Cytospora longdensis J. Q. Li & L. L. Huang, 2025

Li, Jieqiong, Li, Canting, Wang, Ganlin, Zhu, Liangliang & Huang, Lili, 2025, Cytospora longdensis sp. nov. and C. sinensis (Diaporthales, Valsaceae) associated with Populus alba subsp. pyramidalis canker and dieback in China, MycoKeys 118, pp. 345-359 : 345-359

Cytospora longdensis J. Q. Li & L. L. Huang sp. nov.

Fig. 2

Etymology.

Named after the locality, Longde County, Guyuan City, where the fungus was first collected.

Typification.

China • Ningxia Hui Autonomous Region, Guyuan City, Longde County, Shatang Town , 35°35'12.5"N, 106°7'7.4"E, on cankered and diebacked branches of Populus alba subsp. pyramidalis , 30 July 2022, J. Q. Li & L. L. Huang (holotype: NWAFU H 116 , ex-holotype culture: D 116) .

Description.

Sexual morph: not observed. Asexual morph: Conidiomata immersed or semi-immersed in bark, discoid, with multiple locules. Conceptacle absent. Ectostromatic disc greenish black to black, circular to ovoid, (296 –) 351–508 (– 603) μm in diameter, with one ostiole per disc. Ostiole black, circular to ovoid, (42 –) 52–87 (– 105) μm in diameter. Locules numerous, subdivided by invaginations with common walls. Conidiophores hyaline, thin-walled, unbranched, or occasionally branched at the bases, 15.1–26.3 × 1.0–2.1 μm (av. = 18.9 ± 2.9 × 1.4 ± 0.3 μm, n = 30). Conidiogenous cells enteroblastic, phialidic, subcylindrical to cylindrical. Conidia hyaline, smooth, allantoid, aseptate, 4.2–5.7 × 1.6–2.2 μm (av. = 5.0 ± 0.4 × 1.8 ± 0.2 μm, n = 50).

Culture characteristics.

Colonies at 25 ° C on PDA are initially white, flat, reaching 4.7 cm in diameter after three days, becoming buff, and fully covering the 9.0 cm Petri dish after seven days.

Additional materials examined.

China • Ningxia Hui Autonomous Region, Guyuan City, Longde County, Shatang Town , 35°35'12.5"N, 106°7'7.4"E, on cankered branches of Populus alba subsp. pyramidalis , 30 July 2022, J. Q. Li & L. L. Huang ( NWAFU H 117 , culture: D 117; NWAFU H 118 , culture: D 118) .

Notes.

Cytospora longdensis is phylogenetically closely related to C. suecica and C. lhasaensis . However, it is distinct from them by producing larger conidia, i. e., 4.2–5.7 × 1.6–2.2 μm in C. longdensis vs. 0.5–2 × 0.5–1 μm in C. suecica and 3.5–5 × 1–1.5 μm in C. lhasaensis ( Lin et al. 2024) . Additionally, it differs from C. suecica ( CBS 450.51 ) and C. lhasaensis ( CFCC 58706 ) in SNPs for the five gene region sequences ( C. longdensis vs. C. suecica : 23 out of 473 bp in ITS, 28 out of 203 bp in act, 26 out of 644 bp in rpb 2, 70 out of 500 bp in tef 1 - α, and 55 out of 388 bp in tub 2; C. longdensis vs. C. lhasaensis : 17 out of 473 bp in ITS, 19 out of 203 bp in act, 25 out of 644 bp in rpb 2, 75 out of 500 bp in tef 1 - α, and 61 out of 388 bp in tub 2). Additionally, the multi-gene (ITS, act, rpb 2, tef 1 - α, and tub 2) phylogram reveals that C. longdensis represents an independent clade with high support (ML / BI = 100 / 1, Fig. 1 ).

Figures

Figure 1. Phylogenetic tree of Cytospora based on maximum likelihood analysis of a combined DNA sequence dataset of ITS, act, rpb 2, tef 1 - α, and tub 2 genes. Bootstrap values ≥ 50 % (maximum likelihood) and posterior probabilities ≥ 0.5 (Bayesian) are presented at the branches. Values lower than these thresholds are marked with “ * ”, and absent are marked with “ - ”. Type materials are marked with “ T ”. Isolates from this study are highlighted in blue. The tree was rooted to Diaporthe vaccinii (CBS 160.32).

Figure 2. Cytospora longdensis (D 116). A – C. View of conidiomata on branch; D, E. Transverse section through a conidioma; F. Longitudinal section through a conidioma; G. Conidiophores, conidiogenous cells, and conidia; H. Conidia; I. Culture on PDA after five days, front side (left) and back side (right). Scale bars: 500 μm (A); 100 μm (B – F); 5 μm (G, H).