Cytospora myrtagena (G.C. Adams & M.J. Wingf.) G.C. Adams & Rossman, IMA Fungus 6 (1): 147. 2015.

Jiang, Ning, Yang, Qin, Fan, Xin-Lei & Tian, Cheng-Ming, 2020, Identification of six Cytospora species on Chinese chestnut in China, MycoKeys 62, pp. 1-25 : 1

Cytospora myrtagena (G.C. Adams & M.J. Wingf.) G.C. Adams & Rossman, IMA Fungus 6 (1): 147. 2015. Figure 6

Description.

Sexual morph: not observed. Asexual morph: Pycnidial stromata pulvinate, immersed in bark, scattered, erumpent through the surface of bark. Conceptacle absent. Ostiole dark grey to black, conspicuous, at the same level as the disc, (50-)65-75(-82) μm diam. Locules undivided, circular to ovoid, (430-)550-720(-810) µm diam. Peridium comprising few layers of cells of textura angularis, with innermost layer brown, outer layer brown to dark brown. Conidiophores hyaline, unbranched, thin-walled, filamentous. Conidiogenous cells enteroblastic polyphialidic, (6.5-)8.4-12.5(-15.3) × 0.9-1.4 μm (x̄ = 10.2 × 1.2 μm). Conidia hyaline, allantoid, smooth, aseptate, thin-walled, (3.2-)3.4-5.4(-6.2) × 1-1.5 μm (x̄ = 4.7 × 1.3 μm).

Culture characters.

On PDA at 25 °C in darkness. Cultures are initially white, becoming olivaceous buff in centre after 7 d and finally olivaceous at 30 d. The colony is flat, thin with a felt and tight texture in centre. Pycnidia distributed irregularly on medium surface.

Specimens examined.

China, Shaanxi Province, Ankang City, Xiangxidong forest park, 32°40'33"N, 109°18'57"E, on stem barks of Castanea mollissima , 1 July 2017, N. Jiang (BJFC-S1704, living culture CFCC 52454; BJFC-S1705, living culture CFCC 52455).

Notes.

Cytospora myrtagena was introduced from Eucalyptus and Tibouchina in America and Indonesia ( Adams et al. 2005). Two ITS sequences of Cytospora myrtagena were available, AY347363 from the type strain CBS 116843 and AY347380 from CBS 117013. However, there are 14 bp differences between AY347363 and AY347380. Cytospora tibouchinae was introduced as a phylogenically close species to Cytospora myrtagena (Suppl. material 1: Fig. S1), with 21 bp differences to CBS 116843 and 14 bp bp differences to CBS 117013 ( Crous et al. 2016). Two isolates from Castanea mollissima in the present study were close to Cytospora myrtagena and Cytospora tibouchinae (Suppl. material 1: Fig. S1), with 22 bp differences to CBS 116843, 15 bp differences to CBS 117013 and 6 bp differences to Cytospora tibouchinae . Morphologically, they have similar conidial sizes (3.4-5.4 × 1-1.5 μm in BJFC-S1704 vs. 3-4 × 1 μm in C. myrtagena vs. 3-4 × 1.5-2 μm in C. tibouchinae ) ( Adams et al. 2005, Crous et al. 2016). Hence, it is hard to identify our isolates to C. myrtagena or C. tibouchinae , for the large differences between two ITS sequences in C. myrtagena provided by Adams et al. (2005) and absence of ACT and RPB2 loci in C. myrtagena and C. tibouchinae . We give the name Cytospora myrtagena to our isolates provisionally, and hope for more studies on this species.

Figures

Figure 6. Cytospora myrtagena on Castanea mollissima (BJFC-S 1704). A, B Habit of conidiomata on branches C, E transverse section of conidiomata D longitudinal section through conidiomata F, G conidiogenous cells attached with conidia H conidia. Scale bars: 500 μm (B-D), 5 μm (E, G), 10 μm (H).