Longistriata flava Sulzbacher, Orihara, Grebenc, M.P. Martín & Baseia, sp. nov.

MycoBank number: MB 816323; Index Fungorum number: IF 816323; Facesoffungi number: FoF; Figs 3–5

Etymology. Flavus (Latin), refers to the yellow peridium of the species.

Holotype: Brazil, Paraíba State, Mamanguape, Guaribas Biological Reserve, 06°44.545’S, 35°08.535’W, 14.VII.2012, leg. Sulzbacher–393 (UFRN-fungos 1756).

GenBank accession number for ITS, nLSU and TEF1: LT574840; LT574842; LT574844 Description. Basidiomata hypogeous to subhypogeous, 11–24 mm wide, 13–16 mm high; subglobose, depressed subglobose to oblong in older stages, with small folds at the base; with a short stipe (Fig. 3A–B). Peridium <0.8 mm thick, at younger stages yellow (2A6) to light yellow (1A5) then yellowish brown (5D8) to brownish yellow (5C8) at maturity; smooth and glabrous, sometimes finely fibrillose. Sterile base pre- sent, short, 6–8 × 3–4 mm, clavate with a bulbous slightly developed base; color vivid yellow (3A8), brownish yellow (5C8) when bruised; surface glabrous, with small folds and depressions; the inner part is full, subgelatinous and yellowish brown (5D8); connected by scattered and short, thin (0.3–0.5 mm diam), orange (6B8) rhizomorphs. Gleba loculate, non-gelatinized to gelatinized, with irregular locules (0.5–1 mm diam); white (1A1) at younger stages, to finally yellowish brown (5F4) at maturity, immediately turning deep green (30F7) to black when cut in older basidiomata.

Peridium 100–200 µm thick, composed by a cutis of interwoven hyphae and immersed in a gelatinized matrix (Fig. 4C), 2–6 µm diam., with rounded, thin-walled, smooth, terminal hyphae, not readily separable from gleba. Hymenophoral trama formed by parallel to subparallel, smooth and thin-walled, hyaline hyphae, inamyloid, gelatinized in the central part, 3–6 µm diam (Fig. 3C–D). Subhymenium ramose, 46–72 µm deep, hyphae 10–16 × 2–5 µm diam. Hymenial cystidia 38–78.5 × 10–14 µm, lageniform or ventricose, with rounded apex, thin-walled, hyaline, inamyloid (Figs 3E, 4A). Basidia 25–48 × 10–15 µm, clavate, 2 and 4-spored (sterigmata up to 3 µm long.), hyaline. Basidioles 31–46 × 7–12 µm, clavate with rounded apex (Fig. 4B). Basidiospores [30/2/2] 15–19 (–20) × 13–16 (–17) µm (ornamentation included), [L = 17.7 µm, W = 14.7 µm, Q = 1.10–1.40 (–1.50), Qm = 1.20], broadly ellipsoid, sterigmal attachment persistent at maturity, up to 3 µm long; hyaline when young to finally light brown at maturity in 3% KOH, dextrinoid in Melzer’s reagent; walls ornamented (< 2.5 µm width); with a series of thinner longitudinal ridges, in average > 10 complete ridges across the longitudinal axis of the spore with additional irregular, thin and low ridges that are sometimes bifurcated (Figs 3F–G, 4D) or fused together (Fig. 5C); under a scanning electron microscope the surface is clearly longitudinally striated (Fig. 5A–D).

Habitat. Hypogeous to subhypogeous, solitary or scattered, under fallen leaves or in O1 soil horizon, in sandy soil, among trees in Brazil’s Atlantic rainforest, in vicinity of Coccoloba alnifolia Casar., C. laevis Casar. (Polygonaceae) and species of Guapira Aubl. (Nyctaginaceae). Species in both plant genera (Coccoloba and Guapira) have been consistently confirmed as ectomycorrhizal hosts throughout the Neotropics (Tedersoo et al. 2010b). All known specimens were found in silicate silt to sandy soils, with moderately low pH (4.5–5.5), low available nutrients and low water capacity. Despite the close vicinity of the ocean, the absence of halophilic vegetation indicates a lack of salinification or accumulation of NaCl in soils.

Distribution. Known only from the type locality.

Additional specimens examined. Brazil, Paraíba State, Mamanguape, Guari- bas Biological Reserve, 06°44.545’S, 35°08.535’W, 27.VII.2012, leg. Sulzbacher–466 (paratype UFRN-fungos 2110, LJF 1203). GenBank accession number for ITS: LT574839.

Additional Comments. The specimens UFRN-fungos 1756 and UFRN-fungos 2110 are sequestrate to emergent basidiomes that fruit in small groups. The basidiomes have a smooth and vivid yellow peridium that becomes dark green when exposed to air. They also have a central sterile base that is attached to short orange rhizomorphs, a white gleba formed of distinct locules that turns dark green to black when cut and hyaline to light brown, broadly ellipsoid basidiospores covered with a series of thin, dextrinoid longitudinal striations and ridges. These ridges and striations are sometimes bifurcated or irregular and they also cover the entire spore surface. The clavate basidia can be either 2-spored and 4-spored and the lageniform to ventricose cystidia are a no- table feature in the hymenium. This combination of morphological features is unique within the Boletaceae.

Figure 3. A–G Longistriata flava (UFRN-Fungus1756, holotype) A–B fresh mature basidioma C hyme- nophoral trama mounted in 3% KOH with Congo Red D interwoven hyphae of peridium (upper left) and hymenophoral trama mounted in 3% KOH with Congo Red E hymenial cystidia mounted in 3% KOH with Congo Red F basidiospores mounted in Melzer’s reagent G basidiospores mounted in 3% KOH.

Figure 4. A–D Longistriata flava (UFRN-Fungus 1756, holotype) A hymenial cystidia B basidioles and basidium C details of the peridium with interwoven hyphae D polar and longitudinal view of basidiospores.

Figure 5. A–D Basidiospores of Longistriata flava (UFRN-Fungus 1756, holotype) as observed with scanning electron microscopy. Note the persistent sterigmal attachment and a series of thinner longitudinal ridges (on average > 10 complete ridges across the longitudinal axis of the spore) with additional irregular, thin, low and bifurcated or fused ridges.