Helicosporium luteosporum Y.Z. Lu, Boonmee & K.D. Hyde, Phytotaxa 319(3): 248 (2017)
Index Fungorum number: IF 552663; MycoBank number: MB 552663; Facesoffungi number: FoF 02763; Figs. 1, 2
Saprobic on decaying wood. Sexual morph Undetermined. Asexual morph Hyphomycetous, helicosporous. Colonies effuse, yellow, shiny, with crowded by conidial masses. Mycelium composed of partly immersed to superficial, septate, branched, hyaline to brown hyphae. Conidiophores 142–370 µm long, 5–8 µm wide at base, micronematous, mononematous, arising from repent mycelium, tapering toward narrow subacute at apex, fuscous branching and brown at base, brownish to hyaline towards apex, septate, smooth-walled. Conidiogenous cells 3–7.5×2–3 µm, denticulate, holoblastic, monoblastic, bearing lateral minute denticles each with single conidium. Conidia 81–161 µm diam., with conidial filament 6–8 µm wide, with 634–674.5 µm long, loosely coiled 1–2½ times, becoming loosely uncoiled in water, rounded at apical ends, indistinctly multi-septate, not constricted at the septa, bright, hyaline to pale brown, guttulate, smooth-walled.
Culture characteristics – Ascospores germinating on MEA within 24 h and many germ tubes produced from conidium cells. Colonies growing on MEA slowly, less than 5 mm diam. in 7 days at room temperature, slightly raised-radially with entire edge, brownish-gray to pale brown. Mycelium developing superficial, composed of branched, septate, pale brown, reddish-brown to dark brown, with red pigmented hyphal filaments, conidial spores formed on hyphae in culture at 60 days. Conidia 55–112 µm diam., with conidial filament 7.5–8 µm wide, with 445–448 µm long, loosely coiled 1–3½ times, becoming loosely uncoiled in water, rounded at apical ends, indistinctly multi-septate, not constricted at the septa, hyaline, with granular contents.
Material examined – THAILAND, Chanthaburi, Laem Sing, Ban Phlio, on decaying wood in a terrestrial habitat, 7 July 2016, S. Boonmee, NTP02-Ax (MFLU 17-0502, new record), living culture, MFLUCC 16-1233.
GenBank numbers – LSU=KY873624.
Notes – Isolate (MFLUCC 16-1233) was identified as Helicosporium luteosporum based on phylogenetic analysis, but morphological illustrations were not provided (Brahamanage et al. 2017; Lu et al. 2017). A nucleotide base comparison of the LSU sequence reveals that our taxon is 100% similar to the ex-type strain H. luteosporum MFLUCC 16-0266 (Jeewon and Hyde 2016). Further, phylogenetic analyses of a combined ITS, LSU and TEF1-α sequence dataset indicates that our strain clusters with the H. luteosporum strain with 100% MLBS, 1.00 BYPP support (Fig. 3). Therefore, we provide a detailed description, illustration and update phylogenetic tree for H. luteosporum (MFLUCC 16-1233) as a new geographical record in Thailand (Figs. 1 and 2).
Figure 1 – Helicosporium luteosporum (MFLU 17-0502, new record). a Colony on decaying wood. b–d Conidiophores with lateral minute polyblastic denticles and attached conidia. e–i Conidia. Scale bars: a=200 µm, b, c=50 µm, d–i=20 µm
Figure 2 – Helicosporium luteosporum sporulation in culture (MFLUCC 16-1233). a Germinated conidium. b, c Culture on MEA from surface and reverse after 1 month. d–f Mycelium and development of conidia in culture. g–j Conidia. Scale bars: a, d–j=20 µm
Figure 3 – Maximum likelihood phylogenetic tree based on a combined ITS, LSU and TEF1-α sequence data of Helicosporium taxa and related genera in Tubeufiaceae. Thirty-two taxa are included in the combined analyses which comprise a total of 2367 characters. Berkleasmium thailandicum (MFLUCC 15-1248 and MFLUCC 17-1984) are selected as the outgroup taxa. The best RAxML tree with a final likelihood value of − 8690.594891 is presented. RAxML analysis yielded 609 distinct alignment patterns and 25.02% of undetermined characters or gaps. Estimated base frequencies were as follows: A=0.231326, C=0.266395, G=0.273200, T=0.229079, with substitution rates AC=1.159455, AG=2.641204, AT=1.962575, CG=0.673701, CT=9.846706, GT=1.000000; gamma distribution shape parameter alpha=0.182397. Bootstrap support values for maximum likelihood (MLBS, left) equal to or greater than 70% is given above the nodes. Bayesian posterior probabilities (BYPP, right) equal to or greater than 0.95 are given above the nodes. Ex-type strains are in bold and newly generated sequences are in blue