Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 4/14/2010
Publication Date: 6/1/2010
Citation: Weiland, G.E. 2010. Assessment of Pythium diversity from forest nurseries. Phytopathology. 100(6S):S153
Technical Abstract: Pythium species are one of the most important and common damping off pathogens affecting conifer seedling production in the Pacific Northwest. Seedling losses can approach 100% when soil moisture is abundant. Despite their prevalence and importance, relatively little is known about the species of Pythium found in nursery soils. A limited number of studies report that P. irregulare, P. mamillatum, and P. ultimum are the predominant species in the PNW, but most studies do not report Pythium species identity. In an attempt to further characterize Pythium species associated with conifer seedling production, a field survey was conducted at three forest nurseries (2 in OR, 1 in WA) in 2008. Pythium species were isolated by plating soil onto PARP and by baiting with Rhododendron leaf disks and split Douglasfir needles. One hundred isolates were randomly selected from each method and nursery and identified on the basis of ITS sequence. A total of 19 Pythium species were identified from the survey. Species richness and abundance were strongly influenced by both nursery and method. Each nursery was associated with a different predominate Pythium species (P. dissotocum, P. irregulare, and 'P. vipa').