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A collection of 30 Phytophthora cactorum and 12 P. pseudotsugae (subclade 1a) strains isolated from several recent surveys across California was phylogenetically compared to a worldwide collection of 112 conspecific strains using sequences from three barcoding loci. The surveys baited P. cactorum from soil and water across a wide variety of forested ecosystems with a geographic range of more than 1000 km. Two cosmopolitan lineages were identified within the widespread P. cactorum, one being mainly associated with strawberry production and the other more closely associated with apple orchards, oaks and ornamental trees. Two other well-sampled P. cactorum lineages, including one that dominated Californian restoration outplantings, were only found in the western United States, while a third was only found in Japan. Coastal California forest isolates of both Phytophthora species exhibited considerable diversity, suggesting both may be indigenous to the state. Many isolates with sequence accessions deposited as P. cactorum were determined to be P. hedraiandra and P. ×serendipita, with one hybrid lineage appearing relatively common across Europe and Asia. This study contains the first report of P. pseudotsugae from the state of California and one of the only reports of that species since its original description.
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Rhododendron leaf baiting of coastal California watersheds for Phytophthora and Nothophytophthora
For nearly two decades, stream baiting of northern and central California coastal streams has been an important tool in the management of sudden oak death, a devastating forest disease caused by the oomycete Phytophthora ramorum. Phytophthora species are baited with floating rhododendron leaves, serving as an early detection tool for the presence of P. ramorum in watersheds across more than 800 km of California coastline. While this long-standing management tool is focused on a single species of Phytophthora, other species of Phytophthora have been baited alongside P. ramorum, and this study documents the presence and distribution of 22 Phytophthora and Nothophytophthora species across the northern and central coasts of California. Although P. ramorum was isolated at the greatest number of sites, several species in subgeneric clade 6 were also abundant and widespread, a common feature of Phytophthora stream baiting studies. Clade 3 species P. nemorosa, P. pluvialis, and P. pseudosyringae were also frequently isolated in northern coastal streams. The species Nothophytophthora caduca and the genus Nothophytophthora are reported for the first time in North America along with the first report of P. pluvialis in California. Two novel species, Nothophytophthora sp. californica and P. sp. aureomontensis (a member of the P. citricola species complex) are provisionally named. Mitochondrial sequences revealed multiple hybridization events between P. lacustris and P. riparia. Stream monitoring can serve as an important tool for monitoring ongoing Phytophthora invasions as well as establishing baseline pathogen communities, critical data for preventing future invasions.
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- Award ID(s):
- 1753965
- PAR ID:
- 10476865
- Publisher / Repository:
- Myologial Progress
- Date Published:
- Journal Name:
- Mycological Progress
- Volume:
- 22
- Issue:
- 8
- ISSN:
- 1617-416X
- Subject(s) / Keyword(s):
- Phytophthora Phytophthora ramorum Nothophytophthora Biosurveillance Rhododendron Barcode Hybrid Species complex
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1007/s11557-023-01910-8
