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The presence of secreted in xylem genes in Fusarium oxysporum f.sp zingiberi from Australian ginger showing symptoms of Fusarium yellows.

Elizabeth Aitken: School of Agriculture and Food Sciences, The University of Queensland

<div><em>Fusarium oxysporum</em> f.sp <em>zingiberi</em> (<em>Foz</em>) is the causative agent of Fusarium yellows in ginger. The pathogen causes rotting of rhizomes in field grown ginger plants. This disrupts the vascular system of the plant causing foliage yellowing and premature death. <em>Foz</em> is one of the most significant diseases of ginger. An understanding of the diversity of <em>F. oxysporum</em> strains associated with field grown ginger could provide valuable information to manage Fusarium yellows through practices such as preventative measures and early diagnostics. In this study, we sought to establish the genetic diversity of <em>Foz</em> and the presence of <strong><em>s</em></strong><em>ecreted <strong>i</strong>n <strong>x</strong>ylem</em> (<em>SIX</em>) pathogenicity genes in these isolates. Thirty four <em>F. oxysporum</em> like isolates were recovered from ginger rhizomes of plants showing typical Fusarium yellows symptoms. A phylogeny of these isolates was produced using sequence information from the translation elongation factor region. The isolates of <em>F. oxysporum</em> were also screened for the presence of <em>SIX7</em>, <em>SIX9</em>, <em>SIX10</em> and <em>SIX12</em>. Phylogenetic analysis showed that 23 isolates formed a clade which was distinct from the other isolates of <em>F. oxysporum</em>. Interestingly, all of the isolates within this clade were shown to carry the four <em>SIX</em> genes whilst the other isolates of <em>F. oxysporum</em> outside of this clade did not carry any of the <em>SIX</em> genes. As there are few options for controlling <em>Foz</em> in ginger crops these results will be valuable for crop disease management and cross-pathogenicity research.</div>