Pseudoplagiostoma neocastanopsidis Ning Jiang 2025, sp. nov.

Pseudoplagiostoma neocastanopsidis Ning Jiang sp. nov. Fig. 5 Etymology. Name refers to its closest relative, Pseudoplagiostoma castanopsidis. Diagnosis. Distinct from its phylogenetically related species of Ps. castanopsidis and Ps. jasmini by wider conidiogenous cells. Typus. CHINA • Hainan Province, Changjiang Li Autonomous County, Bawangling National Forest Park, on diseased leaves of Castanopsis carlesii, 30 March 2019, Yong Li (holotype CAF 800037; ex-type culture CFCC 54447). Description. Conidiomata pycnidial, solitary, erumpent, globose to pulvinate, brown, 300–700 μm diam., exuding an orange conidial mass. Conidiophores indistinct, often reduced to conidiogenous cells. Conidiogenous cells hyaline, smooth, lageniform to ampulliform, attenuate towards the apex, phialidic, 11.5–22 × 3.5–6.5 μm. Conidia holoblastic, aseptate, hyaline, smooth, thick-walled, multi-guttulate, ellipsoid, oblong-cylindrical, slightly constricted at the middle, slightly curved, base tapering to a flat protruding scar, (18.5 –) 19–22 (– 24) × (8.5 –) 9–10 (– 10.5) μm (n = 50), L / W = 1.8–2.7, with a prominent hilum. Culture characteristics. Colonies on PDA flat, spreading, with abundant aerial mycelia and even margin, forming pale luteous center area, white middle area and smoke grey outer area, fast growing, reaching 90 mm diam. after 1 week at 25 ° C, forming brown conidiomata with orange conidial masses. Colonies on MEA flat, spreading, with flocculent aerial mycelia and undulating margin, white to saffron, fast growing, reaching 90 mm diam. after 1 week at 25 ° C, sterile. Colonies on SNA flat, spreading, with sparse aerial mycelia and feathery margin, pale luteous to orange, slowly growing, reaching 70 mm diam. after 3 weeks at 25 ° C, sterile. Additional material examined. CHINA • Hainan Province, Changjiang Li Autonomous County, Bawangling National Forest Park, on diseased leaves of Castanopsis carlesii, 30 March 2019, Yong Li (culture CFCC 52809). Distribution. China, Hainan Province. Ecology. Associated with leaf spot disease of Castanopsis carlesii. Notes. Two isolates from leaf spots of Castanopsis carlesii clustered in a well-supported clade here newly described as Pseudoplagiostoma neocastanopsidis, which is phylogenetically close to Ps. castanopsidis and Ps. jasmini (Fig. 1). Morphologically, Ps. neocastanopsidis is similar to Ps. castanopsidis and Ps. jasmini in conidial size (Gomdola et al. 2023; Zhang et al. 2025). However, Ps. neocastanopsidis differs from Ps. jasmini in conidial color (hyaline conidia in Ps. neocastanopsidis vs. brown conidia in Ps. jasmini). Furthermore, Ps. neocastanopsidis has wider conidiogenous cells than Ps. castanopsidis and Ps. jasmini (11.5–22 × 3.5–6.5 μm in Ps. neocastanopsidis vs. 9–16.8 × 2.2–2.9 μm in Ps. castanopsidis vs. 7.7–13.7 × 1.6–2.4 μm in Ps. jasmini) (Gomdola et al. 2023; Zhang et al. 2025).