Ganoderma thailandicum is characterised by its laccate deep magenta close to stipe, brownish-red at centre and light yellow of active development towards the margin on pileal surface, white pore surface, brownish-red context and absence of melanoid band.

THAILAND, Nakhon Si Thammarat Province, Khanom District, solitary on stump of Pinus merkusii, 10 December 2018, LT2018-105 (HKAS 104640).

The species epithet “thailandicum” refers to the country where the holotype was collected.

Basidiocarps. Dimidiate, laccate, substipitate to stipitate. Pileus shape. Annual and dimidiate when mature, up to 3–9 cm in length, 3–6 cm in width, up to 0.4–1.8 cm thick at centre of pileus close to the stipe, obtuse from the substrate. Pileus surface. Laccate, glabrous, glossy, smooth, soft, umbonate, distinctly concentrically zonate, greyish-magenta to deep magenta at stipe, greyish-ruby, greyish-red to brownish-red at centre, extended to reddish-orange to slightly pale red with light yellow to vivid yellow of active development towards the margin, thin crust overlaying the pileus, sometimes convex sulcate extending at centre, with distinct concentric zones, with fine furrows at centre extended to the margin, thicker at the base than the margin, consistency hard when young to mature, some cracked when old, non-woody, light in weight when dried. Hymenophore. Trimitic, up to 0.4–2.4 cm thick, heterogeneous with greyish-red close to the upper layers slightly to brownish-red to reddish-brown close to the tubes. Context. Mostly brownish-red to reddish-brown in Melzer’s reagent, absent of melanoid band, with dense context layer. Basidiospores. Ellipsoid to broadly ellipsoid with some globose with double wall (ganodermoid) at maturity, light brown to reddish-brown in Congo red reagent, (6.8)8.4–9.7 (10.2) × (5.8)6.5–7.3 (7.7) μm (x̄ = 9.1 × 6.9 μm, n = 50), with Q = 1.29–1.35, L = 9.13 µm, W = 6.96 µm (including myxosporium), (5.4)7.6–9.6 (10.0) × (4.7)5.8–6.9 (7.4) μm (x̄ = 7.6 × 6.0 μm, n = 50) μm, with Q = 1.32–1.38, L = 8.64 µm, W = 6.42 µm (excluding outer myxosporium). Tubes. Up to 0.5 mm close to margin to 7 mm at centre in length, brown to dark brown, hard, woody when dried; generative hyphae 2.73–4.74 µm in diam., almost colourless, thin-walled with occasionally thick walls, with clamp connections, occasionally branched; skeletal hyphae 3.76–5.81 µm in diam., thick-walled frequently branched at apex; binding hyphae 3.24–5.84 µm in diam., thin to thick-walled, frequently branched at apex. Stipe. Lateral, pale red to vivid red, greyish-red to red when present, with violet brown when mature, different from and darker than pileus, up to 3–5 cm long, 2.5–3.0 cm in diam., 1.8–2.7 cm thick. Margin. Up to 0.4–0.8 cm thick when becoming mature, active growing margin white on the upper and under margin surface when fresh, with a yellow line under the pileus, round, soft, smooth, slippery when touched when young to mature stage, without any zonation, tough when broken. Pores. Angular to round, 4–8 per mm, up to 121–176 × 174–247 µm (x̄ = 155 × 209 μm, n = 50). Pore surface. White when fresh, grey at centre, slightly orange grey at margin, brownish-grey when touched, turning brownish-orange when dry, grey when wet. Hyphal system. Trimitic, light orange to deep orange, reddish-brown in Melzer’s reagent; generative hyphae, 2.65–4.58 µm (x̄ = 3.82, n = 50) in diam., almost colourless, mostly thick-walled, occasionally thin-walled, bearing clamp connections, occasionally with irregular cuticle cells; binding hyphae 3.32–6.28 µm (x̄ = 5.53, n = 50), almost colourless, thin-walled, occasionally branched in the distal end, with clamp connections; skeletal hyphae abundant, up to 3.40–6.78 μm (x̄ = 5.73, n = 50), almost colourless, thick-walled and unbranched. Context. Mostly brownish-red in Melzer’s reagent, reddish-brown, with greyish-red close to crust, dense context layer, agglutinate mass, usually solid in basal part, thick near the base, tough to break when dried; generative hyphae up to 2.80–5.75 μm (x̄ = 4.36, n = 50) in diam., mostly colourless, thick-walled, with clamp connections, occasionally with simple septa; binding hyphae 1.23–4.75 µm (x̄ = 2.49, n = 50), colourless, thin-walled or with a very few branches in the distal end, with clamp connections; abundant skeletal hyphae up to 3.30–7.51 μm (x̄ = 5.75, n = 50), almost colourless, thick-walled, unbranched, with clamp connections and occasionally with simple septa. Cuticle cells. Clavate to narrowly clavate, tuberculate, occasionally with irregular cuticle cells, mostly thick-walled, occasionally thin-walled with simple septa. Basidia. Clavate, with 4 sterigmata, 12.2–19.6 × 8.3–10.9 µm, light brown (5D6) to yellowish in Melzer’s reagent.

THAILAND, Nakhon Si Thammarat Province, Khanom District, solitary on stump of Pinus merkusii, 11°45'58"N, 99°47'43"E, 499 m elev., 10 December 2018, LT2018-105 and LT2018-106, specimens no. HKAS 104640 and HKAS 104641.