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Genomics and effector characterization of the novel sugar beet pathogen Fusarium secorum
Z. BIAN (1), R. De Jonge (2), G. Secor (1), M. Bolton (3). (1) North Dakota State University, Fargo, ND, U.S.A.; (2) Ghent University, Ghent, Belgium; (3) USDA ARS, Fargo, ND, U.S.A.

Sugar beet is an important source of sucrose for human consumption throughout the world. A new disease of sugar beet, named Fusarium yellowing decline, was recently found in in the Red River Valley of MN and ND. This disease is caused by a novel pathogen named <i>Fusarium secorum</i>. To investigate the evolutionary origin of <i>F. secorum</i>, we conducted phylogenetic analyses of the concatenated alignment of approximately 7,000 conserved single-copy core orthologs across 20 <i>Fusarium</i> species for which the entire genome is sequenced. These analyses resulted in the generation of a robust species topology that clusters <i>F. secorum</i> closely to <i>F. acutatum</i> in the <i>F. fujikuroi</i> species complex. Pathogens such as <i>F. secorum</i> secrete proteins during infection called ‘effectors’ that help establish disease.  Here, candidate effectors were identified by screening the set of 15,872 predicted proteins with several bioinformatics tools combined with RNA-seq data. To characterize putative effectors, we developed a transformation system using polyethylene glycol–mediated transformation. Several mutant lines have been made with an effector deleted from the genome using a split-marker knock-out strategy.  To explore their role in pathogenicity, mutant strains have been inoculated to sugarbeet and compared to WT <i>F. secorum</i>. These effector characterization results and a detailed analysis of the <i>F. secorum </i>genome will be presented.

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