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 nine 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 three new species occurring on grapes: A. brasiliensis, A. ibericus, and A. uvarum. Similar studies on the Aspergillus species occurring on coffee beans have evidenced in the last five years that A. carbonarius is an important source of ochratoxin A in coffee. Four new species within the black aspergilli were also identified in coffee beans: A. sclerotioniger, A. lacticoffeatus, A. sclerotiicarbonarius, 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. Within A. flavus and other Aspergillus species capable of aflatoxin production, considerable diversity is found. We summarise the main recent achievements in the diversity of the aflatoxin gene cluster in A. flavus populations, A. parasiticus and the non-toxigenic A. oryzae. Studies are needed in order to characterise the aflatoxin biosynthetic genes in the new related taxa A. minisclerotigenes and A. arachidicola.

The main source of ochratoxin A (OTA) in the wine food chain is the infection of grapes by ''black aspergilli'' in the field. OTA-producing black aspergilli include principally Aspergillus carbonarius, followed by A. niger and possibly A. tubingensis. They are opportunistic fungi that develop particularly on damaged berries at ripening, although they may occur and form OTA on grapes from veraison to harvest. Climatic conditions (high humidity and temperature) and geographical location are important factors favouring OTA accumulation in grape berries. The severity of aspergillus rot is influenced by excessive irrigation and rainfall prior to harvest, which causes berry splitting. In addition, berry wounds caused by insect attack provide preferential entries for black aspergilli. High OTA levels occur in grapes severely damaged by the grape moth, Lobesia botrana, particularly in Mediterranean areas. Some grape varieties display greater susceptibility to aspergillus rot due to intrinsic genetic characteristics and bunch conformation (i.e. compact4sparse). Control measures for toxigenic mycoflora in the vineyards must consider these critical control points. Proper fungicidal and insecticidal treatments can reduce OTA contamination. Nevertheless, knowledge about the fate of OTA and its distribution in wine and winery byproducts is important to manage OTA risk in contaminated stock. In our wine-making experiments, only 4% of the OTA present in grapes remained in the wine -the majority is retained in pressed grape pomaces. OTA concentration remained unchanged in wine after a 1-year aging as well as in all liquid fractions collected during vinification (i.e. must, free run wine, and wine after first and second decantation). Activated carbon can reduce OTA levels in wine but negatively affects wine quality.

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Aspergillus niger has been recently found to produce fumonisin B(2) (FB(2)). Thirty-one strains belonging to four Aspergillus species isolated from grape were evaluated for FB(2) production on agar plates. Four out of eight strains of A. niger produced FB(2) (29-293 microg g(-1)). None of the strains of A. uvarum (n = 7), A. tubingensis (8) and A. carbonarius (8) produced detectable amounts of toxin. The capability to produce FB(2) was also confirmed by some A. niger strains artificially inoculated on grape berries. Natural occurrence of FB(2), at levels of 0.01 and 0.4 microg ml(-1), was found in two samples of must collected in Apulian cellars in 2007. This is the first report of FB(2) contamination in must. These findings suggest that there is a potential risk of exposure to FB(2) in the grape-wine chain for consumers and that A. niger may represent the major fumonisin-producing species among black Aspergilli occurring on grapes.