Cercospora beninensis 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 beninensis Y.Meswaet, Mangelsdorff, Yorou & M.Piepenbr. sp. nov. Figs 2A , 3

Etymology.

The epithet Cercospora beninensis refers to the country of origin of the type specimens, Benin.

Diagnosis.

Cercospora beninensis differs from four Cercospora spp. known on Crotalaria spp. by having only internal hyphae, darker, shorter and narrower conidiophores [(14.5-)28.5-160(-168) × (3-)3.5-4.5(-5) μm] and mostly smaller and narrower conidia [(19-)23.5-122(-150) × (2.5-)3-4(-4.5) μm] (Table 3 ).

Type.

Benin. Borgou: Parakou , c. 363 m a.s.l., 9°20'29"N, 2°37'28"E, on Crotalaria macrocalyx Benth. ( Fabaceae ), 21 Sep 2019, Y. Meswaet and R. Dramani, YMM11 (Holotype: M-0312640; Isotype: UNIPAR). Ex holotype sequences. MW834445 (SSU), MW834433 (LSU), MW834437 (ITS), MW848615 (tef1) .

Description.

Leaf spots amphigenous, subcircular to angular-irregular, (0.5-)1.5-5.5 mm diam., brown to reddish brown, more evident on the adaxial surface of the leaves than on the abaxial side, occasionally with a chlorotic halo, the outermost ring darker than the inner ring, often with indefinite margin. Caespituli amphigenous, mainly epiphyllous, greyish brown to dark brown. Mycelium internal. Internal hyphae conspicuous, branched, 2.5-3.5 μm wide, septate, pale brown. Stromata lacking or formed by few aggregated swollen hyphal cells. Conidiophores in small, loose to moderately dense fascicles of up to approx. 16 conidiophores, occasionally solitary, arising from internal hyphae breaking through the adaxial epidermis of the leaves or penetrating through stomatal openings, erect, straight, subcylindrical, 1-2(-3) times geniculate, sometimes attenuated towards the tips, occasionally branched, (14.5-)28.5-160(-168) × (3-)3.5-4.5(-5) μm, 0-6(-8)-septate, brown to dark brown. Conidiogenous cells monoblastic or proliferating sympodially, sometimes distinctly subdenticulate; loci 1.5-2.5(-3.5) μm wide, thickened and darkened. Conidia solitary, acicular to narrowly obclavate, straight to curved, (19-)23.5-122(-150) × (2.5-)3-4(-4.5) μm, 1-7(-9)-septate, hyaline, smooth, tip acute, base truncate to short obconically truncate, 2.5-3(-4) µm wide, hila thickened and darkened.

Additional specimens examined.

Benin. Borgou: Parakou, on the way to Okpara forest , c. 323 m a.s.l., 9°18'11"N, 2°43'50"E, on Crotalaria macrocalyx , 3 Sep 2019, Y. Meswaet and R. Dramani, YMM274 (Paratypes: M-0312641; UNIPAR) . Benin. Borgou: N’Dali, c. 380 m a.s.l., 9°52'33"N, 2°41'20"E, same host, 31 Aug 2019, Y. Meswaet and A. Tabé, YMM272 (M-0312642) .

Host and distribution.

On Crotalaria macrocalyx ( Fabaceae ) in Benin.

Notes.

Currently, three species and one form of Cercospora are known on Crotalaria spp., namely C. apii , C. canescens , C. demetrioniana G.Winter and C. demetrioniana f. minor Gonz. Frag. & Cif. ( Farr and Rossman 2021). C. beninensis is morphologically distinct from all of them (Table. 3). C. apii differs by conidiophores that are more abundant on the abaxial surface of the leaves, in large and dense fascicles and longer [20-300 µm versus (14.5-)28.5-160(-168) in C. beninensis ] as well as by longer and wider conidia [(25-315 × 3-6 µm versus (19-)23.5-122(-150) × (2.5-)3-4(-4.5) in C. beninensis ] with more numerous septa ( Chupp 1954; Crous and Braun 2003). C. canescens causes larger leaf spots often along the leaf margin, paler conidiophores that are more abundant on the abaxial leaf surface and longer conidia [(30-300) µm versus (19-)23.5-122(-150) μm in C. beninensis ] ( Chupp 1954). The distinctness is confirmed by molecular data. C. demetrioniana produces unbranched, paler, longer and wider conidiophores [40-350 × 4-6(-7) µm, in the original description a length of up to 1 mm is mentioned, versus (14.5-)28.5-160(-168) × (3-)3.5-4.5(-5) in C. beninensis ] and above all, longer and wider conidia (75-230 × 4-7 µm with 7-16 indistinct septa versus (19-)23.5-122(-150) × (2.5-)3-4(-4.5) μm with 1-7(-9) distinct septa in C. beninensis ] ( Winter 1884; Saccardo 1886; Chupp 1954). C. demetrioniana f. minor differs from the present species by shorter and wider conidiophores (110-130 × 5-6 µm) and wider conidia (5-5.5 µm) ( Ciferri and González-Fragoso 1926).

C. beninensis is distinct from all known species for which DNA sequence data are available based on its position in the multi-gene (Fig. 1 ) and in the tef1 phylogeny (see Suppl. material 4). In the ITS phylogeny, C. beninensis cannot be distinguished from other Cercospora spp. (see Suppl. material 3).

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 3. Cercospora beninensis on Crotalaria macrocalyx (YMM 11) A fascicle of conidiophores B individual conidiophores C conidia. Scale bars: 15 μm (A); 10 μm (B, C).