Proliferodiscus, Bien & Damm, 2020

Bien, Steffen & Damm, Ulrike, 2020, Arboricolonus simplex gen. et sp. nov. and novelties in Cadophora, Minutiella and Proliferodiscus from Prunus wood in Germany, MycoKeys 63, pp. 119-161 : 119

Proliferodiscus sp. Figures 5L , 16

Description.

Sexual morph not observed. Asexual morph on OA. Vegetative hyphae hyaline, smooth-walled, septate, branched, 1.5-3 μm wide, lacking chlamydospores. Sporulation abundant, conidia formed in conidiomata. Conidiomata produced on OA, SNA and pine needles in 2-4 wk, solitary or aggregated, subglobose, unilocular, superficial, 125-500 μm wide, luteous, almost glabrous to completely covered with hairs, opening with an irregular rupture. Conidiophores hyaline, smooth-walled, septate, simple or branched, conidiogenous loci formed terminally. Conidiogenus cells enteroblastic, hyaline, smooth-walled, navicular to subulate, tapering towards apices, 9-14 × 1-2 μm, collarettes cylindrical, <1 μm long, opening 0.5-1 μm, periclinal thickening sometimes visible, conidiogenous cells often extend to form new conidiogenous openings, extensions flask-shaped to navicular. Conidia hyaline, smooth-walled, aseptate, mostly globose to obovoid, sometimes cylindrical to ellipsoidal, straight, with both ends rounded, 1.5-2(-3) × 1.5(-2) μm, mean ± SD = 1.9 ± 0.3 × 1.5 ± 0.1 μm, L/W ratio = 1.2.

Culture characteristics.

Colonies on OA flat to effuse with entire to fimbriate margin, white to buff, cinnamon to sienna at the margin, aerial mycelium sparse, white, reverse buff, cinnamon to sienna; 6-14 mm diam. in 2 wk, 16-32 mm diam. in 4 wk. Colonies on SNA flat to effuse with entire to fimbriate margin, white, lacking aerial mycelium, reverse same colour; 6-18 mm diam. in 2 wk, 20-34 mm diam. in 4 wk.

Notes.

In total, five strains of Proliferodiscus sp. have been isolated from wood of Prunus domestica in Saxony (3) and Lower Saxony (1) as well as P. avium in Baden-Württemberg (1). Two subclades are formed by these strains, which differ in one and four nucleotides in the LSU and ITS sequences, respectively. No morphological differences were noticed between strains of the two subclades. They form a well-supported clade (100/100/99%) with eight strains retrieved from GenBank, including the ex-type strain of the recently described Pr. chiangraiensis . The conidial shape of these strains is similar to that of the asexual morph of Pr. pulveraceus observed by Baral and Kriegelsteiner (1985); the conidia are slightly larger, but the measurements overlap. However, we cannot link these strains to Pr. pulveraceus on this basis, because the species was described based on its sexual morph and no sequences of type material are available. Moreover, a recently published sequence, designated as Pr. pulveraceus (MN066320, G Marson unpubl.), belongs to a different clade in our phylogeny.

One striking feature was observed in our collections: new conidiogenous cells grow out of conidiogenous openings (Fig. 16H-J ). This feature has previously been observed in species of other genera, for example, Fusarium graminearum ( Domsch et al. 2007) and several Colletotrichum species ( Damm et al. 2012, 2019).

The anamorphic states of the observed strains of Proliferodiscus sp. differ from Pr. ingens (strain GLMC 1751, this study) by the colour and the smaller size of conidiomata, faster culture growth rate on OA and SNA and the shape of the conidia.

Material examined.

Germany, Saxony, in orchard north of Wölkau, 50°58'42.3"N, 13°49'40.0"E, from brown necrosis in wood of Prunus domestica , 16 Jan 2015, S. Bien leg., GLM-F106310, culture GLMC 460 = CBS 145517 = DSM 109138; Baden-Württemberg, orchard west of Nussbach, 48°31'55.8"N 8°00'52.4"E, from necrotic wood of P. avium , 23 Aug 2016, S. Bien leg., GLM-F110844, culture GLMC 1761 = CBS 145518 = DSM 109137; Saxony, in orchard north of Wölkau, 50°58'42.3"N, 13°49'40.0"E, from brown necrosis in wood of P. domestica , 16 Jan 2015, S. Bien leg., GLM-F106320, culture GLMC 470; Lower Saxony, Hollern-Twielenfleth, orchard, 53°36'13.6"N, 9°31'50.8"E, from brown wedge-shaped necrosis in wood of P. domestica , 8 Oct 2015, S. Bien leg., GLM-F107151, culture GLMC 1301; Saxony, in orchard north of Wölkau, 50°58'42.3"N, 13°49'40.0"E, from brown necrosis in wood of P. domestica , 16 Jan 2015, S. Bien leg., GLM-F106352, culture GLMC 502.

Figures

Figure 5. Colony surface of analysed strains on OA medium. A Arboricolonus simplex GLMC 459 T B Cadophora africana CBS 120890 T C C. bubakii CBS 198.30 T D C. luteo-olivacea GLMC 1264 E C. novi-eboraci GLMC 1472 F C. obscura CBS 269.33 G C. prunicola CBS 120891 T H C. prunicola GLMC 1633 I C. ramosa GLMC 377 T J Minutiella pruni-avium GLMC 1624 T K Proliferodiscus ingens GLMC 1751 T L Proliferodiscus sp. GLMC 460. Cultures A, J-L after 4 wk. Cultures B-I after 2 wk. Strains with a superscript T are ex-type cultures.

Figure 16. Proliferodiscus sp. A conidiomata B conidia formed in conidiomata C-F, I-J conidiogenous cells lining the inner wall of a conidioma G, H detached conidiogenous cells H-J extensions on conidiogenous cells A-J from OA A SM B-J LM. Scale bars: 300 μm (A), 5 μm (B applies to C-J).