DAO prepress abstract   -  DOI: https://doi.org/10.3354/dao03809

ABSTRACT: Fusarium is a huge genus of filamentous fungi that has the potential to cause emerging diseases. Members of this genus can cause infections in plants, animals and humans. Here, we report the isolation of Fusarium oxysporum and Fusarium equiseti from two important fish species, Oncorhynchus mykiss (rainbow trout) and Tor putitora (golden mahseer) respectively. F. oxysporum has emerged as a significant fungal pathogen causing infection in many fish. However, F. equiseti has been isolated mainly from plants. As far as the available literatures are concerned, this is the first report on the isolation of F. oxysporum and F. equiseti from these hosts. The isolates were identified based on growth morphology and microscopic observation. F. oxysporum produced violet pigmentation on potato dextrose agar while F. equiseti had yellow colouration. F. oxysporum produced one to two-celled microconidia along with straight or curved macroconidia having 3-4 septums. F. equiseti produced abundant macroconidia with four or more septums. Species were further confirmed based on the nucleotide sequences of the internal transcribed spacer region. In molecular phylogeny, F. oxysporum and F. equiseti formed two different clades. In antifungal sensitivity assay, F. oxysporum was found to be susceptible to clotrimazole with a minimum inhibitory concentration of 1.0 µg ml^-1 whereas F. equiseti was susceptible to clotrimazole, ketoconazole and fluconazole. Overall, the main findings of this study are the infection of new hosts by Fusarium species and the limited activity of many antifungal drugs against these pathogens.