Isariopsis griseola Sacc., Michelia 1: 273. 1878.

For synonyms see Crous and Braun (2003), Crous et al. (2006) or MycoBank.

Italy. Selva, on Phaseolus vulgaris L. (Fabaceae), Aug 1877, Saccardo, Mycotheca Veneta 1247 (Lectotype: HAL, designated by Videira et al. 2017: 401, MBT378593, n.v.; Epitype: CBS H-19683, designated by Videira et al. 2017: 401, MBT378594, n.v.).

For illustrations see: Saccardo (1881), Fragoso (1927), Deighton (1990), Shin and Kim (2001) or Crous et al. (2006).

Leaf spots amphigenous, subcircular to irregularly angular, 2.5–7(–9.5) mm diam., reddish brown to dark brown or sometimes greyish brown to dark reddish brown, surrounded by a narrow darker margin. Caespituli amphigenous, mainly hypophyllous, reddish brown to olivaceous brown. Mycelium internal and external. External hyphae branched, 2.5–3 μm wide, septate, olivaceous brown to brown, smooth. Conidiophores in dense synnematous fascicles, synnemata up to 250 µm high, 20–40(–65) µm wide, emerging through stomatal openings or erumpent, or conidiophores solitary, arising from external hyphae, straight to sinuous or somewhat geniculate, 3–5(–6.5) μm wide, 1–6-septate, smooth, olivaceous brown to brown. Conidiogenous loci not thickened and not darkened, rather inconspicuous. Conidia solitary, narrowly obclavate to subacicular, straight to curved, (22–)30–78(–83) × (4.5–)5–7 μm, 2–6-septate, olivaceous brown, smooth, apex subacute to rounded, base truncate to obconically truncate, (2.5–)3–4(–4.5) µm wide, hila not thickened and not darkened.

Benin. Borgou: Parakou, Tankaro, c. 360 m a.s.l., 9°23'01"N, 2°30'36"E, on Phaseolus lunatus, 20 Sep 2019, Y. Meswaet and R. Dramani, YMM297A (M-0312675; UNIPAR).

Pseudocercospora griseola. On Phaseolus sp.: USA. Pennsylvania: West Chester, Gardens, Sep 1880, W. T. Harris 1363 (NY 00937289 Holotype of Graphium laxum). On Phaseolus sp.: USA. Pennsylvania: West Chester, Gardens, Sep 1880, W. T. Harris s.n (BPI 448758 Paratype of G. laxum). On Phaseolus sp.: USA. New Jersey: Newfield, 27 Sep 1894, Ellis, s.n (BPI 435104 Paratype of Cercospora columnaris Ellis & Everh.). On P. vulgaris: Italy. Venetia, Selva, Aug 1877, Sacc. Mycoth. Ven. s.n (BPI 449390, isolectotype of Isariopsis griseola).

On Lablab purpureus (L.) Sweet (as Lablab niger Medik.), Lathyrus odoratus L., Macroptilium atropurpureum (DC.) Urb., Phaseolus acutifolius A. Gray, P. coccineus L., P. lunatus, P. vulgaris, Vigna angularis (Willd.) Ohwi & H. Ohashi, V. mungo, V. radiata, V. umbellata (Thunb.) Ohwi & H. Ohashi (as P. pubescens Blume), V. unguiculata (L.) Walp. (Fabaceae) from worldwide, including Angola, Argentina, Armenia, Australia, Austria, Bhutan, Brazil, Bulgaria, Burundi, Cameroon, Canada, China, Colombia, Costa Rica, Croatia, Cuba, Democratic Republic Congo, Dominican Republic, Ecuador, El Salvador, Ethiopia, Fiji, Georgia, Germany, Ghana, Great Britain, Greece, Guatemala, Haiti, Hungary, Jamaica, Japan, India, Indonesia, Iran, Ireland, Israel, Italy, Ivory Coast, Jamaica, Japan, Kenya, Korea, Laos, Latvia, Malawi, Madagascar, Malaysia, Mauritius, Mexico, Mozambique, Nepal, Netherlands, Netherlands Antilles, New Caledonia, New Zealand, Nicaragua, Nigeria, Norfolk Island, Panama, Papua New Guinea, Paraguay, Peru, Philippines, Poland, Portugal, Puerto Rico, Reunion (France), Romania, Russia, Rwanda, Saint Helena (British), Senegal, Sierra Leone, Singapore, Slovenia, Solomon Islands, Somalia, South Africa, Spain, Sudan, Suriname, Swaziland, Switzerland, Taiwan, Tanzania, Thailand, Trinidad and Tobago, Turkey, Uganda, Ukraine, U.S.A., Vanuatu, Venezuela, Virgin Islands, Zambia, Zimbabwe (Crous and Braun 2003; Crous et al. 2006; Farr and Rossman 2021). Ps. griseola is reported here for the first time for Benin.

Four species of Pseudocercospora, namely Ps. cruenta, Ps. glycines (Cooke) Deighton, Ps. griseola and Ps. stizolobii are known agents of leaf spot diseases on Phaseolus spp. (Farr and Rossman 2021). The present Pseudocercospora sp. is phylogenetically (Fig. 1) and morphologically well distinguished from Ps. cruenta, Ps. glycines and Ps. stizolobii (Crous et al. 2006) by forming synnematous fascicles, longer and broader conidiophores and broader conidia. The morphology of this collection from Benin on P. lunatus fits well with the description of Ps. griseola.

Angular leaf spot (ALS) caused by Ps. griseola is a serious disease of common bean (P. vulgaris) all around the world (Ddamulira et al. 2014). It is reported for about 80 countries, where it can cause 45% to 80% losses of yield under conditions favourable for the fungus (Guzmán et al. 1999). The disease is also a major problem for bean production (50–60% of yield losses) in Africa, mainly in the Great Lakes Regions (Kenya, Uganda, Tanzania and Rwanda) where bean growing is popular (Golato and Meossi 1972; Wortmann et al. 1998; Aggarwal et al. 2004). According to Guzmán et al. (1995) and Crous et al. (2006), the species includes two major intraspecific groups, Ps. griseola f. griseola (Andean) and Ps. griseola f. mesoamericana (Middle-American) (Crous et al. 2006). Based on ITS sequence data (see Suppl. material 3), the present isolate from Benin clusters with Ps. griseola f. mesoamericana.