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TECHNICAL SESSION: Mechanisms of fungal and oomycete pathogenicity

Identification of putative effector genes in the causal agent of spinach Fusarium wilt, Fusarium oxysporum f. sp. spinaciae
Alex Batson - Washington State University. Martijn Rep- University of Amsterdam, Tobin Peever- Washington State University, Mara de Sain- University of Amsterdam, Like Fokkens- University of Amsterdam, Lindsey du Toit- Washington State University

The only region suitable for spinach seed production in the United States is the maritime Pacific Northwest, where mild, dry summers with long day length are conducive to high yields of quality seed. Fusarium wilt of spinach, caused by Fusarium oxysporum f. sp. spinaciae (Fos), is the primary biotic limitation to spinach seed production in this region. Host-specificity of other F. oxysporum ff. spp. is associated with unique combinations of effector genes, but it is unclear which genes control pathogenicity to spinach in Fos. Nine Fos isolates and five non-pathogenic, spinach-associated (NPS) isolates were characterized phenotypically using pathogenicity tests on two spinach inbreds. These same isolates were characterized genotypically with effector gene profiles predicted from whole genome sequences based on Illumina (n = 13) and PacBio (n = 1 Fos isolate) platforms. Fos isolates separated into two groups, both of which were distinct phenotypically and genotypically from NPS isolates, based on disease severity on two inbred spinach lines and predicted effector gene profiles, respectively. The association of predicted effector genes and two phenotypic groups of Fos has not been described previously. Characterization of the predicted effector genes and other genomic regions of Fos will aid in understanding mechanisms of pathogenicity, developing molecular tools for rapid detection of this pathogen, and breeding cultivars with increased resistance to Fusarium wilt.