Colletotrichum abelmoschi Fallahi, Jayawar. & K. D. Hyde, 2025

Colletotrichum abelmoschi Fallahi, Jayawar. & K. D. Hyde sp. nov.

Fig. 2 View Figure 2

Etymology.

‘ abelmoschi ’ refers to the host plant genus where the fungus was isolated.

Description.

Fungus causes small, dark brown to black lesions on the okra stems. On the leaves, infection results in angular to irregular-shaped dark brown or black spots that expand into larger areas of necrosis. A yellow halo often surrounds these spots. Sexual morph not observed. Conidiomata acervular, semi-immersed, dark brown, bearing conidial masses. Conidiophore hyaline to pale brown, cylindrical or subcylindrical, branched or unbranched, septate, smooth-walled, 11–27 × 2–4.5 μm (mean = 19 × 3.3 μm, n = 30). Conidiogenous cells cylindrical or doliiform, unbranched, guttulate, 6–18 × 2.2–4 μm (mean = 11.5 × 3 μm, n = 30). Conidia aseptate, straight, cylindrical, the apex and base rounded or tapering at base, guttulate, 8.6–13.7 × 4.2–5.8 μm (mean = 12 × 5 μm, n = 40). Appressoria ellipsoidal to obovate, clavate, entire margin, regular shape, or slightly irregular, brown to dark brown 4–12 × 5–7 μm (mean = 8 × 6 μm, n = 20). Chlamydospores and Setae are absent.

Culture characteristics.

Colonies on PDA reach 60 mm in diameter after 7 days of growth at 25 ° C in the dark, cottony, circular shape, dull surface, entire edge, well-defined margin, with medium density. Upper view white to light grey. Reverse primrose, with no diffusing pigment.

Material examined.

Thailand • Sakon Nakhon Province, Mueang Sakon Nakhon District , on leaf of okra ( Abelmoschus esculentus ), February 2023, Maryam Fallahi, dried culture MF 148-1 ( MFLU 24-0237 , holotype), ex-holotype culture, MFLUCC 24-0239 • ibid., on stem of okra ( Abelmoschus esculentus ), February 2023, Maryam Fallahi, dried culture MF 148 ( MFLU 24-0238 ), living culture, MFLUCC 24-0256 .

Notes.

Phylogenetic analyses showed that strains MFLUCC 24-0239 and MFLUCC 24-0256 form a distinct subclade in the Colletotrichum gloeosporioides species complex, basal to the subclade containing C. tropicale and C. makassarense with 58 % ML, 92 % MP bootstrap support, and 0.95 BYPP (Fig. 1 View Figure 1 ) and are introduced as a new species, namely Colletotrichum abelmoschi . The base pair differences between C. abelmoschi ( MFLUCC 24-0239 , holotype), C. tropicale ( CBS 124949 , holotype), and C. makassarense ( CBS 143664 , ex-type) are presented in Table 2 View Table 2 . Based on the morphology mentioned in Table 3 View Table 3 , Colletotrichum abelmoschi ( MFLUCC 24-0239 ) is different from C. tropicale ( CBS 124949 , holotype) and C. makassarense ( CBS 143664 ) ( Rojas et al. 2010; de Silva et al. 2019). Colletotrichum abelmoschi produced slightly narrower conidia than C. tropicale ( CBS 124949 ) with an L / W ratio = 2.4 (8.6–13.7 × 4.2–5.8 μm in Colletotrichum abelmoschi vs. 10.2–12.7 × 8.2–11.2 μm in C. tropicale ( CBS 124949 )). Moreover, in comparison to C. makassarense , Colletotrichum abelmoschi produced slightly shorter conidia (8.6–13.7 × 4.2–5.8 μm in Colletotrichum abelmoschi ( MFLUCC 24-0239 ) vs. 13–15 × 4.5–5 μm in C. makassarense ( CBS 143664 )) and conidiogenous cells (6–18 × 2.2–4 μm in Colletotrichum abelmoschi ( MFLUCC 24-0239 ) vs. 7–25 × 3–4 μm in C. makassarense ( CBS 143664 )). There are limited reports on Colletotrichum species associated with okra. Colletotrichum plurivorum was identified as the primary causal agent of anthracnose on okra in Brazil ( Batista et al. 2020). Shi et al. (2019) reported the presence of C. gloeosporioides causing anthracnose disease on okra in China ( Shi et al. 2019). Based on morphology and multi-gene analysis, Colletotrichum abelmoschi is introduced as a new species on okra.