Alternaria eureka E. G. Simmons

Bessadat, Nabahat, Bataillé-Simoneau, Nelly, Colou, Justine, Hamon, Bruno, Mabrouk, Kihal & Simoneau, Philippe, 2025, New members of Alternaria (Pleosporales, Pleosporaceae) collected from Apiaceae in Algeria, MycoKeys 113, pp. 169-192 : 169-192

Alternaria eureka E. G. Simmons

Fig. 2

≡ Embellisia eureka (E. G. Simmons) E. G. Simmons , Mycotaxon 38: 260. 1990.

= Lewia eureka E. G. Simmons , Mycotaxon 25: 304. 1986.

≡ Allewia eureka (E. G. Simmons) E. G. Simmons , Mycotaxon 38: 264. 1990.

Specimen examined.

Algeria • Ain Témouchent City, Chabaat El Lahame , from leaves of wild Daucus carota . 08 April, 2021, N. Bessadat, Living culture NB 968 .

Description.

Colonies on PCA velvety to cottony colonies, mostly mycelial, subhyaline, loosely wooly, reaching 75 mm in diameter after 7 days; meager sporulation or lacking until hyphae are disturbed or scarified. Conidiophores emerging from the surface of agar or aerial vegetative hyphae scattered or clustered on cut agar in light-exposed areas. Primary conidiophores mostly simple, rarely branched, 25–75 × 5–6 µm, geniculate with 2–3 (– 4) conidiogenous loci. Secondary conidiophores, short, 3–7 × 3 µm, 1–2 - celled, formed apically or sometimes laterally from primary conidia, mainly with one conidiogenous locus. Further geniculate extensions and conidium production yield several clusters of sporulation at the colony center. Sporulation pattern in single clumps of a few short branching chains consisting of 5–7 conidia. A high percentage of conidia solitary at any age of growth. Conidia ellipsoid to ovoid, with a rounded base and tapered apex; multiple transverse and longitudinal septa, conspicuously constricted near 2 or 3 transverse septa, in short chains. Mature conidia with 2–3 transverse septa and 0–3 longitudinal septa located mainly at the center of the colony, 20–24 × 8–15 µm; slightly older conidia, 25–34 (– 48) × 11–16 (– 22) µm with 3–4 (– 5) transverse septa and 1–3 oblique or longitudinal septa. Conidial body color brown with relatively dark and thick transverse septa (Fig. 2 A, B ); the outer wall smooth or punctate. Formation of protoascomata and chlamydospores in the surface of vegetative mycelium conspicuous after 2–3 weeks of incubation. Chlamydospores hyaline, spherical or ovoid, terminal, sub-terminal or intercalary, measuring 13.5–22.5 × 10–15 µm, mostly single-celled (Fig. 2 C ). Protoascomata subspherical to ovoid, light brown with numerous outgrowths of hyphae, measuring 40–58 µm in diameter (Fig. 2 D ).

Culture characteristics at 25 ° C in 7 d — Colonies on PDA cottony, grayish yellow to yellowish grey (3 C 3 / 3 D 2) with white regular margins, attaining 60.5 ± 1.1 mm diam. (Fig. 2 E ); reverse olive brown to yellowish brown (4 F 6 / 5 F 5). On PCA, velvety to glabrous, olive brown (4 E 5), 67.4 ± 0.4 mm diam. (Fig. 2 F ); reverse olive brown (4 E 4). On MEA, cottony, dull green (28 D 3) with a greenish-grey surface (28 C 2) and white regular margins, 51.9 ± 0.7 mm diam. (Fig. 2 G ), reverse yellowish brown to brownish orange (5 F 5 / 5 C 4). On OA, velvety with a cottony center, yellowish brown to dark blond (5 E 4 / 5 D 4), 60.6 ± 1.5 mm diam. (Fig. 2 H ); reverse brownish grey to yellowish brown (5 F 2 / 5 E 4). Sporulation of NB 968 isolate occurred mainly in PCA and PDA after 7 days of incubation. It was poor on MEA and OA.

Notes.

The multilocus phylogeny revealed that NB 968 significantly clustered with A. eureka (ex-type, CBS 193.86), both forming a branch separated from other species in section Eureka . Cultural characters, sporulation patterns, and conidia shapes of A. eureka are different from other members of section Eureka . A high percentage of conidia have conical apical cells but differ in size and number of transverse septa from A. hungarica (15–30 × 12–13 vs. 25–48 × 8–22, respectively). Conidiogenous axes, conidiophores, and conidia chains of the latter species are longer than those of A. eureka (30–352 × 3.8–5 µm vs. 25–75 × 5–6 µm, respectively). Conidia chain formation of A. eureka is rare, while in A. hungarica , short-branched chains of 3–4 units are conspicuous. Alternaria eureka and A. hungarica conidia consist of numerous longitudinal and / or oblique septa forming multi-celled segments; the two species are, however, distinct from each other according to the sporulation pattern (see A. hungarica notes). Alternaria eureka is the only species from section Eureka known to have a sexual state ( Simmons 1986); it also produces hyaline chlamydospores and sclerotia upon aging, which are lacking in A. hungarica and A. cumini .

Figures

Figure 2. Morphology of Alternaria eureka (strain: NB 968). Conidiophores and conidia on PCA for 7 days at 22 ° C (A) and on inoculated carrot leaves after 24 days (B); Chlamydospores (C) and protoascomata (D) on PCA for 18 days at 22 ° C. Colony phenotypes on PDA (E), PCA (F), MEA (G), and OA (H) for 7 days at 25 ° C. Scale bar: 25 µm (A – D); 10 mm (E – H).