Abstract
Aflatoxins, produced by ubiquitous Aspergillus section Flavi species, are polyketide pathway-derived secondary metabolites and, due to their highly carcinogenic, mutagenic, and teratogenic nature, pose human severe health issues globally. In this study, raw groundnut kernels were collected from groundnut growing districts of Punjab, Pakistan, at pre and post-harvest stages. Groundnut-associated Aspergillus flavus isolates were morphologically identified, and their respective aflatoxins producing potential was determined through cultural methods; UV illumination and ammonia vapor exposure. Three hundred isolates were cultured on differential media, Malt extract agar, and Sabouraud dextrose agar, for studying typical morphocultural characteristics, and detailed microscopy. Observed phenotypic variability assorted isolates into twenty groups. Representative isolate of each group was grown on coconut agar medium and exposed to UV illumination and ammonia vapors to observe possible fluorescence excitation and reverse colony color change, respectively. Results of both cultural methods conformed to each other; 35% of isolates produced fluorescent ring upon UV exposure and pinkish reverse colony color upon ammonia vapors exposure (toxigenic), 50% isolates showed no change (atoxigenic), and 15 % showed unclear results. This study provides evidence that groundnut kernels are highly exposed to toxigenic A. flavus strains both at pre and post-harvest stages.