Curvularia chiangraiensis Yasanthika & A.R. Gomes de Farias, 2023

Erandi Yasanthika, W. A., Tennakoon, Danushka S., Gomes De Farias, Antonio R., Thilini Chethana, K. W., Bhat, D. Jayarama & Wanasinghe, Dhanushka N., 2023, Isolation and characterization of novel Dothideomycetes species from forest soils in Chiang Rai and Krabi (Thailand): additions to the diversity of Curvularia and Verruconis, Phytotaxa 609 (1), pp. 17-44 : 30

Curvularia chiangraiensis Yasanthika & A.R. Gomes de Farias , sp. nov.

Index Fungorum number: IF559984, Faces of Fungi number: FoF 12886, FIGURE 3 .

Etymology—The specific epithet “chiangraiensis” refers to the locality Chiang Rai Province ( Thailand), where the holotype was collected.

Holotype — MFLU 22-0256

Asexual morph: Conidiophores 50–150 × 2–7 μm (x = 117 × 4 μm, n = 20), simple, unbranched, septate, hyaline to brown, micro- to semi-macro-nematous, sometimes geniculate towards upper region. Conidiogenous cells 7–11 × 3–7 (x = 9 × 5 μm, n = 20), polytretic, terminal or intercalary, sometimes proliferating sympodially, cylindrical to sub-cylindrical, smooth to verruculose. Conidia 12–20 × 6–12 μm (x = 17 × 9 μm, n = 30), sublunate to ellipsoid or obovoid, curved, sub-hyaline to pale brown, 1–2 distoseptate when immature, later becoming 2–3 euseptate and pale brown to brown when mature, smooth to verruculose, swollen when mature, with the third cell from base becoming prominent, partially enlarged along the horizontal axis, asymmetrically curved, darker, verrculose than apical and basal septa, with apical and basal septa symmetrical. Hila inconspicuous to slightly conspicuous, slightly thickened 2–3 μm (x = 2.5 μm) wide. Sexual morph: Undetermined.

Culture characteristics:— Colonies on PDA at 25 ℃ raised, filamentous at margin, with sparse aerial mycelia, greyish brown to black, pale brown concentric rings, approximately 3.5 cm diam. at 7 days, reverse black. Hyphae 3–5 μm (x = 4 μm) wide, branched, septate, hyaline to pale brown when immature and later becoming brown, septate hyphae.

Material examined:— Thailand, Chiang Rai, 20.0478N, 99.7619E, 863m, from forest soil, 23 September 2019. W.A.E. Yasanthika ( MFLU 22-0256 , holotype); ex-type living culture MFLUCC 22-0091 )

Notes—In this study, we introduce C. chiangraiensis (MFLU 22-0256) as a novel species isolated from soil in Thailand based on both morphology and phylogeny. Multigene phylogeny indicates that C. chiangraiensis (MFLUCC 22-0091) forms an independent lineage sister to the clade comprising C. brachyspora (CBS 186.50) and C. simmonsii (USJCC-0002) with 77% ML and 0.98 BYPP statistical support ( FIGURE 1 ). The pairwise comparision of ITS, GAPDH and tef 1-α sequences of C. chiangraiensis with closely related species are shown in ( TABLE 4 )

Morphologically, C. chiangraiensis bears relatively smaller conidia. The conidial length-width ratio in C. chiangraiensis is 1.7, while C. brachyspora and C. simmonsii show 1.9 and 2.6, respectively. Curvularia simmonsii (21–27μm) and C. brachyspora (20–26 μm) shows distinct morphology in having longer conidia ( Ferdinandez et al. 2021) than C. chiangraiensis (12–20 μm). In addition, C. chiangraiensis can be distinguished by its relatively shorter conidial lengths (12–20 μm) than C. aeria (18–26 μm) and C. homomorpha (25–42 μm) ( Luttrell et al. 1959, Sivanesan 1987, Almaguer et al. 2013, Tan et al. 2014, Ferdinandez et al. 2021). In C. chiangraiensis , conidial curvature is prominent due to the third cell from base being partially enlarged along the horizontal axis and asymmetrically curved with symmetrical apical and basal septa. In contrast, in C. brachyspora both central cells are approximately the same size. Furthermore, conidia of C. aeria and C. simmonsii show slight curvature ( Madrid et al. 2014, Kusai et al. 2016, Ferdinandez et al. 2021). Curvularia homomorpha has straight conidia in contrast to the curved conidia in C. chiangraiensis ( Sivanesan 1987, Tan et al. 2014). Conidiogenesis in C. chiangraiensis exhibits sympodial proliferation, which is absent in C. brachyspora and C. simmonsii ( Sivanesan 1987, Ferdinandez et al. 2021). Therefore, based on both morphology and phylogenetic evidence, we introduce our species as C. chiangraiensis MFLUCC 22-0091) isolated from forest soil in Thailand.

Figures

FIGURE 1.Maximum likelihood phylogenetic tree generated of the combinedITS-GAPDH-tef1-α sequence data forCurvularia. Bootstrap support values of maximum likelihood greater than 60% and Bayesian posterior probabilities (BYPP) greater than 0.95 are indicated above the nodes. Newly added strains are in blue and ex-type strains are in bold. The tree is rooted to Bipolaris maydis (CBS13629P) and B. panici-miliacei (CBS 19929). Isolated substrates/ habitat is indicated in triangles. Black: Human/ animal, green: plants, brown: soil, pink: air, blue: aquatic habitat. unknown:empty

FIGURE 3. Curvularia chiangraiensis (MFLU22-0256, holotype). a. Colony from above (on PDA). b. Colony from below (on PDA). c. Sporulated colony with conidial attachments on the mycelium. d. Immature hyphae. e. Mature melanized hyphae. f–k. conidiogenesis. l–p. Conidia. Scale bars: g = 25 μm, d–f, h–l = 20 μm, g, m–p= 10 μm.