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Oral: Oomycete Biology


Oomycete species richness in cacao soil assessed by massive amplicon sequencing of the cytochrome oxidase II gene
M. RATTI (1), E. Goss (1), J. Cevallos-Cevallos (2), C. Arias (2) (1) Plant Pathology Department, University of Florida, U.S.A.; (2) Centro de Investigaciones Biotecnologicas del Ecuador CIBE-ESPOL, Ecuador

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Oomycetes are ubiquitous in both natural ecosystems and crops, however diversity studies have focused in temperate regions. Emerging diseases together with climate change highlight the need to study oomycetes in other potential disease hotspots. Our aim was to assess Oomycete species richness and composition in soil samples from cacao farms of Ecuador by using high-throughput multiplexed Illumina sequencing of the cytochrome oxidase II gene (cox2). We used these nucleotide data to test the hypothesis that different oomycete species richness and composition are found between soil from cacao farms and neighboring soils, which included weeds and other cultivated crops. Eight farms were sampled covering three zones of the Coastal Region of Ecuador. Total DNA was extracted directly from collected soil samples and used for library preparation. A positive control, consisting of gDNA from three known Phytophthora species, was included in the analysis. Amplicons of ~580bp were sequenced by Illumina MiSeq 2x300. Resulting reads were filtered before conducting megaBLAST analysis against a custom Oomycete sequence database. Most of the identified species were Phytophthora and Pythium. The majority of known pathogens, such as P. palmivora, were not restricted to cacao farms, rather they were also found in the plant communities adjacent to farms. These results suggest that wild plants and neighboring crops contribute to the ecology of Oomycete pathogens affecting cacao.