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Remarks (internal):Samuels (1976a) listed several species with orange perithecia being connected to anamorphs forming sporodochia and green-coloured conidial masses. Rossman (1983) classified some of these species in the Nectria ralfsii-group. Both authors emphasized the similarities of these species to the Nectria ochroleucagroup (also in Rossman, 1996 and Samuels et al., 1990). Two of these species, N. ralfsii Berk. & Broome and N. pityrodes (Mont.) Mont., are here accepted in Bionectria, with the former classified in subgenus Bionectria and the latter in the newly proposed subgenus Myronectria.
Samuels (1988b) introduced another species group with myrothecium-like anamorphs, striate ascospores, but with sterile, branched interthecial elements. Of this group, ‘Nectria’ chlorogloea Samuels and ‘N.’ septomyrothecii are still not reclassified but are possibly closely related to Peethambara Subram. & D.J. Bhat (with anamorphs in Didymostilbe Henn.; Bionectriaceae). As ‘N.’ chlorogloea and ‘N.’ septomyrothecii, Peethambara spirostriata (Rossman) Rossman possesses sterile interthecial elements and a short, pluglike stroma, which is located only between the outermost bark cells (Samuels, 1988b: Figs 25, 28 for ‘N.’ chlorogloea and ‘N.’ septomyrothecii; Schroers, unpubl., for P. spirostriata).
The connections of Nectriopsis bactridioides (Berk. & Broome) Samuels and Nectriopsis lasioderma (Ellis) Samuels [= Nectriopsis infusaria (Cooke & Harkness) Doi] to myrothecium-like anamorphs, suggested by Tulloch (1972) for the first species and by Doi (1978) for the latter species, were questioned by Samuels (1988a). Instead it was concluded that the myrothecium-like anamorphs belonged to B. pityrodes, which was parasitized by or associated with the Nectriopsis species (Samuels, 1988a). To my knowledge, ascospores of N. bactridioides and N. lasioderma have not been grown in culture again to reconfirm either putative connection.
Hypocrealean fungi with green-coloured conidial masses have been classified in the Hypocreaceae [e.g. anamorphs of Trichoderma and Gliocladium (Rehner & Samuels, 1994, 1995; Rossman et al., 2001) and Bionectriaceae (Schroers, 2000), however, not in genera of the Nectriaceae. Additional taxa such as Myrothecium inundatum Tode : Fr., the type species of Myrothecium, Peethambara sundara Subram. & D.J. Bhat (anamorph Didymostilbe sundara (Subram. & D.J. Bhat) Seifert), Albosynnema elegans E.F. Morris, and Didymostilbe echinofibrosa (E.F. Morris) Rossman, all linked to the Bionectriaceae according to morphological evidence, form a paraphyletic assemblage at the base of a clade comprising taxa of the Hypocreaceae, Clavicipitaceae, and Bionectriaceae based on LSU rDNA sequence data (Rossman et al., 2001). While the absence of such green pigmentations could be of importance for the characterization of the Nectriaceae, at least some genera that do form greenish pigmented conidial masses [e.g., Peethambara (Didymostilbe), Bionectria (Clonostachys), and Hypocrea (Trichoderma)] have variably pigmented conidial masses, among which the greenish shade apparently is just an additional phenotype.
No teleomorphs have been linked to the other Myrothecium- or Hymenopsis species listed by Tulloch (1972). Some of the species of these complexes are treated as coelomycetes (Sutton, 1980; Nag Raj, 1993). The phylogenetic position of most of them has not been studied.
The perithecial wall in B. pityrodes consists of three regions of which the middle region is composed of hyphae (Fig. 59 d, h), as is typical of species of subgenus Bionectria. A difference between the subgenera is seen in the stroma-perithecial wall interface and the morphology of the stroma. While in species of subgenus Bionectria the cells of the stroma are angular and merge with those of the outer perithecial region, cells of the stroma of B. pityrodes are somewhat hyphal, prosenchymatous, and apparently merge with the hyphae of the middle region (Fig. 59 e). The smooth and mostly bean-shaped ascospores (Figs 60 a, b, 61 b) also differ from the mostly warted or striate and ellipsoidal spores of most of the other taxa in Bionectria. The anamorph differs by (i) cupulate sporodochia, the margin of which consists of sterile or fertile hyphae forming a palisade that slightly extends beyond the main sporodochial hymenium (Figs 59 b, 60 d-f, 61 f), (ii) bridges frequently formed between cells of the subhymenium (Fig. 61 d), (iii) subabruptly narrowing phialide tips (Figs 60 c, 61 c-f), and (iv) symmetrical or almost symmetrical conidia (Fig. 61 g). While the characteristic phialide tips and the conidial shape are also found in other species of Bionectria, the cupulate sporodochia are unique to Bionectria/Clonostachys. The isolated position of B. pityrodes among the other taxa of the genus is supported by analyses of rDNA sequences (Schroers, 2000). Based on these deviating character patterns, a new subgenus, Myronectria, is proposed for B. pityrodes. The subgenus Myronectria is unispecific; however, one other holomorphic specimen from Florida (BPI 1107405, G.J.S. 90-242) differed slightly in sequence data of the 28S rDNA (Rossman et al., 2001) and possibly represents another species closely related to B. pityrodes. Its conidiophores and conidia are indistinguishable from those of B. pityrodes, but the strain sporulates sparsely and no sporodochia were observed. The taxon could not be fully characterized because no mature asci and ascospores were found.
 
Description type:Non-original description 
Description:Bionectria pityrodes (Mont.) Schroers, comb. nov.-Figs 59 a-i, 60 a, b, 61 a, b.
≡ Sphaeria pityrodes Mont. in Sagra, Hist. Fis., Pol. Nat. Cuba 2 (Hist. Nat. 9) (IX Criptogamía o plantes cellulaires par Camilo Montagne): 205. 1845.
≡ Nectria pityrodes (Mont.) Mont., Syll. Pl. Crypt.: 224. 1856.
= Nectria pityrodes var. saccharina Berk. & Broome, J. Linn. Soc., Bot. 14: 117. 1873.
= Nectria blumenaviae Rehm, Hedwigia 37: 192. 1898.
= Nectria juruensis Hennings, Hedwigia 43: 244. 1904.
Anamorph: Clonostachys pityrodes Schroers, stat. nov.-Figs 59 b, 60 c-f, 61 c-g; Fig.
22 F in Samuels et al. (1990).
Description from natural substratum: Stroma prosenchymatous, hyphal cells forming a textura porrecta. Perithecia formed on the stroma, or at the base of sporodochia, frequently also on the stroma of black pyrenomycetes, densely crowded in groups of 2 to up to 50, 300-600 µm diam, subglobose, subbasally and apically pinched when dry, yellowish orange to orange, with a warted surface. Perithecial warts small, orange; cells 4-13 x 3-10 µm, with uniformly thickened walls around 2 µm thick; adjacent cells with free space in between; vacuoles not observed. Perithecial wall 60-80 µm thick, consisting of three regions. Outer region 20-35 µm or 5-8 cells thick; cells angular to globose, continuous with the cells of the perithecial warts, not merging with the prosenchymatous stroma. Middle region 17-21 µm thick, consisting of several (up to 8) layers of intertwined hyphae, forming a textura intricata, conspicuous even in longitudinal sections. Inner region to 15-30 µm thick. Asci clavate to broadly clavate, (64-)80.5-89-97(-133) x (7.5-) 11.5-15-18.5(-23) µm (n = 41), frequently with a reduced number of ascospores; apex rounded, without a conspicuous ring. Ascospores slightly curved, beanshaped, broadly rounded, ellipsoidal, equally twocelled, not constricted at the septum, smooth, rough, or very finely warted, particularly while in the ascus, somewhat brownish, (15.4-)24.2-26.8-29(-39.6) × (6.4-)8.2-9.2-10.2(-13.2) µm (n = 292), completely filling the ascus. Sporodochia flat or cupulate, olivegreen because of the conidial masses, independently formed beside the perithecia or on or within the perithecial stroma, up to 650 µm wide and 450 µm high; margin of sporodochia white because of subhymenium mycelium or sterile marginal hyphae; base of the sporodochia prosenchymatous, erumpent through the bark, similar to the perithecial stroma; phialides and conidiophores densely aggregated in a textura porrecta. Sterile mycelium sometimes visible on the bark surface, white, surrounding the base of the perithecia or sporodochia. Description from culture: Colonies reaching 30-40 mm diam in 7 d at 24ºC; optimum for growth 21-27°C (40 mm diam), maximum 33°C. Colony reverse not pigmented or somewhat orange under UV-light, with time becoming olive-grey (2E2) to olive (3E3). Colony surface on CMD with little aerial mycelium, almost smooth; on OA within 21 d finely to coarsely granular because of sporodochia or fluffy cottony if conidiophores or sporodochia arise within aerial mycelium; on PDA similar, but with more aerial mycelium. Sporodochia formed on a stroma or from aerial mycelium, up to 100 µm diam, in older colonies and particularly if formed on a stroma more than 2 mm diam, frequently cupulate with a palisade
of marginal hyphae/conidiophores extending beyond the sporodochial hymenium. Stroma, if formed, orange, KOH-, oval to flat, up to 1.5 mm diam, originating from under the agar surface of older OA cultures. Conidiophores monomorphic, sporodochial, in young aggregates divergently branched, in sporodochia adpressed throughout, often anastomosing, irregularly penicillate, quinquies-verticillate or more. Phialides in irregular whorls of 2-5, often arising from 2 levels, slightly, widening towards the apex or straight, narrowing below the tip, without visible collarette (5.8-)13-14.4- 16.4(-19.6) µm long, (1.4-)1.8-2-2.2(-3.2) µm wide at base, (1.6-)2.2-2.4-2.4(-3) µm wide subapically, the aperture generally less than 1.5 µm wide (n = 68). Conidia greenish hyaline to pale green, smooth, symmetrical (homopolar-polysymmetrical), oval, (4.8-) 5.8-6.6-7.2(-9.0) x (2.4-)2.8-3-3.4(-4) µm (n = 129); hilum not or hardly recognizable, median; conidial chains linear, not imbricate, initially dry, with time sliming down into olive masses; in young sporodochia chains from neighbouring phialides frequently aggregated, columnar; columns from different conidiophores slightly separated from each other; colour of conidial masses, dark green (29F4) in vivo, in water and also in lactic acid, brownish in KOH.
Type for Sphaeria pityrodes: Cuba. S. Marco; on bark of twigs (Montagne, 1856) (specimen not seen).
Type for Clonostachys pityrodes: - Mauritius. Bois du Lait; on bark [dried culture ex CBS 102033 (= IMI 3663387, G.J.S. isolate 95-26), derived from ascospores of BPI 737867 and filed with it (BPI)].
Known distribution: Teleomorph frequent, pantropical. Anamorphic isolates unknown, although sporodochia sometimes occur without associated perithecia.
Habitat: On bark of recently dead woody plants, frequent on other pyrenomycetes.
Published descriptions: Samuels et al. (1990).

 
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