Amanita subhemibapha Zhu L. Yang, Y.Y. Cui & Q. Cai
Index Fungorum number: IF 825004
Basidioma medium-sized to large. Pileus 6.0–10.0 cm diam., convex to plano-convex, lacking an umbo at center, purely orange (5B5–8) when young, but becoming orange (5B5–8) at center and yellow (4A6–8) to yellowish (3A3–6) at margin when mature; universal veil on pileus absent; margin striate (0.25–0.3 R), non-appendiculate; context 4.5–5.0 mm wide, yellow (4A6–8) to yellowish (3A3–6), unchanging. Lamellae free, crowded, white (1A1) to cream (1A4–6), with lamellar edges yellow (4A6–8); lamellulae truncate. Stipe 5–15 × 0.7–1.5 cm, subcylindrical with slightly tapering upwards, with apex slightly expanded, yellow (4A6–8) to orange (5B5–8), with its surface covered with concolorous, snakeskin-shaped squamules; context white (1A1), hollow in center. Bulb absent. Universal veil on stipe base saccate, membranous, up to 5 cm high 3, white (1A1). Partial veil apical to subapical, yellow (4A6–8) to orange (5B5–8). Lamellar trama bilateral, divergent; mediostratum 25–70 μm wide, filamentous hyphae abundant, 2–7 μm wide; ellipsoid, fusiform to clavate inflated cells 30–80 × 10–27 μm; vascular hyphae scarce. Subhymenium 30–50 μm thick in 2–3 layers, with subglobose to ellipsoid cells, 10–25 × 8–20 μm. Basidia 40–50 × 9–12 μm, clavate, 4-spored with sterigmata 3–5 μm long; clamps present at base. Basidiospores (7.0–) 8.0–11.0 × 6.5–8.5 (–9.0) μm, Q = 1.15–1.53 (–1.65), Qm = 1.34 ± 0.08, broadly ellipsoid to ellipsoid, inamyloid, hyaline, thin-walled, smooth; apiculus small. Lamellar edge sterile; filamentous hyphae 2–4 μm wide, hyaline, thin-walled; inflated cells, with subglobose to ellipsoid or sphaeropedunculate, 8–45 × 8–20 μm, single and terminal or in chains of 2–3, hyaline, thin-walled. Pileipellis 90–170 μm thick; 2-layered, upper layer 30–145 μm thick, filamentous hyphae 2–5 μm wide, gelatinized, branching, thin-walled, hyaline; lower layer 30–55 μm thick, filamentous hyphae 3–8 (–10) μm wide, branching, thin-walled, hyaline to light yellow; vascular hyphae scarce. Inner surface of universal veil on stipe base filamentous hyphae dominant 2–10 μm wide, hyaline to light yellow, thin-walled, branching; inflated cells, with subglobose, fusiform to ellipsoid, 55–100 × 20–70 μm, hyaline, thin-walled, mostly terminal or sometimes in chains of 2–3; vascular hyphae rare. Outer surface of universal veil on stipe base similar to structure of inner part, but presenting more abundant inflated cells. Stipe trama longitudinally acrophysalidic; filamentous, undifferentiated hyphae 2–10 (–15) μm wide, thin-walled, frequently branching; acrophysalides 60–260 × 25–65 μm, thin-walled; vascular hyphae rare. Partial veil filamentous hyphae very abundant, 2–10 μm wide, hyaline, thin-walled; inflated cells scarce to locally abundant, subglobose, fusiform to clavate, 20–100 × 10–35 μm, hyaline to light yellow, thin-walled; vascular hyphae rare. Clamp connections present in all tissues of basidioma.
Habitat: Solitary to scattered on soil in subtropical broad-leaved or mixed forests with Dipterocarpaceae, Fagaceae, and Pinaceae.
Distribution: known from China and Thailand (this study).
Specimens examined: Thailand, Chiang Mai Province, Doi Saket District, 18°53′2″ N 99°9′17″ E, alt. 343 m, 26 July 2021, Kumla J. and Suwannarach N., CMUNK0804 (SDBR-CMUNK0804); 18°53′2″ N 99°9′17″ E, alt. 343 m, 2 August 2022, Kumla J. and Suwannarach N., CMUNK0855 (SDBR-CMUNK0855); Lumphun Province, Mueang District, Chiang Mai University Haripunchai Campus, 18°32′34″ N 99°9′231″ E, alt. 450 m, 25, July, 2020, Suwannarach N., CMUNK0781 (SDBR-CMUNK0781); Mae Tha District, 18°27′41″ N 99°10′30″ E, alt. 427 m, 27 August 2020, Kumla J. and Suwannarach N., CMUNK0735 (SDBR-CMUNK0735).
Notes: Morphologically, A. subhemibapha is easily confused with A. hemibapha, A. javanica and A. kitamagotake. Morphological comparisons of A. hemibapha and A. subhemibapha have been included in our remarks pertaining to A. hemibapha. Amanita javanica differs from A. subhemibapha by having a broadly umbonate and much darker yellow tone in the center of the pileus, longer tuberculate striates (0.4–0.5 R) on the margins and smaller basidiospores (7.5–9.0 × 5.8–7.0 μm). Alternatively, A. kitamagotake differs from A. subhemibapha by having an umbonate pileus and narrower basidiospores (9.0–13.5 × 6.5–8.5 μm). Based on multigene phylogeny, A. subhemibapha forms a sister clade with A. fuscoflava Zhu L. Yang, Y.Y. Cui & Q. Cai. However, A. fuscoflava has a dark brown tone in the pileus center, much longer margin striates (0.5–0.7 R) and relatively narrower basidiospores (8.5–10.5 × 6.0–7.0 μm).
Traditionally, morphological characteristics have been the primary basis for the identification of Amanita species. However, identification can be difficult due to the high phenotypic variability that is influenced by differing environmental conditions and geographic distributions. Therefore, it is crucial to identify the Amanita species using DNA-based methods. The current classification of the genus Amanita is based on combined data on their morphological characteristics and molecular data. Moreover, multi-gene molecular phylogeny has provided researchers with a powerful tool for the identification of the Amanita species. In this present study, specimens of the edible Amanita species collected in northern Thailand were identified as A. hemibapha, A. pseudoprinceps, A. rubromarginata, and A. subhemibapha based on morphological characteristics and multi-gene phylogenetic analyses. The results of morphological comparisons of four edible Amanita species in this study are presented. Morphologically, the color of the pileus and the larger spore size found in A. pseudoprinceps clearly differentiate it from those other three species. Additionally, the yellow annulus and narrow spores in A. hemibapha clearly distinguish it from A. rubromarginata and A. subhemibapha. Remarkably, A. rubromarginata has a redder and more of an orange-red-shaded pileus and annulus than A. subhemibapha. The multi-gene phylogenetic analysis also supports the determination that A. hemibapha, A. pseudoprinceps, A. rubromarginata, and A. subhemibapha are different species. Four Amanita species obtained from natural forests, roadsides, and local markets in this study belonged to the Amanita section Caesareae. This section is a highly regarded edible mushroom in the genus Amanita. Prior to this study, the toxicological analysis of A. hemibapha showed that no amatoxins and phallotoxins had been discovered and that it should be regarded as an edible species. However, further research is required to fully understand the edibility and safety of A. pseudoprinceps, A. rubromarginata, and A. subhemibapha based on their toxicological studies. As a result, our study should be considerably important and highly valuable in terms of stimulating deeper investigations of edible macrofungi in Thailand. It will also help researchers in understanding the distribution and ecology of Amanita.
Fig. 1 The phylogenetic tree derived from maximum likelihood analysis of 64 specimens of the combined ITS, nrLSU, rpb2, and tef-1 genes. The tree is rooted with A. retenta and A. shennongjiana. 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. Sequences derived in this study are shown in red. Type species are shown in bold.