Isthmomyces lanceatus (de Hoog & Hennebert) Z. F. Yu & 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 lanceatus (de Hoog & Hennebert) Z. F. Yu & R. F. Castaneda comb. nov.

Figs 4 , 9c

Isthmolongispora lanceata de Hoog & Hennebert, Proc. K. Ned. Akad.Wet., Ser. C, Biol. Med. Sci. 86(3): 343 (1983).

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, thin-walled, 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.

Type.

China, Tibet, Nanyigou Scenic Area , on submerged leaves, October 2016, Z.F. Yu, YMF 1.04794 = CGMCC 3.18827 . China, Yunnan Province, Jade Dragon Snow Mountain , on submerged leaves, September 2015, J. Peng, YMF 1.04514 .

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.

Figures

Figure 4. 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.

Figure 9. Cultural characters of all species in this study after 20 days on PDA at 25 ° C.