First Report of <i>Ceratocystis manginecans</i> Causing Wilt and Sudden Death in <i>Bouea macrophylla</i> (Plum Mango) in Indonesia

Bouea macrophylla (gandaria, plum mango) is a tropical fruit that grows in Southeast Asia, especially Indonesia, Malaysia and the Philippines. In September 2024, symptoms of wilt and stem canker were observed on 6-year-old B. macrophylla trees in the arboretum of Sriwijaya University and several community orchards in Prabumulih, South Sumatra, Indonesia. Affected trees exhibited progressive wilting, with leaves turning yellow to brown (Figure 1A). The diseased stems displayed distinct black lesions on the sapwood and darkly discoloured xylem (Figure 1B). Extensive bark peeling was observed on the branches of affected plants, with wounds caused by squirrel bites potentially serving as primary entry sites for the causal pathogen (Figure 1C) (Muslim et al. 2022). The disease resulted in yield losses exceeding 50% in several orchards. Samples taken from the sapwood through to the vascular tissues were surface-sterilised, placed between fresh carrot discs and incubated at room temperature as described by Pratama et al. (2021a). Perithecia resembling those of Ceratocystis developed after 5–7 days and were subsequently transferred to malt extract agar (MEA). The bases of the ascomata were dark brown to black, subglobose to globose in shape (Figure 2A). Ascomatal necks were erect, occasionally curved, black at the base and becoming subhyaline towards the apex, smooth to slightly roughened. Phialides were pale brown to hyaline (Figure 2B). All isolates had bacilliform and cylindrical conidia (Figure 2C). Chlamydospores were oval, thick-walled and smooth (Figure 2D). Ascospores were hat-shaped (Figure 2E). Based on these morphological characteristics, the isolate was identified as Ceratocystis sp. Amplification of the ITS, β-tubulin and TEF 1-α gene regions (Tarigan et al. 2011) yielded fragments of approximately 550 base pairs (bp). The resulting sequences (BMC1 and BMC2) were submitted to GenBank and assigned Accession Nos. PX393526 and PX443486 for the ITS region, PX589737 and PX89738 for β-tubulin, and PX589735 and PX589736 for TEF 1-α gene regions, respectively. Phylogenetic analyses were conducted using a concatenated dataset combining the ITS, β-tubulin and TEF 1-α gene regions, which confirmed that isolates BMC1 and BMC2 belong to C. manginecans (Figure 3). The pathogenic potential of the fungal isolates was assessed using the under-bark inoculation technique described by Muslim et al. (2025). Six-month-old B. macrophylla seedlings with stem diameters of 4–6 mm and heights of less than 100 cm were used for the pathogenicity assay. The seedlings were cultivated in 10 cm diameter plastic pots containing a soil mixture composed of topsoil, peat and chicken manure, maintained under a 50% shade net and watered daily. Wounds were created on the stems using a cork borer (4 mm diameter), and mycelial plugs of the same diameter, obtained from 14-day-old actively growing colonies of C. manginecans on 2% MEA (Pratama et al. 2021b), were inserted into the wounds with the mycelial surface facing inward. The inoculation sites were sealed with plastic film to minimise contamination and desiccation. Ten seedlings of each tree species were inoculated with sterile MEA plugs to serve as controls. The leaves and stems (Figure 4A,D) of control plants remained healthy and no lesions formed on the sapwood or heartwood (Figure 4F,H). On test plants the first symptoms appeared 14 days after inoculation when the plant stem turned black at the inoculation site on the stem wood (Figure 4E). Forty-five days after inoculation, the seedlings wilted and had desiccated leaves, and the discolouration of the wood extended into the heartwood (Figure 4B,C,F,G,I). Fungal isolates were successfully re-isolated from the inoculated tissues, and their morphology was identical to the inoculated isolates (BMC1 and BMC2), thereby fulfilling Koch's postulates. This study constitutes the first report of C. manginecans causing wilt and dieback in B. macrophylla in Indonesia and globally. The authors would like to express their gratitude to the leadership of the Faculty of Agriculture, Sriwijaya University, Indonesia, for granting permission to use the laboratory and its facilities.