Helminthosporium erythrinicola Crous & M.J. Wingf., Persoonia 42, 357 (2019).
Index Fungorum number: IF830852, MycoBank number: MB830852, Facesoffungi number: FoF16089
Saprobic on Dalbergia cana woody litter. Sexual morph: Undetermined. Asexual morph: Hyphomycetous. Colony on natural substrate effuse, hairy, punctiform, dark brown to black. Mycelium frequently immersed, forming brown stroma-like aggregations on the surface, giving rise conidiophores. Conidiophores 290–700 × 6.5–13 μm (x̅= 482 × 10 μm, n = 20), macronematous, mononematous, straight or slightly curved, multiseptate, roughened, cylindrical to subcylindrical, often wider at the base, unbranched, dark brown, at apex pale brown, solitary or grouped in pairs. Conidiogenous cells 26–41(–51) × 9–12 μm (x̅ = 32 × 10 μm, n = 10), terminal, rarely intercalary, with pores, cylindrical, thick-walled, pale brown. Conidia 93–172 × 8–18 μm (x̅ = 130 × 14 μm, n = 15), L/W ratio = 9.3, obclavate, upper cell tapering towards apex, truncate with dark scar at base, straight to flexuous, sub-obtuse apex, smooth-walled, light brown, 6–14(–19)-distoseptate, with angular lumina, wall 2–4 μm thick. Conidial secession schizolytic.
Culture characteristics – Conidium germinated on PDA within 24 h and a germ tube emerged from one end cell. Colonies reaching 60 mm diam. after one week on PDA at room temperature (25–28 °C), circular, flat, with moderate aerial mycelium, velvety, medium dense, non-pigmented, at the upper surface, from reverse yellowish white, and black at the center.
Material examined – Thailand, Chiang Rai Province, Doi Tung National Park, on dead wood of Dalbergia cana (Fabaceae), 26 March 2022, N. Afshari, 4C1T2R2 (MFLU 24-0402); living culture MFLUCC 24-0531.
GenBank numbers – ITS: PQ800234, LSU: PV072592, SSU: PV072618, tef1-α: PX739623.
Known hosts – Erythrina humeana (Crous et al. 2019b), Dalbergia cana (this study).
Known distribution – South Africa (Crous et al. 2019b), Thailand (this study).
Notes – Phylogenetic analyses of ITS, LSU, SSU, tef1-α, and rpb2 support the close affinity of our isolate (MFLUCC 24-0531) to the ex-type of H. erythrinicola (CBS 145569) and the two grouped with 83% ML bootstrap support. Our isolate shares similar characteristics, such as length of conidiogenous cells, shape, and colour of conidia with H. erythrinicola (CBS 145569) isolated from leaves of Erythrina humeana (Fabaceae) in South Africa (Crous et al. 2019b). However, our collection has shorter conidiophores (290–700 × 6.5–13 μm vs. 500–1200 × 6–10 μm) and larger conidia (93–172 × 8–18 μm vs. (70–)80–90(–110) × (9–)10–11(–12) μm) than those of the holotype (Crous et al. 2019b). Based on morphological and molecular evidence, our new collection represents the first report of H. erythrinicola on Dalbergia cana from Thailand, identifying it as a new host and geographical record.
Figure 1 – Phylogram by maximum-likelihood (ML) method generated using IQ-TREE analysis based on the combined ITS, LSU, SSU, tef1-α, and rpb2 sequence data of Corynesporaceae, Massarinaceae, and Periconiaceae. Tree topology of the maximum likelihood analysis is similar to the Bayesian analysis. Seventy-eight strains are included in the combined analyses, which comprised 4,987 characters (ITS = 581, LSU = 867, SSU = 1,068, tef1-α = 1,358, and rpb2 = 1,113). The best score for log-likelihood of consensus tree is -33915.831. The matrix had 2,011 distinct alignment 4843 patterns, 1,433 parsimony-informative, 253 singleton sites, 3,300 constant sites. Selecting individual models TIM2e+I+G4, TIM2e+I+G4, K2P+I, TN+F+I+G4, and TN+F+I+G4 were applied to ITS, LSU, SSU, tef1-α, and rpb2 using BIC. In the Bayesian analysis, average standard deviation of split frequencies at the end of 10,000,000 MCMC generations was calculated as 0.014442. Bootstrap support values for ML greater than or equal to 80% and Bayesian posterior probabilities greater than or equal to 0.95 are given above the nodes. The strain codes are noted after the species names. The tree is rooted with Cyclothyriella rubronotata (CBS 121892 and CBS 141486). Ex-type strains are in bold. The isolates generated in this study are indicated in bold and blue.
Figure 2 – Helminthosporium chiangraiense (MFLU 24-0401, a new host record). a–c Colonies on Afzelia xylocarpa woody litter. d–f Conidiophores with conidiogenous cells. g, h Apical conidiophores and conidiogenesis. i–r Conidia. s A germinated conidium. t Colonies on PDA (front and reverse). Scale bars: a = 500 μm, b = 200 μm, c–f = 100 μm, g, h, k–s = 50 μm, i, j = 20 μm.