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    Author(s): Tyler B. Bourret; Heather K. Mehl; Kamyar Aram; David M. Rizzo
    Date: 2017
    Source: Proceedings of the sudden oak death sixth science symposium. Gen. Tech. Rep. GTR-PSW-255. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 63.
    Publication Series: General Technical Report (GTR)
    Station: Pacific Southwest Research Station
    PDF: Download Publication  (149.0 KB)

    Description

    For more than a decade, the Rizzo lab and collaborators have monitored northern and central coastal California watersheds each spring and early summer for the presence of Phytophthora using submerged Rhododendron leaves as bait. This served as an early detection tool for the sudden oak death (SOD) pathogen, P. ramorum, but other species of Phytophthora were encountered and notable isolates occasionally saved; in recent years a more concerted effort was made to isolate species of Phytophthora other than ramorum. Twenty-three species were identified using a combination of morphological traits and ITS nrDNA sequences. Three provisional taxa, taxon mendostream (a novel member of Phytophthora clade 9), taxon obispostream (a member of the P. citricola species complex) and taxon sequoiasoil (a close relative of P. cactorum) are introduced based on unique ITS, mtCOX1 and mtCOX2 sequences. Due to the ongoing SOD epidemic, the exotic, invasive P. ramorum was the most common species isolated, followed by members of Phytophthora clades 3 and 6. This is consistent with studies performed in Alaska and Oregon, suggesting that many of these species are native to the area. Maps of infested watersheds are presented, spanning more than 750 km of the California coast.

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    Citation

    Bourret, Tyler B.; Mehl, Heather K.; Aram, Kamyar; Rizzo, David M. 2017. Rhododendron leaf baiting of coastal California watersheds for Phytophthora. In: Frankel, Susan J.; Harrell, Katharine M., tech. coords. Proceedings of the sudden oak death sixth science symposium. Gen. Tech. Rep. GTR-PSW-255. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 63.

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