Increased sensitivity of Aspergillus flavus and Aspergillus parasiticus aflatoxin biosynthesis polyketide synthase mutants to UVB light

One strategy to reduce aflatoxin contamination of maize and cottonseed is to introduce spores of non-aflatoxigenic strains as competitors. Using isogenic mutants we show that, upon 5 or 20 min exposure to 302 nm (UVB) light, the viability of conidia of Aspergillus flavus and Aspergillus parasiticus mutants lacking the ability to accumulate any aflatoxin precursor metabolite is reduced five-fold compared to that of aflatoxin-producing strains or pigmented mutants that accumulate aflatoxin precursors. This result suggests that the long-term viability of introduced non-aflatoxigenic competitor strains may be lower than that of natural aflatoxin-producing isolates when exposed to sunlight.