Identification of a New Genotype of Fusarium oxysporum f. sp. vasinfectum on Cotton in China.

Genetic composition of Fusarium oxysporum f. sp. vasinfectum strains, including race 3, 7, and 8, Australian genotype strain, and 80 strains collected from China, were studied using amplified fragment length polymorphism (AFLP). Based on AFLP analysis, these strains were separated into four groups. Race 3, strain CN3, was the only strain in group A. Race 8, strain CN8, was the only strain in group B. Race 7, strain CN7, was grouped with 75 strains from China in group C. The Australian genotype strain ATCC96291 was grouped with five strains from China in group D. Evolution of the five native strains in group D was studied using multigene genealogies. Phylogenetic tree analysis revealed that the five strains of group D had a closer genetic relationship to the Australian genotype strain than the other races based on the combined elongation factor, β-tubulin, and phosphate permase gene sequence data. Group D was further tested for pathogenicity and virulence on four cotton cultivars from Upland (Gossypium hirsutum) and Sea Island (G. barbadense) cotton. All five strains caused typical Fusarium wilt symptoms on all four cotton cultivars but virulence were relatively low compared with race 3, race 7, and race 8.