Isthmomyces Z. F. Yu, M. Qiao & R. F. Castaneda, 2021

Qiao, Min, Zheng, Hua, Guo, Ji-Shu, Castaneda-Ruiz, Rafael F., Xu, Jian-Ping, Peng, Jie, Zhang, Ke-Qin & Yu, Ze-Fen, 2021, Two new asexual genera and six new asexual species in the family Microthyriaceae (Dothideomycetes, Ascomycota) from China, MycoKeys 85, pp. 1-30 : 1

Isthmomyces Z. F. Yu, M. Qiao & R. F. Castaneda gen. nov.

Etymology.

Latin, isthmus, Greek ( isthmós, “neck”) meaning a narrow cellular structure that connects two larger bodies or cells, Greek, myces, referring to fungus.

Description.

Asexual morph hyphomycetous. Mycelium superficial and immersed. Conidiophores macronematous, mononematous, erect, unbranched, smooth, pale brown or hyaline, septate, sometimes reduced to conidiogenous cells. Conidiogenous cells polyblastic, denticulate, integrated, terminal, sympodial extended. Conidial secession schizolytic. Conidia acrogenous, isthmosporous, composed two cellular isthmic-segment obclavate, clavate, pyriform, obpyriform, lageniform, subulate fusiform to navicular to lanceolate, unicellular or septate, smooth, hyaline, connected by a very narrow, distinct or inconspicuous isthmus. Sexual state: unknown.

Type species.

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

Notes.

Isthmomyces is similar to the genus Isthmolongispora Matsush. in morphology. Isthmolongispora was established with I. intermedia Matsush. as type species ( Matsushima 1971). The genus is characterised by denticulate, sympodially-extending conidiogenous cells and isthmospore conidia made of two or several cellular structures, which are connected by very narrow isthmuses. In this study, specimens with two and more cellular isthmic-segments were collected, respectively. Phylogenetic analysis inferred from two loci showed that our isolates grouped together with Isthmomyces lanceatus ( Isthmolongispora lanceata ) in Microthyriaceae . Combining morphological character and phylogenetic analysis, we finally erected the new genus Isthmomyces to accommodate these isolates and I. lanceata .