Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 8/20/1998
Publication Date: N/A
Technical Abstract: Fusarium oxysporum is divided into formae speciales, races, and clonal lineages (VCGs). Knowledge of the phylogenetic relationships between these taxa is essential for developing proper diagnostic tools as well as for predicting the pathogenic behavior and potential of strains. By comparing DNA sequences of nuclear (EF-1() and mitochondrial (mtSSU rDNA) genes, O'Donnell et al. (1998) were able to demonstrate that F. oxysporum comprises three major clades. Isolates of F. oxysporum f.sp. cubense fell in five phylogenetically distinct lineages within two of the three major clades. The present study was undertaken to test whether other formae speciales also consist of fungi with independent evolutionary origins. EF-1alpha and mtSSU rDNA sequences were analyzed for F. oxysporum f. spp. dianthi, gladioli, lilii, tulipae, and opuntiarum, as well as for a number of nonpathogenic isolates. Members of these formae speciales were nested in all three major clades. Only a single nonpathogenic isolate from lily was nested in clade 1. Clade 2 comprised F. oxysporum f. sp. dianthi, f. sp. lilii, and three VCGs of f. sp. gladioli. Clade 3 comprised F. oxysporum f. sp. tulipae, f. sp. opuntiarum, and three other VCGs of f. sp. gladioli. Biocontrol strains from carnation were not closely related to f. sp. dianthi, nor were nonpathogenic isolates from lily closely related to f. sp. lilii. AFLP analyses supported the distinction of F. oxysporum f. sp. opuntiarum as a monophyletic group and supported the resolution of F. oxysporum f. sp. gladioli into two distinct major clades. The results indicate that F. oxysporum f. sp. dianthi and f. sp. gladioli are paraphyletic with respect to other taxa within the F. oxysporum complex.