Phaeobotryon laricinum Y. T. Zhu & Y. M. Liang, 2025

Zhu, Yeting, Liang, Yingmei & Peng, Cheng, 2025, New species and records of Phaeobotryon (Botryosphaeriales, Botryosphaeriaceae) from Larix in China, MycoKeys 112, pp. 1-15 : 1-15

Phaeobotryon laricinum Y. T. Zhu & Y. M. Liang sp. nov.

Fig. 2

Etymology.

Named after the host genus on which it was collected, Larix .

Descriptions.

Sexual morph: Not observed. Asexual morph: Conidiomata pycnidial, scattered, immersed, or semi-immersed to erumpent from bark surface, globose to ovoid, unilocular, 365–820 µm diam. Disc black, 215–360 µm in diam. Ostioles single, central, 35–75 µm. Conidiophores reduced to conidiogenous cells. Paraphyses present, hyaline, thin-walled, arising from the conidiogenous layer, extending above the level of developing conidia, tip rounded, aseptate, up to 60.5 × 2.5 µm. Conidiogenous cells hyaline, smooth, thin-walled, holoblastic, cylindrical, phialidic, proliferating internally with visible periclinal thickening, 11.0–41.0 × 1.0–3.5 µm. Conidia initially hyaline, becoming brown with age, dark brown, aseptate, smooth with granular contents, guttulate, thick-walled, oblong to cylindrical, straight, both ends broadly rounded, 27.5–37.0 × 10.0–18.0 µm (av. ± S. D. = 32.2 ± 2.08 × 14.01 ± 1.77 µm), L / W = 2.3 ± 0.3.

Culture characteristics.

Colonies on PDA flat, spreading, with flocculent mycelium and uneven edges, initially white, gradually turning greenish-grey from center, finally becoming black, covering 40–50 mm after 7 days at 25 ° C.

Materials examined.

China • Jilin Province, Yanbian Korean Autonomous Prefecture, Yanji City, Maoershan National Forest (42°51'12.96"N, 129°28'24.06"E), alt. 297 m, on branches of Larix olgensis , 7, Sept, 2022, C. Peng, X. Y. Zhang (holotype BJFC -S 2370 , ex-holotype culture CFCC 70805 ; isotype BJFC -2371 , ex-isotype culture CFCC 70806 ) ; China • Heilongjiang Province, Greater Khingan Mountains, Tahe County, Qixiashan Mountains (52°20'32.96"N, 124°41'48.27"E), alt. 456 m, on branches of Larix gmelinii , 10, Sept, 2021, R. Wang, W. T. Yu ( BJFC -S 2369 , living culture CFCC 70804 ) .

Notes.

Phaeobotryon currently comprises 13 species, all of which have reported asexual morphs except for P. cercidis ( Phillips et al. 2005, 2008; Abdollahzadeh et al. 2009; Fan et al. 2015; Daranagama et al. 2016; Zhu et al. 2018; Pan et al. 2019; Wijayawardene et al. 2021; Zhang et al. 2021; Lin et al. 2023; Peng et al. 2023; Wu et al. 2024). However, P. cercidis has been reported on Cercis canadensis in the USA ( Phillips et al. 2008), revealing differences from P. laricinum in terms of both geographic region ( China) and host ( Larix ). The new species can be distinguished from other known species based on conidial characteristics (Table 3 ). Specifically, P. laricinum conidia are aseptate and can be differentiated from other species in the genus, except for P. negundinis , P. quercicola , and P. spiraeae . Furthermore, they can be distinguished by conidial color (dark brown) from P. quercicola (hyaline). Additionally, the conidial size of P. laricinum (27.5–37 × 10–18 μm) is significantly larger than that of both P. negundinis (16–24.5 × 7.9–11.5 μm) and P. spiraeae (21–28.5 × 8.5–13.5 μm). Moreover, P. laricinum (L / W = 2.3 ± 0.3) can be distinguished by its larger conidial L / W ratio when compared to the new species P. longiparaphysium (L / W = 1.7 ± 0.2) (Table 3 ). Phylogenetically, P. laricinum is distinct from other Phaeobotryon species, which are grouped within a separate clade that receives high support (MP / ML / BI = 100 / 100 / 1) (Fig. 1 ). Therefore, P. laricinum is introduced as a novel species.

Figures

Figure 1. Phylogenetic tree inferred from ML analysis based on combined ITS, LSU, and tef 1 - α sequence data of Phaeobotryon isolates. The tree was rooted in Lasiodiplodia theobromae (CBS 164.96). The MP, ML (≥ 50 %), and BI (≥ 0.9) bootstrap values are given at nodes (MP / ML / BI). Isolates from this study are marked in blue, ex-type strains are marked in bold, and new species are in a colored font.

Figure 2. Phaeobotryon laricinum (BJFC - S 2370) A habit of conidiomata on twig B, D longitudinal section through a conidioma C, E transverse section of a conidioma F – K conidiogenous cells and conidia L conidia M colony on PDA after 14 days. Scale bars: 500 µm (A – C); 50 µm (D, E); 10 µm (F – L);