Detection of potentially toxigenic Aspergilli in soil

Key chili and maize growing areas of Pakistan were selected for a focused baseline study of the levels of potentially toxigenic Aspergillus spp. Samples investigated included fresh chilies, year-old corn cobs and soil samples from selected locations. Isolates obtained from corn were screened for aflatoxin production using coconut milk agar, with one strain giving a positive, fluorescent reaction. Whole genome sequencing (WGS) with low coverage techniques were employed to screen the isolates for molecular differences in the ribosomal RNA gene cluster and mitochondrial genome. The WGS study was broadened to incorporate ITS rRNA metabarcoding for determining the microbial biodiversity of the soil samples and screening for the presence of toxigenic strains. Using information gleaned from the WGS results, a putative toxigenic operational taxonomic unit (OTU) was observed in four of the 15 soil samples screened by metabarcoding.