Isthmomyces lanceatus2021

Isthmomyces lanceatus Z. F. Yu & R. F. Castañeda, comb. nov.2021

Fungorum number: IF556158

Facesoffungi Number No: FoF05757

Holotype:

Morphological description :

Asexual morph：hyphomycetous. Colonies on CMA white to dark salmon, reverse pale brown, attaining about 2 cm diam. after 20 days at 25 °C. Mycelium partly superficial, partly immersed, composed of branched, septate, slender, hyaline hyphae. Conidiophores macronematous, mononematous, cylindrical, erect, straight, unbranched, 0–1- septate, smooth, hyaline, up to 30 µm long, 3–3.5 µm wide. Conidiogenous cells polyblastic, cylindrical, denticulate, sympodial extended, integrated, terminal, hyaline. Blastoconidia isthmospore, somewhat fusiform, hyaline or subhyaline, smooth, thinwalled, 21.3–39.7 µm long, strongly constricted at the median septum, narrow, tiny, made of two cellular isthmic-segments: i) basal isthmic-segment narrow-clavate, sometimes cylindrical-clavate, truncated at the base, unicellular, 0–1-septate, 12.5–18.5 × 3.0–4.8 µm; ii) apical isthmic-segment broadly obclavate, obspathulate, rounded at the tip, unicellular, 0–1-septate, 13.0–30.0 × 2.3–3.8 µm. Arthroconidia often formed in the aerial mycelium, disarticulated from fertile hyphae. 

Sexual state: unknown.

Culture characteristics:

Habitat: ,on submerged leaves,

Distribution: China, Tibet, Nanyigou Scenic Area

GenBank: lsu  MH870563; its MH858897.  Lsu MK577813 ; its MK577895. lsu MK577814 ; its MK577896.

Notes: Isthmomyces lanceatus was first isolated by Beverwijk from leaf of Castanea vesca in steam (Hoog and Hennebert 1983). However, the taxonomic status of this species was Ascomycota incertae sedis. In this study, this is the first report of I. lanceatus isolated from Asia. Morphologically, the conidia of our isolates are larger than the holotype CBS 622.66. Our phylogenetic analysis of combined LSU and ITS sequences reveals that the phylogenetic position of I. lanceatus is in Microthyriaceae and I. lanceatus is close to I. dissimilis in this tree.

Reference: [1] Qiao, M. ,  Zheng, H. ,   Guo, J. S. ,  Castaeda-Ruiz, R. F. ,  Xu, J. P. , &  Peng, J. , et al. (2021). Two new asexual genera and six new asexual species in the family microthyriaceae (dothideomycetes, ascomycota) from china. MycoKeys, 85, 1-30.

Isthmomyces lanceatus (YMF 1.04794) a conidia b conidiophores and conidiogenous cells. Scale bars: 10 µm (a, b). The arrow indicates septum inside isthmic-segments.