Pararoussoella lincangensis

Pararoussoella lincangensis G.C. Ren & K.D. Hyde, Mycosphere 15(1): 1044 (2024)

Index Fungorum number: IF 901359; Facesoffungi Number: FoF13893

            Saprobic on dead woody twigs of Heliciopsis terminalis. Sexual morph: Undetermined. Asexual morph: Coelomycetous. Conidiomata 75–140 μm high × 140–160 μm diam., (x̅ = 110 × 150 μm, n = 5), immersed under a blackened pseudoclypeus, appearing as black, solitary or scattered, unilocular, coriaceous, elliptical to ampulliform, brown to dark brown. Ostioles central. Conidiomata wall 10–14 μm wide, 3–4-layered, intermixed with the host tissue, composed of brown outer layers and inner layers comprising hyaline, thick walled cells of textura angularis. Conidiophores reduced to conidiogenous cells. Conidiogenous cells 4.4–5.4 × 2.6–3.6 μm (x̅ = 5 × 3.1 μm, n = 10), enteroblastic, phialidic, determinate, discrete, doliiform to ampulliform, hyaline, smooth walled, arising from the stratum. Conidia 3.1–3.8 × 2–2.2 μm (x̅ = 3.4 × 2.1 μm, n = 30), straight, initially hyaline, becoming yellowish at maturity, ovate, one celled, aseptate, rounded ends, thick and smooth walled.

            Culture characteristics: Conidia germinating on PDA within 24 h at room temperature (25 °C). Germ tubes produced from the basal and apical cell of conidia. Colonies on PDA, reaching 45 mm diameter after two weeks at 20–25 ℃, mycelia superficial, circular, flat, umbonate, entire edge, white at the margin, grey at the center; reverse white at the margin, atrovirens at the center.

Material examined: China, Yunnan Province, Lincang, on dead woody twigs of Heliciopsis terminalis (Proteaceae), 12 August 2020, G.C. Ren, LC55 (HKAS 122756, holotype), ex type culture KUMCC 21-0619, KUMCC 21-0620.

GenBank numbers: KUMCC 21-0619: SSU: OQ168233, LSU: OQ170882, ITS: OQ158960, tef1-α: OR613443; KUMCC 21 0620: SSU: OQ168234, LSU: OQ170883, ITS: OQ158961.

Notes: Our strains (KUMCC 21-0619 and KUMCC 21-0620) clustered with other Pararoussoella species with 75% ML bootstrap support and 0.98 BYPP value. Our collections can be distinguished from P. juglandicola and P. quercina based on its ovate yellowish conidia. In contrast, P. juglandicola has subcylindrical, brown conidia, and P. quercina has broadly ellipsoid, brown conidia (Crous et al. 2019, 2020). In addition, P. juglandicola and P. quercina were found as asexual morphs in sporulated cultures, whereas we obtained our strains asexual morph in nature. We did not find the sexual morph of P. lincangensis in nature. Therefore, a comparison between our new collections and other sexual morphs of Pararoussoella species (Roussoella mangrovei, P. mukdahanensis, P. rosarum) was not possible. However, based on the phylogenetic distinctiveness, P. lincangensis can be distinguished from Roussoella mangrovei, P. Mukdahanensis and P. rosarum. Herein, we introduce Pararoussoella lincangensis as a new species based on its distinct morphology and analysis of the combined LSU, ITS, tef1-α, and rpb2 dataset.

Figure 1. Phylogram generated from ML analysis based on LSU, ITS, tef1-α, and rpb2 sequence data, representing Roussoellaceae. Related sequences are obtained following Zhang et al. (2020b). Sixty strains are included in the combined analyses, which comprise 3136 characters for LSU, ITS, tef1-α, and rpb2 alignment. Torula herbarum (CBS 111855) and T. hollandica (CBS 220.69) were used as the outgroup taxa. The best-scoring RAxML tree with a final likelihood value of -22805.534061 is presented. The matrix had 1172 distinct alignment patterns, with 25.96% of undetermined characters or gaps. Estimated base frequencies were as follows; A = 0.240512, C = 0.264779, G = 0.272734, T = 0.221974; substitution rates AC = 1.942253, AG = 5.228557, AT = 2.132197, CG = 1.362679, CT = 10.344711, GT = 1.0000. The tree topology of the ML analysis is similar to the Bayesian analysis. Bootstrap values for ML equal to or greater than 70% and BYPP values greater than 0.95 (the rounding of values to 2 decimal proportions) are labelled on the nodes. Strains of the newly described species are in blue, while type strains are in bold.