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Relationships among Brazilian and worldwide isolates of Fusarium oxysporum f. sp. lactucae race 1 inferred from IGS-rDNA region and EF-1a gene

Cléia Cabral: Embrapa Hortaliças

<div>Fusarium wilt (<em>Fusarium oxysporum</em> f. sp. <em>lactucae – </em>FOLac), is one of the main lettuce diseases in subtropical regions. Although nationwide surveys indicated the exclusive presence of FOLac race 1 in Brazil, no detailed studies are available providing molecular evidences if these isolates were introduced into the country via contaminated seeds or if they are endemic populations. The translation elongation factor 1α (<em>EF-</em>1α) gene and rDNA intergenic spacer (IGS-rDNA) region are the most comprehensive databases for comparative analyses of <em>Fusarium</em> isolates. The objective of this work was to assess the genetic relationships of 23 Brazilian FOLac race 1 isolates with isolates of worldwide origin. A consistent single-cluster pattern was observed for FOLac race 1 isolates from Brazil, California-USA, Arizona-USA, Japan, and Italy, as well as the novel race 4 isolates from the Netherlands. Our analysis (based upon six single nucleotide polymorphisms identified only in the IGS-rDNA sequence) allowed the identification of intra-race 1 variation with the discrimination of four haplotytes. The low diversity levels and the presence of only a single haplotype across Brazil are strong indications that Brazilian FOLac race 1 isolates are result of recent introduction event(s).</div>