Fumonisin and ochratoxin-producing strains of Aspergillus section Nigri are associated with onion (Allium cepa L.) bulbs sold in markets in southwest Nigeria

A total of 200 isolates of <i>A. niger</i> were isolated from the onion bulbs, and 22 (11%) isolates amplified at least two <i>fum</i> genes, while three (1.5%) amplified the <i>pks15ks</i> gene. All isolates were positive for <i>fum1</i> and <i>fum19</i>. The highest/lowest percentage of the location/isolates of <i>fum</i> and <i>pks15ks</i> was Agbowo/Omi with 32.0%/2.1% and Dugbe/Agbowo with 6.7%/2.3%, respectively. Hence, the use of multiplex PCR to detect FB₂ and OTA biosynthetic genes in the isolated <i>A. niger</i> strains from the locally sourced onion bulbs will assist onion growers in the mass production of healthy onion seedlings with export potential and quality. Early detection of FB₂ and OTA biosynthetic genes is important to predict possible mycotoxin-producing <i>A</i>. section <i>Nigri</i> in onion bulbs.