Didymella degraaffiae Hern.-Restr., L. W. Hou, L. Cai & Crous, 2020

Hou, Lingwei, Hernandez-Restrepo, Margarita, Groenewald, Johannes Zacharias, Cai, Lei & Crous, Pedro W., 2020, Citizen science project reveals high diversity in Didymellaceae (Pleosporales, Dothideomycetes), MycoKeys 65, pp. 49-99 : 49

Didymella degraaffiae Hern.-Restr., L. W. Hou, L. Cai & Crous sp. nov. Figure 3

Etymology.

degraaffiae refers to Janne de Graaff who collected the soil sample from which the ex-type strain was isolated.

Typus.

The Netherlands. Limburg province, Weert, isolated from garden soil, Mar. 2017, J. de Graaff (holotype designated here CBS H-24105, living ex-type culture CBS 144956 = JW 195004).

Conidiomata pycnidial, superficial on the agar or semi-immersed in the agar, scattered or aggregated, mostly confluent, globose, subglobose, lageniform to irregularly-shaped with age, brown to dark brown, ostiolate, covered by hyphal outgrowths, especially near the ostiole, 150-485 × 120-330 μm; non-papillate or with up to two papillate ostioles; pycnidial wall pseudoparenchymatous, 3-6 layers, 10-55 μm thick, outer layers composed of brown, isodiametric cells, 16-33 μm diam. Conidiogenous cells phialidic, hyaline, smooth, ampulliform, lageniform, pyriform or globose, 5.5-8.5 × 5-8 μm. Conidia ellipsoidal, oblong or oval, thin- and smooth-walled, hyaline, aseptate, 4.5-9(-11) × 3-4.5 μm, 2-6-guttulate, small. Conidial matrix milky white.

Culture characteristics.

Colonies after 7 d at 25 °C, on OA reaching 65-70 mm diam, aerial mycelium floccose, orange to olivaceous, margin regular; reverse black near the centre, pale grey towards the periphery. On MEA reaching 55-60 mm diam, aerial mycelium floccose, buff to pale olivaceous, with white mycelium pellet and radially furrowed zones near the centre, margin regular; reverse buff near the centre, olivaceous to yellow towards the periphery. On PDA reaching 50-55 mm diam, aerial mycelium floccose, concentric circles pale brown, pale olivaceous grey, dark olivaceous, honey, margin irregular; reverse black with a pale olivaceous edge. NaOH spot test negative on OA.

Notes.

In our phylogenetic analysis, D. degraaffiae grouped with D. americana and D. maydis (Figure 1 ). However, morphologically, D. americana differs by its smaller conidiogenous cells (3-5 × 3-4 μm) and conidia (5-7 × 2-2.5 μm) ( Boerema 1993); while D. maydis differs in having larger conidia (15-17 × 3.5-5 μm) ( de Gruyter 2002). Furthermore, D. americana and D. maydis occasionally produced 1-septate conidia, while septate conidia were not observed in D. degraaffiae .

Figures

Figure 1. Phylogenetic tree generated from the maximum-likelihood analysis based on the combined ITS, LSU, tub 2 and rpb 2 sequence alignment of Didymellaceae members. The RAxML bootstrap support values (BS), Bayesian posterior probabilities (PP), and parsimony bootstrap support values (PBS) are given at the nodes (BS / PP / PBS). BS and PBS values represent parsimony bootstrap support values> 50 %. Full supported branches are indicated in bold. The scale bar represents the expected number of changes per site. Ex-type strains are represented in bold. Strains obtained in the current study are printed in green; among them, whilst strains that represent new taxa are printed in red. Some of the basal branches were shortened to facilitate layout (the fraction in round parentheses refers to the presented length compared to the actual length of the branch). The tree was rooted to Coniothyrium palmarum CBS 400.71 and Leptosphaeria doliolum CBS 505.75.

Figure 3. Didymella degraaffiae (CBS 144956). A, B Colony on OA (front and reverse) C, D colony on MEA (front and reverse) E, F colony on PDA (front and reverse) G, H pycnidia on OA I section of pycnidium J section of pycnidial wall K, L conidiogenous cells M chlamydospores N conidia. Scale bars: 50 μm (H, I); 10 μm (J); 5 μm (K-N).