Cercospora parakouensis 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 parakouensis Y.Meswaet, Mangelsdorff, Yorou & M.Piepenbr. sp. nov. Figs 2E , 7

Type.

Benin. Borgou: Parakou, Tankaro , c. 360 m a.s.l., 9°23'01"N, 2°30'36"E, on Desmodium tortuosum (Sw.) DC. ( Fabaceae ), 20 Sep 2019, Y. Meswaet and R. Dramani, YMM296A (Holotype: M-0312649; Isotype: UNIPAR). Ex holotype sequences. MW834436 (LSU), MW834442 (ITS), MW848621 (tef1) .

Etymology.

The epithet Cercospora parakouensis refers to the city of the type collection, Parakou, Benin.

Diagnosis.

Cercospora parakouensis differs from the two Cercospora species known on Desmodium spp., namely C. canescens and C. kashiensis Bharadwaj by producing almost no stromata, branched, darker and shorter conidiophores [(12.5-)18-178(-190) μm] and non- pigmented and shorter conidia [(14-)19-88(-113.5) × 3.5-4.5(-5) μm].

Description.

Leaf spots almost lacking to well-developed, amphigenous, subcircular to irregularly angular, 1.5-5 mm diam., darkish brown to reddish brown, often with a diffuse whitish centre surrounded by a darker margin. Caespituli amphigenous, greyish brown to dark brown. Mycelium mainly internal. Stromata lacking. Conidiophores in small, loose fascicles, sometimes arising from internal hyphae, breaking through the adaxial epidermis of the leaves or penetrating through stomatal openings, occasionally solitary, arising through stomatal openings, erect, straight to sinuous or somewhat geniculate, occasionally branched, (12.5-)18-178(-190) × (3.5-)4-5(-5.5) μm, 1-6(-8)-septate, brown to dark brown. Conidiogenous cells terminal or rarely intercalary, usually monoblastic, rarely polyblastic; loci subcircular, 1.5-3 μm wide, thickened and darkened, refractive. Conidia solitary, narrowly obclavate to subacicular, straight to curved, (14-)19-88(-113.5) × 3.5-4.5(-5) μm, 2-6-septate, hyaline, smooth, apex subacute or acute, base truncate to short obconically truncate, 2-3(-3.5) μm wide, hila thickened and darkened.

Additional specimens examined.

Benin. Borgou: Parakou , c. 395 m a.s.l., 9°21'27"N, 2°36'44"E, on Desmodium tortuosum , 17 Sep 2019, Y. Meswaet and A. Tabé, YMM292 (Paratypes: M-0312650; UNIPAR) .

Herbarium specimens examined for comparison.

See Cercospora aff. canescens .

Host and distribution.

On Desmodium tortuosum ( Fabaceae ) from Benin.

Notes.

Currently, two Cercospora species are known from Desmodium spp., namely C. canescens and C. kashiensis ( Farr and Rossman 2021). C. canescens differs from the present species by causing large leaf spots often along the margin of the leaf, 3-15 mm in extent, paler conidiophores and above all, longer conidia [30-300 µm versus (14-)19-88(-113.5) µm in C. parakouensis ] ( Chupp 1954). The distinctness is also confirmed by molecular data (Fig. 1 ). C. kashiensis described on Desmodium gangeticum (L.) DC. from India causes different leaf spots, has unbranched and longer conidiophores (40-282 µm versus (12.5-)18-178(-190) in C. parakouensis ) and above all, pigmented and longer conidia (16-220 µm versus (14-)19-88(-113.5) µm in C. parakouensis ) with 2-15 septa ( Bharadwaj 1971).

In the multi-gene tree (Fig. 1 ), the ITS and the tef1 phylogeny (see Suppl. materials 3, 4), C. parakouensis forms part of a polytomy with a relatively large genetic distance (branch length) in relation to other sequences considered in the analysis.

Based on a MegaBLAST search using the tef1 sequence, the closest matches in NCBI’s GenBank nucleotide database were Cercospora nicotianae on Nicotiana tabacum ( Solanaceae ) from China (GenBank MK881748; Identities 283/291, i.e., 97%), Cercospora cf. sigesbeckiae on Persicaria orientalis L. ( Polygonaceae ) from South Korea (GenBank JX143412; Identities 283/291, i.e., 97%) and Cercospora aff. canescens on a species of Malvaceae from Mexico (GenBank JX143321; Identities 283/291, i.e., 97%).

Figures

Figure 1. The Bayesian phylogenetic tree inferred from DNA sequence data from the multigene alignment (SSU rDNA, LSU rDNA, ITS and tef 1) of cercosporoid species. Nodes receiving Bayesian PP ≥ 0.94 or MLBS ≥ 70 % are considered as strongly supported and are indicated by thickened branches. Names of newly described species are written in bold and red. Species newly reported for Benin are indicated by green letters. Names of host plants are written with blue letters.

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 7. Cercospora parakouensis on Desmodium tortuosum (YMM 296 A) A fascicle of erumpent conidiophores B solitary conidiophores C conidia. Scale bars: 15 μm (A); 10 μm (B, C).