Development of microtitre plate-based assay for evaluation of fungicidal potential of cyanobacterial metabolites

An investigation was undertaken to optimise the microtitre plate-based assay for undertaking in-depth analyses of the potency and mode of action of cyanobacterial metabolites exhibiting fungicidal activity. The 96-well titre plate, using potato dextrose agar medium was standardised for evaluating minimum inhibitory concentration (MIC) of cyanobacterial metabolites against several phytopathogenic fungi, in terms of volume of media, concentration/volume of metabolite, inoculum and wavelength to be used for scanning. The optimised protocol was employed for recording growth inhibition in terms of MIC and facilitating microscopic analyses of morphological abnormalities induced by cyanobacterial metabolites in the fungal hyphae. This study not only illustrated the utility of the newly developed titre plate assay for analyses of large number of samples simultaneously and but also represented a first time report on microscopic observations related to various facets of fungicidal activity exhibited by cyanobacterial metabolites. Future research is directed towards scale up of this method for studies on tripartite interactions of cyanobacterial metabolites, target fungi with selected host plants, as a prelude to their use as biocontrol agents.