Comoclathris xanthoceratis R. Xu, Phukhams. & Y. Li, 2024

Xu, Rong, Su, Wenxin, Wang, Yang, Tian, Shangqing, Li, Yu & Phukhamsakda, Chayanard, 2024, Morphological characteristics and phylogenetic evidence reveal two new species and the first report of Comoclathris (Pleosporaceae, Pleosporales) on dicotyledonous plants from China, MycoKeys 101, pp. 95-112 : 95

Comoclathris xanthoceratis R. Xu, Phukhams. & Y. Li sp. nov.

Fig. 3

Etymology.

Refers to the host genus, Xanthoceras .

Description.

Saprobic on dried stems of Xanthoceras sorbifolium . Sexual morph: Ascomata solitary, scattered or aggregated in small groups, 147-221 × 114-130 μm (x - = 187-124 μm, n = 5), immersed to semi-immersed, subglobose, black, elongated, covered with dark brown setae, without a distinct ostiole. Peridium 13-20 μm wide at the base, 20-32 μm wide at the sides, comprising thick-walled cells of textura angularis, dark brown to black; inner layer composed of thin-walled cells of textura angularis, hyaline. Hamathecium comprising 1.5-4.0 μm wide, septate, filiform, embedded in a gelatinous matrix, rarely branched pseudoparaphyses, extending above the asci. Asci 8-spored, bitunicate, fissitunicate, 99-165 × 36-48 μm (x - = 127 × 42 μm, n = 20), clavate, short pedicellate, apically rounded, with an ocular chamber. Ascospores 23-42 × 9-19 μm (x - = 37 × 16 μm, n = 40), 1-2-seriate, muriform, broadly fusiform, with 3 transverse septa and a vertical septum in second and third cells, brown to dark brown, with obtuse ends, smooth-walled, surrounded by a thick mucilaginous sheath. Asexual morph: Undetermined.

Culture characteristics.

Colonies on PDA reaching 30 mm diam. after three weeks at 25 °C. Cultures from above, dense, round, umbonate, wrinkled and folded, papillate with white aerial mycelium, radial edge, orange at the margin; reverse reddish, white mycelium present at the margin.

Material examined.

China. Jilin Province, Changchun, on dead stem of Xanthoceras sorbifolium Bunge ( Sapindaceae ), 2 July 2022, Rong Xu, XR 71, HMJAU 64846 (holotype); ex-type, CCMJ 13078; MFLU 23-0385 (isotype), ex-isotype, CCMJ 13079 .

Notes.

Comoclathris xanthoceratis (CCMJ 13078 and CCMJ 13079) is closely related to C. clematidis (CCMJ 13076 and CCMJ 13077) (100% ML and 1.00 BPP). The two species are phylogenetically closely related to C. arrhenatheri (MFLUCC 15-0465). However, there are distinct differences in morphology ( Thambugala et al. 2017). The asci of C. arrhenatheri are smaller than C. clematidis and C. xanthoceratis ( C. arrhenatheri vs. C. clematidis vs. C. xanthoceratis : 70-95 × 18.5-25 vs. 114-174 × 27-43 vs. 99-165 × 36-48 μm, respectively). Comoclathris arrhenatheri have ascospores with 4 transverse septa and 2-3 vertical septa, while C. clematidis and C. xanthoceratis only have 3 transverse septa and 2 vertical septa. Additionally, the ascospores of C. arrhenatheri are shorter than C. clematidis and C. xanthoceratis ( C. arrhenatheri vs. C. clematidis vs. C. xanthoceratis : 16.5-22 × 7.7-10.2 vs. 22-39 × 8-21 vs. 23-42 × 9-19 µm).

A pairwise comparison of the ITS region between C. xanthoceratis and C. arrhenatheri demonstrated 8.95% (46/514, no gaps) base-pairs difference, while there were 74 base-pair difference in the rpb 2 gene (10.2%, no gaps). Hence, C. xanthoceratis is introduced as a new species, based on morphological and nucleotide differences. This is also the first report of Comoclathris species found on Xanthoceras sorbifolium .

Figures

Figure 3. Comoclathris xanthoceratis (HMJAU 64846, holotype) A-C appearance of ascomata on host substrate D vertical section of ascoma E peridium F pseudoparaphyses G-J asci (H, I) asci production from the sterile condition) K-Q ascospores R culture characteristics on PDA after three weeks at 25 ° C (black dots indicate the sexual reproduction in culture condition). Scale bars: 200 µm (C); 50 µm (D); 20 µm (G-J); 10 µm (E, K-Q); 5 µm (F).