Diaporthe chamaeropicola D.R.S. Pereira & A.J.L. Phillips, sp. nov.

Index Fungorum number: IF 557847; MycoBank number: MB 557847; Facesoffungi number: FoF 09160; Fig. 1

Etymology – Named after the host genus from which it was collected, Chamaerops humilis.

Holotype – AVE-F-8

Associated with foliar lesions. Sexual morph Undetermined. Asexual morph Conidiomata pycnidial, solitary, occasionally aggregated, subglobose, dark-brown to black, thick-walled, up to 4 mm diam., covered with hyphal outgrows, superficial, lacking an ostiole, dehiscent by irregular fissures on pycnidial wall, exuding a creamy mucoid mass of conidia. Pycnidial wall pseudoparenchymatous of darkbrown textura angularis, cells thick-walled in outer layers, becoming thin-walled and hyaline towards the inner layers. Conidiophores absent. Conidiogenous cells lining the entire cavity, straight, hyaline, smooth-walled, thin-walled, cylindrical, occasionally ampulliform, tapering towards the apex, aseptate or 1–3-septate, unbranched or branched, collarette up to 1 µm long, variable in length, dimorphic, short conidiogenous cells, 4.9–19.4 × 0.9–2.6 µm (mea n ± SD = 13.66 ± 3.68 × 1.75 ± 0.39 µm), long conidiogenous cells, 15.2–49.2 × 1.1–2.7 µm (mean ± SD = 29.5 4 ± 7.28 × 1.75 ± 0.36 µm), mostly phialidic, proliferating at the same level giving rise to periclinal thickenings, enteroblastic, occasionally proliferating percurrently giving rise to 1–2 annellations, often intermingled with paraphyses. Paraphyses straight, flexuous, hyaline, smooth- and thin-walled, cylindrical, tapering towards the apex, with 1–2–(3) basal septa, unbranched or branched below, often one of the branches later functioning as a conidiogenous cell, extending above conidiogenous cells, 26.6–78.8 µm (mean±SD=53.57±12.72 µm) long. Alpha conidia cylindrical to ellipsoidal, mostly with rounded apex and obtuse to truncate base, hyaline, smooth- and thin-walled, aseptate, bi-guttulate, with a conspicuous guttule at each end, occasionally with several minute scattered guttules, straight to slightly curved, 5.6–9.4×1.7–3 µm (mean±SD=7.53± 0.89×2.31±0.30 µm); mean±SD conidium length/width ratio=3.33±0.73. Beta and gamma conidia not seen.

Culture characteristics – Colonies on 1/2 PDA, reaching 60 mm diam. after 7 d at 20 ℃. Surface flat, sparse aerial mycelium, often growing with concentric zones, with filiform margin, circular, pearl white to dirty white, opaque to slightly translucent. Reverse luteous, pale brown towards the centre. No diffusible pigment. Conidiomata black, scattered
over the surface of the colony.

Material examined – PORTUGAL, Lisbon, Parque das Nações, Jardins da Água, near Oceanário de Lisboa, on foliar lesions of segments of Chamaerops humilis (Arecaceae), 16 October 2018, D.R.S. Pereira, HDP 034 (AVE-F-8 a dried culture of CDP 460, holotype), ex-type living culture, CBS XXXX=CDP 460/01.

GenBank Numbers – CAL=MT011068, ITS=MT022111, TEF1-α=MT011074, TUB2=MT011080.

Distribution – Lisbon, Portugal.

Notes – Diaporthe chamaeropicola was found associated with foliar lesions of Chamaerops humilis (Fig. 2), but pathogenicity has not been tested. The phylogenetic position of D. chamaeropicola among accepted Diaporthe species has not clearly been resolved. Nevertheless, this species is phylogenetically related to but distinct from D. ceratozamiae, D. phyllanthicola and D. loropetali (Fig. 2). Diaporthe chamaeropicola is similar to D. ceratozamiae (Fig. 1), producing globose pycnidia, whose internal cavity is lined with cylindrical conidiogenous cells intermingled with long cylindrical, septate and branched paraphyses (Crous et al. 2011). However, D. chamaeropicola has larger conidiomata than D. ceratozamiae (up to 4 mm diam. vs. 300 µm diam.), lacks conidiophores, and alpha conidia have a different shape (cylindrical/ellipsoidal vs. fusiform). In addition, the two species differ in 13 nucleotide positions in ITS. Diaporthe chamaeropicola differs from D. phyllanthicola and D. loropetali in 9 and 13 nucleotide positions in ITS, respectively. No TUB2, TEF1 and CAL sequences are available for D. ceratozamiae, D. phyllanthicola or D. loropetali. 

Figure 1 – Diaporthe chamaeropicola (AVE-F-8, holotype). a Conidiomata formed on 1/2 PDA with conidia oozing in creamy mucoid masses. b–d Short conidiogenous cells (white arrows point to collarettes, black arrows point at periclinal thickenings). e, g Long conidiogenous cells. f, h Paraphyses (black arrow indicates a branch that is functioning as a conidiogenous cell). i Conidia. Scale bars: a=1 mm, b–i=5 μm

Figure 2 – Maximum Likelihood tree generated by RAxML with GTR+G+I nucleotide substitution model using the combined four loci ITS, TEF1-α, TUB and CAL. The sequences were retrieved from GenBank according to BLAST searches with the ITS locus and by reference to the recent literature. Sixty-four strains are included in the combined analyses that comprise 2248 characters (including gaps) (502 characters for ITS, 669 for TUB, 411 for TEF1-α and 554 for CAL) after alignment and manual adjustment. The final likelihood score for the ML tree was − 15269.024241. The matrix had 1121 distinct alignment patterns, with 27.31% undetermined characters or gaps. ML bootstrap support values (>50%) are shown above the branches. The scale bar represents the expected number of nucleotide changes per site. Diaporthe toxica (CBS 534.93) was included as an outgroup. Ex-type/ex-epitype/ex-isotype/ex-neotype cultures are in bold and newly generated sequences are in blue