Xenodidymella weymaniae 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

Xenodidymella weymaniae Hern.-Restr., L. W. Hou, L. Cai & Crous sp. nov. Figure 13

Etymology.

weymaniae refers to Anna Weyman who collected the soil sample from which the ex-type strain was isolated.

Typus.

The Netherlands. Utrecht province, Baarn, isolated from garden soil, Mar. 2017, A. Weyman (holotype designated here CBS H-24113; living ex-type culture CBS 144960 = JW 201005).

Conidiomata pycnidial, semi-immersed on the agar, mostly confluent, sometimes solitary, scattered or aggregated, subglobose or ellipsoidal, irregularly-shaped when confluent, dark brown, ostiolate, glabrous or with long hyphal outgrowths around the ostiole, 100-700 × 100-400(-590) μm; with 1-2(-6) ostioles, papillate or elongated into a long neck, up to 113 μm in length; pycnidial wall pseudoparenchymatous, 3-5 layers, 17-45 μm thick, outer layers composed of pale brown to brown, flattened polygonal cells of 10-35 μm diam. Conidiogenous cells phialidic, hyaline, smooth, sub-globose, ampulliform or lageniform, 4.5-8 × 4-6.5 μm. Conidia oblong, smooth- and thin-walled, hyaline, aseptate, 4-6(-8) × 2-2.5 μm, with two small, polar guttules. Conidial matrix whitish.

Culture characteristics.

Colonies after 7 d at 25 °C, on OA reaching 55-60 mm diam, aerial mycelium floccose near the centre, flat towards the periphery, pale olivaceous to whitish, black pycnidia visible near the centre, margin regular; reverse buff to salmon, pale olivaceous towards the periphery. On MEA reaching 40-45 mm diam, aerial mycelium felty, sectors with cottony mycelium, white, buff to pale olivaceous, margin regular; reverse yellow to orange, dark brown and pale grey near the centre. On PDA reaching 45-60 mm, aerial mycelium floccose, whitish in the centre, honey towards the periphery, margin regular; reverse concentric circles dark brown in centre, orange, yellow, buff towards the periphery. NaOH spot test negative on OA.

Notes.

Xenodidymella weymaniae formed a distinct branch basal to X. applanata (Figure 1 ). Morphologically, X. weymaniae could be clearly differentiated from X. applanata in pycnidial and conidial characteristics. In X. weymaniae pycnidia are dark brown, ostioles have elongated necks, 100-700 × 100-400(-590) μm, and conidia are oblong, with 2 small polar guttules. In X. applanata pycnidia are pale brown, with single, slightly papillate ostioles, 85-175 × 60-145 μm, and ellipsoidal to ovoid conidia, with several guttules ( Chen et al. 2015). Furthermore, the two species can also be distinguished from the NaOH spot test on OA medium (negative vs. pale reddish discoloration). This is the first record of a Xenodidymella species isolated from soil ( Boerema et al. 2004; Chen et al. 2015, 2017).

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 13. Xenodidymella weymaniae (CBS 144960). 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 forming on OA I, J section of pycnidial wall K-N conidiogenous cells O conidia. Scale bars: 50 μm (H); 20 μm (I); 10 μm (J); 5 μm (K-O).