Atoxigenic black aspergilli populations in Trentino: a natural biocontrol threaten by climate change?

Ochratoxin A (OTA) is a potent nephrotoxic and carcinogenic mycotoxin. After cereals, wine is considered the second major source of OTA intake in European diet. Responsible of OTA contamination of grapes are members of Aspergillus Section Nigri, also known as black aspergilli, in particular A. carbonarius and A. niger. Due to the relatively high optimum growth temperature of black aspergilli, OTA contamination represents a particularly severe problem in southern, hot environments. In fact, OTA has been never detected in grape musts produced in the region of Trentino (Northern Italy). A survey conducted in vineyards of Trentino during September 2008 and 2009 revealed that only A. japonicus, an atoxigenic species, was present in large quantity; whereas A. carbonarius could not be detected and isolated A. niger strains did not produce OTA. As illustrated by biocontrol experiments using non-aflatoxigenic A. flavus, atoxigenic strains compete with toxigenic strains for the same sites for growth, resulting in a lowered mycotoxin contamination of the agricultural product. We hypothesise that under the present environmental conditions in Trentino, populations of atoxigenic black aspergilli competitively exclude toxigenic strains, working as natural biocontrol. Observed climate change can have an effect on the interactions of black aspergilli leading to the establishment of toxigenic strains in vineyards of Trentino. This hypothesis will be tested with in vitro experiments to evaluate the effects of temperature on the interactions between atoxigenic and toxigenic black aspergilli strains