Diaporthe lutescens S.T. Huang, J.W. Xia, X.G. Zhang & Z. Li, 2021

Sun, Wenxiu, Huang, Shengting, Xia, Jiwen, Zhang, Xiuguo & Li, Zhuang, 2021, Morphological and molecular identification of Diaporthe species in south-western China, with description of eight new species, MycoKeys 77, pp. 65-95 : 65

Diaporthe lutescens S.T. Huang, J.W. Xia, X.G. Zhang & Z. Li sp. nov. Figure 7

Etymology.

Named after the host Chrysalidocarpus lutescens on which it was collected.

Diagnosis.

Diaporthe lutescens differs from D. pterocarpi (S. Hughes) D. Udayanga et al. and D. pseudoinconspicua T.G.L. Oliveira et al. in longer beta conidia and the types of conidia.

Type.

China, Yunnan Province: Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, on leaves of Chrysalidocarpus lutescens . 19 April 2019, S.T. Huang, HSAUP194.36, holotype, ex-holotype living culture SAUCC194.36.

Description.

Asexual morph: Conidiomata pycnidial, scattered or aggregated, black, erumpent, slightly raised above the surface of the culture medium, subglobose, exuding white creamy conidial droplets from central ostioles after 30 days incubation in light condition at 25 °C on PDA; pycnidial wall consists of black to dark brown, thin-walled cells. Conidiophores 10.2-17.0 × 1.8-3.0 μm, hyaline, unbranched, subcylindrical, septate, smooth, straight or slightly curved, obtuse at the apex, widened at base. Conidiogenous cells 5.7-9.1 × 1.4-2.6 μm, phialidic, cylindrical, terminal, straight to sinuous, tapering towards the apex. Beta conidia 20.8-28.8 × 1.2-2.0 μm (mean = 25.3 × 1.4 μm, n = 20), filiform, hyaline, straight or slightly curved, aseptate, base subtruncate, enlarged towards the apex. Alpha conidia and gamma conidia not observed.

Culture characteristics.

Pure culture was isolated by subbing hyphal tips growing from surface sterilized infected plant material. Colonies on PDA cover the petri plate diameter after incubation for 15 days in dark conditions at 25 °C, initially white, becoming grayish, reverse pale brown, with concentric rings of dense and sparse hyphae, irregular margin, fluffy aerial mycelium. Pycnidia formed in 15 days.

Notes.

From the phylotree, seen on Fig. 1 , Diaporthe lutescens forms an independent clade and is phylogenetically distinct from D. pterocarpi and D. pseudoinconspicua . Diaporthe lutescens can be distinguished from D. pterocarpi in ITS, TUB, TEF and CAL loci by 77 nucleotide differences in concatenated alignment (43 in ITS, 2 in TUB, 29 in TEF and 17 in CAL), and from D. pseudoinconspicua in ITS, TUB, TEF, CAL and HIS loci by 65 nucleotide differences (18 in ITS, 3 in TUB, 23 in TEF, 8 in CAL and 13 in HIS). Moreover, D. lutescens differs from D. pterocarpi and D. pseudoinconspicua in having longer beta conidia (20.8-28.8 × 1.2-2.0 vs. 16.0-23.4 × 1.0-1.4 μm, and 20.8-28.8 × 1.2-2.0 vs. 18.0-21.0 × 1.0-1.5 μm). Furthermore, Diaporthe pterocarpi and D. pseudoinconspicua can produce α-conidia, but D. lutescens cannot ( Crous et al. 2018a; Broge et al. 2020).

Figures

Figure 1. Phylogram of Diaporthe based on combined ITS, TUB, TEF, CAL and HIS genes. The ML and BI bootstrap support values above 50 % and 0.90 BYPP are shown at the first and second position, respectively. Strains marked with " * " are ex-type or ex-epitype. Strains from this study are shown in red. Three branches were shortened to fit the page size - these are indicated by symbol (//) with indication number showing how many times they are shortened.

Figure 7. Diaporthe lutescens (SAUCC 194.36) a leaves of host plant b, c surface (b) and reverse (c) sides of colony after incubation for 15 days on PDA d conidiomata e-g conidiophores and conidiogenous cells h, i beta conidia. Scale bars: 10 μm (e-i).