Phylogeny and Vcg Analysis of Vascular Competent and Incompetent Fusarium Oxysporum F. SP. Vasinfectum Pathotypes

Fov isolates belonging to all known races, biotypes, and most of known genotypes were characterized by phylogenetic and VCG analysis. VCGs with multiple members were sequenced for at least two members, and the resulting sequences were always identical except for VCG01111 members. Vegetative compatibility test provided a more precise finger print of various genotypes than the DNA sequence comparison but it failed to provide any phylogenic relationship among non-complementing groups.  Inclusion of nearly 6 kbp of DNA sequences for the phylogenetic tree construction enabled differentiation of most of the VCGs. Only VCG6, VCG0116 (race 6), and VCG9 cannot be distinguished by sequence type alone. Five clades consisting of  races 1, 2, and 6 lineage (VCG1A, 1B, 1C, 3, 6, 9, 0111, 0112, and 0116), race 8 lineage (VCG2 and 10), races 4 and 7 lineage (VCG16, 17, and 0114), race 3 lineage (VCG7, 14, 15, 0113, 01111, Au2), and the Australian biotype lineage (VCG01111) were observed. Pathogenicity assays indicated that races 1, 3, 6 lineage and race 8 lineage isolates were vascular competent pathotype while race 3, 4, 7 and Australian biotype isolates were vascular incompetent pathotype.  Race 7 isolate failed to vegetatively complement with race 4 isolates. However, California race 4 isolates and Chinese race 7 isolate showed similar pathogenicity profiles which were distinct from that of Australian biotype isolates even though they were all vascular incompetent. The Australian biotype isolates were phylogenetically very close to banana tropical race 4 F. oxysporum f. sp. cubense isolate II5 (VCG01213) and were probably introduced into Australian cotton field through Northern Territory as cubense tropical race 4 associated isolates.