Cercospora tentaculifera Y.Meswaet, Mangelsdorff, Yorou & M.Piepenbr., 2021

Meswaet, Yalemwork, Mangelsdorff, Ralph, Yorou, Nourou S. & Piepenbring, Meike, 2021, Unravelling unexplored diversity of cercosporoid fungi (Mycosphaerellaceae, Mycosphaerellales, Ascomycota) in tropical Africa, MycoKeys 81, pp. 69-138 : 69

Cercospora tentaculifera Y.Meswaet, Mangelsdorff, Yorou & M.Piepenbr. sp. nov. Figs 2H , 11

Type.

Benin. Borgou: Parakou , c. 372 m a.s.l., 9°21'43"N, 2°36'04"E, on Vigna unguiculata (L.) Walp. ( Fabaceae ), 02 August 2017, Y. Meswaet, M. Piepenbring, N. S. Yorou and participants of the summer school 2017, YMM75 (Holotype: M-0312655; Isotype: UNIPAR). Ex holotype sequences. MW834448 (SSU), MW834440 (ITS), MW848614 (tef1) .

Etymology.

The epithet Cercospora tentaculifera refers to the ramified and flexible hyphae.

Diagnosis.

Cercospora tentaculifera differs from other Cercospora spp. on Vigna and Phaseolus in causing inconspicuous or no leaf spots, well-developed external hyphae, mainly adaxial caespituli and up to 435 μm long conidiophores that are constricted at the septa.

Description.

Leaf spots almost lacking or pale brown with reddish brown discolorations. Caespituli amphigenous, mostly epiphyllous, scattered, greyish brown to dark brown. Mycelium internal and external. External hyphae branched, 2-3.5(-4) μm wide, septate, olivaceous brown to brown, smooth. Stromata lacking or formed by few substomatal swollen hyphal cells, immersed in the mesophyll or in substomatal cavities. Conidiophores in small, loose fascicles formed by up to approx. 8 conidiophores, breaking through the adaxial epidermis of the leaves or penetrating through stomatal openings, solitary when arising from external hyphae, erect, straight, curved or slightly 1-2 times geniculate, often constricted at septa, rarely branched, (32.5-)40-400(-435) × (3-)3.5-4.5(-5) μm, (2-)3-8(-10)-septate, brown to dark brown. Conidiogenous cells terminal, rarely subterminal, mostly monoblastic or with few conidiogenous loci; loci mainly apical, sometimes located on the shoulders of geniculations, 2-2.5(-3.5) μm wide, thickened and darkened, refractive, often subcircular or rarely flattened. Conidia solitary, acicular to narrowly obclavate, straight to curved, (29-)38-188(-240) × (2.5-)3-3.5(-4.5) μm, 1-9-septate, hyaline, smooth, tip acute, base truncate to short obconically truncate, 2.5-3(-3.5) µm wide, hila thickened and darkened.

Additional specimen examined.

Benin. Borgou: Parakou, agricultural research site of the University of Parakou, c. 360 m a.s.l., 9°20'10"N, 2°38'53"E, on Phaseolus vulgaris , 20 Aug 2017, Y. Meswaet and A. Tabé, YMM130 (Paratypes: M-0312656; UNIPAR).

Herbarium specimens examined for comparison.

See Cercospora aff. canescens .

Hosts and distribution.

Known on Phaseolus vulgaris and Vigna unguiculata ( Fabaceae ) from Benin.

Notes.

Thirteen Cercospora species have previously been recorded on species of Vigna or Phaseolus (Tables 4 , 5 ).

Among these, C. apii , C. canescens and C. phaseolicola have a morphology similar to the present collections, particularly by relatively long conidiophores (Tables 4 , 5 ). C. apii , however, differs from the present species in causing distinct leaf spots (brown to fairly dark in colour with darker margin), the place of sporulation (caespituli more abundant on the abaxial surface of leaves versus on the adaxial surface of leaves in the case of C. tentaculifera ), paler and shorter conidiophores [20-300 μm versus (32.5-)40-400(-435) μm in C. tentaculifera ] that are occasionally arising from developed (up to 50 μm diam.) stromata and somewhat longer and wider conidia [25-315 × 3-6 μm versus (29-)38-188(-240) × (2.5-)3-3.5(-4) μm in C. tentaculifera ] ( Hsieh and Goh 1990). C. canescens differs from C. tentaculifera in causing different leaf spots and sporulation, producing dense fascicles, paler and shorter conidiophores [20-200 µm versus (32.5-)40-400(-435) µm in C. tentaculifera ] and somewhat longer conidia [25-300 μm versus (29-)38-188(-240) μm in C. tentaculifera ] ( Hsieh and Goh 1990). C. phaseolicola differs from C. tentaculifera in causing zonate leaf spots and producing only internal hyphae, hardly geniculate, much longer and wider conidiophores [300-600 × 4-7 µm, occasionally up to 10 μm wide versus (32.5-)40-400(-435) × (3-)3.5-4.5(-5) µm] ( Braun et al. 1999).

Based on the present phylogenies, it is not possible to distinguish this species from many other Cercospora spp. included in this study. Nevertheless, we propose this species as new to science based on a unique combination of morphological characteristics.

Figures

Figure 2. Leaf spot symptoms associated with Cercospora spp. A Cercospora beninensis on Crotalaria macrocalyx (YMM 11) B Cercospora aff. canescens on Calopogonium sp. (YMM 07) C Cercospora aff. canescens on Vigna subterranea (YMM 01) D Cercospora fagopyri on Lablab sp. (YMM 23 A) E Cercospora parakouensis on Desmodium tortuosum (YMM 296 A) F Cercospora phaseoli-lunati on Vigna radiata (YMM 289) G Cercospora rhynchophora on Vigna unguiculata (YMM 03 B) H Cercospora tentaculifera on Vigna unguiculata (YMM 75) I Cercospora vignae-subterraneae on Vigna subterranea (YMM 293) J Cercospora zorniicola on Zornia glochidiata (YMM 299). Scale bars: 10 mm (A, C, F, G); 12 mm (B, D, E, H, J); 6 mm (I).

Figure 11. Cercospora tentaculifera on Vigna unguiculata (YMM 75) A fascicle of conidiophores growing out from a small stroma immersed in the epidermis B external hyphae C solitary conidiophores D conidia. Scale bars: 20 μm (A); 12 μm (B); 15 μm (C, D).