Basal Stem Rot of Oil Palm in Southern Region of Côte d’Ivoire: Pathogen Identification

Background: Basal stem rot (BSR) affects oil palm cultivation in Côte d’Ivoire. Although the disease has been documented in southern plantations, the identities and pathogenicity of associated fungal isolates remain insufficiently characterised. Aims: To identify fungal isolates associated with BSR in southern Côte d’Ivoire and assess their pathogenicity on oil palm seedlings. Study Design: Laboratory identification and nursery pathogenicity experiments. Place of Study: Oil palm plantations in Ehania, Eloka and Boubo, with pathogenicity testing at the Robert Michaux Research Station, Dabou. Methodology: Basidiocarps were collected from symptomatic palms, and isolates were identified using internal transcribed spacer (ITS) sequencing and phylogenetic analysis. Two-month-old oil palm seedlings were inoculated by immersing their roots in mycelial suspension for 30 minutes. Disease incidence and disease severity index (DSI) were assessed for GN6, GN13 and GN19. Results: Three of 15 sampled basidiocarps exhibited typical Ganoderma characteristics. The three isolates showed 95–96% ITS sequence similarity to Ganoderma zonatum and grouped with this species in the phylogenetic analysis. Seedlings developed chlorosis and necrosis following inoculation. Overall disease incidence was 83.32% for GN6, 69.77% for GN13 and 68% for GN19. At three weeks, DSI values were 83%, 63% and 88%, respectively. GN6 had the highest overall disease incidence, whereas GN19 had the highest week-three DSI. Conclusion: The findings support an association between G. zonatum and BSR in the sampled plantations. Further sampling and pathogenicity testing are required to establish the distribution and variability of the associated isolates.