Volvariella rostricystidiata Niego, Sysouph., K.D. Hyde & Raspé, 2021

Niego, Allen Grace T., Sysouphanthong, Phongeun, Thongklang, Naritsada, Hyde, Kevin D., Phonemany, Monthien, Phookamsak, Rungtiwa & Raspé, Olivier, 2021, A new species of Volvariella and the first record of Volvariella pulla (Agaricales: incertae sedis) from Thailand, Phytotaxa 480 (3), pp. 237-250 : 242-244

Volvariella rostricystidiata Niego, Sysouph., K.D. Hyde & Raspé , sp. nov. ( Figures 2 & 3 )

MycoBank MB 835557, Faces of Fungi 08023

Diagnosis:—Similar to Volvariella pulla ( Malysheva et al. 2019) but differing in a smooth to slightly pubescent stipe, cheilocystidia that are clavate to mostly clavate and consistently showing a rostrate apex. The base pair differences between the two species are 48/381bp (12.6%) in the trimmed ITS alignment and 11/704 bp (1.56%) for LSU.

Type:— THAILAND. Chiang Rai Province: Mae Fah Luang University , 20.0449°N, 99.8943°E, lawn, 27 September 2018, P. Sysouphanthong, MFLU 19-1528 (holotype); GenBank MT 074694 - ITS, MT 078695 - nrLSU .

Etymology:—the epithet ‘ rostricystidiata ’ refers to the cheilocystidia consistently having a rostrate apex.

Description:— Basidiome large. Pileus 55–85 mm diam., plano-convex, greyish brown (6E3) with darker pigment at the center becoming lighter towards the margin, dull, dry, non-hygrophanous, matted-fibrillose, appressedsquamulose surface; margin decurved to plane, crenulate; context light yellow, unchanging when cut, with soft consistency. Lamellae free, crowded, moderately thin, soft, subventricose, white when young (10A1) then light pink (10A2); edge finely fimbriate, concolorous with faces; lamellulae present, mostly in one tier. Stipe 65–85 × 3–5 mm, central, terete, dry, brittle, solid, slender, equal to slightly tapered from the base to apex, greyish brown (5D/E3–4) over the entire length, finely and sparsely pubescent above to sparsely flocculose below; context light yellow, unchanging when cut; annulus absent. Volva thick, free, saccate, brittle; outside brownish grey or greyish brown (5–6D/E2–3) to white near the base; inside off-white to orange grey (4–5B3). Spore print pinkish (7A2). Odor indistinct. Taste mild.

Basidiospores [60,2,2] (5)5.5–6–6.5(7) × (3.5)4–4.5–5(5.5) µm (Q = 1.2–1.7, Q* = 1.4), ellipsoid to broadly ellipsoid, obovoid, thick-walled, hyaline in 5% KOH. Basidia [30,2,2] (17.5)21–24.5–27(29) × (7)7.5–8.3–9.5(10) µm (Q = 2.4–3.9, Q* = 3.0), tetrasporic, clavate, hyaline in 5% KOH. Cheilocystidia [30,2,2] (51)53–61–68(80) × (14) 18–28–38 (39) µm (Q = 1.5–4.0, Q* = 2.2), numerous, grouped together, pedunculate, mostly obovoid, a few ovoid, ellipsoid or broadly ellipsoid, consistently with rostrate apex (8–22 × 3–6 µm), smooth, thin-walled, hyaline in 5% KOH. Pleurocystidia [30,2,2] (41)47–66–79(117) × (10)13–19–24(25) µm (Q = 3.2–3.8, Q* = 3.6), scattered, pedunculate, slender, mostly fusiform, sometimes broadly cylindrical, narrowly clavate, or oblong, with blunt, rounded apex, smooth, thin-walled, hyaline in 5% KOH. Hymenophoral trama inverse, made of thin-walled, hyaline hyphae. Pileipellis a trichoderm; terminal elements [30,2,2] 58–266 × 16–33 µm, cylindrical; with intracellular light brown (6D8) pigment in 5% KOH. Stipitipellis a cutis; terminal elements long and slender, longer and narrower than in the pileipellis, mostly cylindrical [30,2,2] 74–392 × 13–24 µm, with intracellular light brown (6D8) pigment in 5% KOH. Clamp connections not seen.

Habitat and distribution:—Solitary, on the soil on regularly mown lawn, Chiang Rai Province, Thailand.

Additional specimen examined:— THAILAND. Chiang Rai Province: Mae Fah Luang University , 20.0476°N, 99.8957°E, lawn, 27 September 2018, P. Sysouphanthong, MFLU 19-1531 (GenBank MT 074695 - ITS, MT 078696 - nrLSU) .

Notes:— Volvariella rostricystidiata has a smooth to slightly pubescent solid stipe whereas V. pulla has an entirely pubescent stipe ( Malysheva et al. 2019 and this study). Moreover, the cheilocystidia of V. rostricystidiata are mostly clavate to broadly clavate and consistently show a rostrate apex ( Figure 3 ), whereas those of V. pulla are extremely variable in size and shape, ventricose-lageniform, broadly fusiform, spatula-shaped, a small proportion are utriform, sometimes with subglobose or bifurcated apex as described by Malysheva et. al. (2019). In the phylogenetic tree analyses V. pulla belonged in a different clade than V. rostricystidiata . The cheilocystidia of V. rostricystidiata are somewhat similar to those of V. caesiotincta P.D. Orton (1974: 319) , except that the latter has more variable cheilocystidia, which are clavate, fusoid, less frequently subvesiculose or utriform, mostly with a rostrum that is often abruptly connected with a basal part and often irregular, branched to occasionally subcoralloid (Antonín 2012). In our phylogeny, V. rostricystidiata was closely related to V. nivea . However, it is morphologically quite different since the latter has white basidiomes ( Li et al. 2009).

There are other species morphologically similar to Volvariella rostricystidiata , all having a greyish to greyish brown pileus but all differing from V. rostricystidiata in other features. The American Volvariella bakeri ( Murrill 1911: 281) Shaffer (1957: 557) is characterized by a dark fuliginous pileus, becoming lighter with age, up to 100 mm in diameter, and larger basidiospores 6.9–9.3 × 4.6–6.9 µm ( Shaffer 1957, Wartchow 2009). Volvariella morozovae E.F. Malysheva & A.V. Alexandrova (2017: 343) from Vietnam has smaller (20–45 mm diam.), more delicate basidiomes, a hairy pileus and volva, and mostly ellipsoid or lacrymoid basidiospores ( Crous et al. 2017). Volvariella murinella ( Quélet 1883: 391) M.M. Moser (1953: 110) known from Europe produces small basidiomes (10–55 mm) that are whitish when young (Boekhout 1986). Volvariella taylorii (Berk. & Broome 1854: 398) Singer (1951: 401) has smaller (20–50 mm diam.), shiny and often subviscid basidiomes (Boekhout 1986, Wartchow 2009, Le & Chu 2018).

Figures

FIGURE 2. Mature basidiome of Volvariella rostricystidiata. (MFLU 19-1528). Scale bar = 5 cm. Photo by P. Sysouphanthong.

FIGURE 3. Microscopic features of Volvariella rostricystidiata (MFLU 19-1528). a. Cheilocystidia b. Pleurocystidia c. Basidiospores d. Basidia e. Pileipellis terminal elements. f. Stipetipellis terminal elements. Drawings by: M. Phonemany.