Alternaria macrocephalae S.L.L Aung & J.X Deng, 2025

Aung, Sein Lai Lai, Guo, Zhuan Jun, Huang, Jia Hui, Nwe, Zin Mar, Yu, Zhi He & Deng, Jian Xin, 2025, Alternaria macrocephalae sp. nov. (Ascomycota: Pleosporaceae) associated with Atractylodes macrocephala in China, Phytotaxa 681 (1), pp. 70-80 : 75-76

Alternaria macrocephalae S.L.L Aung & J.X Deng , sp. nov. Fig. 2

MycoBank No: 854474.

Etymology:—The epithet ‘ macrocephalae ’ refers to the host species name, Atractylodes macrocephala .

Type:— CHINA, Hubei Province, Hefeng county, Enshi Tujia and Miao autonomous prefecture on infected leaves of Atractylodes macrocephala , 10 June 2023, J.X Deng, (YZU-H-2023153, holotype), ex-type culture YZU 231617.

Description:— Colonies on PDA, vetiver green, hazel at the center, filamentous and cottony, with a vanderpole’s green color and a yellowish olive center in reverse, 66‒67 mm in diameter. On PCA, dark mouse grey, circular, flat in elevation, and dark mouse grey on the reverse, with a diameter of 62‒63 mm. On V8A, fuscous black, greyish sepia margins, circular and undulate margin, with fawn margins on the reverse, 61‒62 mm in diameter. On PCA, conidiophores macronematous, solitary, straight or slightly curved to spring-like structure, unbranched, septate, golden yellow to light brown to brown, 36–144 × 4–8 μm (x = 75 × 6.1, n = 25), 2–9 transverse septa with single conidiogenous locus 6.32–20 × 4.5–9 μm (x = 12 × 6.6, n = 25). Hyphae coil into a ring-like structure with 3–5 conidiophores attached, presenting a distinct morphological feature. Conidiophores extend from the coil, straight or slightly curved, bearing conidia at their apices. Conidia large, solitary at the apex or geniculate loci, long-ovoid or obclavate, narrowing distally into an apical region, rostrate, mostly straight, and slightly curved, with a subtly punctuated or smooth surface, golden to light brown to brown, 42–79 ×13–27 (x = 75 × 6.1, n = 50) μm, typically 3–7 transverse eusepta. Visible internal distoseptum, transverse eusepta, and less frequent longitudinal eusepta in conidia, with darker pigmentation compared to the outer wall of the conidium. Beak hyaline, narrow-tapered, with a second beak arising from the apical cell of the conidium, 35–180×4–8 μm (x = 95 × 6.2, n = 50). On V8A, conidiophores macronematous, solitary, straight or slightly curved to spring-like structure, unbranched, septate, golden yellow to light brown to brown, 57–190 × 4–9 μm (x = 86.95 × 6.5, n = 25), 2–10 transverse septa with single conidiogenous locus 6–32 × 5–9 μm (x = 16 × 6.5, n = 25). Hyphae coil to form a ring-like structure with 3–5 conidiophores. Conidia elongated oval or obclavate bodies that taper towards the tip, rostrate, mostly straight, single unbranched, and occasionally slightly curved, smooth or subtly punctuated surface, golden to light brown to brown, 27–95× 10–24 μm, with 3–8 transverse eusepta. Visible internal distoseptum, transverse eusepta, less frequent longitudinal eusepta in conidia, with darker pigmentation compared to the outer wall of the conidium. Beak hyaline, narrow-tapered, with a second beak irregularly arising from the apical cell of the conidium,42–124× 4–9 μm.

Additional isolate examined:— China, Hubei Province, Hefeng county, Enshi Tujia and Miao autonomous prefecture from leaves spot of Atractylodes macrocephala 10 June, 2023, S.L.L Aung, living culture YZU 231618, YZU 231619, YZU 231623.

Note:—Phylogenetically, Alternaria macrocephalae falls into a unique branch within section Porri , forming a subclade (BI/ML= 0.67/-) with A. guilanica and A. dichondrae . It was also close to A. grandis E.G. Simmons , A. porri (Ellis) Cif. , A. protenta E.G. Simmons , and A. solani (Ellis & G. Martin) L.R. Jones & Grout ( Fig. 1 ). Morphologically, A. macrocephalae is differentiated from these species mainly by its mature conidia morphology, including their size range, beak length/branching and the number of transverse septa (27–95×10–24 μm, beaks up to 124 μm with 0–1 branch and 7–8 transverse septa) compared to A. guilanica (50–135 × 10–20 μm, beaks up to 225 μm with 0–1 branch and 7–9 transverse septa) ( Poursafar et al. 2021), A. dichondrae (conidia 60–85 × 19–27 μm, beaks up to 110 μm with 1–4 branches and 7–10 transverse septa) ( Simmons 2007), A. grandis (conidia 128–198 × 24–38 μm, beaks up to 200 μm commonly with 1–2 (–3) branches and 11–19 transverse septa) ( Simmons 2007), A. porri (conidia 70–105 × 19–24 μm, beaks up to 160 μm commonly with 1–2 branches with 3 beak ends and 8–12 transverse septa) ( Simmons 2007), A. protenta (conidia 80–115 × 14–24 μm, beaks up to 135 μm commonly with 1–2 branches and 8–13 transverse septa) ( Simmons 2007), and A. solani (conidia 80–115 × 16–26 μm, beaks up to 118 μm with 1–3 branches and 7–11 transverse septa) ( Simmons 2007).

Figures

FIGURE 1. Phylogenetic tree based on the combined gene sequences of ITS, GAPDH, Alt a1, TEF1, and RPB2. The Bayesian posterior probabilities>0.60 (PP), maximum likelihood, and maximum parsimony bootstrap support values>60 (BS) are given at the nodes (PP/ BS). Examined strains are in bold.

FIGURE 2. Morphological characteristics of Alternaria macrocephale (YZU 231617, ex-type). a: colony on PDA for 7 days at 25°C; b: colony on PCA for 7 days at 25°C; c: colony on V8A for 7 days at 25°C; d: sporulation patterns on PCA; e: sporulation patterns on V8A; f & h: conidiophore on PCA; g & i: conidiophore on V8A; j: conidia on PCA; k: conidia on V8A. Scale bars: d–k = 50 µm.