Submitted to: Studies in Mycology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/24/2007
Publication Date: 12/21/2007
Citation: Perrone, G., Susca, A., Cozzi, G., Ehrlich, K., Varga, J., Frisvad, J.C., Meijer, M., Noonim, P., Mahakarnchanakul, W., Samson, R.A. 2007. Biodiversity of Aspergillus Species in Some Important Agricultural Products. Studies in Mycology 59:53-66. Interpretive Summary: This manuscript is part of a multi-authored paper reporting studies regarding the causes of Aspergillus diversity. Aspergillus flavus is a fungus that is able to contaminate corn and cotton with the very toxic and cancer-causing chemical, aflatoxin. A. flavus soil populations are very complex and contain two forms that differ in their abilities to produce aflatoxin. The soil also contains some populations that are unable to make aflatoxin. In this review, we describe the current knowledge about the diversity of these populations and how this diversity may be a consequence of agricultural use of the land. We hypothesize that A. flavus in an agricultural environment compared to non-agricultural soil environments more frequently loses the ability to make aflatoxin. Therefore, in time, with an increase in the population of non-aflatoxin-producing types of A. flavus, it is likely that aflatoxin contamination will eventually not be a threat to growing corn and cotton in the United States.
Technical Abstract: 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 summarize 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.