Sirococcus mengyinensis Ning Jiang

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Sirococcus mengyinensis (Shi Wang, Zhao X. Zhang, X. Y. Liu & X. G. Zhang) Ning Jiang, in Jiang, Wijayawardene, Xue & Li, IMA Fungus 17: 14 (2026) Fig. 5 Distribution. China (Shandong Province). New geographical record. Ecology. Isolated from diseased leaves of Castanea mollissima (Fagaceae). Description. Sexual morph not observed. Asexual morph: pycnidial conidiomata aggregated or solitary, erumpent, light-yellow, exuding hyaline conidial masses after 10 d of incubation at 25 ° C in darkness. Conidiophores hyaline, smooth, indistinct, often reduced to conidiogenous cells. Conidiogenous cells phialidic, hyaline, smooth, cylindrical to ampulliform, attenuate towards the apex, 11.4–21.2 × 0.9–1.6 μm. Conidia hyaline, smooth, multi-guttulate, ellipsoid to oblong, straight or slightly curved, base truncate, (5.2 –) 5.4–6.5 (– 7.5) × (2.0 –) 2.1–2.5 (– 2.8) μm, mean ± SD = 5.96 ± 0.54 × 2.30 ± 0.16 μm, n = 34. Culture characteristics. Colonies on PDA at 25 ° C in darkness, attaining 83–85 mm diam. after seven days, spreading, petaloid, greyish-white, with moderate aerial mycelium; margin undulate, circular in outline; reverse concolorous. Additional materials examined. China. • Shandong Province: Taishan District, Shaling Village, 36°02'36"N, 117°01'15"E; ca. 155 m a. s. l., on leaves of Castanea mollissima, 9 October 2024, coll. Y. L. Wang, culture: SAUCC 10843. Notes. Multilocus phylogenetic analysis based on the combined ITS, tef 1, and tub 2 dataset shows that the strain obtained in this study (SAUCC 10843) clusters with Sirococcus mengyinensis with high statistical support (MLBS = 100 %, BIPP = 1.00) (Fig. 1). Pairwise sequence comparisons reveal only minor intraspecific nucleotide differences: 0 % divergence in the ITS region, 2.86 % (18 / 629) in tef 1, and 0.45 % (2 / 442) in tub 2, all of which are well below the interspecific variation thresholds reported for Sirococcus (≥ 1 % for ITS, ≥ 3 % for tef 1, ≥ 1 % for tub 2). Morphologically, the conidial dimensions of the strain in this study (SAUCC 10843; (5.2 –) 5.4–6.5 (– 7.5) × (2.0 –) 2.1–2.5 (– 2.8) μm) overlap substantially with those of the ex-type strain SAUCC MY 0293 (4.5–6.5 × 1.8–2.8 μm), and no stable morphological differences were observed in colony characteristics or conidiogenous cell morphology. Sirococcus mengyinensis was previously known only from Mengyin, Shandong Province. This study provides the first record of S. mengyinensis in Tai’an City, extending its known distribution range approximately 110 km northwestward within Shandong Province. Notably, S. mengyinensis was isolated from symptomatic chestnut (Castanea mollissima) leaves both in this study and in Wang et al. (2022), suggesting that this species is associated with chestnut leaf lesions. However, its precise pathogenic potential and ecological niche remain to be further elucidated. Based on the congruent results of morphological observations and multilocus phylogenetic analysis, we report Sirococcus mengyinensis as a new geographical record for Tai’an City, Shandong Province, China.