scholarly journals First Report of Phytophthora ramorum on Douglas-Fir in California

Plant Disease ◽  
2002 ◽  
Vol 86 (11) ◽  
pp. 1274-1274 ◽  
Author(s):  
J. M. Davidson ◽  
M. Garbelotto ◽  
S. T. Koike ◽  
D. M. Rizzo
Keyword(s):  
Douglas Fir ◽  
Phytophthora Ramorum ◽  
Natural Forests ◽  
Disease Symptoms ◽  
Single Leaf ◽  
Rdna Sequences ◽  
Umbellularia Californica ◽  
Lithocarpus Densiflorus ◽  
Sonoma County ◽  
Internal Transcribed Spacer Rdna

Phytophthora ramorum S. Werres & A.W.A.M. de Cock was isolated from three Douglas-fir (Pseudotsuga menziesii) saplings in a mixedevergreen forest in Sonoma County, California. Symptoms on these saplings included cankers on small branches (0.5 to 1 cm in diameter) resulting in wilting of new shoots, dieback of branches, and loss of leaves as much as 15 cm from the twig tip. Symptoms were observed on most saplings growing in the same area. On several smaller saplings (<1 m tall), P. ramorum infection resulted in the death of the leader and the top several whorls of branches. Isolates were identified as P. ramorum by their abundant chlamydospores and caducous, semi-papillate sporangia (2) and internal transcribed spacer rDNA sequences identical to those of isolates of P. ramorum from Quercus spp., Lithocarpus densiflorus, and Rhododendron (1,2). To test for pathogenicity, foliage inoculations were conducted on seedlings in two trials by misting 30 leaves per trial (five leaves per seedling plus controls) with sterile distilled water and pinning inoculum plugs, taken from the margin of P. ramorum cultures, to the upper surface of leaves. Inoculation resulted in lesions ranging between 1 and 12 mm long, and P. ramorum was recovered from 47% of inoculated leaves. Symptoms were not restricted to inoculated leaves, and in 26 single-leaf inoculations, lesions 17 to 85 mm long developed on branches (five mm in diameter) adjacent to the inoculated leaf. Isolation success from branch lesions was 50%, despite the fact that such lesions were apparently disjunct from the small 1-mm lesions developing on inoculated leaves. Stems of Douglas-fir seedlings (approximately 1 cm in diameter) were wound inoculated (1) in two trials consisting of 10 inoculated seedlings per trial plus 10 controls. After 6 weeks, lesion lengths in the cambium averaged 38 mm (range 12 to 62 mm), and three seedlings were completely girdled. P. ramorum was recovered from 75% of inoculated stems. Mean lesion lengths on seedlings inoculated with P. ramorum were significantly greater (P < 0.05) in both trials than those of control inoculations (mean 9 mm) based on analysis of variance. We have not observed unusual mortality or disease symptoms on overstory Douglas-fir trees in natural forests. The importance of P. ramorum branch tip dieback for growth and reproduction of Douglas-fir is unknown. Douglas-fir is present in many forests in California and Oregon already infested by P. ramorum, yet we have found infection of plants at only one location. At this site, symptomatic Douglas-fir saplings were surrounded by bay laurel (Umbellularia californica) trees with extremely high levels of P. ramorum infection. P. ramorum is known to sporulate prolifically on bay laurel leaves. More studies are necessary to determine if the incidence of P. ramorum in Douglas-fir extends to other locations or if it is limited to this one locale. References: (1) D. M. Rizzo et al. Plant Disease 86:205, 2002. (2) S. Werres et al. Mycol. Res. 105:1155, 2001.

scholarly journals First Report of Phytophthora ramorum on Canyon Live Oak in California

Plant Disease ◽  
2003 ◽  
Vol 87 (3) ◽  
pp. 315-315 ◽  
Author(s):  
S. K. Murphy ◽  
D. M. Rizzo
Keyword(s):  
Phytophthora Ramorum ◽  
First Report ◽  
Rdna Sequences ◽  
Red Oaks ◽  
Live Oak ◽  
Umbellularia Californica ◽  
Long Term Effect ◽  
Lithocarpus Densiflorus ◽  
Understory Trees ◽  
Oak Seedlings

During August 2002, Phytophthora ramorum S. Werres & A.W.A.M. de Cock was isolated from branches <2.0 cm in diameter on a canyon live oak (Quercus chrysolepis) in Mt. Tamalpais State Park, Marin County, CA. The shrub was a cluster of stems <1 m in diameter and 1 m high. Similar cankers were observed on small branches of adjacent canyon live oaks and there was dieback of the branches distal to the lesions. Many tanoak (Lithocarpus densiflorus), California bay laurel (Umbellularia californica), and evergreen huckleberry (Vaccinium ovatum) were also infected by P. ramorum at this site. The isolate was identified as P. ramorum by its abundant chlamydospores and caducous, semi-papillate sporangia and internal transcribed spacer (ITS) rDNA sequences identical to those of isolates of P. ramorum from Quercus spp., tanoak, and Rhododendron (1,3). To test for pathogenicity, two greenhouse trials (5 seedlings per trial plus controls) were conducted on 20- to 24-month-old canyon live oak seedlings. Coast live oak (Q. agrifolia, section Lobatae) seedlings were included in the trials as a comparison because the species is known to be susceptible (1). Stems (approximately 1 cm in diameter) were wound inoculated (1). After 6 weeks, lesion lengths in the cambium of canyon live oak averaged 17.2 mm (range 16 to 30 mm), which was significantly greater (analysis of variance [ANOVA], P < 0.05) in both trials than those of control inoculations (mean = 6 mm). Coast live oak seedlings inoculated at the same time had mean lesion lengths of 22.6 mm (range 15 to 30 mm). P. ramorum was recovered from 100% of inoculated stems. Canyon live oak has a wide geographic range within California, but is not common in the areas currently affected by P. ramorum. We have not observed disease symptoms or unusual mortality on overstory canyon live oaks. Although a number of understory canyon live oaks at the site on Mt. Tamalpais were apparently infected, the long-term effect of P. ramorum infection on understory trees remains unclear. To our knowledge, this is the first report of infection by P. ramorum of an oak species outside of the section Lobatae (red oaks); canyon live oak is classified in the section Protobalanus (intermediate or golden cup oaks) (2). Oaks in the section Quercus (white oaks) have not been observed to be infected by P. ramorum in the field. References: (1) D. M. Rizzo et al. Plant Dis. 86:205, 2002. (2) P. Manos et al. Mol. Phylogenet. Evol. 12:333, 1999. (3) S. Werres et al. Mycol. Res. 105:1155, 2001.

scholarly journals Photosynthetic Declines in Phytophthora ramorum-Infected Plants Develop Prior to Water Stress and in Response to Exogenous Application of Elicitins

2007 ◽  
Vol 97 (7) ◽  
pp. 850-856 ◽  
Author(s):  
Daniel K. Manter ◽  
Rick G. Kelsey ◽  
Joseph J. Karchesy
Keyword(s):  
Water Stress ◽  
Photosynthetic Capacity ◽  
Stomatal Closure ◽  
Phytophthora Ramorum ◽  
Umbellularia Californica ◽  
Lithocarpus Densiflorus ◽  
Shoot Blight ◽  
Oak Mortality ◽  
Stem Lesions ◽  
Stem Girdling

Phytophthora ramorum, causal agent of sudden oak death, is responsible for widespread oak mortality in California and Oregon, and has the potential to infect 100 or more species. Symptoms range from stem girdling and shoot blight to leaf spotting. In this study, we examined the physiological impacts of P. ramorum infection on Rhododendron macrophyllum. In stem-inoculated plants, photosynthetic capacity (Vcmax) significantly declined by ≈21% 3 weeks after inoculation in visibly asymptomatic leaves. By 4 weeks, after the development of significant stem lesions and loss in water transport capacity, water stress led to stomatal closure and additional declines in photosynthetic capacity. We also report the isolation, characterization, and biological activity of two P. ramorum elicitins. Both elicitins were capable of inducing a hypersensitive-like response in one incompatible (Nicotiana tabacum SR1) and three compatible hosts (R. macrophyllum, Lithocarpus densiflorus, and Umbellularia californica). Infiltration of leaves from all three compatible hosts with both P. ramorum elicitins caused significant declines in chlorophyll fluorescence (Fv /Fm). For all four species, the loss of photosynthetic capacity was directly proportional to H+ uptake and ethylene production, two common components of the hypersensitive response. This is the first report of elicitins causing photosynthetic declines in compatible hosts independent of plant water stress.

scholarly journals Sources of Inoculum for Phytophthora ramorum in a Redwood Forest

2008 ◽  
Vol 98 (8) ◽  
pp. 860-866 ◽  
Author(s):  
J. M. Davidson ◽  
H. A. Patterson ◽  
D. M. Rizzo
Keyword(s):  
Field Measurements ◽  
Elevated Risk ◽  
Phytophthora Ramorum ◽  
Late Spring ◽  
Sequoia Sempervirens ◽  
Plant Tissues ◽  
Inoculum Production ◽  
Umbellularia Californica ◽  
Lithocarpus Densiflorus ◽  
Redwood Forest

Sources of inoculum were investigated for dominant hosts of Phytophthora ramorum in a redwood forest. Infected trunks, twigs, and/or leaves of bay laurel (Umbellularia californica), tanoak (Lithocarpus densiflorus), and redwood (Sequoia sempervirens) were tested in the laboratory for sporangia production. Sporangia occurred on all plant tissues with the highest percentage on bay laurel leaves and tanoak twigs. To further compare these two species, field measurements of inoculum production and infection were conducted during the rainy seasons of 2003-04 and 2004-05. Inoculum levels in throughfall rainwater and from individual infections were significantly higher for bay laurel as opposed to tanoak for both seasons. Both measurements of inoculum production from bay laurel were significantly greater during 2004-05 when rainfall extended longer into the spring, while inoculum quantities for tanoak were not significantly different between the 2 years. Tanoak twigs were more likely to be infected than bay laurel leaves in 2003-04, and equally likely to be infected in 2004-05. These results indicate that the majority of P. ramorum inoculum in redwood forest is produced from infections on bay laurel leaves. Years with extended rains pose an elevated risk for tanoak because inoculum levels are higher and infectious periods continue into late spring.

scholarly journals Detection, Distribution, Sporulation, and Survival of Phytophthora ramorum in a California Redwood-Tanoak Forest Soil

2007 ◽  
Vol 97 (10) ◽  
pp. 1366-1375 ◽  
Author(s):  
E. J. Fichtner ◽  
S. C. Lynch ◽  
D. M. Rizzo
Keyword(s):  
Phytophthora Ramorum ◽  
Disease Cycle ◽  
Soil Baiting ◽  
Umbellularia Californica ◽  
Lithocarpus Densiflorus ◽  
Important Host ◽  
The Impact ◽  
Soil Interface ◽  
Leaf Disks

Recovery of Phytophthora ramorum from soils throughout sudden oak death-affected regions of California illustrates that soil may serve as an inoculum reservoir, but the role of soil inoculum in the disease cycle is unknown. This study addresses the efficacy of soil baiting, seasonal pathogen distribution under several epidemiologically important host species, summer survival and chlamydospore production in soil, and the impact of soil drying on pathogen survival. The efficacy of rhododendron leaves and pears as baits for detection of soilborne propagules were compared. Natural inoculum associated with bay laurel (Umbellularia californica), tanoak (Lithocarpus densiflorus), and redwood (Sequoia sempervirens) were determined by monthly baiting. Summer survival and chlamydospore production were assessed in infected rhododendron leaf disks incubated under bay laurel, tanoak, and redwood at either the surface, the litter/soil interface, or in soil. Rhododendron leaf baits were superior to pear baits for sporangia detection, but neither bait detected chlamydospores. Most inoculum was associated with bay laurel and recovery was higher in soil than litter. Soil-incubated inoculum exhibited over 60% survival at the end of summer and also supported elevated chlamydospore production. P. ramorum survives and produces chlamydospores in forest soils over summer, providing a possible inoculum reservoir at the onset of the fall disease cycle.

scholarly journals First Report of Phytophthora ramorum on Coast Redwood in California

Plant Disease ◽  
2002 ◽  
Vol 86 (11) ◽  
pp. 1274-1274 ◽  
Author(s):  
P. E. Maloney ◽  
D. M. Rizzo ◽  
S. T. Koike ◽  
T. Y. Harnik ◽  
M. Garbelotto
Keyword(s):  
Pcr Amplification ◽  
Its Region ◽  
Pcr Primers ◽  
Phytophthora Ramorum ◽  
Natural Forests ◽  
Coast Redwood ◽  
Specific Pcr ◽  
Rdna Sequences ◽  
Quercus Spp ◽  
The Impact

Phytophthora ramorum S. Werres & A.W.A.M. de Cock was isolated from discolored leaves and cankers on small branches (<0.5 cm in diameter) on 27 coast redwood (Sequoia sempervirens) saplings (2 to17 cm in diameter) at two locations in California (Jack London State Park, Sonoma County and Henry Cowell State Park, Santa Cruz County). Symptoms were observed on branches throughout the crowns of affected trees. Isolates were identified as P. ramorum by their abundant chlamydospores and caducous, semi-papillate sporangia (2) and internal transcribed spacer (ITS) rDNA sequences identical to those of P. ramorum from Quercus spp., Lithocarpus densiflorus, and Rhododendron (1,2). P. ramorum was also detected in dying basal sprouts on mature redwood trees from an additional five locations in coastal California by polymerase chain reaction (PCR) amplification of the ITS region using DNA extracted from symptomatic tissue and P. ramorum-specific PCR primers. To test for pathogenicity, foliage inoculations were conducted on redwood seedlings in two trials by misting 30 leaves per trial (five leaves per seedling plus controls) with sterile distilled water and then pinning inoculum plugs to the upper surface of leaves. Inoculation resulted in lesions of 1 to 20 mm on individual leaves, and P. ramorum was recovered from 43% of inoculated leaves. Symptoms were not restricted to inoculated leaves because 15 inoculations of individual leaves led to discoloration of two or more adjacent leaves. On one inoculation, 60 mm of the adjacent stem was killed. Stems of redwood seedling (approximately 1 cm in diameter) were wound inoculated (1) in two trials consisting of 10 inoculated seedlings per trial plus 10 controls. After 6 weeks, lesion lengths in the cambium caused by P. ramorum averaged 13.7 mm (range 4 to 21 mm). P. ramorum was recovered from 100% of inoculated stems. Entire branches near the inoculation point became chlorotic even though no direct connection was evident between the lesion and the branches. No chlorosis was observed among the control inoculations. Mean lesion lengths of inoculated stems were significantly greater in both trials than those of control inoculations (mean 6.2 mm) at P < 0.05 based on analysis of variance (ANOVA). Redwood saplings (2.5 to 4.5 cm in diameter) were also wound inoculated in a separate trial. No phloem or cambial discoloration was observed after 7 weeks, but necrotic lesions in the xylem had a mean length of 39 mm (range 12 to 73 mm). In addition, narrow streaks, 1 to 2 mm in diameter, were also noted in the xylem extending from the necrotic areas upward to 90 cm. P. ramorum was recovered from 70% of inoculated stems in this trial. Mean lesion lengths of P. ramorum were significantly greater in all trials than those of control inoculations (mean 20 mm) at P < 0.05 based on ANOVA. While P. ramorum causes a lethal canker on Quercus spp. and L. densiflorus (1), we have not observed unusual mortality or disease symptoms on overstory redwoods in natural forests. The impact of infection by P. ramorum on understory redwoods is also unclear. However, the pathogen appears to be able to kill sprouts. References: (1) D. M. Rizzo et al. Plant Dis. 86:205, 2002. (2) S. Werres et al. Mycol. Res. 105:1155, 2001.

scholarly journals Detection, Identification, and Significance of Phytoplasmas in Wild Grasses in East Africa

Plant Disease ◽  
2016 ◽  
Vol 100 (1) ◽  
pp. 108-115 ◽  
Author(s):  
George O. Asudi ◽  
Johnnie Van den Berg ◽  
Charles A. O. Midega ◽  
Bernd Schneider ◽  
Erich Seemüller ◽  
...  
Keyword(s):  
East Africa ◽  
Napier Grass ◽  
Pennisetum Purpureum ◽  
Universal Primers ◽  
Grass Species ◽  
Disease Symptoms ◽  
Rdna Sequences ◽  
Northern Tanzania ◽  
White Leaf ◽  
16S Rdna Sequences

Plant-pathogenic phytoplasmas found in wild grasses in East Africa could pose a serious threat to the cultivation of Napier grass, Pennisetum purpureum, the most important livestock fodder in the region. To asses this threat, leaves from plants of 33 grass species were sampled from Mbita, Bungoma, and Busia districts in western Kenya; Tarime district in northern Tanzania; and Busia and Bugiri districts in the eastern Uganda to determine which species host phytoplasmas, the identity of the phytoplasmas, and their relationship with disease symptoms. Phytoplasmas were detected using universal primers based on conserved phytoplasma-specific 16S rDNA sequences from 11 grass species collected. Sequence and phylogenetic analysis revealed the presence of Napier grass stunt-related phytoplasmas in 11 grass species, ‘Candidatus Phytoplasma cynodontis’ in three, and goosegrass white leaf phytoplasma in 2 wild grass species. This study showed that the geographical distribution, diversity of phytoplasmas, and their grass host species in East Africa is greater than antecedently thought and that typical disease symptoms, including white leaf or stunting alone, are not reliable indicators of the presence of phytoplasma. It also shows the need to identify insect vectors responsible for phytoplasma transmission from native grasses to Napier grass or other cereals present in the region.

Phytophthora ramorum. [Distribution map].

2006 ◽  
Author(s):  
Keyword(s):  
South Carolina ◽  
Phytophthora Ramorum ◽  
Distribution Map ◽  
Quercus Agrifolia ◽  
Quercus Kelloggii ◽  
Live Oak ◽  
Lithocarpus Densiflorus ◽  
Black Oak ◽  
New Distribution ◽  
Distribution In Europe

Abstract A new distribution map is provided for Phytophthora ramorum Werres, de Cock & Man in't Veld. Oomycota: Pythiales. Hosts include California black oak (Quercus kelloggii), California live oak (Quercus agrifolia), Rhododendron, shreve oak (Quercus parvula var. shrevei), tanoak (Lithocarpus densiflorus) and Viburnum. Information is given on the geographical distribution in Europe (Belgium, Denmark, France, Germany, Ireland, Italy, Netherlands, Norway, Poland, Slovenia, Spain, Sweden, Switzerland, UK) and North America (Canada (British Columbia), USA (California, Florida, Georgia, Louisiana, Oregon, South Carolina, Tennessee, Virginia, Washington)).

scholarly journals Evaluation of Resistance to Rhabdocline Needlecast in Douglas Fir Variety Shuswap, with Quantitative Polymerase Chain Reaction

2010 ◽  
Vol 100 (4) ◽  
pp. 337-344 ◽  
Author(s):  
M. Catal ◽  
G. C. Adams ◽  
D. W. Fulbright
Keyword(s):  
Polymerase Chain Reaction ◽  
Quantitative Polymerase Chain Reaction ◽  
Douglas Fir ◽  
Chain Reaction ◽  
Disease Symptoms ◽  
Seed Sources ◽  
Release Times ◽  
Spore Release ◽  
Target Dna ◽  
Polymerase Chain

A quantitative polymerase chain reaction assay was developed that could detect DNA of Rhabdocline pseudotsugae and R. oblonga among DNA of Douglas fir needles to a limit as low as three copies of target DNA. Differential infection rates of two varieties (seed sources) of Douglas fir interplanted in a field were studied in relation to staggered bud breaks. Infection of Douglas fir var. San Isabel corresponded to ascospore release times for Rhabdocline spp., whereas infection of var. Shuswap Lake did not occur throughout the spore release period during 2 years of study, despite abundant inoculum and adequate moisture during bud break. Rhabdocline spp. DNA was never detected in Shuswap Lake and disease symptoms were not observed in any year. We provide evidence that Shuswap Lake is resistant and probably immune to Rhabdocline spp. infection and Rhabdocline needlecast under Michigan conditions.

A Comparative Analysis of Detection Techniques Used in US Regulatory Programs to Determine Presence of Phytophthora ramorum in Camellia japonica ‘Nucio's Gem’ in an Infested Nursery in Southern California

2006 ◽  
Vol 7 (1) ◽  
pp. 9 ◽  
Author(s):  
Russ Bulluck ◽  
Pat Shiel ◽  
Phil Berger ◽  
David Kaplan ◽  
Greg Parra ◽  
...  
Keyword(s):  
Growth Medium ◽  
Phytophthora Ramorum ◽  
Molecular Diagnostic ◽  
Medium Ph ◽  
Camellia Japonica ◽  
Disease Symptoms ◽  
Diagnostic Assays ◽  
Detection Techniques ◽  
The Usa ◽  
Diagnostic Sensitivity And Specificity

Phytophthora ramorum (Pram) is a pathogen of regulatory concern in the USA, and accurate diagnostics is a key component in the response to potential pathogen outbreaks. Although the molecular diagnostic protocols used in regulatory programs have been evaluated using regulatory samples, to date, no direct comparison of these methods has been analyzed within a nursery setting. A block of 300 camellia plants within a California nursery known to be infested with Pram was simultaneously assayed for visual symptoms, growth medium pH, and moss presence as well as culture isolation and molecular analysis prior to plant destruction. Disease symptoms such as foliar lesions and leaf drop were recorded for each plant prior to foliar and growth medium sampling. All diagnostic assays were highly correlated with one another and disease symptoms, with nested PCR having the best correlation with symptoms, followed by Real-Time PCR then culture. No correlation with disease or diagnostic assays was observed with moss presence or medium pH. Analysis of results allowed diagnostic sensitivity and specificity of the assays to be determined and the performance of each method for diagnosis of Phytophthora spp. or Phytophthora ramorum in camellia tissues and associated potting medium could be compared. Accepted for publication 12 July 2006. Published 16 October 2006.

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