Abstract
Sesame Sesamum indicum L. is a major oil-based seed crop that has been widely cultivated and consumed in Pakistan. Unfortunately, sesame is highly prone to Aspergillus fungal growth in the field, and under inappropriate storage conditions can become contaminated with aflatoxins, the most potent carcinogen found in nature. Here, we have isolated a high number of Aspergillus isolates from sesame seeds in fresh and stored conditions obtained from rainfed and irrigated zones of Punjab, Pakistan, and characterized them for aflatoxigenic potentials. Using morphological identification techniques, 260 isolates were grouped as potential Aspergillus section Flavi, with 126 and 134 originating from the rainfed and irrigated zones, respectively. Out of 260 in total, 188 isolates were confirmed to produce aflatoxins. There were no significant differences in potential aflatoxigenic isolates with respect to the rainfed and irrigated zones. However, the number of potential aflatoxigenic isolates was significantly higher (p < 0.05) in stored samples than that of those from fresh sesame seeds in the rainfed and irrigated zone. Whole genome sequencing and comparative analyses of 12 select isolates have revealed that one of the A. flavus isolates, which produced very low aflatoxins (AFP10), has an elevated missense variant rate, numerous high impact mutations, and a 600 base pair deletion in the norB gene. In summary, our study provides insights into aflatoxigenic potential and the associated genetic diversity of indigenous Aspergillus section Flavi isolates and potential management strategies for reducing aflatoxin contamination levels in a major crop consumed in Punjab, Pakistan.
Highlights
Aflatoxins are a group of naturally occurring carcinogens and toxic secondary metabolites of the fungal genus Aspergillus [1]
Key Contribution: This study reports the distribution of aflatoxigenic and non-aflatoxigenic isolates of Aspergillus section Flavi in the rainfed and irrigated zones of Punjab, Pakistan and the genomic diversity of 12 indigenous Aspergillus flavus isolates from sesame seeds
The four major aflatoxins commonly isolated from foods and feeds are aflatoxin B1 (AFB1), aflatoxin B2 (AFB2), aflatoxin G1 (AFG1), and aflatoxin G2 (AFG2), which are categorized as group 1 human carcinogens by the International Agency for Research on Cancer (IARC) [3]
Summary
Aflatoxins are a group of naturally occurring carcinogens and toxic secondary metabolites of the fungal genus Aspergillus [1]. (AFG2), which are categorized as group 1 human carcinogens by the International Agency for Research on Cancer (IARC) [3]. AFB1 is the most toxic, common, and widespread food and feed contaminant and is responsible for 75% of all aflatoxin contamination [4]. Over half of the global population (some four billion people), mostly in developing countries, are at threat of chronic exposure to unknown levels of aflatoxins, which can be associated with decreased growth rate and feeding efficiency, reduced liver and kidney function, and immune system suppression [5,6]. 40% of human productivity is lost as a result of disorders associated with aflatoxin contamination [8]
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