Progress Report on a Contemporary Survey of the Fusarium Wilt Fungus In the United States

Knowledge of the genetic and pathogenic diversity present in a pathogen population is required to effectively deploy resistant cultivars.  The only pathogenic survey of Fusarium oxysporum f. sp. vasinfectum in the U.S. was conducted in 1983.  Since then, new distributions of races 3, 4, and 8, and four novel genotypes of this fungus, have been discovered in the U.S.  A multi-state collaboration was initiated with the objective of conducting a comprehensive contemporary survey of the genotypic and pathogenic diversity of F. oxysporum f. sp. vasinfectum in the United States.  Preliminary data are presented.  A 618-bp fragment of the translation elongation factor gene (EF-1α) was sequenced from 39 isolates collected from eight states.  These sequences were compared to those obtained from six isolates from the Ivory Coast and 70 sequences from GenBank.  Maximum parsimony analysis yielded six shortest trees with topologies consistent with previous reports.  Three isolates from Alabama and two isolates from Mississippi were in Lineage IV (race 4).  Other isolates from southeastern states were in Lineages II (race 1) and III (race 8), a clade with genotypes 127 and 140, and an unresolved group related to genotypes 108 and 110.  All isolates from Texas and most isolates from the Ivory Coast were in Lineage II.  None of the isolates sequenced was in Lineages I (race 3) or V (Australian genotypes).  These results support previous reports suggesting F. oxysporum f. sp. vasinfectum in the southeastern U.S. have a high level of genotypic diversity.