Cercospora cf. fagopyri K.Nakata & S.Takim., J. Agric. Exp. Stat. Gov. Gen. Chosen 15: 29. 1928.

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 cf. fagopyri K.Nakata & S.Takim., J. Agric. Exp. Stat. Gov. Gen. Chosen 15: 29. 1928. Figs 2D , 6

Type.

South Korea. Suwon , on Fagopyrum esculentum Moench ( Polygonaceae ), Sep 1934, K. Nakata & S. Takimoto (holotype specimen, not located and not preserved according to Groenewald et al. (2013), neotype: CBS H-21008, n.v) .

For synonyms see Groenewald et al. (2013) or MycoBank.

Description.

Leaf spots amphigenous, circular to subcircular or rarely irregularly angular, 2-5 mm diam., more or less limited by veins, reddish to pale brown, margin dark brown on the adaxial surface, less conspicuous on the abaxial surface. Caespituli amphigenous, conspicuous, greyish brown to dark brown. Mycelium internal and external. External hyphae branched, often inconspicuous, 1.5-3 μm wide, septate, olivaceous brown to brown, smooth. Stromata lacking to well-developed, 10-45 µm diam., dark brown, substomatal or breaking through the epidermis. Conidiophores in small, loose to moderately dense fascicles of up to approx. 14 conidiophores, arising from stromata breaking through the adaxial epidermis of the leaves or through stomatal openings, sometimes solitary arising from external hyphae, erect, straight, subcylindrical to geniculate, unbranched, (22.5-)36-157(-168) × 3-4(-5) μm, 2-6(-8)-septate, brown to dark brown. Conidiogenous cells terminal, with 1-2 loci; loci mainly apical, sometimes located on the shoulders of geniculations, 1.5-2(-3) μm wide, thickened and darkened. Conidia solitary, acicular to narrowly obclavate, straight to somewhat curved, (24-)27.5-70(-78) × (2-)2.5-3(-4) μm, with 2-5(-6) somewhat indistinct septa, hyaline, smooth, tip acute, base truncate to short obconically truncate, 1.5-2.5 μm wide, hila thickened and darkened.

Specimens examined.

Benin. Donga: Taneka-Koko , c. 441 m a.s.l., 9°51'30"N, 1°29'34"E, on Lablab sp., 29 Jul 2017, Y. Meswaet, M. Piepenbring, N. S. Yorou and participants of the summer school 2017, YMM23A ((M-0312647; UNIPAR). Same locality and host, 03 Aug 2016, Y. Meswaet, M. Piepenbring, N. S. Yorou and participants of the summer school 2016, YMM02 (M-0312648).

Hosts and distribution.

On Cercis chinensis ( Fabaceae ), Cosmos bipinnata Cav. ( Asteraceae ), Fallopia dumetorum (L.) Holub and Fagopyrum esculentum ( Polygonaceae ), Hibiscus syriacus ( Malvaceae ), Viola mandshurica W. Becker ( Violaceae ), from China, Japan, South Korea, Taiwan, Uganda and Venezuela ( Hsieh and Goh 1990; Groenewald et al. 2013). C. cf. fagopyri is cited here for the first time on Lablab sp. and the first time for Benin and West Africa.

Notes.

Currently there are two species of the genus Cercospora known on hosts belonging to Lablab , namely C. canescens and C. apii . The present Cercospora sp. (YMM23A) differs from C. canescens in leaf spot size, stromata and septation characteristics, as well as unbranched conidiophores. Above all, the sizes of the conidia of the present species are different [(24-)27.5-70(-78) × (2-)2.5-3(-4) μm versus 30-300 × 2.5-5 (-6) µm in C. canescens ]. C. apii differs by often small or lacking stromata, dense fascicules of up to 30 conidiophores, branched, longer conidiophores [20-300 μm versus (22.5-)36-157(-168) μm in C. cf. fagopyri ] and above all, longer and wider conidia [25-315 × 3-6 μm versus (24-)27.5-70(-78) × (2-)2.5-3(-4) μm in C. cf. fagopyri ] ( Chupp 1954).

Our sequence of the tef1 region of the specimen YMM23A from Benin is 100% similar to a sequence of Cercospora fagopyri on Fallopia dumetorum (GenBank JX143353) (Identities 233/233, i.e., 100%) and 99% similar to a further sequence of C. fagopyri on Fagopyrum esculentum (GenBank JX143352; Identities; 233/234, i.e., 99%). The identification of the present specimen as C. cf. fagopyri is only based on molecular data. Morphologically, descriptions of specimens of C. fagopyri on diverse host species in the literature differ and are quite confusing ( Hsieh and Goh 1990; Groenewald et al. 2013). In order to establish a morphological concept and to know the host range of C. fagopyri , fresh specimens need to be collected once again on Fagopyrum esculentum in Korea, where this species was originally collected and pathogenicity needs to be proven for diverse host species.

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 6. Cercospora cf. fagopyri on Lablab sp. (YMM 23 A) A fascicle of conidiophores growing out from a slightly developed stroma in the epidermis shown as part of a transverse section of a leaf B solitary conidiophores C conidia. Scale bars: 15 μm (A); 10 μm (B, C).