Standardizing the nomenclature for clonal lineages of the sudden oak death pathogen, Phytophthora ramorum.

Phytopathology (Impact Factor: 2.97). 08/2009; 99(7):792-5. DOI: 10.1094/PHYTO-99-7-0792
Source: PubMed

ABSTRACT Phytophthora ramorum, the causal agent of sudden oak death and ramorum blight, is known to exist as three distinct clonal lineages which can only be distinguished by performing molecular marker-based analyses. However, in the recent literature there exists no consensus on naming of these lineages. Here we propose a system for naming clonal lineages of P. ramorum based on a consensus established by the P. ramorum research community. Clonal lineages are named with a two letter identifier for the continent on which they were first found (e.g., NA = North America; EU = Europe) followed by a number indicating order of appearance. Clonal lineages known to date are designated NA1 (mating type: A2; distribution: North America; environment: forest and nurseries), NA2 (A2; North America; nurseries), and EU1 (predominantly A1, rarely A2; Europe and North America; nurseries and gardens). It is expected that novel lineages or new variants within the existing three clonal lineages could in time emerge.

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    ABSTRACT: Invasive oomycete pathogens have been causing significant damage to native ecosystems worldwide for over a century. A recent well‐known example is Phytophthora ramorum, the causal agent of sudden oak death, which emerged in the 1990s in Europe and North America. In Europe, this pathogen is mainly restricted to woody ornamentals in nurseries and public greens, while severe outbreaks in the wild have only been reported in the UK. This study presents the results of the P. ramorum survey conducted in Swiss nurseries between 2003 and 2011. In all 120 nurseries subjected to the plant passport system, the main P. ramorum hosts were visually checked for above ground infections. Phytophthora species were isolated from tissue showing symptoms and identified on the basis of the morphological features of the cultures and sequencing of the ribosomal ITS region. Phytophthora was detected on 125 plants (66 Viburnum, 58 Rhododendron and one Pieris). Phytophthora ramorum was the most frequent species (59·2% of the plants), followed by P. plurivora, P. cactorum, P. citrophthora, P. cinnamomi, P. cactorum/P. hedraiandra, P. multivora and P. taxon PgChlamydo. The highest incidence of P. ramorum was observed on Viburnum × bodnantense. Microsatellite genotyping showed that the Swiss P. ramorum population is highly clonal and consists of seven genotypes (five previously reported in Europe, two new), all belonging to the European EU1 clonal lineage. It can therefore be assumed that P. ramorum entered Switzerland through nursery trade. Despite sanitation measures, repeated P. ramorum infections have been recorded in seven nurseries, suggesting either reintroduction or unsuccessful eradication efforts.
    Plant Pathology 01/2013; · 2.73 Impact Factor
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    ABSTRACT: Phytophthora plant pathogens contain many hundreds of effectors potentially involved in infection of host plants. Comparative genomic analyses have shown that these effectors evolve rapidly and have been subject to recent expansions. We examined the recent sequence evolution of RXLR-class effector gene families in the sudden oak death pathogen, P. ramorum. We found that P. ramorum RXLR effectors have taken multiple evolutionary paths, including loss or gain of repeated domains, recombination or gene conversion among paralogs, and selection on point mutations. Sequencing of homologs from two subfamilies in P. ramorum's closest known relatives revealed repeated gene duplication and divergence since speciation with P. lateralis. One family showed strong signatures of recombination while the other family has evolved primarily by point mutation. Comparison of a small number of the hundreds of RXLR-class effectors across three clonal lineages of P. ramorum shows striking divergence in alleles among lineages, suggesting the potential for functional differences between lineages. Our results suggest future avenues for examination of rapidly evolving effectors in P. ramorum, including investigation of the functional and coevolutionary significance of the patterns of sequence evolution that we observed.
    PLoS ONE 01/2013; 8(11):e79347. · 3.73 Impact Factor
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    ABSTRACT: Phytophthora ramorum is a generalist plant pathogen that has been subject to a remarkable amount of research activity. One decade after its description, this oomycete now affects a wide range of hosts in both North America and Europe, both in the wild and in ornamental plant trade (e.g., Camellia, Rhododendron, Pieris). Research on the biology, epidemiology and management of P. ramorum has not only rapidly expanded, but has also become increasingly interdisciplinary. In this overview, three examples of interdisciplinary collaboration concerning P. ramorum are presented: (1) network epidemiology (the application of network theory to epidemiology), (2) landscape pathology (the use of landscape ecology tools in the study of regional outbreaks of tree pathogens) and (3) conservation biogeography (a biogeographical perspective in conservation biology). Building on these approaches, three-way collaboration among network epidemiologists, landscape pathologists and conservation biogeographers (as well as e.g., molecular biologists, social and climate change scientists) is now needed to improve our understanding and management of the P. ramorum emergency, and many other challenges to plant health worldwide.
    CAB Reviews Perspectives in Agriculture Veterinary Science Nutrition and Natural Resources 04/2013; 8(024).

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