Molecular Diagnosis of Toxigenic Fusarium Species

Abstract

Correct identification of species in Fusarium genera is important because many species are plant pathogens and same isolates produce potent mycotoxins (Marasas et al., 1984). Methods that have been used in Fusarium systematics include DNA-DNA hybridization (Ellis, 1988), RFLP analysis (Manicom & Baayen, 1993), RAPD markers (Schilling et al., 1996), isozyme (Huss et al, 1993), sequence analysis (O’Donnell, 1996) and electrophoretic karyotyping (Fekete et al., 1993). DNA-DNA hybridization may reflect relatedness at the level of isolates, but RFLP and karyotype analyses typically differentiate at level of genetically isolated groups. Problem with F. oxysporum in Boehm et al. (1994) where they found karyotype variation in strains belonging to the same VCG. RAPDs have been used to detect genetic differences between and within species. Variation in nucleotide sequence demonstrates relatedness at different levels depending on the sequence chosen for analysis. O’Donnell (1996) recently have developed a DNA sequence database using four loci: beta tubulin gene introns/exons, mitochondrial small subunit (mtSSU) rDNA, nuclear large subunit (LSU) rDNA, and nuclear rDNA internal transcribed spacer (ITS) region. We found positive correlation between phylogeny, secondary metabolites production and the sequence of nuclear LSU 28S rDNA.