Pseudorobillarda camelliae-sinensis Rathnayaka, C.H. Kuo & K.D. Hyde, 2021

Rathnayaka, Achala R., Chethana, K. W. Thilini, Tennakoon, Danushka S., Lumyong, Saisamorn & Hyde, Kevin D., 2021, Additions to the microfungi in Taiwan: introducing Pseudorobillarda camelliaesinensis sp. nov., (Pseudorobillardaceae) and new host records of pleosporalean taxa in mountainous habitats, Phytotaxa 516 (2), pp. 115-139 : 122-125

Pseudorobillarda camelliae-sinensis Rathnayaka, C.H. Kuo & K.D. Hyde , sp. nov.

Index Fungorum number: IF558144; Facesoffungi number: FoF 0952; FIGURE 5 .

Etymology: In reference to Camellia sinensis , the host where the fungus was collected

Holotype: MFLU 21-0007

Saprobic on dead leaves of Camellia sinensis (L.) Kuntze. Sexual morph: undetermined. Asexual morph: Conidiomata pycnidial, 106–120 μm diam., 120–155 μm high (x̄ = 112 × 140 μm; n = 10), foliicolous, scattered, semi-immersed in the host leaf, globose to subglobose, black. Conidiomatal wall 7–20 μm wide, composed of thick-walled, 2–3 layers, pale brown to hyaline cells of textura prismatica. Conidiophores reduced to conidiogenous cells. Paraphyses 2–4 μm wide, hyaline, filiform, aseptate, unbranched, mixed with conidiophores. Conidiogenous cells 5–15 × 2–4 (x̄ = 10 × 3 μm; n = 20) μm, hyaline, enteroblastic, phialidic, subcylindrical, thick- and smooth-walled. Conidia 13–14 × 2–4 μm (x̄ = 13.4 × 3 μm; n = 35) subcylindrical, rounded at apex, truncated at base, hyaline, aseptate, thick-walled, smooth, bearing 2–4-unbranched, flexuous, extracellular, apical appendages (10–16 μm long).

Culture characteristics: Conidia germinated on PDA within 24 hours, germ tube produced one-end of the conidia. Colonies on PDA, reached up to 3–4 cm diam. after 1 weeks at 25 °C, colony from above: flat, scant cottony surface, initially white, gradually becoming pale grey to orange in middle and grey at the margin; from below: filamentous, pale orange at the middle and dark grey at the margin.

Material examined: TAIWAN, Alishan Mountain, on dead leaves of Camellia sinensis (Theaceae) , 16 August 2019, Achala Rathnayaka (MFLU 21-0007, holotype); ex-type living culture NCYUCC 19-0408.

GenBank accession numbers: SSU: MW478590 , LSU : MW478592 , ITS : MW478596 , rpb 2: MW478492

Notes: Pseudorobillarda camelliae-sinensis fits within the generic concept of Pseudorobillarda in having pycnidial conidiomata and subcylindrical conidia with apical appendages ( Tangthirasunun et al. 2014). Based on multi-gene phylogeny (SSU, LSU, ITS and rpb 2), P. camelliae-sinensis constitutes a distant lineage basal to P. eucalypti , P. parasiamensis , P. siamensis and P. sojae , with 92% ML and 0.99 PP bootstrap support. Pseudorobillarda camelliaesinensis shows a close phylogenetic affinity with P. parasiamensis ( FIGURE 1 ). Detailed morphological comparison of this species is provided in TABLE 1. Some Pseudorobillarda species , such as P. agrostidis , P. aquatica , P. asparagus , P. bolusanthi , P. indica , P. jaczewskii , P. magna , P. monica , P. peltigerae , P. phragmitis , P. texana and P. setariae have paraphyses, while others, P. bambusae , P. eucalypti , P. muhlenbergiae , P. parasiamensis , P. siamensis , P. sojae and P. subfusca not exist paraphyses. Pseudorobillarda camelliae-sinensis also have paraphyses.

The length/width (L/W) ratio of conidia in Pseudorobillarda species ranges from 2.8–7.7. Pseudorobillarda camelliae-sinensis shows L/W of 4.3 closer to P. bolusanthi (4.1), P. indica (4.2) and P. monica (4.4). When considering the conidial septation, most of the Pseudorobillarda species have septate conidia. Pseudorobillarda eucalypti , P. parasiamensis , P. siamensis and P. texana have aseptate conidia similar to our new taxon, P. camelliae-sinensis . Pseudorobillarda aquatica has aseptate and rarely septate conidia. However, the L/W ratio of Pseudorobillarda camelliae-sinensis (4.3) is different from other Pseudorobillarda species with aseptate conidia ( TABLE 1). Base pair differences between Pseudorobillarda spp. are shown in TABLE 2. When considering the base pair comparison between our strain with other Pseudorobillarda strains, LSU shows around 7% average base pair differences, while ITS shows around 20% average base pair differences (without gaps). A very few Pseudorobillarda species have rpb 2 sequences and it shows 20% of average base pair difference between P. camelliae-sinensis and other Pseudorobillarda strains ( TABLE 2). Pseudorobillarda parasiamensis shows the highest ITS base pair differences (28.3%), while P. sojae (MFLUCC 12-0421) shows the lowest value (16.3%) with P. camelliae-sinensis . Due to the distinct morphology and phylogenetic evidence, we introduce P. camelliae-sinensis as a new species in Pseudorobillarda .

*Species with molecular data

Notes: ‘-‘ do not have sequences

Figures

FIGURE 1. RAxML tree generated from combined dataset of SSU, LSU, ITS and rpb2. Related sequences were acquired from GenBank and Li et al. (2020).The tree is rooted to Dendrographa decolorans Ertz 5003 (BR). Bootstrap support values for ML ≥ 70 % and Bayesian posterior probabilities (PP) ≥ 0.95 are noted at the nodes. Strain numbers are noted at the end of the species name. Newly introduced species is represented as blue and type strains are in bold.

FIGURE 5. Pseudorobillarda camelliae-sinensis (MFLU 21-0007, holotype) on leaf of Camellia sinensis. a Specimen. b Appearance of conidiomata on host surface. c Close-up of conidioma. d Vertical section of conidioma. e Section through peridium. f–h Paraphyses, conidiogenous cells with developing conidia. i–l Conidia. m Germinating conidium (indicated by an arrow). n Colony from above. o Colony from below. Scale bars: b = 500 μm, c = 100 μm, d = 50 μm, f, i–m = 10 μm, e, g, h = 5 μm.