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ARS Home » Pacific West Area » Corvallis, Oregon » Horticultural Crops Research » Research » Publications at this Location » Publication #347997

Research Project: Integrated Disease Management of Exotic and Emerging Plant Diseases of Horticultural Crops

Location: Horticultural Crops Research

Title: Genetic diversity of Phytophthora pluvialis, a pathogen of conifers, in New Zealand and the west coast of the United States of America

Author
item Brar, S - Massey University
item Tabima, Javier - Oregon State University
item Mcdougal, R - New Zealand Forest Research Institute
item Dupont, P - Massey University
item Feau, N - University Of British Columbia
item Hamelin, R - University Of British Columbia
item Panda, P - University Of British Columbia
item Leboldus, J - Oregon State University
item Grunwald, Niklaus - Nik
item Hansen, E - Oregon State University
item Bradshaw, R - Massey University
item Williams, N - Massey University

Submitted to: Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/17/2017
Publication Date: 1/30/2018
Citation: Brar, S., Tabima, J.F., Mcdougal, R.L., Dupont, P.Y., Feau, N., Hamelin, R.C., Panda, P., Leboldus, J.M., Grunwald, N.J., Hansen, E.M., Bradshaw, R.E., Williams, N.M. 2018. Genetic diversity of Phytophthora pluvialis, a pathogen of conifers, in New Zealand and the west coast of the United States of America. Plant Pathology. 67:1131–1139. https://doi.org/10.1111/ppa.12812.
DOI: https://doi.org/10.1111/ppa.12812

Interpretive Summary: The plant pathogen Phytophthora pluvialis is the causal agent of red needle cast on radiata pine in New Zealand. It was first discovered in 2005 but had previously been recovered from tanoak and Douglas-fir trees in Oregon, USA in 2002. Phytophthora pluvialis was subsequently described as a new species in 2013. The aim of this project was to gain a better understanding of the genetic diversity, population structure and origin of this pathogen. A total of 360 pathogen isolates were collected from the USA and New Zealand. The genome sequences of two P. pluvialis strains were used to identify 27 single nucleotide polymorphism (SNP) markers, that were then used to genotype the two populations. The US population of the pathogen has higher genetic diversity compared to the New Zealand population. Genetic analysis suggests two potential introductions of P. pluvialis into New Zealand from the USA. This study provides novel insight into the genetic structure of P. pluvialis in New Zealand and the USA.

Technical Abstract: Phytophthora pluvialis is the causal agent of red needle cast on Pinus radiata in New Zealand. It was first discovered in 2005 but had previously been recovered from tanoak (Lithocarpus densiflorus) and Douglas-fir (Pseudotsuga menziesii) trees in Oregon, USA in 2002. Phytophthora pluvialis was subsequently described as a new species in 2013 and classified as a clade III Phytophthora species. The aim of this project was to gain a better understanding of the genetic diversity, population structure and origin of this pathogen. A total of 360 P. pluvialis isolates were collected from the USA and New Zealand. The genome sequences of two P. pluvialis strains were used to identify 27 single nucleotide polymorphism (SNP) markers, that were then used to genotype the two populations. The genotypic data showed that the USA population of P. pluvialis had twice the genetic diversity and a greater number of multi locus genotypes (MLG) compared to the New Zealand population with 126 and 24 MLGs respectively. The majority of the sub-populations within the USA and New Zealand showed linkage disequilibrium. All sub-populations had a negative fixation index, indicating that clonal reproduction is prevalent in both countries. A minimum spanning network (MSN) showed two unique clusters of isolates in the New Zealand population, suggesting two potential introductions of P. pluvialis into New Zealand from the USA. There was no significant structure within the New Zealand or USA populations. This study provides novel insight into the genetic structure of P. pluvialis in New Zealand and the USA.