Irenopsis crotonicola X.Y. Zeng, T.C. Wen & K.D. Hyde, sp. nov., MycoBank: MB 819817
Etymology: Referring to the host genus Croton.
Epiphytes on the surface of living leaves. Colonies epiphyllous, subdense to dense, confluent, black. Hyphae superficial, brown, straight, radiating outwardly, branched, septate, darker at septa, reticulate, without hyphal setae. Appressoria two-celled, brown, spathulate, form near the septa, alternate, antrorse, 12–22 × 10–14 μm (x̅ = 15 × 12 μm, n = 20). Sexual morph Ascomata up to 160 μm diam., superficial, subdense, globose to subglobose, thick-walled, with ostiole and ascomata setae. Ascomata setae dark brown, straight, blunt, up to 100 μm long, verrucose at the apex. Peridium comprising two strata, outer strata of cells with dark brown walls of textura angularis and hyaline inner strata. Hamathecium with evanescent paraphyses. Asci unitunicate, 2–3-spored, ovoid at young state, with short pedicel, asci wall attenuated or broken when mature, without a fixed shape. Ascospores 2–3-seriate, cylindrical or oblong, hyaline when young, becoming dark brown when mature, 4-septate, constricted and darker at the septa, rounded at both ends, apical cell sometimes tapering at the tip, smooth-walled, 38–42 × 15–17 μm (x̅ = 39 × 16 μm, n = 20). Asexual morph Phialides opposite, ampulliform, forming two at top of hyphal cell separate from appressoria, 15–19(−22) × 7–9 μm (x̅ = 18 × 8 μm, n = 10). Conidia not observed.
Material examined: THAILAND, Chiang Rai, Mae Fah Luang University, on living leaves of Croton persimilis (Euphorbiaceae), 3 Feb. 2014, Xiang-Yu Zeng (MFLU 14-0078, holotype). Sequence GenBank accession numbers: SSU KY554796; ITS-LSU KY554798; TEF KY554790; β-tubulin KY554792; GPDH KY554794.
Notes: This new species was found on Croton persimilis and is recognized as a species of Irenopsis based on its branched, dark brown, superficial hyphae with phialides and two-celled appressoria; dark brown, superficial ascomata with setae, and dark brown, 4-septate ascospores. Irenopsis crotonis is the only Irenopsis species previously reported from Croton(Zeng et al. 2017), and it has hooked setae and amphigenous, thin colonies. The new collection has larger ascomata and ascospores, straight setae and epiphyllous, subdense colonies. Phylogenetic analyses indicate that the new collection clusters within the clade that represents the genus Irenopsis, and, together with I. walsurae, forms a distinct subclade. It is 92% (1417/1538 nucleotides, 26/1538 gaps) similar to the ITS-LSU sequence of I. walsurae. Morphologically, the new collection differs from I. walsurae in having subdense colony and ascomata, shorter ascomata setae, and longer ascospores.
Fig. Irenopsis crotonicola MFLU 14-0078 (holotype). a Colony on surface of leaf. b, c Ascomata on host substrate. d Hyphae with capitate appressoria. e Hypha with phialides. f Ascomata seta. g–n Asci from young to mature state. o Ascospore.
Fig. Phylogram showing the phylogenetic relationships within the order Meliolales based on LSU sequence data. Maximum parsimony/likelihood bootstrap support values greater than 50% and Bayesian posterior probabilities greater than 0.90 are shown above and below the branches. New data generated in this study are in bold and branches with strong support are shown in bold. The tree is rooted with Chaetosphaeria innumeraSMH 2748 (Chaetosphaeriaceae, Chaetosphaeriales). TreeBASE no.: 21674