African yam bean (AYB; Sphenostylis stenocarpa) is an underutilized legume indigenous to Africa with great potential to enhance food security and offer nutritional and medicinal opportunities. However, low grain yield caused by fungal diseases, including pod blight and leaf tip dieback, deters farmers from large‐scale cultivation. To determine the prevalence of fungal diseases affecting leaves, pods and flowers of AYB, a survey was conducted in 2018 and 2019 in major AYB‐growing areas in Nigeria. Leaf tip dieback, flower bud rot and pod blight were the most common symptoms. Morphological and molecular assays were conducted to identify the causal agents of the observed diseases. In all the samples examined, fungi from eight genera were isolated from diseased leaves, buds and pods. Koch's postulates were fulfilled only for fungi belonging to the Colletotrichum genus. Fungi from the other seven genera did not produce disease symptoms in healthy AYB tissues. Several Colletotrichum isolates were characterized by sequencing the rDNA internal transcribed spacer (ITS), glyceraldehyde‐3‐phosphate dehydrogenase, calmodulin and ApMAT loci. A combined phylogenetic analysis revealed four Colletotrichum species: C. siamense, C. theobromicola and C. fructicola, which were recovered from diseased leaves, and C. truncatum, recovered from diseased pods and buds. Our results are useful to gear efforts to develop integrated management strategies to control diseases affecting AYB in Nigeria and elsewhere. Availability of such strategies may stimulate greater AYB cultivation, which can contribute to diet diversification, something repeatedly advocated by a range of stakeholders to increase food security and prosperity of smallholder farmers.

Part of this study, forming a component of the first author's doctoral dissertation, was presented at the British Society of Plant Pathology (BSPP) 2021—Our Plants, Our Future Conference in Birmingham, UK, facilitated by a BSPP Career Support Grant. The authors express sincere gratitude to the farmers and students (Olomitutu Oluwaseyi and Jeffrey Iheanacho) that provided access to their farms/research fields and allowed us to collect diseased tissues for conducting this research. The technical ...

https://doi.org/10.1111/ppa.13995

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Olaniyi Oyatomihttps://orcid.org/0000-0003-3094-374X

Michael Abbertonhttps://orcid.org/0000-0003-2555-9591

Alejandro Ortega-Beltranhttps://orcid.org/0000-0003-3747-8094

https://doi.org/10.1111/ppa.13995

Biotech and Plant Breeding; Plant Production and Health

Agronomy; Disease Control; Food Security; Plant Breeding; Plant Diseases; Plant Health; Plant Production; Smallholder Farmers

African Yam Beans; Integrated Management; Plant Diseases; Smallholder Farmers

Africa; West Africa

Nigeria

Headquarters and Western Africa Hub

Plant Pathology