genetic epidemiology of the sudden oak death pathogen phytophthora ramorum in california. | a total of 669 isolates of phytophthora ramorum, the pathogen responsible for sudden oak death, were collected from 34 californian forests and from the ornamental plant-trade. seven microsatellite markers revealed 82 multilocus genotypes (mgs) of which only three were abundant (>10%). iteratively collapsing based upon minimum phi(st), yielded five meta-samples and five singleton populations. populations in the same meta-sample were geographically contiguous, with one exception, possibly explaine ... | 2009 | 19840268 |
interacting disturbances: wildfire severity affected by stage of forest disease invasion. | sudden oak death (sod) is an emerging forest disease causing extensive tree mortality in coastal california forests. recent california wildfires provided an opportunity to test a major assumption underlying discussions of sod and land management: sod mortality will increase fire severity. we examined prefire fuels from host species in a forest monitoring plot network in big sur, california (usa), to understand the interactions between disease-caused mortality and wildfire severity during the 200 ... | 2011 | 21563563 |
population genetic analysis infers migration pathways of phytophthora ramorum in us nurseries. | recently introduced, exotic plant pathogens may exhibit low genetic diversity and be limited to clonal reproduction. however, rapidly mutating molecular markers such as microsatellites can reveal genetic variation within these populations and be used to model putative migration patterns. phytophthora ramorum is the exotic pathogen, discovered in the late 1990s, that is responsible for sudden oak death in california forests and ramorum blight of common ornamentals. the nursery trade has moved thi ... | 2009 | 19774068 |
migration patterns of the emerging plant pathogen phytophthora ramorum on the west coast of the united states of america. | phytophthora ramorum (oomycetes) is the causal agent of sudden oak death and ramorum blight on trees, shrubs, and woody ornamentals in the forests of coastal california and southwestern oregon and in nurseries of california, oregon, and washington. in this study, we investigated the genetic structure of p. ramorum on the west coast of the united states, focusing particularly on population differentiation potentially indicative of gene flow. in total, 576 isolates recovered from 2001 to 2005 were ... | 2009 | 19453234 |
survival, dispersal, and potential soil-mediated suppression of phytophthora ramorum in a california redwood-tanoak forest. | because the role of soil inoculum of phytophthora ramorum in the sudden oak death disease cycle is not well understood, this work addresses survival, chlamydospore production, pathogen suppression, and splash dispersal of the pathogen in infested forest soils. colonized rhododendron and bay laurel leaf disks were placed in mesh sachets before transfer to the field in january 2005 and 2006. sachets were placed under tanoak, bay laurel, and redwood at three vertical locations: leaf litter surface, ... | 2009 | 19351257 |
aflps detect low genetic diversity for phytophthora nemorosa and p. pseudosyringae in the us and europe. | in california and oregon, two recently described oomycete forest pathogens, phytophthora nemorosa and p. pseudosyringae, overlap in their host and geographic ranges with the virulent p. ramorum, causal agent of "sudden oak death." epidemiological observations, namely broader geographic distribution and lack of landscape-level mortality, led to the hypothesis they are native to this region, whereas multiple lines of evidence indicate p. ramorum is exotic to north america. we used aflp analysis to ... | 2009 | 19061958 |
early detection of emerging forest disease using dispersal estimation and ecological niche modeling. | distinguishing the manner in which dispersal limitation and niche requirements control the spread of invasive pathogens is important for prediction and early detection of disease outbreaks. here, we use niche modeling augmented by dispersal estimation to examine the degree to which local habitat conditions vs. force of infection predict invasion of phytophthora ramorum, the causal agent of the emerging infectious tree disease sudden oak death. we sampled 890 field plots for the presence of p. ra ... | 2008 | 18488603 |
mitochondrial haplotype determination in the oomycete plant pathogen phytophthora ramorum. | the mitochondrial genome of an isolate of phytophthora ramorum from europe (eu) was sequenced and compared to the previously published genome sequence of an isolate from california (na). the eu mitochondrial genome had the identical gene order and encoded for the same suite of genes as the na mitochondrial genome, but had 13 single nucleotide polymorphisms (snps) and at 39,494 bp was 180 bp longer. this length difference was due to an increase in the size of the spacer region between the nad5 an ... | 2008 | 18488228 |
reconstruction of the sudden oak death epidemic in california through microsatellite analysis of the pathogen phytophthora ramorum. | the genetic structure of the clonally reproducing sudden oak death (sod) pathogen in california was investigated using seven variable microsatellites. a total of 35 multilocus genotypes were identified among 292 samples representative of populations from 14 forest sites and of the nursery trade. amova indicated significant genetic variability both within (44.34%) and among populations (55.66%). spatial autocorrelation analyses indicated that moran's index of similarity reached a minimum of 0.1 a ... | 2008 | 18444982 |
susceptibility to phytophthora ramorum in a key infectious host: landscape variation in host genotype, host phenotype, and environmental factors. | sudden oak death is an emerging forest disease caused by the invasive pathogen phytophthora ramorum. genetic and environmental factors affecting susceptibility to p. ramorum in the key inoculum-producing host tree umbellularia californica (bay laurel) were examined across a heterogeneous landscape in california, usa. laboratory susceptibility trials were conducted on detached leaves and assessed field disease levels for 97 host trees from 12 225-m(2) plots. genotype and phenotype characteristics ... | 2008 | 18069961 |
demography and recruitment limitations of three oak species in california. | we review published studies on the demography and recruitment of california oak trees and focus on the widespread dominant species of the foothill woodlands, quercus douglasii, q. lobata, and q. agrifolia, to ascertain the nature and strength of evidence for a decline in populations of these species. the vast majority of studies have been of short duration (less than three years), focused on the acorn and seedling life stages, and conducted at few locations within each species geographic range. ... | 2006 | 16776062 |
phytophthora ramorum: integrative research and management of an emerging pathogen in california and oregon forests. | phytophthora ramorum, causal agent of sudden oak death, is an emerging plant pathogen first observed in north america associated with mortality of tanoak (lithocarpus densiflorus) and coast live oak (quercus agrifolia) in coastal forests of california during the mid-1990s. the pathogen is now known to occur in north america and europe and have a host range of over 40 plant genera. sudden oak death has become an example of unintended linkages between the horticultural industry and potential impac ... | 2005 | 16078887 |
examining the strength and possible causes of the relationship between fire history and sudden oak death. | fire can be a dominant process in the ecology of forest vegetation and can also affect forest disease dynamics. little is known about the relationship between fire and an emerging disease epidemic called sudden oak death, which is caused by a new pathogen, phytophthora ramorum. this disease has spread across a large, fire-prone portion of california, killing great numbers of oaks and tanoaks and infecting most associated woody plants. suitable hosts cover a much broader geographic range, raising ... | 2005 | 15891855 |
is variation in susceptibility to phytophthora ramorum correlated with population genetic structure in coast live oak (quercus agrifolia)? | california coastal woodlands are suffering severe disease and mortality as a result of infection from phytophthora ramorum. quercus agrifolia is one of the major woodland species at risk. this study investigated within- and among-population variation in host susceptibility to inoculation with p. ramorum and compared this with population genetic structure using molecular markers. susceptibility was assessed using a branch-cutting inoculation test. trees were selected from seven natural population ... | 2005 | 15720634 |
aflp and phylogenetic analyses of north american and european populations of phytophthora ramorum. | the genetic structure within and between usa and european populations of the emerging phytopathogen phytophthora ramorum was examined. four primer combinations were used for amplified fragment length polymorphism (aflp) fingerprinting of 67 usa isolates from california and oregon, and 18 european isolates from belgium, germany, the netherlands, spain and the uk. in addition, three dna regions (its, cox ii, and nad 5) of additional phytophthora species were amplified by polymerase chain reaction, ... | 2004 | 15209278 |
phylogenetic relationships of phytophthora ramorum, p. nemorosa, and p. pseudosyringae, three species recovered from areas in california with sudden oak death. | sudden oak death has been an emerging disease problem in coastal california and has caused significant losses in forest ecosystems in some regions of the state. the causal agent of this disease has been described as phytophthora ramorum with two other less aggressive species, p. nemorosa and p. pseudosyringae, recovered from some symptomatic plants. the phylogenetic relationship of these species with other members of the genus was examined by sequence alignment of 667 bp of the mitochondrially-e ... | 2003 | 15000239 |
molecular differentiation and diversity among the california red oaks (fagaceae; quercus section lobatae). | a recent epidemic of phytopthora (sudden oak death) in coastal woodlands of california is causing severe mortality in some oak species belonging to the red oak (lobatae) group. to predict the risks of spread of this disease, an understanding of the relationships among california's red oak species and of their population genetic structure is needed. we focus here on relationships among the four species of red oak. whereas morphological distinction of quercus wislizeni and quercus parvula can pose ... | 2003 | 12761621 |
host phenology and leaf effects on susceptibility of california bay laurel to phytophthora ramorum. | spread of the plant pathogen phytophthora ramorum, causal agent of the forest disease sudden oak death, is driven by a few competent hosts that support spore production from foliar lesions. the relationship between traits of a principal foliar host, california bay laurel (umbellularia californica), and susceptibility to p. ramorum infection were investigated with multiple p. ramorum isolates and leaves collected from multiple trees in leaf-droplet assays. we examined whether susceptibility varie ... | 2016 | 26439707 |
modeling when, where, and how to manage a forest epidemic, motivated by sudden oak death in california. | sudden oak death, caused by phytophthora ramorum, has killed millions of oak and tanoak in california since its first detection in 1995. despite some localized small-scale management, there has been no large-scale attempt to slow the spread of the pathogen in california. here we use a stochastic spatially explicit model parameterized using data on the spread of p. ramorum to investigate whether and how the epidemic can be controlled. we find that slowing the spread of p. ramorum is now not possi ... | 2016 | 27140631 |
effects of individual, community, and landscape drivers on the dynamics of a wildland forest epidemic. | the challenges posed by observing host-pathogen-environment interactions across large geographic extents and over meaningful time scales limit our ability to understand and manage wildland epidemics. we conducted a landscape-scale, longitudinal study designed to analyze the dynamics of sudden oak death (an emerging forest disease caused by phytophthora ramorum) across hierarchical levels of ecological interactions, from individual hosts up to the community and across the broader landscape. from ... | 2016 | 27197392 |
host-induced aneuploidy and phenotypic diversification in the sudden oak death pathogen phytophthora ramorum. | aneuploidy can result in significant phenotypic changes, which can sometimes be selectively advantageous. for example, aneuploidy confers resistance to antifungal drugs in human pathogenic fungi. aneuploidy has also been observed in invasive fungal and oomycete plant pathogens in the field. environments conducive to the generation of aneuploids, the underlying genetic mechanisms, and the contribution of aneuploidy to invasiveness are underexplored. we studied phenotypic diversification and assoc ... | 2016 | 27206972 |
impacts of an introduced forest pathogen on the risk of lyme disease in california. | global changes such as deforestation, climate change, and invasive species have the potential to greatly alter zoonotic disease systems through impacts on biodiversity. this study examined the impact of the invasive pathogen that causes sudden oak death (sod) on the ecology of lyme disease in california. the lyme disease bacterium, borrelia burgdorferi, is maintained in the far western united states by a suite of animal reservoirs including the dusky-footed woodrat (neotoma fuscipes) and deer mo ... | 2012 | 22607076 |
landscape epidemiology and control of pathogens with cryptic and long-distance dispersal: sudden oak death in northern californian forests. | exotic pathogens and pests threaten ecosystem service, biodiversity, and crop security globally. if an invasive agent can disperse asymptomatically over long distances, multiple spatial and temporal scales interplay, making identification of effective strategies to regulate, monitor, and control disease extremely difficult. the management of outbreaks is also challenged by limited data on the actual area infested and the dynamics of spatial spread, due to financial, technological, or social cons ... | 2012 | 22241973 |
forest type influences transmission of phytophthora ramorum in california oak woodlands. | the transmission ecology of phytophthora ramorum from bay laurel (umbellularia californica) leaves was compared between mixed-evergreen and redwood forest types throughout winter and summer disease cycles in central, coastal california. in a preliminary multisite study, we found that abscission rates of infected leaves were higher at mixed-evergreen sites. in addition, final infection counts were slightly higher at mixed-evergreen sites or not significantly different than at redwood sites, in pa ... | 2011 | 21391827 |
predicting the economic costs and property value losses attributed to sudden oak death damage in california (2010-2020). | phytophthora ramorum, cause of sudden oak death, is a quarantined, non-native, invasive forest pathogen resulting in substantial mortality in coastal live oak (quercus agrifolia) and several other related tree species on the pacific coast of the united states. we estimate the discounted cost of oak treatment, removal, and replacement on developed land in california communities using simulations of p. ramorum spread and infection risk over the next decade (2010-2020). an estimated 734 thousand oa ... | 2011 | 21224033 |
effects of an invasive forest pathogen on abundance of ticks and their vertebrate hosts in a california lyme disease focus. | invasive species, including pathogens, can have important effects on local ecosystems, including indirect consequences on native species. this study focuses on the effects of an invasive plant pathogen on a vertebrate community and ixodes pacificus, the vector of the lyme disease pathogen (borrelia burgdorferi) in california. phytophthora ramorum, the causative agent of sudden oak death, is a non-native pathogen killing trees in california and oregon. we conducted a multi-year study using a grad ... | 2010 | 20941513 |
lessons learned from a decade of sudden oak death in california: evaluating local management. | sudden oak death has been impacting california's coastal forests for more than a decade. in that time, and in the absence of a centrally organized and coordinated set of mandatory management actions for this disease in california's wildlands and open spaces, many local communities have initiated their own management programs. we present five case studies to explore how local-level management has attempted to control this disease. from these case studies, we glean three lessons: connections count ... | 2010 | 20559634 |
spatial and temporal analysis of populations of the sudden oak death pathogen in oregon forests. | sudden oak death caused by the oomycete phytophthora ramorum was first discovered in california toward the end of the 20th century and subsequently emerged on tanoak forests in oregon before its first detection in 2001 by aerial surveys. the oregon department of forestry has since monitored the epidemic and sampled symptomatic tanoak trees from 2001 to the present. populations sampled over this period were genotyped using microsatellites and studied to infer the population genetic history. to da ... | 2015 | 26068281 |
detection, diversity, and population dynamics of waterborne phytophthora ramorum populations. | sudden oak death, the tree disease caused by phytophthora ramorum, has significant environmental and economic impacts on natural forests on the u.s. west coast, plantations in the united kingdom, and in the worldwide nursery trade. stream baiting is vital for monitoring and early detection of the pathogen in high-risk areas and is performed routinely; however, little is known about the nature of water-borne p. ramorum populations. two drainages in an infested california forest were monitored int ... | 2015 | 25026455 |
population dynamics of aerial and terrestrial populations of phytophthora ramorum in a california forest under different climatic conditions. | limited information is available on how soil and leaf populations of the sudden oak death pathogen, phytophthora ramorum, may differ in their response to changing weather conditions, and their corresponding role in initiating the next disease cycle after unfavorable weather conditions. we sampled and cultured from 425 trees in six sites, three times at the end of a 3-year-long drought and twice during a wet year that followed. soil was also sampled twice with similar frequency and design used fo ... | 2013 | 23745672 |
the key host for an invasive forest pathogen also facilitates the pathogen's survival of wildfire in california forests. | the first wildfires in sudden oak death-impacted forests occurred in 2008 in the big sur region of california, creating the rare opportunity to study the interaction between an invasive forest pathogen and a historically recurring disturbance. to determine whether and how the sudden oak death pathogen, phytophthora ramorum, survived the wildfires, we completed intensive vegetation-based surveys in forest plots that were known to be infested before the wildfires. we then used 24 plot-based variab ... | 2012 | 23046069 |
phenotypic diversification is associated with host-induced transposon derepression in the sudden oak death pathogen phytophthora ramorum. | the oomycete pathogen phytophthora ramorum is responsible for sudden oak death (sod) in california coastal forests. p. ramorum is a generalist pathogen with over 100 known host species. three or four closely related genotypes of p. ramorum (from a single lineage) were originally introduced in california forests and the pathogen reproduces clonally. because of this the genetic diversity of p. ramorum is extremely low in californian forests. however, p. ramorum shows diverse phenotypic variation i ... | 2012 | 22529930 |