Molecular Phylogenomics and Population Structure of <i>Phytophthora pluvialis</i>

Phytophthora pluvialis is an oomycete that was first isolated from soil, water, and tree foliage in mixed Douglas-fir−tanoak forests of the U.S. Pacific Northwest (PNW). It then identified as causal agent red needle cast radiata pine (Pinus radiata) New Zealand (NZ). Genotyping-by-sequencing used to obtain 1,543 single nucleotide polymorphisms across 145 P. isolates characterize population structure PNW NZ. We tested hypothesis introduced NZ using genetic distance measurements analyses among locations between countries. The low distance, heterozygosity, lack geographic suggest a colonization event United States followed by clonal expansion Coast Range proposed presumptive center origin currently known distribution based on its range position central cluster minimum spanning network. Coastal were located at root every emerged earlier than all clusters. had highest degree heterozygosity (Hs = 0.254) median pairwise (0.093) relative any other cluster. Finally, rapid host diversification closely related indicate this pathogen has potential infect broader hosts recognized.