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Phytophthora Species (phytophthora + species)

Distribution by Scientific Domains

Life Sciences	100%

Distribution within Life Sciences

Plant Pathology	61%
Plant Science	38%

Selected Abstracts

Validation of a real-time PCR method for the detection of Phytophthora ramorum1

EPPO BULLETIN, Issue 2 2006
A. Chandelier
To validate a real-time PCR method for the detection of Phytophthora ramorum, an intra-laboratory procedure was developed. The specificity of the TaqMan probe/primer sets was determined by carrying out real-time PCR on total DNA extracted from pure culture of several Phytophthora species. The limit of detection and the potential effects of plant substrates were evaluated by conducting the test on total DNA from healthy plant materials (Rhododendron spp., Viburnum spp. and Pieris spp.) spiked with known amounts of P. ramorum genomic DNA. The PCR efficiency was estimated through the linear regression of the dilution curve. Precision of the TaqMan assay was assessed on material from a single artificially infected plant (Rhododendron spp.). Two kinds of tissues were tested: a severely infected twig and an apparently healthy leaf. Intra-assay repeatability was evaluated on 10 replicates of the same DNA sample analysed in a single assay. Inter-assay reproducibility was evaluated on the same DNA sample amplified over five separate assays while the intersample reproducibility was evaluated on separate DNA extractions of four samples from both plant tissues amplified in a single assay. [source]

Involvement of Phytophthora species in white oak (Quercus alba) decline in southern Ohio

FOREST PATHOLOGY, Issue 5 2010
Y. Balci
Summary This study was initiated to investigate the possible role of Phytophthora species in white oak decline (Quercus alba) in southern Ohio at Scioto Trail State Forest. Surveys demonstrated the presence of four species of Phytophthora including one novel species. By far, the most common species was P. cinnamomi; P. citricola and P. cambivora were isolated infrequently. In few instances, P. cinnamomi was isolated from fine roots and necroses on larger roots. No special pattern of incidence was found, but P. cinnamomi was more commonly isolated from greater Integrated Moisture Index values suggesting moist lower bottomlands favour this Phytophthora species. When tree crown condition was examined relative to the presence of Phytophthora, no significant association was found. However, roots of declining P. cinnamomi -infested trees had 2.5 times less fine roots than non-infested and healthy trees, which was significantly different. The population densities of P. cinnamomi from declining trees were significantly greater than from healthy trees, suggesting increased pathogen activity that has the potential to cause dieback and decline and possibly the cause of a reduced fine root amount found on declining trees. [source]

Foliar susceptibility of eastern oak species to Phytophthora infection

FOREST PATHOLOGY, Issue 5 2008
Y. Balci
Summary Seven different Phytophthora species were used to test the foliar susceptibility of the common eastern US oak species and understory plants to Phytophthora infection. The Phytophthora species employed were Phytophthora cambivora, Phytophthora cinnamomi, Phytophthora citricola, Phytophthora europaea, Phytophthora quercetorum, Phytophthora quercina -like and Phytophthora sp1. Inoculation of detached-leaves with agar plugs containing mycelia of Phytophthora provided an estimate of their relative susceptibility. Lesions were always greater when foliage was wounded and young. On deciduous plants, lesion sizes were considerably reduced with the increasing foliar age, although with evergreen plants lesion sizes remained similar regardless of foliar age when more aggressive isolates were tested. Infections seldom resulted when foliage was not wounded. With young and mature foliage, P. citricola usually produced the largest lesions. Young foliage of Quercus rubra was the most susceptible to infection followed by Castanea dentata for both wounded and non-wounded inoculations. Mature foliage of Hamamelis virginiana, Kalmia latifolia and Quercus alba were the most susceptible to wound and non-wound inoculations. [source]

Incidence of Phytophthora species in oak forests in Austria and their possible involvement in oak decline

FOREST PATHOLOGY, Issue 3 2003
Y. Balci
Summary A survey on the occurrence of Phytophthora species in oak ecosystems in Austria was conducted from April to May 1999 and in June 2000. The investigations were carried out at 35 study sites distributed throughout the zone of oak forests in eastern Austria. Four oak species, including Quercus robur, Q. petraea, Q. cerris and Q. pubescens were considered in the survey. Rhizosphere soil samples were taken from sample trees, which consisted of healthy and declining trees as indicated by their crown transparency. Young oak leaflets were used as baits to recover Phytophthora species. The assemblage of Phytophthora spp. detected in Austrian oak forests consisted of five species, including Phytophthora quercina, P. citricola, P. gonapodyides, P. europaea and P. syringae. P. quercina and P. citricola were isolated from 11 and seven sites, respectively, and were thus the most common and most widely distributed species. The three other species were recovered only sporadically. P. citricola could be separated into two morphologically and genetically well-characterized types (A and B). Phytophthora species, in particular the common P. quercina and P. citricola occurred on sites showing a wide variety of soil types, soil textures and moisture classes. There was mild evidence for connection between deteriorating crown status and the presence of Phytophthora spp. Furthermore, significant differences in contents of magnesium, as well as calcium, aluminium, nitrogen and carbon at different soil depths (0,10, 10,20 and 20,40 cm) were detected between Phytophthora -infested and Phytophthora -free sites. The results of the present study provide circumstantial evidence that Phytophthora species are involved in oak decline at certain sites in Austria. Résumé Une prospection des espèces de Phytophthora dans les écosystèmes de chênaie a été réalisée en Autriche en avril-mai 1999 et en juin 2000. Les recherches ont été conduites dans 35 sites répartis dans l'ensemble des chênaies de l'est de l'Autriche. Quatre espèces de chênes ont été prises en considération: Quercus robur, Q. petraea, Q. cerris et Q. pubescens. Des échantillons de sol rhizosphérique ont été prélevés au pied d'arbres sains ou dépérissants, jugés d'après la transparence de leur houppier. De jeunes feuilles de chênes ont été utilisées comme piège. Les Phytophthora spp. détectés dans les chênaies autrichiennes appartenaient à cinq espèces : P. quercina, P. citricola, P. gonapodyides, P. europaea et P. syringae. Phytophthora quercina et P. citricola ont été isolés dans 11 et 7 sites respectivement; ils étaient les plus fréquents et les plus largement répandus. Les trois autres espèces n'ont été trouvées que sporadiquement. Chez P. citricola, deux types (A et B) ont pu être distingués, morphologiquement et génétiquement différents. Les espèces de Phytophthora, en particulier P. quercina et P. citricola,étaient présents dans des sites très variés pour les types de sol, leur texture et l'humidité. Phythophthora spp. tendaient àêtre plus fréquemment présents en lien avec la détérioration des houppiers. Par ailleurs, des différences significatives ont été trouvées entre les sites avec ou sans Phytophthora, pour les teneurs en magnésium ainsi qu'en calcium, aluminium, azote et carbone à différentes profondeurs du sol (0,10, 10,20 et 20,40 cm). Les résultats montrent que des espèces de Phytophthora sont impliquées dans le dépérissement des chênes dans certains sites en Autriche. Zusammenfassung Im Rahmen einer breit angelegten Erhebung wurde im April und Mai 1999 sowie im Juni 2000 das Auftreten von Phytophthora -Arten in Eichenwaldökosystemen in Österreich untersucht. Die Erhebungen wurden an 35 Standorten durchgeführt, die über das gesamte natürliche Eichenwaldvorkommen in Ostösterreich verteilt waren. In die Untersuchung wurden die vier Eichenarten Quercus robur, Q. petraea, Q. cerris und Q. pubescens einbezogen. Von jeder , anhand ihres Kronenzustands als gesund bzw. krank eingestuften , Eiche wurden Bodenproben entnommen und aus diesen mittels ,Eichenblatt'-Ködermethode die Phytophthora -Arten isoliert. Das Spektrum der in Österreich isolierten Phytophthora -Arten umfasste die 5 Arten Phytophthora quercina, P. citricola, P. gonapodyides, P. europaea und P. syringae. P. quercina und P. citricola wurden von 11 bzw. 7 der untersuchten Standorte isoliert und waren somit die häufigsten und am weitesten verbreiteten Arten. Die drei anderen Phytophthora -Arten traten hingegen nur sporadisch auf. Innerhalb von P. citricola konnten anhand morphologischer und genetischer Merkmale 2 Typen (Typ A und Typ B) unterschieden werden. Phytophthora -Arten, insbesondere die häufig nachgewiesenen Arten P. quercina und P. citricola wurden an Standorten mit den unterschiedlichsten Bodentypen, -textur und -feuchteklassen nachgewissen. Es wurde ein schwach signifikanter Zusammenhang zwischen dem sich verschlechternden Kronenzustand und dem Vorhandensein von Phytophthora nachgewissen. Darüber hinaus unterschieden sich Phytophthora -infizierte und Phytophthora -freie Standorte in verschiedenen Bodentiefen (0,10, 10,20 und 20,40 cm) signifikant in ihren Magnesium, Kalzium, Aluminium, Stickstoff und Kohlenstoff-Gehalten. Die Ergebnisse der vorliegenden Studie lassen den Schluss zu, dass Phytophthora -Arten an einigen Untersuchungsstandorten in Österreich am Eichensterben beteiligt sind. [source]

First records of soilborne Phytophthora species in Swedish oak forests

FOREST PATHOLOGY, Issue 3 2003
U. Jönsson
Summary Thirty-two oak stands in southern Sweden, 27 with predominantly declining trees and five with a higher proportion of healthy trees were investigated regarding the presence of soilborne Phytophthora species. Phytophthora quercina, an oak-specific fine root pathogen, was isolated from rhizosphere soil samples in 10 of the 27 declining stands. Additionally, P. cactorum and P. cambivora were recovered from one stand each. No Phytophthora species were isolated from the healthy oak stands. The soil conditions at the sites from which Phytophthora spp. were recovered ranged from mesic sediments to moraines, with clayey to silty textures and with soil pH (BaCl2) between 3.5 and 5.0. The results show that P. quercina is geographically widespread in oak stands in southern Sweden and indicate that this pathogen may be one of the factors involved in oak decline in Northern Europe as has already been shown for western, Central and parts of southern Europe. Zusammenfassung In Südschweden wurden 27 erkrankte und 5 gesunde Eichenbestände auf das Vorkommen bodenbürtiger Phytophthora, Arten untersucht. Dabei wurde P. quercina, ein für Eichen spezifisches Feinwurzelpathogen, aus Rhizosphären , Proben von 10 der 27 erkrankten Bestände isoliert. Zusätzlich wurden P. cactorum und P. cambivora in jeweils einem erkrankten Bestand gefunden. Im Gegensatz dazu konnte in den gesunden Beständen keine Phytophthora, Art nachgewiesen werden. Die Bodenverhältnisse der Bestände, in denen Phytophthora spp. gefunden wurden, reichten von frischen bis feuchten Böden aus Sedimenten und Moränen mit schluffiger bis toniger Textur und pH , Werten (BaCl2) zwischen 3.5 und 5.0. Die weite Verbreitung von P. quercina in erkrankten Eichenbeständen in Südschweden spricht dafür, dass das Pathogen im Krankheitskomplex des Eichensterbens in Nordeuropa eine Rolle spielt, wie dies bereits für Mittel- und Westeuropa sowie Teile Südeuropas gezeigt worden ist. Résumé La présence d'espèces de Phytophthora telluriques a été recherchée dans trente-deux chênaies du sud de la Suède, 27 à dominance d'arbres dépérissants et 5 avec une plus forte proportion d'arbres sains. P. quercina, pathogène des racines fines et spécifique des chênes, a été isolé dans 10 des 27 échantillons de sol, prélevés dans la rhizosphère, des peuplements dépérissants. P. cactorum et P. cambivora ont également été isolés, chacun dans un de ces peuplements. Aucune espèce de Phytophthora n'a été isolée des peuplements sains. Les conditions édaphiques des sites d'où ont été isolés des Phytophthora spp. varient de sédiments mésiques à des moraines, avec des textures argileuses à limoneuses et un pH (BaCl2) compris entre 3.5 et 5.0. Ces résultats montrent que P. quercina présente une large répartition géographique dans les chênaies du sud de la Suède et indiquent que ce pathogène pourrait être l'un des facteurs impliqués dans les dépérissements de chênes du Nord de l'Europe, comme il a déjàété montré pour l'Europe Centrale, de l'Ouest et certaines zones de l'Europe du Sud. [source]

Occurrence of Phytophthora species in oak stands in Italy and their association with declining oak trees

FOREST PATHOLOGY, Issue 1 2002
A. M. VETTRAINO
Soil-borne species of Phytophthora were isolated from 19 of 30 examined oak forest areas in Italy. The frequency of isolated Phytophthora spp. (35.2%) was significantly correlated with soil pH and longitude of the sites. Eleven Phytophthora species were detected. Phytophthora cambivora, P. cinnamomi and P. cactorum were recovered from sites in central and southern Italy whereas P. quercina was isolated in the northern and central part of the country. Phytophthora citricola occurred all over Italy. Phytophthora quercina was the only species significantly associated with declining oak trees. Les Phytophthora dans les chênaies d'Italie et leur association avec les chênes dépérissants Des Phytophthora ont été isolés du sol dans 19 sites parmi 30 sites analysés dans des chênaies italiennes. La fréquence d'isolement de Phytophthora spp. (35,2%) était corrélée significativement avec le pH du sol et la longitude des sites. Onze espèces de Phytophthora ont été trouvées. Phytophthora cambivora, P. cinnamomi et P. cactorum ont été trouvés dans le centre et le sud de l'Italie et le P. quercina dans le nord et le centre. Phytophthora citricolaétait présent dans l'ensemble de l'Italie. Phytophthora quercinaétait la seule espèce associée significativement avec des chênes dépérissants. Vorkommen von Phytophthora Arten in Eichenbeständen in Italien und deren Bezug zu absterbenden Eichen Bodenbürtige Phytophthora Arten wurden in 19 von 30 untersuchten Eichenbeständen in Italien isoliert. Die Korrelationen zwischen der Häufigkeit der isolierten Phytophthora spp. und dem Boden pH sowie der geographischen Länge der Standorte waren statistisch signifikant. Phytophthora cambivora, P. cinnamomi und P. cactorum wurden an Standorten in Zentral- und Süditalien nachgewiesen, während P. quercina in Zentral- und Norditalien vorhanden waren. Phytophthora citricola kam in ganz Italien vor. Phytophthora quercina war die einzige Arte mit einer deutlichen Vergesellschaftung mit absterbenden Eichen. [source]

Cloning, Expression and Characterization of Protein Elicitors from the Soyabean Pathogenic Fungus Phytophthora sojae

JOURNAL OF PHYTOPATHOLOGY, Issue 3 2000
J. Becker
The oomycete Phytophthora sojae is a severe pathogen of soybean. Several resistance genes against races of P. sojae exist in soybean but the nature of corresponding avirulence genes is unknown. Clones encoding four different isoforms of a protein elicitor from P. sojae (sojein 1,4) belonging to the class of acidic ,-elicitins have been isolated. These 98 amino acid proteins show high homology to elicitins from other Phytophthora species. The different sojein isoforms were expressed in Escherichia coli as His-tagged fusion proteins. Purified sojein as well as recombinant sojein isoforms induce hypersensitive reaction (HR)-like lesions in tobacco but are not active as race-specific elicitors in soybean. However all sojein isoforms induce defence-related genes like those encoding phenylalanine ammonia lyase, glutathione-S-transferase and chalcone synthase in tobacco and soybean plants and cell cultures. It is concluded that sojeins contribute to the induction of defence responses but that they are not involved in race specific recognition of the P. sojae races by soybean plants. Zusammenfassung Klonierung, Expression und Charactier von Proteinelictoren aus dem Soyabohnenpathogen Phytophthora sojae Der Oomycet Phytophthora sojae ist ein ernstes Pathogen der Sojabohne. In der Sojabohne gibt es mehrere Resistenzgene gegen verschiedene Rassen von P. sojae, jedoch ist die Natur der korrespondierenden Avirulenzgene unbekannt. Wir haben 4 verschiedene Isoformen eines Protein-Elicitors aus P. sojae (Sojein 1,4) kloniert, die zur Klasse der sauren ,-Elicitine gehören. Sie kodieren für Proteine mit 98 Aminosäuren und zeigen hohe Homologie zu Elicitinen aus anderen Phytophthora Spezies. Aus genomischer DNA und aus revers-transkribierter mRNA wurden die gleichen 4 Isoformen erhalten. Die verschiedenen Sojeine wurden in Escherichia coli als His-markierte Fusionproteine exprimiert. Sowohl gereinigtes als auch rekombinantes Sojein induziert HR-ähnliche Läsionen in Tabak. In der Sojabohne sind sie allerdings nicht als rassenspezifische Elicitoren aktiv. Dagegen induzieren alle Sojein-Isoformen Abwehrgene wie die Phenylalanin Ammonium-Lyase, Glutathion-S-Transferase und Chalkonsynthase in Tabak-und Sojabohnenpflanzen und Zellkulturen. Die Sojeine tragen also zur Induktion von Abwehrreaktionen bei, sind aber nicht in die rassenspezifische Erkennung von P. sojae durch Sojabohnenpflanzen involviert. [source]

Evaluation of a rapid diagnostic field test kit for identification of Phytophthora species, including P. ramorum and P. kernoviae at the point of inspection

PLANT PATHOLOGY, Issue 5 2007
C. R. Lane
Plant health regulations to prevent the introduction and spread of Phytophthora ramorum and P. kernoviae require rapid, cost effective diagnostic methods for screening large numbers of plant samples at the time of inspection. Current on-site techniques require expensive equipment, considerable expertise and are not suited for plant health inspectors. Therefore, an extensive evaluation of a commercially available lateral flow device (LFD) for Phytophthora species was performed involving four separate trials and 634 samples. The assay proved simple to use, provided results in a few minutes and on every occasion a control line reacted positively confirming the validity of the test. LFD results were compared with those from testing a parallel sample, using laboratory methods (isolation and real-time PCR). The diagnostic sensitivity of the LFD (87·6%) compared favourably with the standard laboratory methods although the diagnostic specificity was not as stringent (82·9%). There were a small number (n = 28) of false negatives, but for statutory purposes where all positive samples must be identified to species level by laboratory testing, overall efficiency was 95·6% as compared with visual assessment of symptoms of between 20-30% for P. ramorum and P. kernoviae. This work demonstrates the value of the LFD for diagnosing Phytophthora species at the time of inspection and as a useful primary screen for selecting samples for laboratory testing to determine the species identification. [source]

Novel microsatellite markers for the analysis of Phytophthora infestans populations

PLANT PATHOLOGY, Issue 3 2006
A. K. Lees
Co-dominant microsatellite molecular markers for Phytophthora infestans were developed and their potential for monitoring the genetic variation in populations was demonstrated in the UK, across Europe and worldwide. Markers were developed according to two strategies. First, several thousand P. infestans expressed sequence tag (EST) and bacterial artificial chromosome (BAC) sequences were screened for the presence of simple sequence repeat (SSR) motifs, and, of these, 100 candidate loci were selected for further investigation. Primer pairs developed to these loci were tested against a panel of 10 P. infestans isolates and approximately 10% were shown to be polymorphic and therefore appropriate for further testing. Secondly, the construction and screening of a partial genomic library resulted in the development of one additional polymorphic marker. The resulting 12 SSR markers were converted to higher-throughput fluorescence-based assays and used in combination with two previously published markers to characterize a wider collection of 90 P. infestans isolates from the UK and six other countries. Several isolates from the closely related species P. mirabilis, P. ipomoea and P. phaseoli collected from around the world were also genotyped using these markers. Amongst the 90 isolates of P. infestans examined, considerable SSR diversity was observed, with 68 different genotypes and an average of 3·9 (range 2,9) alleles per locus. When other Phytophthora species were genotyped, all loci were successfully amplified and the majority were polymorphic, indicating their transferability for the potential study of other closely related taxa. [source]

Molecular analysis of the major Phytophthora species on cocoa

PLANT PATHOLOGY, Issue 2 2004
A. A. Appiah
The internally transcribed spacer (ITS) regions of the ribosomal RNA (rRNA) gene cluster of 161 isolates of Phytophthora species involved in pod rot, stem canker and leaf blight of cocoa were analysed to determine inter- and intraspecific variation in this disease complex. The species P. palmivora, P. megakarya, P. capsici, P. citrophthora and P. nicotianae could all be clearly distinguished by PCR amplification of the ITS region followed by restriction analysis with HaeIII, HinfI, PvuII and AluI. This method provided a relatively rapid identification procedure for these species, and was able to distinguish isolates that had previously been misidentified by morphological methods. Sequence analysis showed that the four main cocoa-associated species formed two distinct groups, one comprising P. capsici and P. citrophthora, and the other P. palmivora and P. megakarya. Detailed sequence analysis and comparison with published literature suggested that P. capsici isolates from cocoa may be closely related to P. tropicalis, a species recently described from Cyclamen and Dianthus. [source]

NPP1, a Phytophthora -associated trigger of plant defense in parsley and Arabidopsis

THE PLANT JOURNAL, Issue 3 2002
Guido Fellbrich
Summary Activation of non-cultivar-specific plant defense against attempted microbial infection is mediated through the recognition of pathogen-derived elicitors. Previously, we have identified a peptide fragment (Pep-13) within a 42-kDa cell wall transglutaminase from various Phytophthora species that triggers a multifacetted defense response in parsley cells. Many of these oomycete species have now been shown to possess another cell wall protein (24 kDa), that evoked the same pattern of responses in parsley as Pep-13. Unlike Pep-13, necrosis-inducing Phytophthora protein 1 (NPP1) purified from P. parasitica also induced hypersensitive cell death-like lesions in parsley. NPP1 structural homologs were found in oomycetes, fungi, and bacteria, but not in plants. Structure,activity relationship studies revealed the intact protein as well as two cysteine residues to be essential for elicitor activity. NPP1-mediated activation of pathogen defense in parsley does not employ the Pep-13 receptor. However, early induced cellular responses implicated in elicitor signal transmission (increased levels of cytoplasmic calcium, production of reactive oxygen species, MAP kinase activation) were stimulated by either elicitor, suggesting the existence of converging signaling pathways in parsley. Infiltration of NPP1 into leaves of Arabidopsis thaliana Col-0 plants resulted in transcript accumulation of pathogenesis-related (PR) genes, production of ROS and ethylene, callose apposition, and HR-like cell death. NPP1-mediated induction of the PR1 gene is salicylic acid-dependent, and, unlike the P. syringae pv. tomato DC3000(avrRpm1)-induced PR1 gene expression, requires both functional NDR1 and PAD4. In summary, Arabidopsis plants infiltrated with NPP1 constitute an experimental system that is amenable to forward genetic approaches aiming at the dissection of signaling pathways implicated in the activation of non-cultivar-specific plant defense. [source]