First Report of Ganoderma ryvardenii causing Basal Stem Rot (BSR) disease on oil palm (Elaeis guineensis Jacq.) in Ghana

Abstract

Backgrounds Oil palm ( Elaeis guineensis Jacq.), is the most significant and highest-yielding crop among oil-producing crops worldwide. In 2020/2022, Basal stem rot (BSR) disease was observed in six oil palm growing Districts in Ghana. Methods Field study and laboratory analysis were conducted. A random sampling technique was used to select five plantation blocks from each District. Single-point disease assessments were done using Standard Operating Procedure (SOP) with a severity scale of 0-4. Molecular assays were performed on each sample using nucleic acid as a template. ITS and GanET sequence analysis were performed along with the formation of a phylogenetic tree using the FASTA algorithm with the Fungus database from EBI and NCBI GenBank. Koch’s postulate was followed to confirm the disease. Results The disease incidence was 11.3 % with the highest severity score of 4. BSR is characterised by stem decay large-perennial, woody brackets basidiocarps of average measurement of 2-65 cm in diameter on infected palms. Culture colonies were white, striated, undulating, woolly-cottony, and creamish pigment on the reverse depicting attributes of Ganoderma fungus. Molecular confirmation was done by combining ITS sequence of top matches of >97% to members of the genus Ganoderma , >98% and 99.3% identity to three sequences of Ganoderma sp. (HM138671; HM138670 and HM138672) generated from strains assigned to Ganoderma ryvardenii and compared with 132 published sequences of Ganoderma isolates. Conclusion This is the first report of Ganoderma ryvardenii causing BSR disease on oil palm in Ghana and possibly the second report in Africa. However, the pathogen was first reported to cause similar diseases in oil palm in Cameroon.