Phylogeography of the wide-host range panglobal plant pathogen phytophthora cinnamomi

Authors: SHAKYA, SHANKAR - Oregon State University; Grunwald, Niklaus - Nik; FIELAND, VALERIE - Oregon State University; KNAUS, BRIAN - Oregon State University; Weiland, Gerald - Jerry; MAIA, CRISTIANA - University Of Algarve; DRENTH, ANDRE - University Of Queensland; GUEST, DAVID - University Of Sydney; LIEW, EDWARD - Royal Botanical Gardens; CRANE, COLIN - Vegetation Health Service; CHANG, TUN-TSCHU - Taiwan Forestry Research Institute; FU, CHUEN-HSU - Taiwan Forestry Research Institute; CHI, NGUYEN MINH - Vietnamese Academy Of Forest Sciences; THU, PHAM QUANG - Vietnamese Academy Of Forest Sciences; SCANU, BRUNO - Dipartimento Di Agraria, Universita Degli Studi Di Sassari; JUNG, MARILIA - Mendel University; JUNG, THOMAS - Mendel University

Submitted to: Molecular Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/28/2021
Publication Date: 8/16/2021
Citation: Shakya, S.K., Grunwald, N.J., Fieland, V.J., Knaus, B.J., Weiland, G.E., Maia, C., Drenth, A., Guest, D.I., Liew, E.C., Crane, C., Chang, T., Fu, C., Chi, N., Thu, P., Scanu, B., Jung, M.H., Jung, T. 2021. Phylogeography of the wide-host range panglobal plant pathogen phytophthora cinnamomi. Molecular Ecology. 30(20):5164-5178. https://doi.org/10.1111/mec.16109.
DOI: https://doi.org/10.1111/mec.16109

Interpretive Summary: Phytophthora cinnamomi is a devastating, highly invasive soilborne plant pathogen associated with epidemics of agricultural, horticultural and forest plantations and native ecosystems worldwide. Various hypotheses have been proposed regarding the origin of this plant. We conducted an analysis of populations of this pathogen sampled in Asia, Australia, Europe, southern and northern Africa, South America, and North America. Based on genetic analysis, we observed the highest genetic diversity in Taiwan and Vietnam, followed by Australia and South Africa. Based on an evolutionary analysis, Taiwan is considered the ancestral area based on our analysis, indicating that this region might be near or at the center of origin for this pathogen as speculated previously. The Australian and South African populations appear to be a secondary center of diversity following migration from Taiwan or Vietnam. Further surveys of natural forests across Southeast Asia are needed to definitively locate the actual center of origin of this important plant pathogen.

Technical Abstract: Various hypotheses have been proposed regarding the origin of the plant pathogen Phytophthora cinnamomi. P. cinnamomi is a devastating, highly invasive soilborne pathogen associated with epidemics of agricultural, horticultural and forest plantations and native ecosystems worldwide. We conducted a phylogeographic analysis of populations of this pathogen sampled in Asia, Australia, Europe, southern and northern Africa, South America, and North America. Based on genotyping-by-sequencing, we observed the highest genotypic diversity in Taiwan and Vietnam, followed by Australia and South Africa. Mating type ratios were in equal proportions in Asia as expected for a sexual population. Simulations based on the index of association suggest a partially sexual, semi-clonal mode of reproduction for the Taiwanese and Vietnamese populations while populations outside of Asia are clonal. Ancestral area reconstruction provides new evidence supporting Taiwan as the ancestral area, given our sample, indicating that this region might be near or at the center of origin for this pathogen as speculated previously. The Australian and South African populations appear to be a secondary center of diversity following migration from Taiwan or Vietnam. Our work also identified two panglobal, clonal lineages PcG1-A2 and PcG2-A2 of A2 mating type found on all continents. Further surveys of natural forests across Southeast Asia are needed to definitively locate the actual center of origin of this important plant pathogen.