Revision of the genera Agrocybe and Cyclocybe (Strophariaceae, Agaricales, Basidiomycota) in Argentina

Agrocybe is characterized by the collybioid to tricholomatoid basidiomata with rusty to dark spore-print, a hymeniform pileipellis, and basidiosspores with a reduced to broad germ-pore. Recently, the species with reduced germ-pore were segregated to Cyclocybe. The knowledge of these genera in Argentina is scanty, although they have been partially studied in the country, but there is not a field that deals exhaustively with it. Macroand micromorphological characters of specimens obtained in the feld and from different national herbaria (BAFC, CTES, LIL, LPS) were analyzed. Cultivation techniques were used to obtain basidiomata, allowing for a macroand micromorphological study of fresh developing basidiomes. We concluded that in Argentina there are, so far, 14 species of Agrocybe (one of them with 3 varieties) and two of Cyclocybe including to C. wrightii, which is proposed as a new combination. Sixteen species are described and a key to the Argentinian species of Agrocybe and Cyclocybe is proposed.


Introduction
Agrocybe Singer is characterized by the collibioid to tricholomatoid basidiomata with rusty brown, tobacco brown or dark brown sporeprint, a glabrous or sometimes aerolate pileus surface, its basidiospores with a broad germpore (sometimes some reduced), a hymeniform pileipellis composed of a palisade of inflated cell and with conspicuous cheilocystidia (Pegler 1983;Singer 1986;Largent & Baroni 1988).
In addition, these genera have a practical importance since several species of Agrocybe and Cyclocybe are edible and can be commercially cultivated (Singer 1986;Uhart et al. 2008), and some antibiotics have been described, as Agrocybin (Ngai et al. 2005) and Agrocybenine (Koshino et al. 1996).

Macro-and micromorphology
We examined all Agrocybe specimens from Argentina deposited in BAFC, CTES, LIL and LPS herbaria. Examination of microscopic features of basidiomatas was undertaken following Albertó et al. (1996), mounting free-hand sections in 5% KOH and 1% phloxine. New specimens collected were deposited in BAFC Mycological Herbarium (Buenos Aires, Argentina). For species lacking fresh collections, dry specimens from herbaria were examined, and the anatomical features were only described microscopically. In these cases, a transcription of the description based on fresh specimens made by different authors (Singer & Digilio 1952;Singer 1959Singer , 1973Horak 1980;Lechner 2015) is presented. Colour names are according to Maerz & Paul (1930). Names of author's taxa are according to the Index Fungorum web page (<www.Indexfungorum.org>). Herbaria abbreviations follow Thiers (2017 -continuously updated). Synonymy was included only when considered relevant for Argentinean taxa.

Basidiomata culturing
To complement the study of macro-and micromorphology, fresh basidiomata were obtained according the methodology proposed by Uhart et al. (2008). Supplemented wheat straw was introduced in polypropylene bags and autoclaved at 121 °C during 2.5 h. After cooling, bags were inoculated with spawn of different strains and incubated under controlled conditions in the dark at 25 °C. After 40 days, bags were kept at 18-20 ºC with 9 h light and 15 h dark photoperiod to induce basidiomata production.

Strains
Strains used for basidiomata production are conserved in the ICFC (
The specimens reported by Horak (1980) and Raithelhuber (1988) from Tierra del Fuego are similar to the tropical specimens described by Pegler (1983). Dennis (1953) considered Naucoria earlei Murril as a synonym of A. broadwayi, however, the type material of the former has predominantly bisporic basidia and smaller basidiospores, reaching up to 12.5 mm long. (Singer 1965).
Even though there are a wide world discussion about the taxonomy of this species complex, there are not abundant descriptions of South American specimens. Coimbra (2015) cites this species in South America only in Argentina, where it is recordered by Singer (1969) and Wright & Albertó (2002). Singer (1969) described in the same work two varieties, A. pediades var. pediades, A. pediades var. bispora (as A. semiorbicularis), and characterized the first by the smaller spores (11-15 × 7-10.5 µm), absence of veil, the fulvous ochraceus pileus surface and palid stipe, wich is slightly silky to fibrillose and glabrescent.
Geographical distribution: known from Europe (Nauta 2004) and South America (Coimbra 2015), where it was described from Brazil (Watling 1992) and Argentina (Spegazzini 1899;Singer 1950). Habitat and substrate: in rain forest, grassland and coastal dunes, on dung and soil.
In the specimens analyzed, we found an overlap in the spore size between A. perfecta and A. platensis, however, the presence of free lamellae could be considered as a diagnostic character to separate both taxa. There is no doubt that a more exhaustive study is necessary to clarify the identity of these species unequivocally.
Agrocybe platensis is similar to A. dura, but differs from the latter because A. platensis has a whitish pileus, absence of mucronate pleurocystidia and closer adnexed lamellae (Singer & Digilio 1952).
Geographical distribution: Northwestern and central Argentina and Chile (Singer & Digilio 1952). Habitat and substrate: in open places, on rich soils.
Agrocybe molesta (Lasch) Singer is another species of sect. Agrocybe that has often been confused with A. praecox (Flynn & Miller 1990). Agrocybe molesta differs from the A. praecox complex by the spore size (7-11.5 × 5-8 mm in A. praecox and 11-14 × 7-8 mm in A. molesta, ss. Watling 1982) and is restricted to grasses as substrate, while the four biological species of the group A. praecox are able to degrade also fragmented wood, branches and forest debris (Flynn & Miller 1990). Agrocybe molesta was also recognized as another biological species according to sexual compatibility studies (Flynn & Miller 1990).
Geographical distribution: South America. Reported from southern Brazil (Spegazzini 1889) and north of Argentina (Singer & Digilio 1952;Raithelhuber 2004). Habitat and substrate: inside the forest, on ground between herbs, and on decaying wood.
The cystidia described by Singer (1959) could not be observed in this study, probably due to the poor condition of the material: pleurocystidia 36-39 × 5.3-9.3 mm, cylindrical to ampullaceous, thin walled, scattered; cheilocystidia 24.7-30 × 3.3-7.3 mm, fusoid to ampullaceous, the apical part very thin (1.7 mm diam.) and obtuse to acute, sometimes with some inconspicuous cristal-line incrustation at the apex, thin-walled, hyaline, not forming an heteromorphous edge since they are interrupted by numerous basidia. Dermatocystidia similar to cheilocystidia but with a pointed apical excrescence.
Pileus brown, generally darker in the center and almost white in the margin, uniform dark brown in primordia, not hygrophanous, not viscid, glabrous, eventually sulcate or striate in some specimens but usually smooth and silky; convex to flat, 8-200 mm broad. Lamellae white, light grey and eventually strong brown or dark brown, Figure 13 -Agrocybe xerophytica -a:.basidiospores; b. basidia; c. sclerotized basidia; d. pileipellis cell. Scale bar = 20 mm. a b c d moderately broad, tight, adnated, sinuated, or subdecurrent, edge smooth or crenate. Stipe white to very pale brown, with scales to fibrillose, cylindrical, solid, 10-150 × 2-25 mm. Veil forming a broad and persistent ring. Spore-print strong brown. Context white. Odour and taste pleasant, fruity. Gregarious.