Host-induced genome alterations in Phytophthora ramorum, I. NA1 lineage on coast live oak in California, II. EU1 lineage on Chamaecyparis lawsoniana in UK

Abstract

Rapid phenotypic diversification in clonal invasive populations is often observed, although the underlying genetic mechanisms remain elusive. Lineages of the sudden oak death pathogen Phytophthora ramorum are exclusively clonal, yet isolates of the NA1 lineage from oak (Quercus spp.) frequently exhibit hostdependent, unstable colony phenotypes called non-wild type (nwt, fig. 1) (Brasier and others 2006). This phenotypic variation is seen despite the fact that population genetic and host-specificity studies negate any host-driven population subdivision. We also found comparable nwt phenotypes in EU1 isolates from Lawson cypress (Chamaecyparis lawsoniana) in the UK (fig. 2): isolates from the middle of a large ~4m long lesion on a mature tree were normal wild type (wt), while those from the extremities were variable nwt types. Previously only wt isolates were known in the EU1 lineage, including those from larch (Larix). Based on a large survey of genotypes from different hosts, we hypothesize that the environment in the bark of oak and Lawson cypress is responsible for the unusual phenotypic diversification in P. ramorum.

Parent Publication

• Proceedings of the sudden oak death sixth science symposium

Citation

Kasuga, Takao; Bui, Mai; Bernhardt, Elizabeth; Swiecki, Tedmund; Aram, Kamyar; Bertier, Lien; Yuzon, Jennifer; Cano, Liliana M.; Webber, Joan; Brasier, Clive; Press, Caroline; Grünwald, Niklaus; Rizzo, David; Garbelotto, Matteo. 2017. Host-induced genome alterations in Phytophthora ramorum, I. NA1 lineage on coast live oak in California, II. EU1 lineage on Chamaecyparis lawsoniana in UK. In: Frankel, Susan J.; Harrell, Katharine M., tech. coords. Proceedings of the sudden oak death sixth science symposium. Gen. Tech. Rep. GTR-PSW-255. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 37-39.