ABSTRACT
The fungal genus Fusarium contains some of the most economically and socially important species of plant pathogens affecting agriculture and horticulture. Diseases such as head blight of wheat and Fusarium wilt of bananas have not only caused enormous losses to crops, such as wheat and bananas around the world, but also have had a huge impact on the communities that depend on these crops (McMullen et al., 1997; Ploetz, 1990; Windels, 2000). The genus is a complex, polyphyletic grouping whose taxonomy has been controversial for at least a century, with recognized species numbers ranging from over 1000 at the beginning of the 1900s to as few as nine in the 1950s and 1960s. Current estimates are around 50 (Kirk et al., 2001). While there has been considerable research on genetic diversity within many taxa in the genus, because of their economic importance, the available information is still less than for many other pathogens of similar or lesser economic import. The research that has been conducted has practical implications in terms of plant breeding and epidemiology, with effective controls now available for many important Fusarium diseases. Indeed, it is within this disease context that even the most basic of studies has been conducted. Studies of genetic diversity in the genus, usually in biogeographical or evolutionary biology contexts, have increased as molecular tools that detect variation with no observable impact on morphological characters have become available. To appreciate these relatively recent genetic diversity studies, an understanding of the identification, nomenclature and taxonomy of taxa within the genus Fusarium is needed.
