Chapter Four

21
(Ranghoo, 1998). The traditional key for species identification was proposed by
Carolus Linnaeus in 1735 and has been accepted as the binomial nomenclature which
is mainly based upon morphological and biological characters. This system, however,
was considered several limitations. Generally, one major obstacle for fungal
identification is the difficulty in implementing the recognition criteria of homology
working with morphology at higher taxonomic levels (Morales et al., 1995). This
particularly occurs when these characters are highly variable and few in numbers
when compared to the large number of species described (Morales et al., 1995).
With the development of molecular techniques, the problem of homology has
decreased (Berres et al., 1995). Molecular biology is now widely used in fungal
systematics because it can clarify the relationship among taxa which can not delineate
using morphological characters. Fusarium, is a very complicated genus to identify
since morphologically species very similar in appearance. Brayford (1996) suggested
that the use of DNA sequencing is the ultimate means to assess the phylogeny of
Fusarium.
From the last dcade, molecular biology has developed rapidly with a variety of
techniques which are now available to mycologists to help understanding the
phylogenetic relationships of species and genera and concepts at higher taxonomic
levels. Traditionally taxonomy and identification of all living organisms has depended
on morphological characters. However, modern molecular methods are now being
used to detect cryptic species, separate closely related species, and determine
phylogenies. Within the fungi, where morphological characters are limited, molecular
techniques are proving very useful. Nowadays, there are many techniques used in
fungal studies and molecular tools utilize ITS rDNA, small and large subunit rDNA,