Alder Canopy Dieback and Damage in Western Oregon Riparian Ecosystems

Sims, Laura; Goheen, E. M.; Kanaskie, Alan; Hansen, E. M.

doi:10.3955/046.089.0103

Cited by 7 publications

(13 citation statements)

References 28 publications

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“…Species such as P. alni, a serious pathogen on Alnus trees in Europe, appear to be recently formed stable hybrid lineages with increased host specificity and virulence (25,26). Within clade 6, the hybrid species P. ϫ stagnum nothosp.…”

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Phytophthora Species in Rivers and Streams of the Southwestern United States

Stamler

Sanogo

Goldberg

et al. 2016

Appl Environ Microbiol

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Phytophthora species were isolated from rivers and streams in the southwestern United States by leaf baiting and identified by sequence analysis of internal transcribed spacer (ITS) ribosomal DNA (rDNA). The major waterways examined included the Rio Grande River, Gila River, Colorado River, and San Juan River. The most prevalent species identified in rivers and streams were Phytophthora lacustris and P. riparia, both members of Phytophthora ITS clade 6. P. gonapodyides, P. cinnamomi, and an uncharacterized Phytophthora species in clade 9 were also recovered. In addition, six isolates recovered from the Rio Grande River were shown to be hybrids of P. lacustris ؋ P. riparia. Pathogenicity assays using P. riparia and P. lacustris failed to produce any disease symptoms on commonly grown crops in the southwestern United States. Inoculation of Capsicum annuum with P. riparia was shown to inhibit disease symptom development when subsequently challenged with P. capsici, a pathogenic Phytophthora species. IMPORTANCEMany Phytophthora species are significant plant pathogens causing disease on a large variety of crops worldwide. Closer examinations of streams, rivers, and forest soils have also identified numerous Phytophthora species that do not appear to be phytopathogens and likely act as early saprophytes in aquatic and saturated environments. To date, the Phytophthora species composition in rivers and streams of the southwestern United States has not been evaluated. This article details a study to determine the identity and prevalence of Phytophthora species in rivers and streams located in New Mexico, Arizona, Colorado, Utah, and Texas. Isolated species were evaluated for pathogenicity on crop plants and for their potential to act as biological control agents.

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confidence: 99%

“…Numerous natural and artificial Phytophthora species hybrids have been characterized to date, typically with closely related parental genotypes (18)(19)(20)(21)(22)(23)(24)(25)(26). Species such as P. alni, a serious pathogen on Alnus trees in Europe, appear to be recently formed stable hybrid lineages with increased host specificity and virulence (25,26).…”

mentioning

confidence: 99%

Phytophthora Species in Rivers and Streams of the Southwestern United States

Stamler

Sanogo

Goldberg

et al. 2016

Appl Environ Microbiol

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“…In 2010, collaborative surveys by the United States Forest Service, Oregon Department of Forestry, and Oregon State University were begun to identify possible causal agents of riparian alder dieback with a focus on Phytophthora species (Sims et al. ; L.L. Sims, W. Sutton, P. Reeser, E.M. Hansen, in review).…”

Section: Introductionmentioning

confidence: 99%

“…From the surveys, Phytophthora siskiyouensis Reeser & E.M. Hansen was isolated from cankered stem tissues as well as from necrotic alder roots (Sims et al. ). Phytophthora siskiyouensis was initially reported to be a minor pathogen of tanoak ( Notholithocarpus densiflorus) and Oregon myrtle ( Umbellularia californica ) (Reeser et al.…”

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Pathogenicity to alder of Phytophthora species from riparian ecosystems in western Oregon

2015

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Described as one of the most destructive pathogens of agricultural crops and forest trees, Phytophthora is a genus of microorganisms containing over 100 known species. Phytophthora alni has caused collar and root disease in alders throughout Europe, and a subspecies has recently been isolated in North America. Reports of canopy dieback in red alder, Alnus rubra, prompted a survey of their overall health and to determine whether P. alni was present in western Oregon riparian ecosystems. Over 1100 Phytophthora isolates were recovered, representing 20 species and 2 taxa. Phytophthora-type cankers were observed in many trees, and their incidence was positively correlated with canopy dieback. High levels of mortality for red alder were not observed, which suggests these Phytophthora species are not aggressive pathogens. To test this hypothesis, three stem wound inoculations and one root dip were conducted on red alder seedlings using 13 Phytophthora species recovered from the riparian survey. Ten of the 13 Phytophthora species produced significant lesions in at least one pathogenicity test. Phytophthora siskiyouensis produced the largest lesions on red alder from the two stem wound inoculation tests conducted under summer conditions, while P. taxon Pgchlamydo caused the largest lesions during the winter stem wound inoculation test. Phytophthora gonapodyides, P. taxon Pgchlamydo and P. siskiyouensis have previously been found associated with necrotic alder roots and bole cankers in the field, and with the pathogenicity results reported here, we have established these species as causes of Phytophthora root disease and Phytophthora bole canker of alder in Oregon. While none of the Phytophthora species were especially aggressive towards red alder in the pathogenicity tests, they did cause localized disease symptoms. By weakening the root systems or boles of alders, the Phytophthoras could be leaving alders more susceptible to other insects and pathogens.

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Ecology and pathology ofPhytophthoraITS clade 3 species in forests in western Oregon, USA

2017

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Phytophthora species are widespread and diverse in forest ecosystems, but little is known about their ecology. We explore ecological attributes of the closely related clade 3 species that occur sympatrically in western North American forests. We address the population structure, pathology, and epidemiology of P. ilicis, P. nemorosa, P. pluvialis, P. pseudosyringae, and P. psychrophila. Phytophthora species were isolated from plant tissues, rainwater falling through the forest canopy, streams, and soils in forests in western Oregon. Species identifications were based on morphology in culture with molecular confirmation using COX spacer and internal transcribed spacer (ITS) sequences. All five clade 3 Phytophthora species are present in western Oregon forests, although P. ilicis (only 1 forest isolate) and P. psychrophila (only 12 isolates) are apparently rare. P. ilicis is known only from holly in horticultural situations and once from a naturalized seedling in an urban forest. The known distribution of P. nemorosa in forest settings coincides with the ranges of its principle hosts, tanoak and myrtlewood, in Oregon and California. Although it is regularly identified from streams within the tanoak range, it has not been recovered from streams beyond that range. P. pluvialis is primarily associated with Douglas-fir canopies. It was identified from scattered locations throughout western Oregon in rain traps beneath Douglas-fir plantations and from diseased needles. P. pseudosyringae is also isolated from tanoak and myrtlewood in southwest Oregon and California, but its distribution, in streams at least, extends throughout much of western Oregon. P. psychrophila in Oregon is known only from rain traps beneath tanoak trees. Little intraspecific variation was detected in the nuclear rDNA ITS of clade 3 species. Variation in the mitochondrial COX spacer region was more frequent, with 2 to 10 haplotypes identified in the clade 3 species, for which we had multiple isolates.

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Alder Canopy Dieback and Damage in Western Oregon Riparian Ecosystems

Cited by 7 publications

References 28 publications

Phytophthora Species in Rivers and Streams of the Southwestern United States

Phytophthora Species in Rivers and Streams of the Southwestern United States

Pathogenicity to alder of Phytophthora species from riparian ecosystems in western Oregon

Ecology and pathology ofPhytophthoraITS clade 3 species in forests in western Oregon, USA

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