Populations of Phytophthora rubi show little differentiation and high rates of migration among states in the Western United States

Authors: TABIMA, JAVIER - Oregon State University; COFFEY, M - University Of California; Zasada, Inga; Grunwald, Niklaus - Nik

Submitted to: Molecular Plant-Microbe Interactions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/22/2018
Publication Date: 4/11/2018
Citation: Tabima, J.F., Coffey, M.D., Zasada, I.A., Grunwald, N.J. 2018. Populations of Phytophthora rubi show little differentiation and high rates of migration among states in the Western United States. Molecular Plant-Microbe Interactions. 31(6):614-622. https://doi.org/10.1094/MPMI-10-17-0258-R.
DOI: https://doi.org/10.1094/MPMI-10-17-0258-R

Interpretive Summary: Population genetics is a powerful tool to understand patterns and evolutionary processes that are involved in plant pathogen emergence and adaptation to agricultural ecosystems. We are interested in studying the population dynamics of Phytophthora rubi, the causal agent of Phytophthora root rot in raspberry. P. rubi is found in the western U.S., where the majority of the fresh and processed raspberries are produced. We characterized genetic diversity in populations of P. rubi sampled in the U.S. and other countries. Overall, populations of P. rubi show low levels of genetic diversity across the western U.S. We found no evidence for population structure at a global or regional (Western U.S.) level. This report provides new insights into the structure of global and U.S. populations of the raspberry pathogen P. rubi indicating that human agricultural activity might be involved in moving the pathogen.

Technical Abstract: Population genetics is a powerful tool to understand patterns and evolutionary processes that are involved in plant pathogen emergence and adaptation to agricultural ecosystems. We are interested in studying the population dynamics of Phytophthora rubi, the causal agent of Phytophthora root rot in raspberry. P. rubi is found in the western U.S., where the majority of the fresh and processed raspberries are produced. We used genotyping-by-sequencing (GBS) to characterize genetic diversity in populations of P. rubi sampled in the U.S. and other countries. Our results confirm that P. rubi is a monophyletic species with complete lineage sorting from its sister taxon P. fragariae. Overall, populations of P. rubi show low genetic diversity across the western U.S. Demographic analyses suggest that populations of P. rubi from the western U.S. are the source of pathogen migration to Europe. We found no evidence for population differentiation at a global or regional (Western U.S.) level. Finally, our results provide evidence of migration from fields in California and Oregon into Washington. This report provides new insights into the structure of global and U.S. West coast populations of the raspberry pathogen P. rubi indicating that human agricultural activity might be involved in moving the pathogen.