Scytalidium circinatum Sigler & C. J. K. Wang

6.Scytalidium circinatumSigler & C. J. K. Wang, Mycologia 82: 399 (1990) Description and illustration. Sigler and Wang (1990). Notes. Scytalidium circinatum was initially isolated and established by Sigler and Wang (1990) from preservative-treated utility poles. Scytalidium circinatum is phylogenetically closely related to S. album, S. assmuthi, S. aurantiacum, S. rodionovae, S. terrigenum, and S. tongrenense (Figs 1, 2). The distinctions between S. circinatum and S. album, S. assmuthi, S. aurantiacum, S. rodionovae, S. terrigenum, and S. tongrenense are detailed in the respective notes for S. album, S. assmuthi, S. aurantiacum, and S. rodionovae. Scytalidium circinatum is distinguished from S. terrigenum and S. tongrenense by the shape, size, and aseptate of its chlamydospore-like cells (aseptate, globose, lobed, or irregularly shaped, 4–9 × 3–9 μm in S. circinatum vs. septate, oval-shaped, 5.4–13 × 4.2–8.1 μm in S. terrigenum; and septate, oblong to globose, subcylindrical, guttulate, or irregular, measuring 5–12.5 × 4–6 μm in S. tongrenense) (Jeong et al. 2025). Additionally, based on a pairwise comparison of ITS and LSU, S. circinatum (ex-type CBS 654.89) differs from S. terrigenum (ex-type KNUF- 23-236) by 7.2 % (42 / 583 bp, six gaps) in the ITS and 4 % (24 / 597 bp, two gaps) in the LSU; from S. tongrenense (ex-type CGMCC 3.28994) by 9.1 % (50 / 547 bp, 11 gaps) in the ITS and 3.6 % (22 / 612 bp, one gap) in the LSU. This species exhibits capabilities for wood decay and resistance to chemical preservatives. It is widely distributed, having been reported in diverse environments such as underground mines in Minnesota, USA, urban trees in Singapore, and tobacco fields in Bijie, Guizhou, China (Held et al. 2020; Wang et al. 2022; Hong et al. 2023).