Publications

detection and quantification of phytophthora ramorum, p. kernoviae, p. citricola and p. quercina in symptomatic leaves by multiplex real-time pcr.	summary new species of phytophthora such as phytophthora ramorum, p. kernoviae and p. quercina together with p. citricola are plant pathogens which impact on forest health, natural ecosystem stability and international trade. a real-time multiplex pcr approach based on taqman pcr was developed to simultaneously identify and detect these four phytophthora species. specific primers and probes labelled with fam (p. ramorum), yakima yellow (p. kernoviae), rox (p. citricola) and cy5 (p. quercina) wer ...	2006	20507453
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
balancing detection and eradication for control of epidemics: sudden oak death in mixed-species stands.	culling of infected individuals is a widely used measure for the control of several plant and animal pathogens but culling first requires detection of often cryptically-infected hosts. in this paper, we address the problem of how to allocate resources between detection and culling when the budget for disease management is limited. the results are generic but we motivate the problem for the control of a botanical epidemic in a natural ecosystem: sudden oak death in mixed evergreen forests in coas ...	2010	20856850
phytophthora ramorum in canada: evidence for migration within north america and from europe.	phytophthora ramorum, the cause of sudden oak death on oak and ramorum blight on woody ornamentals, has been reported in ornamental nurseries on the west coast of north america from british columbia to california. long-distance migration of p. ramorum has occurred via the nursery trade, and shipments of host plants are known to have crossed the u.s.-canadian border. we investigated the genotypic diversity of p. ramorum in canadian nurseries and compared the canadian population with u.s. and euro ...	2011	20879846
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
oospores progenies from phytophthora ramorum.	oospores of phytophthora ramorum were produced from intraspecific pairings between a european a1 and european or american a2 strains. their viability was evaluated through colouration with tetrazolium bromide. the distribution of oospores in the different classes of colouration was similar to that found in other phytophthora species (homothallic and heterothallic): most of the oospores stained purple, which corresponds to spores in dormancy. in order to produce single-oospore cultures, a method ...	2010	20943147
networks in plant epidemiology: from genes to landscapes, countries, and continents.	there is increasing use of networks in ecology and epidemiology, but still relatively little application in phytopathology. networks are sets of elements (nodes) connected in various ways by links (edges). network analysis aims to understand system dynamics and outcomes in relation to network characteristics. many existing natural, social, and technological networks have been shown to have small-world (local connectivity with short-cuts) and scale-free (presence of super-connected nodes) propert ...	2011	21062110
analyses of genome architecture and gene expression reveal novel candidate virulence factors in the secretome of phytophthora infestans.	phytophthora infestans is the most devastating pathogen of potato and a model organism for the oomycetes. it exhibits high evolutionary potential and rapidly adapts to host plants. the p. infestans genome experienced a repeat-driven expansion relative to the genomes of phytophthora sojae and phytophthora ramorum and shows a discontinuous distribution of gene density. effector genes, such as members of the rxlr and crinkler (crn) families, localize to expanded, repeat-rich and gene-sparse regions ...	2010	21080964
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
aberrant genome size and instability of phytophthora ramorum oospore progenies.	the functionality of the sexual cycle in the heterothallic pathogen phytophthora ramorum, causal agent of sudden oak death, has recently been demonstrated. sexual reproduction could create genotypic variation and increase the pathogen's ability to adapt to other host plants or changing environments. genetic characterization using co-dominant microsatellite markers and flow cytometry of single-oospore progeny of crosses between a european a1 isolate and north american or european a2 isolates reve ...	2011	21272658
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
genetic characterization of phytophthora nicotianae by the analysis of polymorphic regions of the mitochondrial dna.	a new method based on the analysis of mitochondrial intergenic regions characterized by intraspecific variation in dna sequences was developed and applied to the study of the plant pathogen phytophthora nicotianae. two regions flanked by genes trny and rns and trnw and cox2 were identified by comparing the whole mitochondrial genomes of phytophthora infestans, phytophthora ramorum, and phytophthora sojae and amplified using primers designed from the flanking conserved genes. these regions were s ...	2011	21530925
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
genetic diversity, structure, and demographic change in tanoak, lithocarpus densiflorus (fagaceae), the most susceptible species to sudden oak death in california.	knowledge of population genetic structure of tanoak (lithocarpus densiflorus) is of interest to pathologists seeking natural variation in resistance to sudden oak death disease, to resource managers who need indications of conservation priorities in this species now threatened by the introduced pathogen (phytophthora ramorum), and to biologists with interests in demographic processes that have shaped plant populations. we investigated population genetic structure using nuclear and chloroplast dn ...	2009	21622338
learning from history, predicting the future: the uk dutch elm disease outbreak in relation to contemporary tree disease threats.	expanding international trade and increased transportation are heavily implicated in the growing threat posed by invasive pathogens to biodiversity and landscapes. with trees and woodland in the uk now facing threats from a number of disease systems, this paper looks to historical experience with the dutch elm disease (ded) epidemic of the 1970s to see what can be learned about an outbreak and attempts to prevent, manage and control it. the paper draws on an interdisciplinary investigation into ...	2011	21624917
identification of new polymorphic microsatellite markers in the na1 and na2 lineages of phytophthora ramorum.	phytophthora ramorum is a recently introduced pathogen in europe and north america consisting of three clonal lineages. due to the very limited intra-lineage genetic variation, only a few polymorphic markers are available for use in studies involving the epidemiology and evolution of p. ramorum. a total of 159 primer pairs for candidate polymorphic ssr loci were tested with universal labeling. four polymorphic microsatellite loci were identified within the na1 lineage and one within the na2 line ...	2011	21642345
a test system to quantify inoculum in runoff from phytophthora ramorum-infected plant roots.	foliar hosts of phytophthora ramorum are often susceptible to root infection, but the epidemiological significance of such infections is unknown. a standardized test system was developed to quantify inoculum in runoff from root-infected viburnum tinus 'spring bouquet' or rhododendron 'cunningham's white' cuttings. cuttings of both species gave off a maximum amount of inoculum 1 to 3 weeks after inoculation. the greatest amount of inoculum was recovered from viburnum roots that were 48 to 70 days ...	2011	21830955
Horizontal gene transfer facilitated the evolution of plant parasitic mechanisms in the oomycetes.	Horizontal gene transfer (HGT) can radically alter the genomes of microorganisms, providing the capacity to adapt to new lifestyles, environments, and hosts. However, the extent of HGT between eukaryotes is unclear. Using whole-genome, gene-by-gene phylogenetic analysis we demonstrate an extensive pattern of cross-kingdom HGT between fungi and oomycetes. Comparative genomics, including the de novo genome sequence of Hyphochytrium catenoides, a free-living sister of the oomycetes, shows that thes ...	2011	21878562
forest species diversity reduces disease risk in a generalist plant pathogen invasion.	empirical evidence suggests that biodiversity loss can increase disease transmission, yet our understanding of the 'diversity-disease hypothesis' for generalist pathogens in natural ecosystems is limited. we used a landscape epidemiological approach to examine two scenarios regarding diversity effects on the emerging plant pathogen phytophthora ramorum across a broad, heterogeneous ecoregion: (1) an amplification effect exists where disease risk is greater in areas with higher plant diversity du ...	2011	21884563
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
the inclusion of downy mildews in a multi-locus-dataset and its reanalysis reveals a high degree of paraphyly in phytophthora.	pathogens belonging to the oomycota, a group of heterokont, fungal-like organisms, are amongst the most notorious pathogens in agriculture. in particular, the obligate biotrophic downy mildews and the hemibiotrophic members of the genus phytophthora are responsible for a huge variety of destructive diseases, including sudden oak death caused by p. ramorum, potato late blight caused by p. infestans, cucurbit downy mildew caused by pseudoperonospora cubensis, and grape downy mildew caused by plasm ...	2011	22679601
genome-wide identification of laccase gene family in three phytophthora species.	phytophthora spp. is a primary pathogen in oomycete, causing economically and environmentally devastating epidemics of plants. laccases have been found in all domains of life but have not been reported in oomycte. in this paper, laccase genes of phytophthora spp. were identified in three genomes (phytophthora capsici, phytophthora sojae and phytophthora ramorum). 18 laccase genes were identified in total, including four in p. capsici genome, six in p. sojae genome and eight in p. ramorum genome. ...	2012	23283515