PCR‐RFLP markers identify three lineages of the North American and European populations of Phytophthora ramorum

Abstract

SummaryPhytophthora ramorum, the cause of sudden oak death and ramorum blight, has three major clonal lineages and two mating types. Molecular tests currently available for detecting P. ramorum do not distinguish between clonal lineages and mating type is determined by cultural methods on a limited number of samples. In some molecular diagnostic tests, cross-reaction with other closely related species such as P. hibernalis, P. foliorum or P. lateralis can occur. Regions in the mitochondrial gene Cox1 are different among P. ramorum lineages and mitochondrial genotyping of the North American and European populations seems to be sufficient to differentiate between mating types, because the EU1 lineage is mostly A1 and both NA1 and NA2 lineages are A2. In our study, we were able to identify P. ramorum isolates according to lineage using polymerase chain reaction-restriction fragment-length polymorphism (PCR-RFLP) of the Cox1 gene, first by using ApoI to separate P. ramorum from other species and EU1 from North American populations, and then AvaI to distinguish between NA1 and NA2 genotypes. However, P. foliorum had the same restriction profile as P. ramorum NA1 isolates.

Effects of systemic and contact fungicides on life stages and symptom expression of Phytophthora ramorum in vitro and in planta

“…Molecular data indicate that there are four distinct clonal lineages of P. ramorum, one originally discovered in Europe, but also found in western North America (EU1), a new lineage recently detected in Europe (EU2), and two lineages only present in North America (NA1 and NA2) (Grünwald et al, 2012;Van Poucke et al, 2012;Elliott et al, 2009). The known host range of P. ramorum is very broad (more than 100 host plants) and includes species such as rhododendrons, viburnum, beech, Oregon grape, salal, arbutus, and other woody ornamentals.…”

Scientific Opinion on the Pest Risk Analysis onPhytophthora ramorumprepared by the FP6 project RAPRA

“…A first report of phenotypic differences among lineages has now been published (Elliott et al, 2009b). This paper shows that NA2 and EU1 lineages are more aggressive than the NA1 lineage.…”

“…In spite of clear differences among lineages on individual hosts (Appendix A. ), the three known lineages are extremely similar in broad ecological and virulence traits (Elliott et al, 2009b), and there is no strong evidence suggesting the three lineages would each behave radically differently. This indicates that knowledge of ecology and biology of one lineage can be reasonably extended to other lineages.…”

“…Although evidence of within lineage differentiations has been presented both for wild and nursery populations Goss et al, 2009a;Mascheretti et al, 2008;Vercauteren et al, 2010) there is currently no published evidence of different phenotypes consistently associated with different genotypes within lineage. Conversely, at least two reports compare phenotypes of different lineages Elliott et al, 2009b) and identify differences in mating type, growth rate, and virulence. Evidence presented at the sudden oak death COMTF meeting in 2010 in San Rafael, (Pathogen and Host Variability: How Will They Affect the Spread of SOD in Heterogeneous Environments in: http://www.suddenoakdeath.org/news-and-events/past-events/2010-annual-meeting/) indicates that in replicated experiments NA1 and NA2 display different virulence levels with NA2 being more aggressive than the widespread NA1.…”

“…Further progress is being made in developing markers to identify the three P. ramorum lineages (Elliott et al, 2009b), in examining virulence, sporulation and elicitin production of the same lineages (Manter et al, 2010) and in reconstructing the evolutionary history of the three lineages (Goss et al, 2009a; already referred to in the RAPRA report). These are thought to have been diverging for a length of time sufficient to have allowed independent evolution prior to the independent introductions to North America and Europe (Goss et al, 2009a).…”