scholarly journals Diversity of Foliar Phytophthora Species on Rhododendron in Oregon Nurseries

Plant Disease ◽  
2015 ◽  
Vol 99 (10) ◽  
pp. 1326-1332 ◽  
Author(s):  
B. J. Knaus ◽  
V. J. Fieland ◽  
K. A. Graham ◽  
N. J. Grünwald
Keyword(s):  
Community Structure ◽  
Plant Pathogens ◽  
Phytophthora Species ◽  
Phytophthora Ramorum ◽  
Sudden Oak Death ◽  
Recent Emergence ◽  
Nursery Crops ◽  
The U.S

The genus Phytophthora contains some of the most notorious plant pathogens affecting nursery crops. Given the recent emergence of the sudden oak death pathogen Phytophthora ramorum, particularly in association with Rhododendron spp., characterization of Phytophthora communities associated with this host in nursery environments is prudent. Many taxa may present symptoms similar to P. ramorum but we do not necessarily know their identity, frequency, and importance. Here, we present a survey of Phytophthora taxa observed from seven nurseries in the U.S. state of Oregon. Incidence and diversity of Phytophthora communities differed significantly among nurseries and among seasons within nursery. The taxa P. syringae and P. plurivora were widespread and detected at most of the nurseries sampled. Nine other taxa were also detected but were found either in a single nursery or were shared among only a few nurseries. Characterization of the Phytophthora communities present in nurseries is an important step toward understanding the ecology of these organisms as well as an aid to nursery managers in determining what risks may be present when symptomatic plants are observed. This study builds on an increasing literature, which characterizes Phytophthora community structure in nurseries.

scholarly journals Response of Selected Nursery Crop Plants to Inoculation with Isolates of Phytophthora ramorum and Other Phytophthora Species

2006 ◽  
Vol 16 (2) ◽  
pp. 216-224 ◽  
Author(s):  
R.G. Linderman ◽  
E.A. Davis ◽  
J.L. Marlow
Keyword(s):  
Plant Species ◽  
The United States ◽  
Phytophthora Species ◽  
Phytophthora Ramorum ◽  
Experimental Conditions ◽  
Pathogen Virulence ◽  
Detached Leaves ◽  
Nursery Crops ◽  
Relative Differences ◽  
Selection Of

Many nursery crops are susceptible to root and foliage diseases caused by numerous species of Phytophthora. Phytophthora ramorum causes sudden oak death of trees and ramorum leaf blight and shoot dieback on numerous nursery plants, including rhododendron (Rhododendron spp.), viburnum (Viburnum spp.), pieris (Pieris spp.), and camellia (Camellia spp.) in Europe, the United States, and British Columbia, Canada. We sought to evaluate relative susceptibility of a selection of ornamental nursery crops by inoculating detached leaves with several species of Phytophthora known to infect rhododendrons, and to compare the relative virulence on those species to isolates of P. ramorum. The results indicated that many plants were susceptible under these experimental conditions, while others were not. On a given host, symptoms caused by all species of Phytophthora were identical except for differences in pathogen virulence. Plant species were identical except for differences in pathogen virulence. Plant species within genera or cultivars within species varied in susceptibility to isolates of P. ramorum and other species of Phytophthora. Phytophthora ramorum, P. citricola, P. citrophthora, and P. nicotianae were the most virulent pathogens on most of the host plants inoculated. Some plants were susceptible to several species of Phytophthora, while others were susceptible only to P. ramorum. Inoculation of detached leaves of `Nova Zembla' rhododendron, lilac (Syringa vulgaris), or doublefile viburnum (Viburnum plicatum var. tomentosum) under controlled conditions with different species of Phytophthora or isolates of P. ramorum (both mating types) indicated significant relative differences in species or isolate virulence.

Evaluation of Chemical Agents for the Control of Phytophthora ramorum and Other Species of Phytophthora on Nursery Crops

2008 ◽  
Vol 9 (1) ◽  
pp. 26 ◽  
Author(s):  
Robert G. Linderman ◽  
E. Anne Davis
Keyword(s):  
Foliar Application ◽  
Management Strategies ◽  
Phytophthora Species ◽  
Phytophthora Ramorum ◽  
Detached Leaf ◽  
Chemical Agents ◽  
Mycelial Plug ◽  
Previously Treated ◽  
Nursery Crops ◽  
Leaf Test

Phytophthora diseases occur frequently in nurseries, and the recent incidence of ramorum blight, caused by P. ramorum, on nursery crops has underscored the need for improved management strategies against all Phytophthora diseases. We evaluated several chemicals that target Oomycete pathogens, inoculating detached rhododendron or lilac leaves removed from plants previously treated with various chemicals, or chemically-treated leaves on intact plants. Results indicated that Subdue MAXX (drench or foliar application) was the most effective chemical in suppressing infections caused by all species of Phytophthora tested (P. ramorum, P. citricola, P. citrophthora, and P. nicotianae) except P. citrophthora; with P. ramorum, it was active for at least 6 weeks after spray application. More chemicals were effective when sporangial rather than mycelial plug inoculum of P. ramorum was used, including Aliette, Ranman, Stature DM, and Fenamidone. All chemicals tested were fungistatic, not fungicidal. These tests indicate that several materials inhibit infection by Phytophthora species, and that the detached leaf test is effective in evaluating efficacy of chemical agents for the suppression of Phytophthora pathogens from nurseries. Accepted for publication 10 November 2007. Published 11 February 2008.

scholarly journals Characterization of Phytophthora Species from Leaves of Nursery Woody Ornamentals in Tennessee

HortScience ◽  
2008 ◽  
Vol 43 (6) ◽  
pp. 1833-1837 ◽  
Author(s):  
Ryan S. Donahoo ◽  
Kurt H. Lamour
Keyword(s):  
Direct Sequencing ◽  
Genotypic Diversity ◽  
Common Species ◽  
Morphological Characters ◽  
Phytophthora Species ◽  
Phytophthora Ramorum ◽  
National Surveys ◽  
Woody Ornamentals ◽  
Insight Into

Species of Phytophthora are ubiquitous in ornamental production resulting in significant crop losses. In Tennessee, national surveys for the sudden oak death pathogen Phytophthora ramorum in 2004 and 2005 led to the isolation of Phytophthora species causing disease in nursery-grown or handled woody ornamentals or both. Isolates recovered were identified to species using direct sequencing of the internal transcribed spacer and examination of morphological characters. Six known species (P. cactorum, P. citricola, P. citrophthora, P. nicotianae, P. palmivora, P. tropicalis) and one newly described species (P. foliorum) were recovered from ericaceous hosts. The most common species recovered were P. citricola and P. citrophthora. Genetic analysis using amplified fragment length polymorphism (AFLP) markers revealed intraspecific genotypic diversity as well as isolates with identical AFLP genotypes from multiple locations across multiple years. This work provides evidence for species and genotypic diversity of Phytophthora recovered in Tennessee as well as insight into the movement of individual genotypes in woody ornamental production.

Differentiating Phytophthora ramorum and P. kernoviae from Other Species Isolated from Foliage of Rhododendrons

2010 ◽  
Vol 11 (1) ◽  
pp. 22 ◽  
Author(s):  
T. L. Widmer
Keyword(s):  
New Species ◽  
Plant Pathogens ◽  
Colony Growth ◽  
Culture Collection ◽  
Phytophthora Species ◽  
Phytophthora Ramorum ◽  
Molecular Tools ◽  
Plant Parts ◽  
Dichotomous Key

Phytophthora species are among plant pathogens that are the most threatening to agriculture. After the discovery of P. ramorum, surveys have identified new species and new reports on rhododendrons. Based upon propagule production, morphology, and colony growth, a dichotomous key was produced that can differentiate P. ramorum and P. kernoviae from other species known to be pathogenic to aerial plant parts of rhododendrons. These distinctions were made without molecular tools and wide-ranging variables such as propagule sizes and can be made without the need for a large culture collection. Accepted for publication 17 December 2009. Published 17 March 2010.

scholarly journals Susceptibility of Camellia to Phytophthora ramorum

2006 ◽  
Vol 7 (1) ◽  
pp. 28 ◽  
Author(s):  
Nina Shishkoff
Keyword(s):  
Phytophthora Ramorum ◽  
Sudden Oak Death ◽  
Stem Tissue ◽  
Relative Susceptibility ◽  
Stem Blight ◽  
Nursery Stock ◽  
The U.S

Camellia is a known host of Phytophthora ramorum, the “sudden oak death” pathogen. During 2003-2004, the organism was shipped from California throughout the U.S. on infected nursery stock, leading to a nationwide effort to recover the infected plants. This paper describes the symptoms on Camellia and the relative susceptibility of nine species and four hybrids. Camellias varied widely in susceptibility, with Camellia × ‘Roni gaki’ showing the worst overall symptoms, while some other cultivars showed little or none. Obvious symptoms include leaf lesions and stem blight; defoliation, while more difficult to observe, was also characteristic in camellias. The pathogen persisted in diseased plants, notably in stem tissue, for at least a month as demonstrated by isolation. One month after inoculation, roots remained Accepted for publication 23 December 2005. Published 15 March 2006.

scholarly journals Membrane-Based Oligonucleotide Array Developed from Multiple Markers for the Detection of Many Phytophthora Species

2013 ◽  
Vol 103 (1) ◽  
pp. 43-54 ◽  
Author(s):  
Wen Chen ◽  
Zeinab Robleh Djama ◽  
Michael D. Coffey ◽  
Frank N. Martin ◽  
Guillaume J. Bilodeau ◽  
...  
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Plant Pathogens ◽  
Sequence Data ◽  
Phytophthora Species ◽  
Phytophthora Ramorum ◽  
Oligonucleotide Array ◽  
Data Set ◽  
Phytophthora Spp ◽  
Field Samples

Most Phytophthora spp. are destructive plant pathogens; therefore, effective monitoring and accurate early detection are important means of preventing potential epidemics and outbreaks of diseases. In the current study, a membrane-based oligonucleotide array was developed that can detect Phytophthora spp. reliably using three DNA regions; namely, the internal transcribed spacer (ITS), the 5′ end of cytochrome c oxidase 1 gene (cox1), and the intergenic region between cytochrome c oxidase 2 gene (cox2) and cox1 (cox2-1 spacer). Each sequence data set contained ≈250 sequences representing 98 described and 15 undescribed species of Phytophthora. The array was validated with 143 pure cultures and 35 field samples. Together, nonrejected oligonucleotides from all three markers have the ability to reliably detect 82 described and 8 undescribed Phytophthora spp., including several quarantine or regulated pathogens such as Phytophthora ramorum. Our results showed that a DNA array containing signature oligonucleotides designed from multiple genomic regions provided robustness and redundancy for the detection and differentiation of closely related taxon groups. This array has the potential to be used as a routine diagnostic tool for Phytophthora spp. from complex environmental samples without the need for extensive growth of cultures.

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