Touré, O. Y., N. K. A. Chabi, G. C. Tchemadon, E. G. Achigan-Dako, B. Nebie, and L. A. C. Afouda. 2025. “First Report of Agroathelia rolfsii Causing Stem Rot on Kersting’s Groundnut (Macrotyloma geocarpum) in Benin.” New Disease Reports 52, no. 2: e70074. https://doi.org/10.1002/ndr2.70074
Kersting’s groundnut (Macrotyloma geocarpum) is an opportunity crop cultivated in several West African countries, mainly Benin (Agossou et al. 2023). It is highly prized for its nutritional, cultural and economic value. Despite its potential, this legume is considered a neglected and underutilised species, subject to several constraints, including disease, which is a bottleneck inproduction.
During September and October 2021, stem rot was detected in Kersting’s groundnut growing in the central Benin cotton and clay soil zones, with incidence rates of 0.74% and 0.21%, respectively. Stem rot symptoms were mainly observed near the base of the stems. The infected stems exhibited slightly depressed, brown lesions covered with rapidly growing white mycelial mats (Figure 1). Dark brown sclerotia were also observed in these plants. In the laboratory, samples of infected plants were cut into small pieces, disinfected in 0.35% sodium hypochlorite for1 min, then in 70% alcohol for 1 min, and rinsed three times with sterile distilled water. After air drying, they were placed in Petri dishes containing potato dextrose agar (PDA) medium and incubated at 25◦C for 7 days. After this incubation period, white mycelia and sclerotia formed on PDA. Pure cultures were obtained by removing mycelial fragments and transferring them to new Petri dishes containing PDA. The plates were incubated for 5–10 days at 25◦C. Sclerotia,1–2 mm in diameter, formed on the fungal colonies and gradually turned from white to dark brown with age (Figure 2). Clamp connections were also observed (Figure 3).
