Morphological and Molecular Characterization of Fungal Species Associated with Fusarium oxysporum f.sp. cubenese (Foc) in Gatundu North, Kenya

Abstract

Banana (Musa spp.) is the most produced fruit globally, serving as a vital food security crop and a rich source of nutrients. It is a staple food and a significant source of income for millions of people in tropical and subtropical regions. However, the current and future production of bananas is severely threatened by Fusarium wilt, also known as Panama disease, caused by Fusarium oxysporum f.sp. cubense (Foc). The banana rhizosphere hosts various fungal species that may be associated with the pathogenicity of Foc. This study characterized the fungal microbiome of bananas from three wards in Gatundu North, Kiambu County, Kenya. A total of 612 soil samples exhibiting symptoms of Fusarium wilt were collected from the sampling sites. Ninety-eight fungal species were isolated using serial dilution on potato dextrose agar (PDA) and subsequently characterized morphologically. DNA extraction from each species was performed using the internal transcribed spacer (ITS) regions of ribosomal DNA (rDNA) (ITS1 and ITS4), followed by sequencing via Sanger sequencing. The sequences were compared to the GenBank database using the Basic Local Alignment Search Tool (BLAST), and a phylogenetic tree was constructed using the neighbor-joining method in MEGA X software (version 6.1). The characterized isolates belonged to the following genera: Fusarium, Penicillium, Paecilomyces, Rhizoctonia,Trichoderma, Simplicillium, Epicoccum, Curvularia, Alternaria, Bipolaris, Exserohilum, Setosphaeria, Cochliobolus, Syncephalastrum,and several unidentified species. This study identifies fungal species associated with the pathogenesis of Foc in bananas in Gatundu North, Kiambu County, Kenya, and highlights the potential for developing biocontrol strategies for managing Panama disease. Abbreviations: Biocontrol Agent (BCA), Cetyltrimethylammonium bromide (CTAB), Fusarium oxysporum f.sp. cubenese ( Foc), Fusarium Wilt of Banana (FWB), Institute of Biotechnology Research (IBR), Internal Transcribed Spacers (ITS), Molecular Evolutionary Genetic Analysis (MEGA), Polymerase Chain Reaction (PCR), Potato Dextrose Agar (PDA)