Brachiaria (syn. Urochloa) grass is rapidly gaining popularity as a new forage option in sub-Saharan Africa including Rwanda. During disease surveillance in Rwanda in 2018–2019, Brachiaria foliage was found with necrotic purple spots with a whitish centre on the upper surface of leaves (Figure 1). Diseased leaves were collected from farmers’ fields in Bugesera (02°08'33.4'' S, 030°09'08.8'' E), Huye (02°28'54.8 S, 29°46'.56.9 E), Nyagatare (01°18'56.16 S, 030°18'18.24 E) and Rwamagana (01°58'49.62 S, 030°27'29.82 E) districts. Pathogen isolation and identification was done in the Plant Pathology Laboratory of the Rwanda Agriculture and Animal Resources Development Board in Rubona, Rwanda. The pathogen was isolated and grown on commercial potato dextrose agar (PDA) amended with ampicillin (100 μg ml 1) and incubated at 24°C for two weeks (Ghimire et al., 2011). A total of four isolates, one isolate from each district, were used for morphological characterisation, molecular identification and pathogenicity testing. Morphological characterisation included colony growth patterns, colour, shape and size of conidia and conidiophores. The molecular identity was determined based on the internal transcribed spacer (ITS) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene sequences (White et al., 1990; Berbee et al., 1999). Pathogenicity testing was performed for individual isolates by inoculation of one-month old Brachiaria humidicola cv. Humidicola seedlings with a conidial suspension of 105 spores ml 1 (Fajolu, 2012). The colony colour was whitish to brownish at the bottom with irregular edges until the first ten days then became blacker with whitish and irregular edges at 14 days. The conidia measured 61–77 × 12–14 μm while conidiophores measured 268–284 × 6–8 μm. The ITS sequences of the four isolates had the highest identity (97.6 - 99.6%) with Bipolaris secalis (GenBank Accession No. MH864688.1) and their GAPDH sequences had the highest identity (98.7- 99.8%) with Bipolaris secalis isolectotype culture (KJ415409.1). The sequences of these four isolates were deposited in GenBank (MW159735, MW159737, MW159741 and MW159745 for ITS; OP588632-OP588635 for GAPDH). The organisms reisolated from inoculated seedlings had similar morphology, and identical ITS and GAPDH sequences to the isolates used in inoculations. This is the first report of Bipolaris secalis as the causal agent of leaf spot disease of Brachiaria grass. Bipolaris species are reported to have a broad host range, primarily within the family Poaceae (Manamgoda et al., 2014). The morphological characteristics of conidia and conidiophores in this study were within the ranges reported previously for the species (Sisterna, 1989; Bernardi et al., 2018). Bipolaris species have been grown on PDA and other media, on which similar features, including colony colour, have been reported (Manamgoda et al., 2014). The GAPDH gene has been recommended as the best marker to discriminate Bipolaris species (Bhunjun et al., 2020). Despite a wider distribution of Bipolaris secalis in Rwanda the implications for Brachiaria and other forage species in sub-Saharan Africa are yet to be determined.

FROM：https://bsppjournals.onlinelibrary.wiley.com/doi/full/10.1002/ndr2.12156