Digitopodium citri J.R. Liang, Senan., & M. Luo, 2023

Liang, Jie-Rong, Senanayake, Indunil C., Dong, Zhang-Yong, Hongsanan, Sinang & Luo, Mei, 2023, Digitopodium citri sp. nov.; an endophytic species associated with Citrus medica L. var. sarcodactylis from Guangdong Province, China, Phytotaxa 616 (1), pp. 69-78 : 73

Digitopodium citri J.R. Liang, Senan., & M. Luo sp. nov. ( FIGURE 3 )

Index Fungorum number: IF900515

Etymology: Epithet refers to the host genus Citrus .

Holotype: ZHKU 23-0005

Endophytic, isolated from peels of Citrus medica var. sarcodactylis (Siebold ex Hoola van Nooten) Swingle. Sexual morph: not observed. Asexual morph: Mycelium 1.5–2.5 μm wide, consisting of hyaline, smooth, branched, septate. Conidiophores solitary or in loose groups, straight to slightly curved, occasionally branched, 75 (–220) × 2–4 µm or even longer, septate, dark brown, smooth, occasionally enlarged at the base. Conidiogenous cells integrated, terminal, subcylindrical, 6.5–18 × 2–3.5 μm, tips somewhat curved, loci sympodially arrange, slightly thickened, slightly darkened, 1–2 μm diam. Conidiogenous loci slightly thickened and darkened, 1–2 µm diam. Conidia branched, acropetal chains. Primary ramoconidia fusoid-ellipsoidal to subcylindrical, 4.5–13 × 1.5–4 μm, 0–1-septate, guttulate, hyaline to pale olivaceous, smooth, hila thickened and darkened, 1 μm diam. Intermediary conidia hyaline, guttulate, fusoid-ellipsoid, 5.5–13 × 2–4 µm, hila 2 per conidium, 1 μm diam. Terminal conidia smooth, guttulate, hyaline, aseptate, fusoid-ellipsoid, 4–9 × 2–3.5 µm, loci thickened and darkened, 0.5 µm diam.

Culture characteristics: Colonies reach 30 mm diam. on PDA plates after three weeks at 25 °C, slow growing, edge entire, aerial mycelium either sparse or dense, becoming olivaceous-grey toward the margin, reverse olivaceous-grey.

Material examined: CHINA. Guangdong Province, Zhaoqing City, isolated from healthy peels of Citrus medica var. sarcodactylis (Rutaceae) , November 2021, J. R. Liang, ( ZHKU 23-0005, CGMCC 3.25233, holotype), ex-type culture ZHKUCC 23-0016, other living cultures ZHKUCC 23-0017, ZHKUCC 23-0018.

Notes: The combined gene analyses of ITS and LSU ( FIGURE 2 ) showed that our collection clustered with Digitopodium species and formed a sister subclade to Digitopodium tectonae with ML/MP/BYPP = 81%/69%/0.85 bootstrap support. Our collection differs from other Digitopodium species ( Table 2 ), especially from D. tectonae by having rhizoid conidiophores, shorter conidiogenous cells (6.5–18 µm vs. 15–30 µm), shorter primary ramoconidia (4.5–13 µm vs. 30–35 µm), and shorter intermediary conidia (5.5–13 µm vs. 10–15 µm). Digitopodium tectonae was collected as a rust pathogen from Olivea tectonae on leaves of Tectona grandis in Minas Gerais City, Brazil ( Crous et al. 2014, Colmán et al. 2021). Given that no extant species fit with our new collection and, we introduce Digitopodium citri as a new species based on polyphasic approaches discussed in Maharachchikumbura et al. (2021).

Figures

FIGURE 2. Phylogram generated fromBayesian analysis based oncombined LSU andITS sequence.Bootstrap support values forBayesian posterior probabilities (BYPP) equal to or greater than 0.80, maximum likelihood (ML) and maximum parsimony (MP) analyzable to higher than 50% are indicated at the nodes, respectively. Ex-type strains are in bold. The newly generated sequences are in red.

FIGURE 3. Digitopodium citri (ZHKU 23-0005, holotype). a, b Colony on PDA after three weeks of incubation under 28 ℃—front and reverse. c Mycelial coils. d Conidial chains. e, h, i Conidiophores, conidiogenous cell, primary ramoconidia. f Chlamydospores. g Immature conidiophores.