Neocucurbitaria subribicola R. Xu, W.X. Su, Phukhams. & Y. Li

Xu, Rong, Su, Wenxin, Li, Yu, Li, Xiao & Li, Changtian, 2024, Multiple evidence reveals a new species of Neocucurbitaria (Cucurbitariaceae, Pleosporales) from China, Phytotaxa 650 (3), pp. 249-261 : 254-255

Neocucurbitaria subribicola R. Xu, W.X. Su, Phukhams. & Y. Li , sp. nov. ( Fig. 2 )

MycoBank number MB852895

Etymology: —referring to the affinity to Neocucurbitaria ribicola

Holotype: —HMJAU 64823

Saprobic on dead stems of Xanthoceras sorbifolium . Sexual morph: Undetermined. Asexual morph: Stromata multiloculate, with 1–5 locules forming groups, immersed or semi-immersed. Conidiomata 128–147 × 96–110 μm (x = 139 × 103 μm, n = 6), aggregated, multiple aggregates together to form groups , pycnidia, globular to subglobular, coriaceous, without distinguishable ostioles. Pycnidial wall 7–17 μm wide, composed of 3–11 layers of thin-walled cells of textura angularis, dark brown outside, gradually light to brown inside, subhyaline under the inner layer, and bearing conidiogenous cells in the lining. Conidiophores reduced to conidiogenous cells. Conidiogenous cells 8–15 × 1–3 μm (x = 11 × 2 μm, n = 30), flattened near the spherical upper end, arising from the inner layer of conidioma, smooth-walled, hyaline. Conidia 3–5 × 1–2 μm (x = 3 × 1.5 μm, n = 50), oval to spherical, hyaline, aseptate, smooth, with a minute guttule.

Cultural characters:— Colonies on PDA reaching 22–29 mm diam at 25 °C after two weeks, from above, circular, dense, convex, rough, celadon, olive green at the irregular margins; reverse greyish-green to dark green, with concentric circles and obvious cracks.

Material examined: — CHINA. Jilin Province: Siping, on dead stems of Xanthoceras sorbifolium Bunge ( Sapindaceae ), 11 August 2021, Rong Xu and Wenxin Su, HMJAU 64823 (holotype), ex-type living culture, CCMJ 13055 ; isotype = HMJAU 64824 ; ex-isotype living culture, CCMJ 13056 .

Notes: —Morphologically, the conidiomata of Neocucurbitaria subribicola are larger than those of N. ribicola (139 × 103 μm vs. 70–100 μm) on natural hosts ( Jaklitsch et al. 2018). The conidia of N. subribicola are oval to spherical, while N. rhamni and N. ribicola have oblong to ellipsoid or drop-like conidia ( Jaklitsch et al. 2018). Additionally, the conidiogenous cells of N. subribicola are solitary and cylindrical, while the conidiogenous cells of N. rhamnicola and N. rhamnioides are lageniform, basally inflated, arranged in dense clusters, and lageniform to cylindrical and straight or curved, respectively ( Jaklitsch et al. 2018).

In the BLASTn search, the ITS sequence of N. subribicola was 97.37% similar to N. vachelliae (CBS 142397, Vachellia gummifera ) with 98% query cover which translates to 95.42% similarity, and LSU sequence showed 95.67% similarity with N. keratinophila (CBS 121759, human corneal scrapings). The rpb 2 gene region showed 87.48% similarity to N. acerina (C255) with 94% query cover, while tef 1- α and tub 2 showed lower query coverage and similarity. In the phylogenetic analysis, Neocucurbitaria subribicola formed a distinct lineage to N. rhami , N. rhamnioides and N. ribicola ( Fig. 1 ). Therefore, to accommodate this taxon, a new species is described, and this is the first report of a Neocucurbitaria species on X. sorbifolium

Figures

FIGURE 1. Phylogram of Neocucurbitaria based on ITS, LSU, rpb2, tef1-α and tub2 genes.Maximum likelihood bootstrap support values ≥ 70% (ML) and Bayesian posterior probabilities ≥ 0.9 (BPP) are given at the nodes as ML/BPP. The tree is rooted with Cucurbitaria berberidis (CBS 142401) and C. oromediterranea (CBS 142399). The type strains are in bold and marked with T. The new isolates are indicated in bold blue.

FIGURE 2. Neocucurbitaria subribicola (HMJAU 64823, holotype). a–b. Appearance of conidiomata on host substrate. c–d. Vertical section of conidiomata. e. Section of conidioma wall. f–h. Conidiogenous cells. i. Conidia. j. Culture characteristics on PDA. Scale bars: b = 200 μm, c–d = 100 μm, e–h = 10 μm, i = 5 μm.