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ARS Home » Pacific West Area » Corvallis, Oregon » Horticultural Crops Research Unit » Research » Publications at this Location » Publication #233481
Title: PCR-RFLP Markers Identify Three Lineages of the North American and European Populations of Phytophthora ramorum

Author
item ELLIOTT, M - CANADIAN FOREST SERVICE
item SUMAMPONG, G - CANADIAN FOREST SERVICE
item VARGA, A - CANADIAN FOOD INSPECTION
item SHAMOUN, S - CANADIAN FOREST SERVICE
item JAMES, D - CANADIAN FOOD INSPECTION
item MASRI, S - CANADIAN FOOD INSPECTION
item BRIERE, S - CANADIAN FOOD INSPECTION
item Grunwald, Niklaus - Nik

Submitted to: Forest Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/20/2008
Publication Date: 2/10/2009
Citation: Elliott, M., Sumampong, G., Varga, A., Shamoun, S.F., James, D., Masri, S., Briere, S.C., Grunwald, N.J. 2009. PCR-RFLP markers identify threelineages of the North American and European populations of Phytophthora ramorum. Forest Pathology. 39:266-278.

Interpretive Summary: Phytophthora ramorum, the cause of Sudden Oak Death, has a wide host range and is found in the northern hemisphere. It is thought to be introduced to North America and Europe, but its origin is unknown. It has three major clonal lineages and two mating types. Sexual reproduction can only occur when both mating types, referred to as A1 and A2, are present in the same location. At present, the European lineage, called EU1, consisting mostly of the A1 mating type, has been consistently found in Europe and occasionally in North American nurseries. The North American lineages, referred to as NA1 and NA2, have not been found in Europe and are of A2 mating type. 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. Here, we report on a novel method of identifying clones of Phytophthora ramorum based on molecular approaches.

Technical Abstract: Phytophthora ramorum, the cause of Sudden Oak Death, has a wide host range and is found in the northern hemisphere. It is thought to be introduced to North America and Europe, but its origin is unknown. It has three major clonal lineages and two mating types. Sexual reproduction can only occur when both mating types are present in the same location. At present, the European lineage (EU1, mostly A1 mating type) has been consistently found in Europe and occasionally in North American nurseries. The North American lineages (NA1 and NA2, all A2 mating type) have not been found in Europe. 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 since the EU1 lineage is mostly A1 and both NA1 and NA2 lineages are A2. Phytophthora ramorum isolates can be identified to lineage using PCR-RFLP of the Cox1 gene, first using Apo1 to separate P. ramorum from other species and EU1 from North American populations and then Ava1 to distinguish between NA1 and NA2 genotypes. However, P. foliorum had the same restriction profile as P. ramorum NA1 isolates.