Didymella kooimaniorum 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 kooimaniorum Hern.-Restr., L. W. Hou, L. Cai & Crous sp. nov. Figure 4

Etymology.

kooimaniorum refers to Noud & Robin Kooiman who collected the soil sample from which the ex-type strain was isolated.

Typus.

The Netherlands. Utrecht province, Vleuten, isolated from garden soil, Mar. 2017, N. Kooiman & R. Kooiman (holotype designated here CBS H-24106, living ex-type culture CBS 144951 = JW 27006).

Conidiomata pycnidial, superficial or semi-immersed, scattered or solitary, sometimes confluent, globose to subglobose, irregularly-shaped with age, pale brown to brown, covered by hyphal outgrowths, especially near the ostioles, 200-375 × 195-280 μm; with 1-3(-6) papillate ostioles; pycnidial wall pseudoparenchymatous, 3-5 layers, 10-35 μm thick, outer layers composed of pale brown, flattened polygonal cells of 16-32 μm diam. Conidiogenous cells phialidic, hyaline, smooth, ampulliform, lageniform or somewhat isodiametric, (4.5-)5.5-10 × 3.5-9 μm. Conidia ellipsoidal to oblong, straight, thin- and smooth-walled, hyaline, aseptate, 3.5-7 × 2-3 μm, 2-guttulate, big. Conidial matrix buff.

Culture characteristics.

Colonies after 7 d at 25 °C, on OA reaching 55-60 mm diam, aerial mycelium floccose, pale smoke grey, pale brown towards periphery, abundant production of confluent pycnidia, margin regular; reverse pale olivaceous, with some olivaceous black zones. On MEA reaching 50-55 mm diam, aerial mycelium woolly, pale olivaceous grey, margin irregular; reverse buff near the centre, dark brown with orange edge. On PDA reaching 50-55 mm diam, aerial mycelium floccose, pale mouse grey with olivaceous edge, margin irregular; reverse dark brown with pale brown edge. NaOH spot test negative on OA.

Notes.

Based on the multi-gene phylogenetic analyses, D. kooimaniorum forms an independent branch, clearly separated from other species in Didymella (Figure 1 ). Morphologically, D. kooimaniorum is characterised by pale brown pycnidia densely covered by long hairs, and ostioles with up to six papillae with a darker neck.

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 4. Didymella kooimaniorum (CBS 144951). 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 pycnidia forming on OA H pycnidia I section of pycnidium J section of pycnidial wall K-M conidiogenous cells N conidia. Scale bars: 100 μm (H); 50 μm (I); 10 μm (J); 5 μm (K-N).