Polyporales » Polyporaceae » Panus

Panus  sribuabanensis 

Panus  sribuabanensis  J.  Kumla,  N.  Suwannarach  &  S.,  Lumyong

MycoBank number: MB849810

Basidiomata medium to large. Pileus 25–160 mm diam, weakly depressed in the center or infundibuliform, concentric zone absent, squamu­lose when young, almost glabrous with age, brown­ish orange (5C4–C3) to brown (6E8) at the center when young, become orange white (5A2) to yellow­ish white (4A2) in age, margin entire, dentate or irregularly lobed. Hymenophore lamellate. Lamellae 3–5 tiers, decurrent, sometimes dichotomously branched, white (3A1) to yellowish white (3A2). Context up to 5 mm thick, white (3A1). Stipe 45–85 × 5–15 mm, central, cylindrical, tapering toward the base in age, solid, surface glabrous to matted fibrillose or strigose, sometimes with sparse and scattered squamules, yellowish white (4A2) near lamellae with brownish orange (5C4–C3) to brown (6E8) at the base. Odor not distinctive. Spore print white.

Basidiospores [280/5/5] (4–) 4.5–5.8 (–6) × (3–) 3.25–4 μm, L’ = 5.1 μm, W’ = 3.5 μm, Q = (1.30–) 1.38–1.45 (–1.50), Qm = 1.42 ± 0.12, broadly ellipsoid to ellipsoid, hyaline, smooth, thin-walled, and inamyloid. Basidia 28–40 × 5.5–8.0 μm, clavate, hya­line, 4-spored, sterigmata up to 7.0 μm long. Pleurocystidia 32.0–70.0 × 6.5–10.0 μm, subcylindrical or fusoid-ventricose with a slightly prolonged apex, hyaline, thin-walled. Cheilocystidia 21.0–70.0 × 5.0–9.0 μm, versiform, generally flexuose, branched toward apex, hyaline, smooth, thin-walled, with obtuse ends. Hyphal pegs absent. Hymenial trama radially arranged and dimitic. Generative hyphae 2.0–5.5 μm wide, hyaline, smooth, thin to slightly thick-walled (up to 1 μm), frequently branched, clamp connections abundant. Skeletal hyphae domi­nant, 2.0–6.0 μm wide, hyaline, thick-walled (1.0–1.5 μm), mostly unbranched, rarely branched, septations not observed. Pileal trama radially arranged. Generative hyphae 2.0–5.0 μm wide, rarely inflated up to 10.0 μm, hyaline, smooth, thin to slightly thick-walled (up to 1 μm), frequently branched, clamp connections abundant. Skeletal hyphae dominant, 2.0–6.0 μm wide, hyaline, thick-walled (1.0–1.5 μm), mostly unbranched, rarely branched, septations not observed. Pileipellis cutis, trichoderm to intricate trichoderm, 2.5–6.0 μm wide, up to 100 μm long, hyaline, thin to slightly thick-walled (up to 1.0 μm), clamp connections abundant, obtuse ends. Stipe trama interwoven. Generative hyphae 2.0–5.5 μm wide, hyaline, smooth, and thin to slightly thickwalled (up to 1.0 μm), fre­quently branched, clamp connections abundant. Skeletal hyphae 2.0–6.0 μm wide, hyaline, thick-walled (1.0–1.5 μm), mostly unbranched, rarely branched, septations not observed. Stipitipellis similar as pile­ipellis. hyphae 2–4 μm wide, hyaline, mostly thin-walled, with obtuse ends. Clamp connections abundant at all tissues.


Ecology and distribution: Fruiting solitary or gre­garious on soil and decaying wood in a tropical deciduous forest. Known only from the type locality in northern Thailand.

Additional specimens examined: THAILAND, Lamphun Province, Mae Tha District, 18°27’41”N 99°10’30”E, elevation 427 m, 16 August 2020, J. Kumla and N. Suwannarach, SDBR-CMUNK0924 and SDBR-CMUNK0930; Mueang District, Sri Bua Ban Subdistrict, Chiang Mai University Haripunchai Campus, 18°32’26”N 99°7’31”E, elevation 475 m, on decaying wood in a tropical deciduous forest, 16 August 2020, N. Suwannarach, SDBR-CMUNK0940; 18°32’34”N 99°8’22”E, elevation 448 m, on decaying wood in a tropical deciduous forest, 10 October 2020, J. Kumla SDBR-CMUNK1100.

Note: Panus sribuabanensis was similar to P. bam­businus, P. caespiticola, and P. tephroleucus based on the color of the pileus. However, the longer size of the cylindrical basidiospores (6.0–8.0 × 3.0–5.5 μm) and the shorter size of basidia (18.0–20.0 × 5.0–6.0 μm) in P. tephroleucus differ from P. sribuabanen­sis. Notably, the presence of the smaller basidiospores in P. sribuabanensis clearly distin­guishes it from P. caespiticola (5.0–7.5 × 4.0–5.5 μm). Additionally, the narrower size of the basid­iospores (4.0–6.0 × 3.0–4.0 μm, Qm = 1.42) in P. sri­buabanensis clearly distinguishes it from P. bambusinus (5.0–6.5 × 4.0–4.5 μm, Qm = 1.32). Moreover, the wider size of cheilocystidia (21.0–70.0 × 5.0–9.0 μm) in P. sribuabanensis clearly differs from P. bambusinus (22.0–68.0 × 3.0–5.0 μm). Phylogenetically, P. sribuabanensis formed a monophyletic clade and sister taxon to P. bambusi­nus and P. purpuratus. Traditionally, the main criterion for identifying Panus species was morphological characteristics. On the other hand, identification could be difficult with regard to the morphological variability that can be influenced by developmental stages of basidiomata, varied environmental condi­tions, and geographic distributions. Thus, DNA-based techniques are essential for identification of the Panus species. Consequently, combined morpholog­ical characteristics and molecular data are currently used to identify Panus species. In this study, a new edible Panus species discovered in northern Thailand was identified as P. sribuabanen­sis based on morphological characteristics and phy­logenetic analyses. Panus sribuabanensis can be distinguished from certain Panus species with pileus colors ranging from pinkish, reddish brown, brown, to purple-gray due to its distinctive orange-white to yellowish-white pileus color. However, it shares a similar pileus color with other species like P. bam­businus, P. caespiticola, and P. tephroleucus, which also exhibit shades ranging from yellowish-white to pale ocher shades. The relevant micro­scopic features and distribution of P. sribuabanensis have been compared with P. bambusinus, P. caespit­icola, and P. tephroleucus . The different characteristics of the microscopic fea­tures of P. bambusinus, P. caespiticola, P. sribuaban­ensis, and P. tephleucus have been mentioned above. In addition, P. bambusinus is distributed only throughout India, while P. caespiticola was found in Cuba, India, Mali, Mozambique, and Tanzania. Furthermore, P. tephroleucus was recorded from Brazil, Cuba, India, and Mexico.

According to a phylogenetic analysis of the com­bined ITS and nrLSU sequences, P. sribuabanensis established a monophyletic clade that was clearly distinct from the other previously known Panus spe­cies and formed a sister taxon to P. bambusinus and P. purpuratus. Moreover, the phylogenetic tree clearly separated P. sribuabanensis from P. bam­businus and P. tephroleucus. However, there is still a need to acquire the molecular data of P. caespiticola to confirm its phylogenetic placement. Subsequently, a nucleotide comparison of the ITS gene indicated that P. sribuabanensis differs from P. bambusinus, P. purpuratus, and P. tephroleucus by 3.76% (20/531 bp), 7.21% (43/596 bp), and 12.16% (72/592 bp), respec­tively. According to Jeewon and Hyde, a nucle­otide comparison of reliable genes must reveal a difference of more than 1.5% to confirm the exis­tence of a new species. Therefore, P. sribuabanensis can be considered a new species. findings from previous published studies on edible Panus species, it was observed that the protein con­tent of P. sribuabanensis was relatively higher than P. lecomtei (17.3%–20.0% dry weight). Additionally, P. lecomtei had higher carbohydrate content (44.4%–52.1% dry weight) than P. sribuaban­ensis. The fat content in P. sribuabanensis was higher than that of P. lecomtei (0.5%–1.0% dry weight).

Fig. 1 Phylogenetic tree derived from maximum likelihood analysis of combined ITS and nrLSU genes of 40 specimens. Lentinus polychrous and Polyporus thailandensis were set as the outgroup. Numbers above branches are the bootstrap per­centages (left) and Bayesian posterior probabilities (right). Bootstrap values > 75% and Bayesian posterior probabilities > 0.90 are shown. The scale bar displays the expected number of nucleotide substitutions per site. Type species are shown in bold. Sequences derived in this study are shown in red.