern Thailand based on evidence from morphological characteristics and molecular data. The species produces annual, resupinate, white and waxy fresh basidiocarps, which become bone hard when dry, and has a very thin subiculum (<0.1 mm), tomentose tube openings, weakly dextrinoid hyphae, variably shaped cystidioles, thin-walled and subglobose to globose basidiospores (4.8–5.8 × 4–4.9 μm) mostly with a large guttule and grows on charred pine wood.

The new taxon is rather similar to O. rivulosa in both morphology and ecology, but O. rivulosa has fragile tubes when dry, a thick subiculum (up to 1 mm wide), smooth tube openings, indextrinoid hyphae, rhomboidal to irregular rosettes crystals on the tramal hyphae and long basidia (16–27 × 6–9.5 μm). In the phylogeny inferred from an ITS dataset, the new species forms a distinct lineage in the Obba clade and is closely related to O. rivulosa.