Boletales » Boletaceae » Sutorius

Sutorius maculatoides

Sutorius maculatoides (E. Horak) Vadthanarat, Raspé and Lumyong comb.

MycoBank: MB838055

Pileus (1.8) 2.4 to 4.6 cm in diameter, at first hemispherical with straight margin becoming convex with deflexed margin; surface subrugulose, dull, minutely tomentose, at first dark lilac (10–11F3–6) becoming purplish to reddish brown to brown (8F6, 7E5) in age, gradually paler to the margin. Pileus context 4–5 mm thick halfway to the margin, firm, yellowish off-white (4A2), near the center grayish to purplish white (14–15C–E2) at first, then yellowish white (4A2) in age, with scattered small violet–brown (11F4–6) encrustations. Stipe central, terete to slightly compressed, cylindrical, slightly wider at the base, 2.4–4.5 × 0.6–1.2 cm; surface finely scabrous with groups of brown to dark brown (7–8F4–6) granulose squamules on purplish gray (15C2, 15D3) background; basal tomentum little developed, white. Stipe context solid, pale grayish orange (5B2), virgated with grayish purple (15– 16C3), with scattered small violet–brown (11F4–6) encrustations. Hymenophore tubulose, subventricose to adnexed to broadly adnexed, depressed around stipe; tubes easily separable, at first grayish brown (7D3) then brownish orange (6C6) with age, 8– 9 mm long halfway to the margin; pores 0.2–0.4(0.7) mm wide at midradius, regular roundish; at first lilac-gray (15–16E3 to 15C2) slightly paler near the margin, becoming pale reddish brown (9D–E4) with age. Odor fungoid. Taste mild. Spore print reddish brown (8E/F5). Macrochemical reactions: KOH: pale greenish yellow on pileus, pileus context, stipe and stipe context; pale brownish orange on hymenophore. NH4OH: pale greenish yellow on pileus, on pileus context bluish white (21A2) when young or negative in mature basidiomes; greenish yellow on stipe; greenish yellow then purplish on stipe context. Basidiospores [165/3/3] (7.8–) 8.3–10.9–13.2 (–14.1) × (3–) 3.3–4–4.7 (–5.6) µm, Q = (2.02–) 2.24–2.69–3.18 (–3.41), narrowly ellipsoid to subcylindrical with slight suprahilar depression, thin-walled, smooth, brownish to yellowish hyaline in water, yellowish hyaline in KOH or NH4OH, inamyloid. Basidia 4-spored (23–) 23–26–31 (–32) × (10–) 10–11–13 (– 14) µm, with sterigmata up to 4 µm long, clavate, hyaline, inamyloid. Cheilocystidia (19–) 19–22–27 (–27) × (6–) 6–8–9 (–9) µm, frequent, fusiform, thin-walled, hyaline. Pleurocystidia (32–) 32–38–45 (–45) × (6–) 6–8–10 (–10) µm, infrequent, narrowly fusiform, thin-walled, hyaline. Hymenophoral trama divergent becoming boletoid in age, 21–52 µm wide, with regular mediostratum 9–22 µm wide. Pileipellis a sub-ixotrichoderm to intricate trichoderm, 135–212 µm thick, terminal cells (12– 55 × 5–11 µm) fusiform with slightly tapering apex, pale yellowish brown in water, mostly hyaline to pale yellowish brown in KOH or NH4OH, with scattered loose crystals. Pileus context made of strongly interwoven, hyaline, thin-walled hyphae, 8– 13 µm wide, with scattered loose crystals. Stipitipellis a disrupted hymeniderm, 100–120 µm thick, composed of parallel hyphae, with terminal cell 11–33 × 7–10 µm of thin-walled, hyaline hyphae, giving rise to clusters of caulocystidia and basidiole-like cells, with scattered loose crystals. Caulocystidia (18–) 18–26–37 (–38) × (8–) 8–11–15 (–15) µm, frequent, fusiform to broadly fusiform with subacute apex, thin-walled, hyaline. Stipe context composed of parallel, 4- to 12-µm-wide hyphae, with scattered loose crystals. Clamp connections not seen in any tissue. Microscopic description (based on WAT25793): Basidiospores (11.4–) 11.5–12.1–12.7 (–13.5) × (4.1–) 4.2–4.5–4.8 (–4.9) µm, Q = (2.42–) 2.42–2.68–2.94 (–3.05), N = 72, narrowly ellipsoid to subcylindrical with slight suprahilar depression, thin-walled, smooth, brownish to yellowish hyaline in water, yellowish hyaline in KOH and NH4OH, inamyloid. Basidia 4-spored (21–) 21– 24–28 (–29) × (9–) 10–11–12 (–12) µm, with sterigmata up to 3 µm long, clavate, yellowish hyaline to yellowishbrown in KOH, inamyloid. Cheilocystidia (15–) 16–21–24 (– 24) × (6–) 6–7–8 (–8) µm, frequent, fusiform, thin-walled hyaline. Pleurocystidia (31–) 31–36–43 (–43) × (5–) 5–6–7 (–7) µm, quite rare, narrowly fusiform, thin-walled, hyaline. Pileipellis a sub-ixotrichoderm to intricate trichoderm, 67- to 132-µm-thick, thin-walled hyphae, with fusiform terminal cells (11–53 × 6–11 µm) with slightly tapering apex. Pileus context made of moderately interwoven hyaline hyphae, 6–13 µm wide. Stipitipellis a disrupted hymeniderm, 65–85 µm thick, composed of parallel hyphae, with rounded terminal cell 14–40 × 5– 10 µm of thin-walled, hyaline hyphae; at places the terminal cells grouped with caulocystidia into clusters, with scattered loose crystals. Stipe context composed of parallel 4- to 14- µm-wide hyaline, thin-walled hyphae. Caulocystidia (20–) 20– 28–37 (–37) × (7–) 8–11–15 (–15) µm, frequent, fusiform to broadly fusiform with subacute apex, thin-walled, hyaline. Clamp connections not seen in any tissue. (Fig. 2 a–e, Fig. 3)

Habitat: Solitary to gregarious on soil, in hill forest dominated by Dipterocarpus obtusifolius, Dipterocarpus tuberculatus, Shorea obtusa, and Shorea siamensis.

Distribution: Malaysia, Singapore, and Thailand.

Specimen examined: MALAYSIA: Forest Research Institute Kepong, MNS foray along rovers’ trail, 27 February 1994, Roy Watling, WAT25793 (E). THAILAND: Chiang Mai Province: Doi Suthep-Pui National Park, 18◦ 480 4700N–98◦ 560 1100E, elev. 540 m, May 18, 2015, Olivier Raspé, OR0626 (BKF, CMUB); –ibid., 18◦ 470 3700N–98◦ 550 4100E, elev. 770 m, May 24, 2015, Olivier Raspé and Santhiti Vadthanarat, OR0754 (BKF, CMUB); –ibid., 18◦ 470 3800N–98◦ 550 4200E, elev. 770 m, May 26, 2015, Olivier Raspé and Santhiti Vadthanarat, OR0758 (BKF, CMUB); Mae On District, Ban Huay Kaew community forest, 18◦ 520 7.1500N–99◦ 170 38.9200E. 750 m, July 17, 2017, Olivier Raspé, OR1414 (CMUB, BR).

Notes: Corner (1972) described B. maculatus from Malaysia. However, it was a later non-homotypic homonym of B. maculatus Raddi described in 1807. Consequently, Horak (2011) gave the new epithet maculatoides. He also transferred the species to Tylopilus. Here, we present phylogenetic evidence supporting placement in Sutorius. In our phylogenetic inference (Figure 1), all S. maculatoides collections clustered together in a wellsupported terminal clade (clade 13), within the Sutorius clade. The macromorphological and micromorphological characters of S. maculatoides also support its position in Sutorius. Therefore, the new combination S. maculatoides is proposed for T. maculatoides. In our phylogeny, among the S. maculatoides specimens, the Thai collections (OR0626 and OR0758) were molecularly slightly divergent from the Malaysian specimen (WAT25793). Being the amount of divergence is lower than the one observed between sister species, we consider those differences in the range of intraspecific genetic variability and compatible with conspecific, geographically distant populations. Sutorius maculatoides is characterized by the following characteristics: dark lilac pileus with lilac gray pores at first, with age becoming reddish brown and reddish pale brown, respectively; presence of cheilocystidia and infrequent pleurocystidia; pileipellis a sub-ixotrichoderm composed of moderately interwoven hyphae, with fusiform terminal cells that slightly taper at the apex. In this study, S. maculatoides is redescribed based on specimens from Thailand (OR0626 and OR0758) and Malaysia (WAT25793), which were compared to the description of T. maculatoides E. Horak (Horak, 2011). Microcharacteristics of Watling’s specimen were similar to Horak’s description including size and shape of basidiospores, basidia, and pileipellis. However, the cheilocystidia in Watling’s specimen (15–24 × 6–8 µm) are shorter than in Horak’s description (35–45 × 6–11 µm), but Horak did not separately describe the length of cheilocystidia and pleurocystidia. He also did not mention the frequency of both types of cystidia. By comparison, microscopic characters between Watling’s specimen and the Thai specimens were almost identical. However, the minimum value of the length of basidiospores in Watling’s specimen (11.4–13.5 × 4.1–4.9 µm) is higher than for the Thai specimens (7.8–14.1 × 3–5.6 µm). The lower minimum value of length of basidiospores in Thai specimens could be explained by small quantitative differences between geographically distant populations or the less mature stage of some basidiomata from Thai collections. Moreover, according to our observations on Sutorius, this genus usually shows high within-species variation in spore size, which was also noted originally by Halling et al. (2012). (notes: from Vadthanarat et al 2021)

Fig. 1 Phylogenetic tree inferred from the three-gene dataset (atp6, rpb2 and tef1), of Sutorius species and selected Boletaceae in Pulveroboletus group, using Maximum Likelihood and Bayesian Inference methods (ML bipartition tree is presented). The three Butyriboletus species were used as outgroup. All generic clades, excluding Sutorius, that were highly supported were collapsed. Seventeen species-level clades within Sutorius are indicated with label. Bootstrap support values (BS  70%) and posterior probabilities (PP 0.90) are shown above the supported branches. The star (*) indicates additional collections with exactly identical sequences or sequences differing only by heteromorphisms in tef1 (with the number of heteromorphisms mentioned in square brackets. (Phylogenetic tree from Vadthanarat et al 2021)


Fig.  2 (A–E) Fresh basidiomata of Sutorius maculatoides (A,B: OR0626; C,D: OR0754; E: OR758). Scale bars: (A–E) = 1 cm.