Aflatoxin levels and Aspergillus species in maize in the Province of Isabela, Philippines

The province of Isabela is the top maize producer in the Philippines. The intensive cultivation and the tropical climate in the region may favour fungal growth and aflatoxin contamination in maize grains. Thus, the study aimed to determine the occurrence of aflatoxin and mycotoxigenic Aspergillus species in maize varieties in this region. Samples were obtained in six municipalities from hybrid (Bt) maize (n = 101) and open-pollinated varieties (n = 6) during the dry season (March and April) of 2019. Aflatoxin levels were quantified through enzyme-linked immunosorbent assay, and Aspergillus species were identified through cultural and molecular methods. Aflatoxin was detected in 50.5% of maize samples; 49.5% of samples were less than the limit of detection (3 mu g/kg), 16.8% with 3-20 mu g/kg, 10.9% with 21-50 mu g/kg and 22.8% above 50 mu g/kg. Samples within the acceptable level were 66.3% for food (<20 mu g/kg) and 77.2% for animal feed (<50 mu g/kg), while 22.8% of samples were above the acceptable level of the Philippine National Standard for raw maize grains. More than 90% of Aspergillus species detected were A. flavus. Other species identified were A. tamarii and A. terreus. Despite the dry production season in the province with low relative humidity during harvesting, inadequate post-harvest practices and the presence of A. flavus elevated the level of aflatoxin in sample grains. Additional work involving multi-year surveys is needed to confirm the results and conclusions of this study.