Mycotoxin Production and Genetic Diversity of Aspergillus flavus Isolates Recovered from Stored Pistachio Nuts

Abstract

Stored pistachio nuts are highly susceptible to contamination by Aspergillus flavus, a toxigenic fungus responsible for aflatoxin production, posing serious risks to food safety and trade quality. The present study investigates mycotoxin production potential and genetic diversity among A. flavus isolates recovered from stored pistachio samples. Fungal isolation was carried out from visibly moldy and asymptomatic nuts on selective media, and isolates were characterized based on colony morphology, conidial structure, and growth rate. Aflatoxin production was quantified under laboratory conditions using standard analytical techniques, revealing considerable variation in toxigenic potential among isolates. Molecular characterization was performed using ITS rDNA and aflR gene sequencing to assess genetic diversity and toxin-related gene presence. Phylogenetic analysis demonstrated significant genetic variability, with isolates clustering into distinct lineages corresponding to high- and low-aflatoxin producers. This variation suggests the coexistence of genetically diverse populations within storage environments. Environmental factors such as moisture content and storage temperature were found to influence both fungal proliferation and mycotoxin synthesis, with higher toxin production under warm and humid conditions. The study highlights a strong correlation between genetic makeup and aflatoxin-producing ability, emphasizing the importance of molecular tools in identifying high-risk strains. These findings underscore the need for improved postharvest handling, proper drying, and storage practices to minimize fungal contamination. Overall, the results provide important insights into the genetic diversity and mycotoxin potential of A. flavus in pistachio storage systems and contribute to the development of effective strategies for managing aflatoxin contamination in nut crops, ensuring food safety and market quality compliance.