Structure of an Aspergillus flavus population from maize kernels in northern Italy.

In order to gain insight into the causal agents of aflatoxin contamination of maize in Italy, populations of Aspergillus flavus on maize produced in the most affected area were characterized. Forty-six percent of A. flavus, isolated from maize kernels collected in 5 districts of northern Italy between 2003 and 2010, were unable to produce detectable levels of aflatoxins. The genetic diversity of the population was assessed by analysis of vegetative compatibility groups (VCGs) and presence or absence of several aflatoxin biosynthesis genes. Forty-eight VCGs were identified through complementation between nitrate non-utilizing mutants. Twenty-five VCGs contained only atoxigenic isolates, and the remaining 23 only aflatoxin producers. Members of the largest atoxigenic VCG (IT6) were found in 4 of the 5 districts sampled. Six deletion patterns of genes in the aflatoxin biosynthesis gene cluster were detected. No deletions in the cluster were detected for twelve atoxigenic isolates and 10 had the entire cluster deleted. One isolate had a deletion pattern only seen once before in Nigeria. The basis for initial selection of endemic atoxigenic strains of A. flavus for biological control of aflatoxin contamination of maize in Italy is provided.