Phyllactinia undetermined

Phyllactinia sp. on Carpinus caroliniana Fig. 8 Description. Mycelium amphigenous, mostly effuse but sometimes forming thin white patches; hyphae branched, septate, hyaline, thin-walled, smooth; hyphal appressoria not observed; anamorph not observed. Chasmothecia scattered, sphaeroid or nearly so, 180–200 µm in diameter; peridium cells large, light brown, irregularly polygonal, up to 30 µm long; appendages equatorial, between 4 and 10 per chasmothecium, aseptate, hyaline, up to 1.5 times the chasmothecial diameter, 5–7 µm wide, straight or almost so, rigid, acicular with bulbous swelling at the base (up to 40 µm wide); asci absent or poorly formed, indistinct, yellowish; ascospores not observed. Specimen examined. USA • North Carolina, Carteret County, Theodore Roosevelt State Natural Area, Bogue Banks, town of Pine Knoll Shores, on leaves of Carpinus caroliniana, 26 November 2004, L. F. Grand and C. A. Vernia (NCSLG 17103). Notes. Owing to the morphological similarity, Braun and Cook (2012) assigned Phyllactinia on Carpinus caroliniana in North America tentatively to P. carpini. The Asian P. carpinicola is morphologically readily distinguishable from P. carpini by having apiculate conidia (Braun and Cook 2012), and it is phylogenetically distinct (Takamatsu et al. 2008; Bradshaw et al. 2025 b). Sequences obtained from the Phyllactinia specimen collected in North Carolina on C. carolinana clearly showed that this powdery mildew fungus does not pertain to the European P. carpini. However, it is premature to introduce a new species for this Phyllactinia. There are only sequences obtained from a single immature specimen, without the anamorph and immature chasmothecia without mature asci and ascospores. Additional sequenced collections are needed. A further problem refers to P. carpini, from which there is only one sequence retrieved from Carpinus orientalis available (Bradshaw et al. 2025 b) which is not the type host of this species. The North American Phyllactinia on Carpinus caroliniana is probably an undescribed species, but additional sequence data from mature specimens are needed, as well as an examination of European specimens on Carpinus betulus, the type host of P. carpini.