Neocosmospora sp. Fig. 10 Description. Associated with contaminated rubber latex. Sexual morph: Undetermined. Asexual morph: Fruiting bodies observed on the PDA plate covered with a natural rubber disc. Mycelium 3–7 μm wide, hyaline, septate, granulate. Conidiophores borne on aerial mycelium, slightly tapering upward, micronematous, mononematous, erect, simple, straight or slightly flexuous, smooth-walled, thin-walled, hyaline, sometimes reduced to conidiogenous cells. Conidiogenous cells 23–100 (– 108) × 3–9 μm (x – = 65 × 4, n = 25), solitary or sympodial, integrated, determinate, terminal, hyaline, on substrate mycelium. Conidia 9–27 × 3–6 μm (x – = 15 × 4.5, n = 70), solitary, hyaline, ellipsoidal, acrogenous, simple, smooth-walled, 0–1 - septate, straight to curved, reniform. Chlamydospores 7–13 μm diam., abundantly formed, globose to subglobose, smooth- and thick-walled, terminal or intercalary in hyphae, in chains or in clusters. Culture characteristics. Colonies on PDA at room temperature (20–25 ° C) covered the entire plate within one week, white to pale yellow with aerial mycelium. Sporulation was observed after incubation on PDA covered with natural rubber discs. Material examined. Thailand, • Chiang Rai Province, contaminated rubber latex, 19 December 2023, Rui-Fang Xu, T 21 (MFLU 26–0038), living culture MFLUCC 26–0156. Notes. Phylogenetically, strain MFLUCC 26–0156 clustered near Neocosmospora parva with 100 % ML and low BI support (Fig. 6). Although ITS and LSU sequences showed high similarity to species within the Neocosmospora solani species complex, the absence of tef 1 - α sequence data prevented reliable species delimitation. The tef 1 - α gene is crucial for the molecular identification and phylogenetic analysis of Neocosmospora species, especially when combined with ITS and rpb 2 genes (Zhang et al. 2024; Ismail et al. 2025). These genes together offer high taxonomic resolution, helping to distinguish closely related species within the genus. Therefore, this isolate is classified as Neocosmospora sp. until sufficient evidence is available to determine its species. This isolate was collected from a container located near a rubber tree during the productive phase in Chiang Rai, Thailand. This is the first observation that Neocosmospora sp. can cause oxidative surface alteration of natural rubber.

Published as part of Xu, Rui-Fang, Karunarathna, Samantha C., Hyde, Kevin D., Phukhamsakda, Chayanard, Rapior, Sylvie, Dai, Dong-Qin, Wang, Mei-Mei, Ali, Sajad, Yang, Jing-Ya, Kakumyan, Pattana & Tibpromma, Saowaluck, 2026, Screening and identification of fungal species associated with early-stage deterioration of natural rubber, pp. 119-156 in MycoKeys 134 on pages 119-156, DOI: 10.3897/mycokeys.134.195079