Biodiversity of Aspergillus species in some important agricultural products.

The genus Aspergillus is one of the most important filamentous fungal genera. Aspergillus species are used in the fermentation industry, but they are also responsible of various plant and food secondary rot, with the consequence of possible accumulation of mycotoxins. The aflatoxin producing A. flavus and A. parasiticus, and ochratoxinogenic A. niger, A. ochraceus and A. carbonarius species are frequently encountered in agricultural products. Studies on the biodiversity of toxigenic Aspergillus species is useful to clarify molecular, ecological and biochemical characteristics of the different species in relation to their different adaptation to environmental and geographical conditions, and to their potential toxigenicity. Here we analyzed the biodiversity of ochratoxin producing species occurring on two important crops: grapes and coffee, and the genetic diversity of A. flavus populations occurring in agricultural fields. Altogether 9 different black Aspergillus species can be found on grapes which are often difficult to identify with classical methods. The polyphasic approach used in our studies led to the identification of 3 new species occurring on grapes A. brasiliensis, A. ibericus, and A. uvarum. The same studies on the Aspergillus species occurring coffee beans have evidenced in the last five years that A. carbonarius is an important source of ochratoxin A in coffee together with the previously known A. ochraceus. Four new species within the black aspergilli were also identified in coffee beans which namely are: A. sclerotioniger, A. lacticoffeatus, A. sclerocarbonarius, and A. aculeatinus. The genetic diversity within A. flavus populations has been widely studied in relation to their potential aflatoxigenicity and morphological variants L- and S-strains. We summarize the main recent achievements in aflatoxin gene clusters diversity in A. flavus populations, A. parasiticus and the atoxigenic A. oryzae, new studies are needed in order to characterize the aflatoxin genes in the new related taxa A. minisclerotigenes and A. arachidicola.