Nigrograna lincangensis R.F. Xu & Tibpromma, 2024

Xu, Rui-Fang, Karunarathna, Samantha C., Phukhamsakda, Chayanard, Dai, Dong-Qin, Elgorban, Abdallah M., Suwannarach, Nakarin, Kumla, Jaturong, Wang, Xiao-Yan & Tibpromma, Saowaluck, 2024, Four new species of Dothideomycetes (Ascomycota) from Para Rubber (Hevea brasiliensis) in Yunnan Province, China, MycoKeys 103, pp. 71-95 : 71

Nigrograna lincangensis R.F. Xu & Tibpromma sp. nov.

Fig. 4

Etymology.

The name refers to the location "Lincang, Yunnan, China", where the holotype was collected.

Holotype.

ZHKU 23-0104.

Description.

Saprobic on a dead branch of Hevea brasiliensis . Sexual morph: Ascomata 285-360 μm high, 230-307 μm diam. (x‾ = 337 × 272 μm, n = 5), immersed, under the clypeus, sometimes inconspicuous on host surface and small bumps can be seen, solitary, dark brown, globose or ellipsoid, with papilla. Ostioles 117-217 × 68-124 μm (x‾ = 152 × 99 μm, n = 10), central, brown, papillate. Peridium 16-45 μm wide, comprising several layers with dark-brown to dark cells of textura angularis. Hamathecium comprises 1.5-3 μm wide, unbranched, septate, hyaline, pseudoparaphyses. Asci 45-70 × 9-12 μm (x‾ = 57 × 10 μm, n = 10), 8-spored, bitunicate, pedicellate, club shape, cylindrical to clavate, straight or slightly curved, apically rounded, thick-walled. Ascospores 10-15 × 4-6 μm (x‾ = 13 × 4.8 μm, n = 30), 1-2-seriate, initially 1-septate, becoming 3-septate at the maturity, fusoid to narrowly ellipsoid, upper part or second cell slightly wider and tapering towards narrow ends, constricted at the septa, hyaline to yellow-brown to brown with age, guttulate, think-walled. Asexual morph: Undetermined.

Culture characteristics.

Spores germinated within 12 hours, colonies grow on PDA at 28 °C, circular, floppy, entire edge, raised, grey to taupe, reverse dark brown.

Material examined.

China, Yunnan Province, Lincang , on a dead branch of Hevea brasiliensis , 28 July 2022, Rui-Fang Xu, LCR06, (ZHKU 23-0104, holotype); ex-type ZHKUCC 23-0798, ZHKUCC 23-0799 .

GenBank numbers.

ZHKUCC 23-0798 = ITS: OR853099, LSU: OR922323, SSU: OR941079, tef 1-α: OR966282, rpb 2: OR966280; ZHKUCC 23-0799 = ITS: OR853100, LSU: OR922324, SSU: OR941080, tef1-α: OR966283, rpb 2: OR966281.

Notes.

In the phylogenetic analyses, Nigrograna lincangensis (ZHKUCC 23-0798) forms a closely-related clade to N. asexualis (ZHKUCC 22-0214), N. aquilariae (ZHKUCC 23-0070) and N. verniciae with 100% ML and 1.00 PP support (Fig. 3 ). However, we could not compare the morphological characteristics of N. lincangensis and N. asexualis , because N. lincangensis was described only from its sexual morph in nature, while N. asexualis was described by its asexual morph in nature from coffee in China. A comparison of the ITS region of N. lincangensis and N. asexualis revealed 16 base pair differences (3.46%) across 462 nucleotides, 40 base pair differences (4.21%) across 949 nucleotides in tef 1-α gene, 124 base pair differences (12%) across 1033 nucleotides in rpb 2 gene. Nigrograna aquilariae and N. verniciae have very similar morphological characteristics, but they can be differentiated by having wider ascomata (285-360 μm vs. 180-270 μm), larger asci (45-70 × 9-12 μm vs. 49-57 × 7-9 μm) and larger ascospores (10-15 × 4-6 μm vs. 10-13 × 3.5-4.5 µm) in N. lincangensis ( Du et al. 2024); while N. verniciae has larger ascomata (340-360 × 350-370 μm vs. 85-360 μm × 230-307 μm) and asci with knob-like to furcate pedicels ( Li et al. 2023).

Nigrograna lincangensis has similar ascomata, asci and ascospore characteristics similar to other Nigrograna species ( Jaklitsch and Voglmayr 2016; Hyde et al. 2017; Tibpromma et al. 2017; Dayarathne et al. 2020; Mapook et al. 2020; Lu et al. 2022). However, N. lincangensis differs from N. cangshanensis by having larger ascomata (285-360 × 230-307 μm vs. 120-135 × 135-155 μm) ( Tibpromma et al. 2017). Nigrograna chromolaenae can be distinguished from N. lincangensis in having smaller ascomata (160-280 × 115-130 μm vs. 285-360 × 230-307 μm), smaller asci (40-55 × 7-10 μm vs. 45-70 × 9-12 μm), and greyish-brown to dark brown ascospores ( Mapook et al. 2020). Nigrograna coffeae differs from N. cangshanensis by having smaller ascomata (90-140 × 140-200 μm vs. 285-360 × 230-307 μm), 1-septate ascospores ( Lu et al. 2022). Nigrograna novergica differs from N. lincangensis as it occurs on pseudostromata from the host of Diaporthe sp. ( Jaklitsch and Voglmayr 2016). Nigrograna mycophila and N. obliqua are distinct from N. lincangensis by having dark brown ascospores ( Jaklitsch and Voglmayr 2016). Nigrograna puerensis differs from N. lincangensis by having acute apical and basal cells and the apical cells are wider than the basal cells ( Lu et al. 2022). Nigrograna samueliana differs from N. lincangensis by the absence of ostiole ( Dayarathne et al. 2020). Nigrograna thymi can be easily distinguished from N. lincangensis in having 4-5 septate ( Hyde et al. 2017). Therefore, N. lincangensis is described here as a new species, based on phylogeny and morphology.

Figures

Figure 3. Phylogram generated from Maximum Likelihood analysis based on combined LSU, ITS, SSU, tef 1 - α and rpb 2 sequence data of 119 taxa, which comprised 4399 base pairs (LSU = 908 bp, ITS = 512 bp, SSU = 1000 bp, tef 1 - α = 925 bp, rpb 2 = 1054 bp). The best scoring RAxML tree with a final likelihood value of - 38918.764563 is presented. The matrix had 2023 distinct alignment patterns, with 39.00 % of undetermined characters or gaps. Estimated base frequencies were as follows: A = 0.245191, C = 0.247520, G = 0.268228, T = 0.239061; substitution rates: AC = 1.533778, AG = 3.877174, AT = 1.672983, CG = 1.254032, CT = 8.838860, GT = 1.000000; gamma distribution shape parameter α = 0.208600. Bootstrap support values for ML equal to or greater than 60 % and Bayesian Inference analysis values equal to or greater than 0.90 PP are labelled at each node. The tree is rooted with Seriascoma didymospora (MFLUCC 11 - 0179) and S. didymospora (MFLUCC 11 - 0194). Related sequences were obtained from De Silva et al. (2022), Lu et al. (2022) and Li et al. (2023). The new isolates are indicated in red and the ex-type strains are in bold.

Figure 4. Nigrograna lincangensis (ZHKU 23 - 0104, holotype) a-c appearance of ascomata on the host surface d vertical section of an ascoma e vertical section of ostiole f hamathecium and asci g section of peridium h-k asci l ascospores m a germinated ascospore n, o colonies on PDA (n-front and o-reverse views). Scale bars: 100 µm (d); 50 µm (e); 30 µm (f); 200 µm (g); 10 µm (h-k); 5 µm (l); 20 µm (m).