Macroascochyta grandis L.W. Hou, L. Cai & Crous, sp. nov.
MycoBank number: MB 833498; Index Fungorum number: IF 833498; Facesoffungi number: FoF 11515; Fig. 10.
Etymology: Name reflects the large (= grandis in Latin) conidia produced by this species.
Description: Conidiomata pycnidial, (semi-)immersed in the agar, solitary, scattered or aggregated, mostly (sub-)globose to flask- shaped, pale to dark brown, with hyphal outgrowths, ostiolate, 175 – 400 × 160 – 375 μm. Ostioles single, central, slightly papillate. Pycnidial wall pseudoparenchymatous, composed of oblong to isodiametric cells, 4 – 6 layers, 18.5 – 35.5 μm thick, without pigmented layers or outer 1– 4 cell layers slightly pigmented. Conidiogenous cells phialidic, hyaline, smooth, (sub-) globose, ampulliform to lageniform, with minute periclinal thickening, 7 – 13.5 × 6.5 – 12.5 μm. Conidia cylindrical, bacilliform to fusiform, hyaline, smooth- and thin-walled, aseptate, 12.5 – 21 × 4.5 – 7 μm, with 6– 10 small guttules each end. Chlamydospores hyaline or pale brown, intercalary, unicellular, (sub-)globose, solitary, eguttulate, thin-walled. Conidial matrix orange.
Culture characteristics: Colonies on OA reaching 70– 75 mm diam after 7 d at 25 °C, margin irregular, aerial mycelium flat, buff to vinaceous buff, abundant production of pycnidia, orange conidial mass exuding from pycnidia; reverse pale cinnamon.
Colonies on MEA reaching 75 – 80 mm diam after 7 d, margin irregular, covered by woolly aerial mycelium, whitish to pale grey; reverse orange to leaden black, yellow towards periphery. Colonies on PDA reaching 75 – 80 mm diam after 7 d, margin regular, aerial mycelium woolly, whitish to buff; reverse buff to pale brown. NaOH spot test negative on OA.
Typus: New Zealand, South Auckland, Alfriston, from Tradescantia sp. (Commelinaceae; in post entry quarantine), date unknown, coll. K. Ramsay, isol. C.F. Hill (holotype CBS H-23675, ex-type living culture CBS 100409).
Notes: Phoma commelinicola (basionym: Phyllosticta commeli- nicola) was originally reported from Commelina nudiflora in Puerto Rico, with conidia measuring 9.6 – 14.4 × 4.8 – 7.2 μm (Young 1915). The isolate CBS 100409 was collected from Tradescantia sp., the same host family as Phoma commelinicola (Commelinaceae), and therefore it was initially identified as “Phoma commelinicola” (De Gruyter 2002). However, its conidia [(10.5 –)13– 17(– 21) × (4–)5– 6.5 μm] were found to differ from the original description of Phoma commelinicola. Phylogenetically, CBS 100409 formed a distinct lineage, separated from all genera previously described in Didymellaceae. Thus, a new genus and species, Macroascochyta grandis, was introduced to accommodate this isolate.
Fig. 10. Macroascochyta grandis (CBS 100409). A–B. Colony on OA (front and reverse). C–D. Colony on MEA (front and reverse). E– F. Colony on PDA (front and reverse). G. Pycnidia forming on OA. H. Pycnidium. I. Section through pycnidium. J. Section of pycnidial wall. K–M. Conidiogenous cells. N–O. Chlamydospores. P. Conidia. Scale bars: H– I = 50 μm; J– P = 10 μm.