Hygrophorus alboflavescens A. Naseer & A.N. Khalid sp. nov. Figures 1, 2

Diagnosis.

Hygrophorus alboflavescens can be distinguished from related species by its white, centrally depressed pileus having yellow dots, with straight, even margins; occurrence of white stipe with yellow patches at lower half and broader (4.98 μm) basidiospores.

Typification.

PAKISTAN. Khyber Pakhtunkhwa Province, Swat, Shawar Valley, 2100 m alt., solitary or in pairs, on soil under Quercus incana, 14 July 2014, Arooj Naseer & Abdul Nasir Khalid, ASSW36 (holotype: LAH35243).

Etymology.

The species epithet refers to the white pileus with yellow dots and white stipe with yellow patches.

Basidiomata medium to large sized. Pileus 7-10.5 cm in diameter, butter white (0.1B 8.8/0.3) with yellow (5.2Y 4.3/4) dots, plane, centrally depressed, context moderately thick, margin, even, smooth, straight, sometime incurved. Lamellae white (5.1GY 7.9/1.9) with yellow (6.1 Y 6.8/5.5) and pink (2.8Y 6.9/3.9) colouration, decurrent, thick, distant, L = 30-41, even, entire. Lamellulae irregular, of variable length, alternating with lamellae. Stipe 1.5-2.5 cm thick at apex, 0.5-1.5 cm at base, 8 -12.5 cm long, white (0.1B 8.8/0.3) with yellow (5.4Y 5.3/4) patches at lower half, cylindrical, slightly tapering at base, central, hollow.

Basidiospores [60/3/2] (5.52-) 5.6-7.9 (-8.1) × (3.84-) 3.9-6.5 (-6.7), avL × avW = 6.64 × 4.98, Q = (1.20-) 1.21 × 1.40 (-1.43), avQ = 1.34, light green to hyaline in 5% KOH, ellipsoid, oblong, thick-walled. Basidia 31.6-48.8 × 5.8-6.7 μm, hyaline in 5% KOH, four-spored, clavate with long sterigmata (up to 3.0-4.2 μm), densely guttulated. Hymenophoral Trama 4-5.2 μm in diameter, thin-walled, branched, septate, oil contents, clamp connection present. Pileipellis an ixocutis of wide, thick hyphae, 3.0-5.5 μm in diameter. Stipitipellis a cutis of parallel and erect hyphae, 3.1-5.3 μm in diameter, light yellow in 5% KOH, septate. Clamp Connections present in all tissues.

Habit and distribution.

Solitary and in pairs on soil under Quercus incana, at 2100 m a.s.l., in thick moist temperate forest of the western Himalaya.

Additional material examined.

PAKISTAN, Khyber Pakhtunkhwa province, Swat, Shawar Valley, 2100 m a.s.l., solitary or in a pair, on soil under Quercus incana, 14 July 2014, Arooj Naseer & Abdul Nasir Khalid, ASSW81 (LAH35244; FLAS-F-59457).

Notes.

Hygrophorus alboflavescens nom. prov. can be distinguished from closely related species by the following combination of characters: a white, plane, centrally depressed pileus having straight margins; stipe that is white above and yellow below; and broadly ellipsoid spores. The closely related species Hygrophorus penarioides is also an oak-specific species (Table 1). However, they differ morphologically. Hygrophorus penarioides can easily be distinguished by its convex pileus with broad umbo and its involute margins (Jacobsson and Larsson 2007), whereas H. alboflavescens has centrally depressed pileus (without umbo) and straight margins. Hygrophorus penarioides has a pure white pileus and stipe which become cream or slightly pinkish with age, whereas H. alboflavescens has a white stipe and pileus with yellow colouration on both. Hygrophorus alboflavescens has a longer stipe (8-12.5 cm) and broader spores (3.9-6.7 μm) as compared to H. penarioides . Hygrophorus alboflavescens is further differentiated from closely related taxa, H. sordidus, which has a convex, expanded to plane pileus that is larger (8-20 cm broad) compared with the smaller (7-10.5 cm broad), centrally depressed pileus of H. alboflavescens . Hygrophorus alboflavescens has even, smooth and straight margins that differ from involute and subnoccose margins of H. sordidus . Molecular analyses based on ITS and LSU regions also support H. alboflavescens as a distinct taxon and demonstrate its ECM relationship with oak in Pakistan.