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Oral: Plant Pathologists of the Future: Showcasing the Top Graduate Students from APS Division Meetings


Searching for genomic signatures of host jumping onto raspberry and strawberry in two Phytophthora sister taxa.
J. Tabima (1), B. Kronmiller (2), B. Knaus (3), C. Press (4), I. Zasada (4), B. Tyler (2), N. Gr├╝nwald (4), D. Shen (5) (1) Oregon State University, U.S.A.; (2) Oregon State University, U.S.A.; (3) USDA ARS, U.S.A.; (4) USDA ARS, U.S.A.; (5) Nanjing Agric

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Contrasting the genomes of sister taxa with narrow but different host ranges provides an ideal system for studying host adaptation. Selection pressures imposed by different hosts are expected to lead to adaptation by gradual divergence of populations and eventual speciation due to reproductive isolation. This process of host-mediated speciation is expected to leave signatures (such as mutations, recombination, indels, or duplications) in the corresponding pathogen genomes. We sequenced and annotated the genomes of two sister species in the plant pathogen genus Phytophthora, P. rubi and P. fragariae, to study which genomic signatures are involved in host adaptation (P. rubi and P. fragariae exclusively infects the genus Rubus or Fragariae, respectively). Genomes were assembled using SOAPdenovo version 1.05. Gene calling was performed using MAKER. The genomes of P. rubi and P. fragariae yielded 9,434 scaffolds and an estimated 23,476 genes for P. rubi and 8,511 scaffolds and 20,448 genes for P. fragariae. Functional annotation showed a similar number of genes involved in different biochemical pathways, such as sugar processing, metabolism, and amino acid synthesis between the two species. Positive selection (dN/dS) was detected for RxLR and CRN effector proteins and five carbohydrate-enzyme genes. Work is ongoing to identify other candidate genes under selection and genomic signatures that may have been involved in the process of speciation via host jumping.