Neodothiora populina Crous, G.C. Adams & Winton, sp. nov.

MycoBank number: MB 837858; Index Fungorum number: IF 837858; Facesoffungi number: FoF 11102;

Etymology. Name refers to the host genus Populus from which it was isolated.

On PNA: Conidiomata solitary, erumpent, brown, subglobose, pycnidial, with central ostiole, 130 –180 µm diam, exuding a crystalline mucoid conidial cirrhus; wall of 6 – 8 layers of brown textura angularis. Conidiophores reduced to conidiogenous cells lining the inner cavity, hyaline, smooth, ampulliform, proliferating percurrently, 5 –7 × 4 – 6 µm. Conidiogenous cells also occurring solitary on superficial hyphae, ampulliform to subcylindrical, hyaline, smooth, 5 –10 × 2 – 5 µm, proliferating percurrently at apex. Conidia solitary, hyaline, smooth, aseptate, guttulate, ellipsoid, apex subobtuse, tapering to truncate apex, 5 – 6(–7) × 2.5 – 3 µm.

Culture characteristics — Colonies flat, spreading, with sparse aerial mycelium and feathery, uneven margin, covering dish after 2 wk at 25 °C. On MEA surface mucoid, saffron, reverse saffron with patches of umber; on PDA surface and reverse umber, margin black; on OA surface umber.

Typus. USA, Alaska, -148.7762872 64.63940972, on stem cankers of Populus tremuloides (Salicaceae), 24 June 2018, G. Adams & L.M. Winton (holotype CBS H-24556, culture ex-type CPC 39399 = CBS 147087, ITS, LSU, tef1 and tub2 sequences GenBank MW175365.1, MW175405.1, MW173127.1 and MW173142.1).

Additional materials examined. USA, Alaska, -148.7672229 64.64259316, on stems of P. tremuloides, 25 June 2018, G. Adams & L.M. Winton, CPC 39397 = CBS 147085, ITS sequence GenBank MW175366.1; USA, Alaska, -148.3288146 64.73376442, on stems of P. tremuloides, 19 June 2018, 75367. Adams & L.M. Winton, CPC 39398 = CBS 147086, ITS sequence GenBank MW175367.1; Alaska, Bonanza Creek Experimental Forest, -148.33106. 64.73243, on stems of P. tremuloides, 15. Sept. 2020, L.M. Winton, Univ. of Alaska Herbarium (ALA) H1280665, H1280672; ibid., on stems of P. tremuloides, Jan. 2020, L.M. Winton, H1280666–H1280671.

Notes — Neodothiora is reminiscent of the genus Dothiora, having Dothichiza and hormonema-like morphs in culture (Crous & Groenewald 2016, 2017). However, it clusters apart from the type species, D. pyrenophora, and thus a new genus is herewith introduced to accommodate this pathogen, which is associated with severe cankers of Populus tremuloides in Alaska. In field inoculations, conidiomata developed on the tree bark around points of inoculation, which resembled those that developed in culture (on agar and on PNA).