scholarly journals Interactions Between Root Rotting Phytophthora, Abies Christmas Trees, and Environment

Plant Disease ◽  
2019 ◽  
Vol 103 (3) ◽  
pp. 538-545 ◽  
Author(s):  
Kathleen M. McKeever ◽  
Gary A Chastagner
Keyword(s):  
Host Species ◽  
Root Rot ◽  
Regional Scale ◽  
Phytophthora Species ◽  
Host Responses ◽  
Phytophthora Root Rot ◽  
Ambient Temperatures ◽  
Christmas Trees ◽  
Host Mortality ◽  
Production Areas

Defining host-pathogen interactions between species of root-rotting Phytophthora and Abies in Christmas tree production areas is important for tailoring management activities on a regional scale and for developing molecular tools for identifying resistant host species. Classifying Abies species as resistant or susceptible is complicated by regional variation in abundance and aggressiveness of Phytophthora species and the influence of environment on symptom expression and host vigor. Because previous studies performed to assess host response to Phytophthora root rot (PRR) have focused on one or a few species of either the host or pathogen, a multifactorial experiment was conducted to assess the responses of seven species of Abies challenged with three isolates each of four Phytophthora species under contrasting temperature conditions. Evaluation of mortality, root rot severity, and remaining root biomass after 16 weeks of exposure to the pathogen confirmed prior inferences regarding inherent variation in the resistance responses of various species of Abies and demonstrated evidence of variation in aggressiveness among species of Phytophthora as well as different isolates of the same Phytophthora species. The ambient temperatures at which studies were conducted had a conspicuous effect on host mortality, root rot severity, and radial growth of Phytophthora. Understanding how host responses differ under variable pathogen attack and ambient environment will improve efforts to control PRR using host species substitutions on infested ground.

Virulence of five Phytophthora species causing rhododendron root rot in Oregon.

Plant Disease ◽  
2021 ◽  
Author(s):  
Gabe O. Sacher ◽  
Carolyn F. Scagel ◽  
E. Anne Davis ◽  
Bryan R. Beck ◽  
Jerry E. Weiland
Keyword(s):  
Root Rot ◽  
Phytophthora Cinnamomi ◽  
Block Design ◽  
Abundant Species ◽  
Phytophthora Species ◽  
Phytophthora Root Rot ◽  
Moderate Disease ◽  
Randomized Complete Block Design ◽  
Infested Field ◽  
Production Areas

Phytophthora root rot is a destructive disease of rhododendron, causing substantial losses of this nursery crop in infested field and container production areas. Historically, Phytophthora cinnamomi was considered the main causal agent of the disease. However, a recent survey of soilborne Phytophthora species from symptomatic rhododendrons in Oregon revealed that P. plurivora is more common than P. cinnamomi and that several other Phytophthora species may also be involved. We investigated the ability of the five most abundant species from the survey to cause root rot: P. plurivora, P. cinnamomi, P. pini, P. pseudocryptogea, and P. cambivora. Three to four isolates were selected for each species from across six Oregon nurseries. Media of containerized Rhododendron catawbiense ‘Boursault’ was infested with single isolates in a randomized complete block design in a greenhouse. Phytophthora cinnamomi, P. pini, and P. plurivora rapidly caused ≥ 90% incidence of severe root rot while P. pseudocryptogea caused more moderate disease with 46% incidence of severe root rot. Phytophthora cambivora failed to produce enough inoculum and was used at a lower inoculum density than the other four species, but occasionally caused severe root rot (5% incidence). No differences in virulence were observed among isolates of same species, except for one isolate of P. plurivora that caused less disease than other P. plurivora isolates. This study demonstrates that all five Phytophthora species, which were representative of 94% of the survey isolates, are capable of causing severe root rot and plant death, but that not all species are equally virulent.

scholarly journals Variation in Disease Severity Caused by Phytophthora cinnamomi, P. plurivora, and Pythium cryptoirregulare on Two Rhododendron Cultivars

Plant Disease ◽  
2018 ◽  
Vol 102 (12) ◽  
pp. 2560-2570 ◽  
Author(s):  
Jerry E. Weiland ◽  
Carolyn F. Scagel ◽  
Niklaus J. Grünwald ◽  
E. Anne Davis ◽  
Bryan R. Beck ◽  
...  
Keyword(s):  
Disease Control ◽  
Root Rot ◽  
Phytophthora Cinnamomi ◽  
Severe Disease ◽  
Phytophthora Species ◽  
Relative Resistance ◽  
Inoculum Level ◽  
Phytophthora Root Rot ◽  
Mild Disease ◽  
Comparative Information

Rhododendrons are an important crop in the ornamental nursery industry, but are prone to Phytophthora root rot. Phytophthora root rot is a continuing issue on rhododendrons despite decades of research. Several Phytophthora species are known to cause root rot, but most research has focused on P. cinnamomi, and comparative information on pathogenicity is limited for other commonly encountered oomycetes, including Phytophthora plurivora and Pythium cryptoirregulare. In this study, three isolates each of P. cinnamomi, P. plurivora, and Py. cryptoirregulare were used to inoculate rhododendron cultivars Cunningham’s White and Yaku Princess at two different inoculum levels. All three species caused disease, especially at the higher inoculum level. P. cinnamomi and P. plurivora were the most aggressive pathogens, causing severe root rot, whereas Py. cryptoirregulare was a weak pathogen that only caused mild disease. Within each pathogen species, isolate had no influence on disease. Both P. cinnamomi and P. plurivora caused more severe disease on Cunningham’s White than on Yaku Princess, suggesting that the relative resistance and susceptibility among rhododendron cultivars might be similar for both pathogens. Reisolation of P. cinnamomi and P. plurivora was also greater from plants exhibiting aboveground symptoms of wilting and plant death and belowground symptoms of root rot than from those without symptoms. Results show that both P. cinnamomi and P. plurivora, but not Py. cryptoirregulare, are important pathogens causing severe root rot in rhododendron. This study establishes the risks for disease resulting from low and high levels of inoculum for each pathogen. Further research is needed to evaluate longer term risks associated with low inoculum levels on rhododendron health and to explore whether differences among pathogen species affect disease control.

Susceptibility of Garden Plants to Phytophthora Root Rot

Plant Disease ◽  
2020 ◽  
Author(s):  
Liz Beal ◽  
Ian Waghorn ◽  
Joe Perry ◽  
Gerard R G Clover ◽  
Matthew Cromey
Keyword(s):  
Host Range ◽  
Root Rot ◽  
Woody Plants ◽  
Integrated Management ◽  
Common Species ◽  
Phytophthora Species ◽  
High Index ◽  
Phytophthora Root Rot ◽  
Wide Host Range ◽  
Serious Disease

Phytophthora root rot (PRR) is a serious disease of horticultural, forest and ornamental plant species caused by species of the oomycete genus Phytophthora. Their wide host range makes choice of resistant plants in management of the disease difficult. We used the Royal Horticultural Society diagnostic dataset of PRR records from U.K. gardens to compare the susceptibility of different host genera to the disease. The dataset was compared with existing reports of plants recorded as notably resistant or notably susceptible to PRR. An index-based approach was used to separate 177 genera of woody plants into three categories: 85 were low-index (<0.10: rarely affected), 34 were medium-index (0.10 – 0.20: sometimes affected) and 58 were high-index (>0.20: frequently affected). Similarly, genera of non-woody plants were separated into: 45 low-index (<0.22), 16 medium-index (0.22 – 0.44) and 18 high-index (>0.44). Taxus was the genus with the highest index, while most genera in the Malvales and Ericales were in the high index group. Most genera in the Myrtales, Fabales and Monocotyledons were low index. Whilst 30 Phytophthora species were recorded in our study, the wide host range spp., P. plurivora, P. cryptogea and P. cinnamomi represented 63% of identifications. Phytophthora plurivora was the most common species on woody plants and P. cryptogea on non-woody plants. These results provide confidence in the use of host resistance as part of the integrated management of PRR.

The challenges of managing Phytophthora root rot in the nursery industry

2021 ◽  
Author(s):  
Jerry E Weiland
Keyword(s):  
Disease Control ◽  
Root Rot ◽  
Phytophthora Species ◽  
Control Measures ◽  
Community Members ◽  
Phytophthora Root Rot ◽  
Severe Problem ◽  
Successful Control ◽  
The Individual ◽  
Intensive Sampling

For nearly 100 years, Phytophthora root rot (PRR) has been a severe problem in nurseries. Early surveys found only one or two Phytophthora species on any one host. However, recent surveys show that nurseries are impacted by increasingly complex Phytophthora communities that vary by host, nursery, and region. Individual community members have diverse biological characteristics and differ in their responses to disease control measures. These differences may shift community composition towards members that are less sensitive to treatment, thereby decreasing overall disease control. Together, this suggests that PRR is better approached as a disease complex rather than as a disease caused by a single entity. Yet, most experiments use only a single Phytophthora isolate and therefore overlook the potential for other community members to be less responsive to treatment. Successful control is further limited by a lack of data on the disease losses and soilborne inoculum levels encountered in the nursery industry, which are essential for establishing risks for infection, pathogen movement, and for evaluating disease control efficacy. Focused surveys with intensive sampling are needed to better characterize the Phytophthora communities occurring on major nursery crops. Experiments should utilize a representative set of species and isolates to ensure treatments are effective. The presence of diverse Phytophthora communities in the nursery industry makes it less likely that any one disease control tactic will be broadly effective. Instead, a combination of approaches that take into account the individual weaknesses of each community member will likely be necessary to achieve long-term PRR control.

scholarly journals Phytophthora root rot: its impact in botanic gardens and on threatened species conservation

2020 ◽  
pp. 89-104
Author(s):  
Brett Summerell ◽  
Edward Liew
Keyword(s):  
Threatened Species ◽  
Root Rot ◽  
Species Conservation ◽  
Phytophthora Species ◽  
Ex Situ ◽  
Botanic Gardens ◽  
Natural Ecosystems ◽  
Phytophthora Root Rot ◽  
A Site ◽  
The Impact

Phytophthora root rot is one of the most devastating diseases of perennial plants worldwide, affecting plants in food production, amenity plantings and in natural ecosystems. The impact of these diseases in botanic gardens can be substantial and can affect how a site may be used for months and years ahead. Management is critically dependent on avoidance of the introduction of the pathogen and effective hygiene protocols are key to achieving this. Additionally, botanic gardens have a key role to play in protecting plants and enhancing conservation outcomes through surveillance, education and ex situ conservation programmes, as well as through the recognition that they can be critical as sentinel sites to detect new incursions of pests anddiseases. The impact of several Phytophthora species on the in situ and ex situ management of the critically endangered Wollemia nobilis (Wollemi pine), which is highly susceptible to phytophthora root rot, is used to highlight the need to ensure management of these pathogens is a critical component of threatened species recovery and management.

scholarly journals Grafting Fraser Fir onto Rootstocks of Selected Abies Species

HortScience ◽  
2002 ◽  
Vol 37 (5) ◽  
pp. 815-818 ◽  
Author(s):  
Eric Hinesley ◽  
John Frampton
Keyword(s):  
North Carolina ◽  
Root Rot ◽  
Field Experiments ◽  
Interspecific Variation ◽  
Phytophthora Root Rot ◽  
Fraser Fir ◽  
Christmas Trees ◽  
Nordmann Fir ◽  
Canaan Valley ◽  
Turkish Fir

Orthotropic shoots (tips of primary axes) from 3-year-old Fraser fir seedlings [Abies fraseri (Pursh) Poir.] were grafted onto rootstocks of Fraser fir, Korean fir (A. koreana Wils.), momi fir (A. firma Sieb. & Zucc.), Nordmann fir (A. nordmanniana (Steven) Spach.), Turkish fir (A. bornmuelleriana Mattf.), and West Virginia balsam fir from Canaan Valley (Canaan fir) [A. balsamea (L.) Mill. var. phanerolepis Fern.]. Firstyear survival in the greenhouse was 92% to 98% except for momi fir (83%). The percentage of grafted plants with orthotropic shoots was 92% to 98%, except for Korean (81%) and momi fir (86%). Plants were subsequently established in replicated field experiments on three sites in the piedmont and mountains of North Carolina. In general, leader elongation of grafted Fraser fir scions was greater than leader growth on nongrafted transplants, including Fraser fir. Differences in survival appear to reflect interspecific variation in resistance to phytophthora root rot and/or tolerance of warm environments. Grafting may offer the potential to grow Abies Christmas trees on previously unsuitable sites, or to reclaim or continue using sites already seriously impacted by root rot.

Phytophthora Species Differ in Response to Phosphorous Acid and Mefenoxam for the Management of Phytophthora Root Rot in Rhododendron

Plant Disease ◽  
2020 ◽  
Author(s):  
Jerry E. Weiland ◽  
Carolyn F. Scagel ◽  
Niklaus J. Grünwald ◽  
E. Anne Davis ◽  
Bryan R. Beck
Keyword(s):  
Root Rot ◽  
Production Systems ◽  
Foliar Spray ◽  
Phosphorous Acid ◽  
Phytophthora Species ◽  
Phytophthora Root Rot ◽  
Application Method ◽  
Affect Control ◽  
Pathogen Diversity ◽  
Significant Disease

Phytophthora root rot, caused by many soilborne Phytophthora species, is a significant disease affecting the $42 million rhododendron nursery industry. Rhododendron growers have increasingly reported failure by two systemic fungicides, phosphorous acid and mefenoxam, to adequately control root rot. Both fungicides may be applied as a foliar spray or soil drench, but it is unknown how application method, fungicide chemistry, or pathogen diversity affects disease control. Therefore, two experiments were conducted to (i) determine whether differences in application method or fungicide chemistry affect control of root rot caused by P. cinnamomi and P. plurivora and (ii) evaluate the sensitivity of Phytophthora species and isolates from the rhododendron industry to each fungicide. Results demonstrated that soil drenches of either fungicide were more effective than foliar sprays for control of P. cinnamomi, but were ineffective for P. plurivora. Furthermore, Phytophthora species and isolates varied in sensitivity to phosphorous acid and mefenoxam, and there were multiple fungicide insensitive isolates, especially within P. plurivora. Differences in sensitivity were also observed among isolates from different nurseries and production systems, with some nurseries having less sensitive isolates than others and with container systems generally having less sensitive isolates than field systems. Our results provide three potential reasons for why fungicide control of Phytophthora root rot might fail: (i) the fungicide can be applied to the wrong portion of the plant for optimal control, (ii) there are differences in fungicide sensitivity among soilborne Phytophthora species and isolates infecting rhododendron, and (iii) fungicide insensitive isolates are present in the rhododendron nursery industry.

scholarly journals Cellulase Activity as a Mechanism for Suppression of Phytophthora Root Rot in Mulches

2011 ◽  
Vol 101 (2) ◽  
pp. 223-230 ◽  
Author(s):  
Brantlee Spakes Richter ◽  
Kelly Ivors ◽  
Wei Shi ◽  
D. M. Benson
Keyword(s):  
Root Rot ◽  
Phytophthora Cinnamomi ◽  
Cellulase Activity ◽  
Enzyme Concentration ◽  
Disease Suppression ◽  
In Vitro Assays ◽  
Infested Soil ◽  
Phytophthora Root Rot ◽  
Standard Curve

Wood-based mulches are used in avocado production and are being tested on Fraser fir for reduction of Phytophthora root rot, caused by Phytophthora cinnamomi. Research with avocado has suggested a role of microbial cellulase enzymes in pathogen suppression through effects on the cellulosic cell walls of Phytophthora. This work was conducted to determine whether cellulase activity could account for disease suppression in mulch systems. A standard curve was developed to correlate cellulase activity in mulches with concentrations of a cellulase product. Based on this curve, cellulase activity in mulch samples was equivalent to a cellulase enzyme concentration of 25 U ml–1 or greater of product. Sustained exposure of P. cinnamomi to cellulase at 10 to 50 U ml–1 significantly reduced sporangia production, but biomass was only reduced with concentrations over 100 U ml–1. In a lupine bioassay, cellulase was applied to infested soil at 100 or 1,000 U ml–1 with three timings. Cellulase activity diminished by 47% between 1 and 15 days after application. Cellulase applied at 100 U ml–1 2 weeks before planting yielded activity of 20.08 μmol glucose equivalents per gram of soil water (GE g–1 aq) at planting, a level equivalent to mulch samples. Cellulase activity at planting ranged from 3.35 to 48.67 μmol GE g–1 aq, but no treatment significantly affected disease progress. Based on in vitro assays, cellulase activity in mulch was sufficient to impair sporangia production of P. cinnamomi, but not always sufficient to impact vegetative biomass.

scholarly journals Phytophthora mediterranea sp. nov., a New Species Closely Related to Phytophthora cinnamomi from Nursery Plants of Myrtus communis in Italy

Forests ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 682
Author(s):  
Carlo Bregant ◽  
Antonio A. Mulas ◽  
Giovanni Rossetto ◽  
Antonio Deidda ◽  
Lucia Maddau ◽  
...  
Keyword(s):  
New Species ◽  
Root Rot ◽  
Phytophthora Cinnamomi ◽  
Colony Growth ◽  
Phytophthora Species ◽  
Maximum Temperature ◽  
Pathogenicity Test ◽  
Forest Nurseries ◽  
Collar And Root Rot ◽  
A New Species

Monitoring surveys of Phytophthora related diseases in four forest nurseries in Italy revealed the occurrence of fourteen Phytophthora species to be associated with collar and root rot on fourteen plants typical of Mediterranean and alpine regions. In addition, a multilocus phylogeny analysis based on nuclear ITS and ß-tubulin and mitochondrial cox1 sequences, as well as micromorphological features, supported the description of a new species belonging to the phylogenetic clade 7c, Phytophthora mediterranea sp. nov. Phytophthora mediterranea was shown to be associated with collar and root rot symptoms on myrtle seedlings. Phylogenetically, P. mediterranea is closely related to P. cinnamomi but the two species differ in 87 nucleotides in the three studied DNA regions. Morphologically P. mediterranea can be easily distinguished from P. cinnamomi on the basis of its smaller sporangia, colony growth pattern and higher optimum and maximum temperature values. Data from the pathogenicity test showed that P. mediterranea has the potential to threaten the native Mediterranean maquis vegetation. Finally, the discovery of P. cinnamomi in alpine nurseries, confirms the progressive expansion of this species towards cold environments, probably driven by climate change.

Restriction fragment length polymorphisms demonstrate single origin of infection centers in Phellinus weirii

1994 ◽  
Vol 72 (4) ◽  
pp. 440-447 ◽  
Author(s):  
Hanhong Bae ◽  
Everett M. Hansen ◽  
Steven H. Strauss
Keyword(s):  
Mitochondrial Dna ◽  
Restriction Fragment ◽  
Ribosomal Dna ◽  
Fragment Length ◽  
Host Species ◽  
Root Rot ◽  
Biological Species ◽  
Douglas Fir ◽  
Dna Probes ◽  
Restriction Fragment Length

Restriction fragment length polymorphism (RFLP) markers were used to study genetic variation in the basidiomycete fungus Phellinus weirii (Murr.) Gilbertson, the cause of laminated root rot of conifers. In an initial study, three isolates each from the Douglas-fir type and the cedar-type biological species were surveyed with 12 restriction enzymes and 20 random, mitochondrial, and nuclear-ribosomal gene probes. The two biological species were distinct with most probe–enzyme combinations (91%). Variation within biological species was detected for the random and ribosomal DNA probes but not for the mitochondrial DNA probes. In a subsequent study 65 probe–enzyme combinations (13 × 5) that had detected variation within the Douglas-fir type biological species were used to analyze 27 isolates derived from six infection centers, two host species, and two geographic areas in western Oregon. Infection centers differed from one another in numerous probe–enzyme combinations but were nearly genetically uniform within. Isolates from the two host species, Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and mountain hemlock (Tsuga mertensiana (Bong.) Carr.), showed few RFLP differences. Initiation of infection centers, and subsequent vegetative or basdiospore initiated immigration, appear to be rare events. Key words: ribosomal DNA, mitochondrial DNA, RFLP, root rot, conifer.

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