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Subject: Phytophthora ramorum mating type A1 detected in North America
Date posted: September 12, 2003
Source: Plant Disease
Phytophthora ramorum, the causal agent of sudden oak death, is known to occur in coastal forests and a few horticultural nurseries in the western United States and in nurseries and landscape plantings in Europe. There are two types of P. ramorum that are genetically distinct: the A1 mating type found in Europe and the A2 mating type in North America. During the summer of 2003, P. ramorum was isolated from infected Viburnum and Pieris cultivars in a northern Oregon nursery and Camellia cultivars from a southern Oregon nursery. Oregon nursery and forest isolates, as well as European isolates were paired to test for mating types. Mating type tests revealed that isolates from the northern Oregon nursery were the A1 mating type, whilst isolates from the southern nursery were A2. This is the first report of P. ramorum mating type A1 in the United States. Interestingly, a single isolate of mating type A2 was recently detected for the first time in Belgium. This was the first detection of the A2 mating type in Europe, however for Europe, the pathogen is still only associated with nursery plants and their forests remain unaffected.

For the full story see:
Hansen, E.M., P.W. Reeser, W. Sutton, L.M. Winton, and N. Osterbauer. 2003. First report of A1 mating type of Phytophthora ramorum in North America. Plant Disease 87: 1267.

Werres, S. and D. De Merlier. 2003. First detection of Phytophthora ramorum mating type A2 in Europe. Plant Disease 87: 1266.

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For more information on Phytophthora ramorum see the following website: