Isthmomyces oxysporus2021

Isthmomyces oxysporus Z. F. Yu, M. Qiao & R. F. Castañeda, sp. nov. 2021

Fungorum number: IF556127

Facesoffungi Number No: FoF05741

Holotype YMF 1.04513

Morphological description :

Asexual morph: hyphomycetous. Colonies on CMA pale mouse grey to dark mouse grey, reverse olivaceous-grey, attaining about 2 cm diam. after 20 days at 25 °C. Mycelium mostly immersed, composed of branched, septate, subhyaline to hyaline hyphae. Conidiophores macronematous, mononematous, cylindrical, erect, smooth, 0–1-septate, subhyaline to hyaline, mostly reduced to conidiogenous cells, up to 30 µm long, 2.5–3 µm wide, arising from the creeping hyphae. Conidiogenous cells polyblastic, cylindrical, denticulate, integrated, terminal, sympodial extended, hyaline. Conidia isthmospore, fusiform, hyaline, smooth, 20.5–25.5 µm long, strongly constricted at the narrow, tiny central isthmus, composed of two cellular isthmicsegments: i) basal isthmic-segment broadly clavate to clavate, unicellular, hyaline 9.7–13 × 2.0–4.0 µm; ii) apical isthmic-segment narrow obclavate to obclavate, obpyriform or rarely lecythiform, unicellular, hyaline, 9.0–13.0 × 2.0–3.0 µm.

Sexual state: unknown

Culture characteristics:

Habitat: on submerged leaves,

Distribution: China, Hainan Province, Diaoluo Mountain Natural Reserve, 

GenBank:  lsu MK577810 ; its MF740793.

Notes: . Morphologically, Isthmomyces oxysporus resembles Isthmolongispora asymmetrica Aramb. & Cabello in having both tapering isthmic-segment ends, but Is. asymmetrica has asymmetrical conidia, in which the basal isthmic-segment is longer (17– 20 µm long) (Arambarri et al. 1987). Besides, I. oxysporusis is somewhat similar to Is. rotundata Matsush. in conidial sizes, but the apical isthmic-segments in Is. rotundatus are rounded at the tip (Matsushima 1987).

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 oxysporus (Holotype YMF 1.04513) a conidia b conidiophores and conidiogenous cells. Scale bars: 10 µm (a, b)