Arthrinium descalsii Pintos & P. Alvarado

Pintos, Angel, Alvarado, Pablo, Planas, Juan & Jarling, Rene, 2019, Six new species of Arthrinium from Europe and notes about A. caricicola and other species found in Carex spp. hosts, MycoKeys 49, pp. 15-48 : 15

Arthrinium descalsii Pintos & P. Alvarado sp. nov. Fig. 6

Etymology.

Named to honor the eminent mycologist Enric Descals Callisen.

Diagnosis.

Sexual morph: Stromata forming black fusiform spots that merge with each other with age, forming an erumpent black mass visible at the naked eye, 2-10 × 0.2-0.5 mm in size, with the long axis broken at the top revealing the ostioles of pseudothecia. Ascomata pseudothecia, subglobose with a flattened base, arranged in rows, brown to dark brown, 150-220 μm high × 150-250 μm wide (n = 20). Peridium with several layers of cells arranged in textura angularis, with a conspicuous ostiole 50-80 μm in diameter, periphysate. Hamathecium paraphyses hyphae-like, septate, hyaline. Asci cylindrical, clavate, with a short or indistinct pedicel, with rounded apices, measuring (73 –)82–95(– 111) × (16 –)17–20(– 23) μm (n = 30). Ascospores uniseriate to biseriate, hyaline, smooth-walled, apiosporic, composed of a large curved upper cell and smaller lower cell, fusiform to slightly curved in shape with narrowly rounded ends, guttulated, sometimes with a thick gelatinous sheath, (17 –)18–22(– 24) × (6 –)7–9(– 10) μm, and a basal cell 3-5 μm (n = 45). Asexual morph: Mycelium hyaline, septate, branched, hyphae 1.5-4.5 μm in diameter Conidiophores reduced to the conidiogenous cells. Conidiogenous cells solitary on hyphae, ampuliform, hyaline to brown, 5 × 4 μm. Conidia brown, smooth, guttulate, globose to ellipsoid (5 –)7(– 8) µm long (n = 20) in face view, lenticular with a paler equatorial slit and 6-7 μm long in side view (n = 10). Sterile cells elongated, sometimes mixed among conidia. Culture characteristics: ascospores germinating on MEA 2% within 24-48 h. Colonies flat, spreading, with sparse aerial mycelium, pale siena.

Notes.

Arthrinium descalsii is closely related with A. phragmitis and A. balearicum . It was found in the Mediterranean grass Ampelodesmos mauritanicus , although additional samples are needed before concluding if it could be exclusively associated with this endemic host. Ascospore size is often smaller than that of A. balearicum , (23 –)26–30(– 32) × (7 –)9–10(– 12) µm, but it matches that reported in the protologue of A. phragmitis , (20 –)22–24(– 25) × (7 –)8–9(– 10) µm. However, the conidiophores of A. descalsii are reduced to conidiogenous cells, while those of A. phragmitis measure about 10-45 × 1.5-2 µm, and conidia are slightly smaller in face view, measuring (5 –)7(– 8) µm long in A. descalsii and up to 8 –10(– 11) µm in A. phragmitis .

Type.

Spain: Balearic Islands: Mallorca, es Capdella, on dead stems of Ampelodesmos mauritanicus , 31 Jan. 2018, A. Pintos (MA-Fungi 91724 holotype, AP31118A isotype, CBS 145130 ex-type culture).