Diaporthe arecae (H.C. Srivast., Zakia & Govindar.) R.R. Gomes, Glienke & Crous, Persoonia 31: 16 (2013), emended.
Index Fungorum number: IF 802924; MycoBank number: MB 802924; Facesoffungi number: FoF 14193; Fig. 1
Saprobic on dead leaves of monocotyledon plants. Sexual morph: Undetermined. Asexual morph: Conidiomata 60–320×120–160 µm (x=255×148 µm, n=10), immersed just beneath the epidermis, scattered on substrate, solitary, subglobose, compressed globose to irregular, dark brown, coriaceous, ostiolate. Conidiomatal wall 10–17 µm wide (x=15 µm, n=10), comprises pale brown, thick-walled, cells of textura angularis. Conidiophores reduce to conidiogenous cells. Alpha conidiogenous cells 7–13×2–3 µm (x=11×2.5 µm), annellidic, with visible periclinal thickening, collarets not flared, terminal, ampulliform, slightly tapered towards the apex, straight, aseptate, unbranched, densely aggregated, hyaline, thick-walled. Alpha conidia 3.7–7×2.2–2.8 µm (x=6.3×2.6 µm, n=20), fusoid, ends pointed, aguttulate to biguttulate, hyaline, unicellular. Beta conidiogenous cells 7–11×3–4 µm (x=10×3.5 µm), phialidic, terminal, cylindrical, slightly tapered towards the apex, straight, aseptate, unbranched, densely aggregated, hyaline, thick-walled. Beta conidia 8–15×1–2 µm (x=12×1.5 µm), filiform, hamate or slightly curved, base truncate, tapering towards one apex, hyaline, aseptate.
Culture characteristics – Colonies on PDA reaching 6 cm diam. after 10 days in dark at 25 °C, floccose, flat, circular, filiform margin, white, filamentous mycelia spread out from the center, reverse off-white, no pigments produced.
Material examined – China, Guangdong Province, Guangzhou City, Baiyun Mountain (23° 09′ 35″ N 113° 17′ 40″ E), on leaves of Cycas sp. (Cycadaceae), 16 August 2021, I.C. Senanayake, 102-1, (MHZU 22-0110), living cultures ZHKUCC 22-0182, ZHKUCC 22-0192; Danxia Mountain, on leaves of Livistona chinensis (Arecaceae), 23 September 2021, I.C. Senanayake, 48 (MHZU 22-0105), living cultures ZHKUCC 22-0177, ZHKUCC 22-0187; Nansha District, near Baihuitian reservoir, on leaves of Trachycarpus fortunei (Arecaceae), 15 July 2021, I.C. Senanayake, 45 (MHZU 22-0104), living cultures ZHKUCC 22-0176, ZHKUCC 22-0186; Shenzhen City, Nanshan District, Yangtai Mountain Forest Park, 22° 39′ 21.26″ N 113° 57′ 18.53″ E, on leaves of Dypsis lutescens (Arecaceae), 23 September 2021, I.C. Senanayake, 101-2, (MHZU 22-0109), living cultures ZHKUCC 22-0181, ZHKUCC 22-0191.
GenBank numbers – ITS: OR164924, OR164925, OR164930, OR164931, OR164932, OR164933, OR164926, OR164927. β-tubulin: OR166305, OR166306, OR166303, OR166304, OR166311, OR166312. tef1-α: OR166273, OR166274, OR166275, OR166276. cal: OR166295, OR166296.
Notes – The phylogenetic analysis (Fig. 2) showed that our isolates clustered with in the Diaporthe arecae species complex. Phylogenetic network from the concatenated dataset based on the LogDet transformation and the NeighborNet algorithm, inferred by SplitsTree also shows that our isolates clustered with the species members of the Diaporthe arecae species complex and they are distinct from other well delimitated species (Fig. 3a). Our collections share similar characters and all of them were collected from monocotyledons plants in Guangdong Province, China. Therefore, we emended Diaporthe arecae species complex providing additional data.
Figure 1 – Diaporthe arecae (MHZU 22-0109 (a–d); MHZU 22-0104 (e–h); MHZU 22-0109 (i–m), MHZU 22-0105 (n–q). a, e, i, n Conidiomata on substrates. b, f, j, o Cross sections of conidiomata. k Beta conidia attached to conidiogenous cells. c, g, l, p Alpha conidia attached to conidiogenous cells. d, h, m, q Alpha conidia. Scale bars: b, f, j, o=100 µm, c, g, l, p, k, d, h, m, q=15 µm
Figure 2 – Phylogram generated from maximum likelihood analysis based on combined ITS, β-tubulin, tef1-α and cal sequence data which comprised 1801 characters (ITS=590, β-tubulin=399,tef1-α=401, cal=411). The best scoring RAxML tree with a final likelihood value of − 66,138.215080 is presented. The matrix had 1373 distinct alignment patterns, with 21.86% of undetermined characters or gaps. Estimated base frequencies were as follows: A=0.220620, C=0.327829, G=0.221919, T=0.229632; substitution rates: AC=1.155068, AG=3.569724, AT=1.178946, CG=0.924185, CT=4.411577, GT=1.0; gamma distribution shape parameter α=0.524319. Bootstrap support for maximum likelihood (ML) equal to or greater than 50% and clade credibility values greater than 0.90 (the rounding of values to 2 decimal proportions) from Bayesian inference analysis are labelled at each node. Ex-type strains are in bold, while the new isolate is indicated in blue bold. Except D. arecae species complex, other all species complexes are compressed. The tree is rooted to Cytospora disciformis (CBS 116827) and C. leucostoma (SXYLt)
Figure 3 – Phylogenetic network from the concatenated data (ITS, β-tubulin, tef1-α, cal) representing the structure of the a Diaporthe arecae, c D. eres species complexes and other well-delimitated species b the newly generated Diaporthe strains, based on the LogDet transformation and the NeighborNet algorithm, inferred by SplitsTree. The scale bar represents the expected number of substitutions per nucleotide position