Alternaria alternata (Fr.) Keissl., Beih. bot. Zbl., Abt. 2 29: 434 (1912)

Index Fungorum number: IF 119834; MycoBank number: MB 119834; Facesoffungi number: FoF 03825; Fig. 1

Basionym – Torula alternata Fr., Syst. mycol. (Lundae) 3(2): 500 (1832)

Neotype – L 910.262-129 (Designated by Simmons 1967); Epitype: CBS 916.96 (Designated by de Hoog and Horré 2002).

Pathogenic caused leaf spot of Impatiens balsamina L. Sexual morph: The detailed characterization offered by Ariyawansa et al. (2015b). Asexual morph: Hyphae 3.3–6.7 μm (x=5.0 μm, n=20), superficial or submerged, pale brown, branched, smooth to verruculose, septate. Conidiophores 3.4–67.7×3.1–5.6 μm (x=38.6×4.7 μm, n = 20), solitary, simple or branched, brown, multi-septate, with a single terminal conidiogenous loci. Conidia 7.3–26.7×6.8–14 μm (x=17.1×10.7 μm, n=50), solitary or in branched chains of 20 or more, first 1–2 conidia in each chain longer than others, straight, ellipsoidal or ovoid, pale to dark brown to olivaceous green, with smooth outer wall, some muriform, usually with 1–6-transverse septa and 0–3-longitudinal septa, rounded apex, conidial beaks pale brown to subhyaline, not branched, 9.1–27.2×3.4–4.5 μm (x=16.2×4.1 μm, n=20).

Culture characteristics – Colonies on PDA reached a 40 mm diameter in the dark after 2 weeks at 25 °C. Initially, the colony was grey, dense, circular, with an entire edge, becoming creamy white, slightly raised at the center and greenish grey towards margin after 2 weeks, and reverse light brown. Two months old cultures on the WA sporulated with grey to dark, chained conidia and greyish green, septate and branched hyphae.

Material examined – China, Sichuan Province, Pengzhou City, Huilonggou, on fresh leaves of Impatiens balsamina (Balsaminaceae), N31° 17′ 34, E103° 4′ 64, 28 July 2021, Y. Chen, HLG661 (HUEST 21.0017), living culture, UESTCC 21.0017.

Host and distribution – Causing leaf spot on Fagopyrum tataricum (L.). Gaertn. (Li et al. 2021), Rumex vesicarius L. (Sankar et al. 2012), as well as various hosts worldwide (Mirkova and Konstantinova 2003; Bajwa et al. 2010; Noelting et al. 2011).

GenBank numbers – ITS: OL741379, tef1-α: ON411269, rpb2: OL742706, gapdh: ON411271.

Notes – gapdh, ITS, rpb2, and tef1-α sequences of our collection (HUEST 21.0017) give Alternaria species as the closest matches with NCBI. Our isolate clusters with the epitype strain of A. alternata (CBS 916.96). Our collection is morphologically similar to the holotype of A. alternata by its chained conidia, hypha, and colony characteristics on PDA (Woudenberg et al. 2013). Therefore, we identified our isolate as A. alternata and this is the first record of A. alternata from Impatiens balsamina (Fig. 2).

Figure 1 – Alternaria alternata (HUEST 21.0017). a, b Diseased leaves infected by A. alternata front and reverse view. c Sporulation on the water agar. d Conidia and conidiophores attached to hyphae. e Hyphae. f Reverse view of colony on PDA. g Surface view of colony on PDA. h Conidia, conidiophores and conidiogenous cells. i Conidia. Scale bars: d=20 µm; e, h, i=10 µm

Figure 2 – The best scoring RAxML tree with a combined dataset of gapdh, ITS, rpb2, and tef1-α sequence data. The topology and clade stability of the combined gene analyses was compared to the single gene analyses and no significant differences. The tree is rooted with Stemphylium herbarum (CBS 191.86). The matrix had 476 distinct alignment patterns with 1.86% undetermined characters and gaps. Estimated base frequencies were as follows; A=0.245, C=0.282, G=0.241, T=0.233; substitution rates AC=1.201041, AG=3.391612, AT=1.290665, CG=0.667892, CT=7.923937, GT=1.0; gamma distribution shape parameter α=0.263849 and final likelihood value of − 8057. Ex-type strains are in bold and newly generated sequences are in blue bold. Bootstrap support for ML≥75% and BI≥0.95 are given at the nodes. The scale bar presents the expected number of nucleotide substitutions per site