Fusarium

The genus Fusarium comprises a high number of fungal species that can be plant-pathogenic, causing diseases in several agriculturally important crops including cereals, and also can be harmful for humans and animals. Many of them produce a wide range of biologically active secondary metabolites (eg, mycotoxins) with an extraordinary chemical diversity. The biological activity of Fusarium mycotoxins can be detrimental to plants, and associated with cancer and other diseases in humans and domesticated animals. The combined effect of Fusarium species infecting several crops and producing mycotoxins in the field is the contamination of cereal grains and other plant-based foods. With many pathogenic and opportunistic species of the genus colonizing plants as part of a complex of Fusarium species, it provides an interesting example of biodiversity as well as a consequence of the different environmental conditions that exist in the various agro-ecosystems in which crops are cultivated. These conditions can also influence the fungal-plant interactions of the single species and their capability to produce mycotoxins. Moreover, the ability of various Fusarium species within the complexes to produce different classes of secondary metabolites combined with their ability to coexist in the same host or/and occur in quick succession have allowed these complexes to become "invincible armadas" against many plants.1 Plant infections by Fusarium can occur at all developmental stages, from germinating seeds to mature vegetative tissues, depending on the host plant and Fusarium species involved. Therefore, since most Fusarium species have specific mycotoxin profiles, early and accurate identification of the Fusarium species occurring in the plants at every step of their growth is critical to predict the potential toxicological risk to which plants are exposed and to prevent toxins entering the food chain. However, the unambiguous identification of mycotoxigenic Fusarium species still remains a most critical issue, given that the number of species (which stands now over 80)2 recognized in the genus has been constantly changing in the last century in accordace with the different taxonomic systems. Furthermore, this genus is provided of few morphological characters useful for species discrimination based only on traditional technique, although, fortunately, some of the most important toxigenic and pathogenic Fusarium species can be diagnosed, with some experience, by using only their morphological traits. Considering that the current criteria for Fusarium species identification [eg, morphological (MSR),3,4 biological (BSR) 5 and phylogenetic species recognition (PSR)6] rarely agree to each other, and that there are over 81 of the 101 most economically important plants each having at least one associated Fusarium disease 2 and each Fusarium species keeping its own toxicological profile,7 it is a challenge to ascertain the taxonomic status of Fusarium species on their phenotypical characteristics (including pathogenicity and toxigenicity) alone (www.apsnet.org/online/common/search.asp).