Screening of fungal contaminants in banana tissue cultures in Jkuat, Kenya

Abstract

Tissue culture is prone to high costs of production arising from losses incurred from fungal contamination. The aim of the study was to characterise fungal contaminants and elucidate the exhibited mode of resistance to most preferred sterilants. Twenty nine fungal samples were collected at the different stages of tissue culture growth, using purposive sampling technique. Morphology results were confirmed by molecular characterization using fungal 18S rRNA sequences. Biochemical and antibiosis tests, identification of genes for capsulation and ATP binding Cassete (ABC) transporters, were performed to show the relationship between the fungi and sterilants resistance. Amylases and proteases were highly expressed by all isolates while xylanases and lipases were moderately expressed and esterases were lowly expressed. Only fourteen isolates had antagonistic activity for Candida albicans while nine of them had antagonistic activity for Pseudomonas aeruginosa. Three isolates were both antagonistic for Staphylococcus aureus and for Escherichia coli. Cunninghamella bainieri (10R) recorded a unique antibiosis and extra cellular enzymatic activity (p<0.05). All the isolates were positive for mdr1 gene and three isolates had CAP64 capsule genes. Aspergillus sp., Penincillium sp., Cladosporium sp., Cunninghamella sp. and Fusarium sp. were identified to be the major fungal contaminants of tissue culture banana cultures in JKUAT laboratories. Key words: Tissue culture, 18S rRNA, fungal contaminants, banana cultures.