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Canker
Kinds of Canker Terms modified by Canker Selected AbstractsDetection and Identification of Brenneria nigrifluens, the Causal Agent of the Shallow Bark Canker of Walnut by, PCR AmplificationJOURNAL OF PHYTOPATHOLOGY, Issue 7-8 2008S. Loreti Abstract A 1 kb DNA band from strains of Brenneria nigrifluens, as shown by amplification of their genomic DNA by polymerase chain reaction (PCR) using minisatellite primer designed on the minisatellite sequence of the M13 phage, was isolated, cloned and sequenced. Specific oligonucleotides (F1,C3) were selected into this 1 kb DNA sequence and used in a PCR assay to detect and identify strains of B. nigrifluens. Several strains of B. nigrifluens were assessed with F1,C3 primers producing a specific band of approximately 250 bp pairs in length. This target was successfully amplified from purified genomic DNA, from bacterial culture and directly from infected walnut bark tissue. No amplification was obtained when the PCR assay was performed on other plant-pathogenic species from the following genera Brenneria, Erwinia, Agrobacterium, Pseudomonas, Ralstonia, Pectobacterium, Xanthomonas and from walnut-associated bacteria, indicating the specificity of these primers. The PCR assay with the primers described here provides a rapid, specific and sensitive diagnostic method for B. nigrifluens and a useful tool for epidemiological studies. [source] Characteristics of the Cryphonectria parasitica isolated from Quercus in SlovakiaFOREST PATHOLOGY, Issue 5 2010K. Adam, íková Summary The occurrence of chestnut blight (Cryphonectria parasitica) on oaks in mixed chestnut-oak forests was studied in 2003,2008 in Slovakia. Infections on living Quercus trees were found at four of seven localities. The disease incidence on oaks ranged from 1.3% to 15.8%. The symptoms on infected oaks were similar to those on chestnut, but less conspicuous. Cankers of C. parasitica were found only on Quercus robur and Q. petraea. A total of 22 isolates of C. parasitica, all virulent, were isolated. Each site yielded only a single vc type (EU12 or EU13). Field inoculation experiments on chestnuts with seven strains of C. parasitica from oaks and an isolate from Castanea sativa showed no differences in virulence. On Quercus robur stems, the cankered area was significantly smaller than on C. sativa and the cankers developed very slowly. [source] Anisogramma virgultorum on saplings of Betula pendula and Betula pubescens in a district of northern SwedenFOREST PATHOLOGY, Issue 4-5 2002J. WITZELL Summary During the autumn of 1999, the occurrence of the ascomycete Anisogramma virgultorum on saplings of Betula pubescens and Betula pendula was studied in two stands of B. pubescens, two stands of B. pendula and two mixed (B. pubescens and Pinus sylvestris) stands (age approximately 10 years, mean height 2,4 m, d.b.h. 10,20 mm) in a district in the vicinity of Umeå, northern Sweden. Stem and branch cankers associated with A. virgultorum were found on 54.8% of the investigated saplings, without significant difference between B. pendula and B. pubescens. Cankers were observed on 16.0% of stems and on branches of 54.2% of the saplings. Stem cankers appeared on the current year's shoot, as well as at the base of the trees. The mean diameter of the damaged saplings was significantly greater than the mean diameter of undamaged saplings. All samples of cankers with stromata examined in the laboratory showed perithecia with asci. Résumé Anisogramma virgultorum sur jeunes plants de Betula pendula et Betula pubescens dans un district du nord de la Suède Pendant l'été 1999, le développement de l'ascomycète Anisogramma virgultorum a étéétudié sur de jeunes plants de Betula pendula et Betula pubescens dans deux peuplements de B. pubescens, deux peuplements de B. pendula et deux peuplements mélangés (B. pubescens et Pinus sylvestris) (âge: environ 10 ans, hauteur moyenne: 2 à 4 m, dbh: 10 à 20 mm), dans un district près d'Umeå au nord de la Suède. Des chancres de tige et de branches associés àA. virgultorum ont été trouvés sur 54,8% des plants, sans différences significative entre B. pendula et B. pubescens. Les chancres de tige étaient présents sur 16% des plants, et les chancres de branches sur 54,2%. Les chancres de tige étaient situés sur les pousses de l'année en cours aussi bien qu'à la base des arbres. La diamètre moyen des plants attaqués était significativement plus grand que celui des arbres sains. Tous les chancres avec stromas examinés au laboratoire présentaient des périthèces avec des asques. Zusammenfassung Anisogramma virgultorum an Sämlingen von Betula pendula und Betula pubescens in einem Distrikt in Nordschweden Im Herbst 1999 wurde das Vorkommen des Ascomyceten Anisogramma virgultorum an Betula pubescens und Betula pendula in jeweils zwei Reinbeständen dieser Baumarten sowie in zwei Mischbeständen (B. pubescens und Pinus sylvestris) in einem Distrikt in der Nähe von Umeå, Nordschweden, untersucht (Alter ca. 10 Jahre, mittlere Baumhöhe 2,4 m, DBH 10,20 mm). Bei 54,8 % der untersuchten Bäumchen wurden an Stamm und Zweigen Krebse gefunden, die für A.virgultorum typisch sind. Zwischen B. pendula und B. pubescens gab es keine signifikanten Unterschiede. Bei 16 % der Pflanzen wurden Krebse an den Stämmen, bei 54,2 % an den Zweigen beobachtet. Die Stammkrebse traten sowohl am diesjährigen Gipfeltrieb auf als auch an der Stammbasis. Der mittlere Durchmesser geschädigter Pflanzen war signifikant grösser als derjenige von ungeschädigten Pflanzen. Alle Proben von Krebsen mit Stromata, die im Labor untersucht wurden, enthielten Perithecien mit Asci. [source] Subcellular localization of proteins labeled with GFP in Xanthomonas citri ssp. citri: targeting the division septumFEMS MICROBIOLOGY LETTERS, Issue 1 2010Paula M.M. Martins Abstract Xanthomonas citri ssp. citri (Xac) is the causal agent of citrus canker, an economically important disease that affects citrus worldwide. To initiate the characterization of essential biological processes of Xac, we constructed integrative plasmids for the ectopic expression of green fluorescent protein (GFP)-labeled proteins within this bacterium. Here, we show that the disruption of the ,-amylase gene (amy), the site of plasmid integration into the bacterial chromosome, does not alter its pathogenesis while abolishing completely the ability of Xac to degrade starch. Furthermore, our GFP expression system was used to characterize ORF XAC3408, a hypothetical protein encoded by Xac that shares significant homology to the FtsZ-stabilizing factor ZapA from Bacillus subtilis (ZapABsu). GFP-XAC3408 expressed in Xac exhibited a septal localization pattern typical of GFP-ZapABsu, which indicates that XAC3408 is the Xac orthologue of the cell division protein ZapABsu. The results demonstrate the potential of GFP labeling for protein functional characterizations in Xac, and, in addition, the Xac mutant strain labeled at the septum constitutes a biological model for the exploration of antibacterial compounds able to inhibit cell division in this plant pathogen. [source] Associations among symptoms of dieback in even-aged stands of ash (Fraxinus excelsior L.)FOREST PATHOLOGY, Issue 1 2010J. P. Skovsgaard Summary The objective of this study was to establish statistically based associations among macroscopic symptoms of crown dieback, cankers due to Chalara fraxinea, and symptoms caused by other pathogens and pests on Fraxinus excelsior. A total of 454 trees were observed in two plots of a 15-year-old experimental stand. The symptoms included: (i) overall extent of crown dieback; (ii) dieback of upper parts of the crown; (iii) canker in upper parts of the crown; (iv) wilting foliage; (v) cankers and bark proliferations at the lower part of the stem; and (vi) discolouration at stump or stem base. The analysis suggested that the observed symptoms of crown dieback are caused by a primary disease. The macroscopic symptoms attributed to dieback and canker in the crown were strongly associated. Moreover, the disease was associated with symptoms of Armillaria gallica, but no associations were found for symptoms of Neonectria galligena, Pseudomonas syringae subsp. savastanoi pv. fraxini, Hylesinus fraxini or H. varius when considered collectively. Dieback was more frequent on trees of average or below-average size, suggesting that individual tree resistance decreased with decreasing growth potential or tree vigour. The extent of canker in the crown depended on site conditions and possibly on silvicultural practices. The development of phytosanitary prescriptions for silviculture should primarily be targeted towards young stands as these represent the most critical phases of stand development. [source] Methods for inoculum production and inoculation of Cistella japonica, the causal agent of resinous stem canker in Chamaecyparis obtusaFOREST PATHOLOGY, Issue 1 2008T. Yamanobe Summary The ascomycete Cistella japonica was cultured on potato dextrose agar medium (PDA) for inoculation into Chamaecyparis obtusa, enabling the development of an inoculation method suitable for use in a breeding programme aimed at selecting for families of Ch. obtusa resistant to resinous stem canker. Using PDA to generate the inoculum resolved the problems encountered with the previously used mixed medium of rice bran and wheat bran, including unfavourable characteristics, uncertain growth of Ci. japonica mycelia, and a complex culturing operation. The inoculation test induced resin exudation similar to that observed in natural infections, and reproduced clonal differences with regard to damage severity. [source] Screening wild cherry (Prunus avium) for resistance to bacterial canker by laboratory and field testsFOREST PATHOLOGY, Issue 6 2004F. Santi Summary Currently, bacterial canker caused by Pseudomonas syringae is a major cause of dieback and tree death in wild cherry (Prunus avium) plantations. The evaluation of breeding collections is needed to produce less susceptible clones or cultivars. Resistance tests were performed using excised shoots (1 and 2 years old) from 79 clones in the laboratory. A subset of 10 clones was also tested in the field. The clones were inoculated with four to seven isolates of a set of 15 isolates of P. s. pv. morsprunorum, P. s. pv. syringae, P. s. pv. persicae, P. syringae pv. avii and P. fluorescens. In the laboratory tests, older and larger shoots were more susceptible. In the field test, size and age of the shoots were not related to girdling by the bacterial canker. Two-year-old shoots were best for clonal discrimination. Correlations between 1 and 2-year-old shoots were significant but not high. The isolates varied a lot between experiments, but as the clone × isolate interactions were always low, breeding could thus be facilitated. The ranking of clones was conserved quite well between two laboratory tests, but not between two others. Good agreement was found for the best clones in the laboratory tests and in the field test. However, the two worst clones in the latter were among the best in one laboratory test. At least two independent tests in the laboratory are needed to evaluate resistance/susceptibility of clones. Broad sense heritability for resistance varied from 0.27 to 0.51. Although moderate, such heritability clearly encourages a breeding approach to reduce the problem of bacterial canker. Résumé Le chancre bactérien (Pseudomonas syringae) est une cause majeure de dépérissement dans les plantations de merisier du nord de la France. Nous devons évaluer les collections pour produire des variétés moins sensibles. Des branches coupées de un ou deux ans de 79 clones ont été testées au laboratoire. Dix de ces clones ont également été testés dans un test en extérieur. Les clones ont été inoculés avec un total de 15 isolats de P. s. pv. morsprunorum, P. s. pv. syringae, P. s. pv. persicae, P. s. pv. avii et P. fluorescens. Les plus fortes infections, mesurées par la longueur du chancre, ont été observées sur les branches les plus âgées et les plus épaisses, mais la taille et l'âge des branches n'ont eu aucune influence sur la note de ceinturation du test au champ. Les branches de deux ans se sont révélées meilleures pour discriminer les clones. Les corrélations entre moyennes de clones avec les branches de un et deux ans étaient significatives mais pas très élevées. Les isolats variaient beaucoup entre expériences, mais comme les interactions clone × bactérie étaient toujours faibles, la sélection clonale en devrait être facilitée. Le classement des clones était bien conservé entre deux tests de laboratoire, mais pas entre deux autres. Le classement entre tests au laboratoire et au champ se trouvait conservé, mais les deux plus mauvais clones dans ce dernier ont été bien classés dans un test de laboratoire, ce qui signifie qu'un seul test a laboratoire est insuffisant pour l'évaluation des clones. Les héritabilités au sens large variaient de 0.27 à 0.51. Bien que modérées, de telles héritabilités encouragent clairement à sélectionner des génotypes moins sensibles pour solutionner le problème du chancre bactérien. Zusammenfassung Der durch Pseudomonas syringae verursachte Bakterienkrebs ist eine der häufigsten Ursachen für das Absterben von Süsskirschen (Prunus avium) in Pflanzungen. Die Prüfung von Zuchtformen auf Resistenz ist nötig, um weniger anfällige Klone und Sorten zu fördern. Die Resistenz von 79 Klonen wurde im Labor an abgeschnittenen ein- und zweijährigen Trieben getestet. Zehn Klone wurden auch im Feld getestet. Die Klone wurden mit je vier bis sieben von insgesamt 15 Isolaten von P. s. pv. morsprunorum, P. s. pv. syringae, P. s. pv. persicae, P. s. pv. avii und P. fluorescens inokuliert. In den Labortests waren die älteren, dickeren Triebe anfälliger, währenddem in den Feldversuchen weder Alter noch Dicke der Triebe eine Rolle spielten. Zweijährige Triebe eigneten sich zur Differenzierung der Klone hinsichtlich ihrer Resistenz besser. Korrelationen zwischen ein- und zweijährigen Trieben waren signifikant aber nicht hoch. Die Reaktionen auf die Isolate variierten stark zwischen den Experimenten, aber die statistisch nachgewiesenen Wechselwirkungen zwischen Klonen und Isolaten waren stets schwach, was die Züchtung neuer Klone erleichtern dürfte. In zwei Labortests erzielten die Klone analoge Bewertungen, währenddem sie in zwei anderen Labortests unterschiedlich reagierten. Die Resultate aus Labor- und Feldversuchen stimmten für die resistentesten Klone gut überein, die anfälligsten Klone im Feldversuch waren jedoch unter den resistentesten in den Laborversuchen. Es sind also mindestens zwei unabhängige Labortests nötig, um den Grad der Resistenz eines Klones zu bestimmen. Der Vererbarkeit der Resistenz variierte zwischen 0.27 und 0.51. Obschon diese Werte moderat sind, sollen sie dazu ermuntern, mittels Züchtung auf eine Reduktion von durch den Bakterienkrebs bedingten Ausfällen hinzuarbeiten. [source] Incomplete movement of Cryphonectria hypovirus 1 within a vegetative compatibility type of Cryphonectria parasitica in natural cankers on grafted American chestnut treesFOREST PATHOLOGY, Issue 6 2002E. P. Hogan Summary American chestnut trees, grafted in 1980 from large survivors, were inoculated in 1982 and 1983 with four white (European) hypovirulent strains of Cryphonectria parasitica, infected with C. hypovirus 1 (CHV1); this hypovirus has been shown to be capable of moving rapidly within the mycelium of a vegetative compatibility (vc) type of C. parasitica in blight cankers. Using a 49-cell lattice plot, 17.8×17.8 cm, the spatial patterns and frequencies of white and pigmented isolates and white and pigmented vc types were investigated within superficial cankers on the grafts located outside the hypovirulent-strain-inoculated zone. Four of six cankers assayed contained white isolates, and three of the four had random spatial patterns of white isolates, based on join-count statistics. Vc tests, using pigmented isolates and pigmented single-spore colonies of white isolates, indicated that the majority of white and pigmented isolates recovered from each of two cankers assayed were in one vc type. White and pigmented lattice-plot cells of the same vc type were frequently in contact with each other, indicating incomplete movement of CHV1 within a vc type. Nine and 10 vc types were found in the two cankers; it is hypothesized that small, white vc type areas in each canker may be a source of CHV1 transmission to the major vc types. Based on join-count statistics, the spatial pattern of the single, major vc type in one canker was non-random (aggregated), whereas the other canker had a random major vc type pattern. White and pigmented in vitro variants (sectors) of C. parasitica, that resemble white and pigmented in vivo variants in spatial contact and vc compatibility, were intermediate hypovirulent and virulent on forest American chestnuts, and dsRNA positive and negative, respectively. Incomplete movement of CHV1 within a vc type could be a major cause of the prevalence of pigmented isolates in superficial cankers on chestnut trees. Résumé Des châtaigniers américains greffés en 1980 à partir de grands arbres survivants, ont été inoculés en 1982 et 1983 avec quatre souches blanches (européennes) hypovirulentes de Cryphonectria parasitica, infectées par l'hypovirus 1 (CHV 1). Cet hypovirus avait été montré capable de migrer rapidement dans le mycélium végétativement compatible (vc) de C. parasitica dans des chancres. Grâce un dispositif à 49 cellules (17,8×17,8 cm), la répartition spatiale et la fréquence des isolats blancs et pigmentés, et des GCV, ont étéétudiées dans des chancres superficiels chez les greffons, en dehors de la zone inoculée par les souches hypovirulentes. Quatre des six chancres étudiés contenaient des isolats blancs, dont la répartition spatiale était erratique chez trois d'entre eux. Les tests de compatibilité végétative, utilisant des isolats pigmentés et des colonies pigmentées mono-sporées d'isolats blancs, ont montré que la majorité des isolats blancs et des isolats colorés trouvés dans chacun des deux chancres analysés, était d'un seul type végétatif. Les cellules du dispositif, blanches ou pigmentées du même GCV, étaient fréquemment en contact, ce qui indique un mouvement incomplet de CHV1 dans un GCV. Neuf et dix GCV ont été trouvés dans les deux chancres et on avance l'hypothèse que de petites zones à GCV blancs dans chaque chancre peuvent être une source de transmission de CHV1 aux types végétatifs majoritaires. L'unique GCV majoritaire dans un des chancres n'était pas réparti au hasard (agrégé), mais il l'était dans l'autre chancre. Les variants blancs et pigmentés in vitro (secteurs) de C. parasitica, qui ressemblent aux variants blancs et pigmentés in vivo en contact spatial, étaient intermédiaires en hypovirulence et en virulence sur les châtaigniers américains, et respectivement positifs et négatifs pour le dsRNA. Un mouvement incomplet de CHV1 dans un GCV pourrait être la principale cause de la prévalence d'isolats pigmentés dans des chancres superficiels. Zusammenfassung Amerikanische Kastanien (Castanea dentata), die im Jahr 1980 von adulten überlebenden Exemplaren veredelt worden waren, wurden 1982 und 1983 mit vier unpigmentierten, hypovirulenten Stämmen von Cryphonectria parasitica aus Europa inokuliert, die mit dem Cryphonectria parasitica - hypovirus 1 (CHV 1) infiziert waren. Es war nachgewiesen, dass sich dieses Hypovirus rasch innerhalb des Myzels eines vc-Typs von C. parasitica in Krebsen ausbreiten konnte. Bei oberflächlichen Krebsen an veredelten Bäumen ausserhalb der mit dem hypovirulenten Stamm inokulierten Zone wurde auf einer 17,8×17,8 cm grossen Fläche (die in 49 Quadrate unterteilt wurde) die räumliche Verteilung und die Häufigkeit von unpigmentierten und pigmentierten Isolaten sowie der vc-Typen untersucht. Vier von sechs analysierten Krebsen enthielten weisse Isolate und drei davon zeigten zufällige Verteilungsmuster der Isolate (gemäss Joint-Count-Statistik). Vc-Tests mit pigmentierten Isolaten und pigmentierten Einzelsporkulturen von weissen Isolaten zeigten, dass die Mehrheit der weissen und der pigmentierten Isolate von zwei Krebsen zur gleichen vc-Gruppe gehörten. Weisse und pigmentierte Probepunkte mit dem gleichen vc-Typ waren häufig benachbart, was eine unvollständige Ausbreitung des CHV 1 innerhalb eines vc-Typs anzeigt. In den 2 Krebsen wurden 9 bzw. 10 vc-Typen nachgewiesen und es wird vermutet, dass kleine Bereiche mit weissem vc-Typ innerhalb eines Krebses als Reservoir für die Übertragung des Virus zu den dominanten vc-Typen fungieren können. Mit Hilfe der Joint-Count-Statistik wurde nachgewiesen, dass das räumliche Muster des einen, dominanten vc-Typs in einem Krebs nicht zufällig, sondern aggregiert war, während der andere Krebs ein zufälliges Verteilungsmuster der vc-Typen aufwies. Weisse und pigmentierte Varianten von C. parasitica, die in vitro auftraten (Sektoren), und die den weissen und pigmentierten Varianten sehr ähnlich sind, die in der Natur in räumlichem Kontakt zueinander auftreten, und die vegetativ kompatibel sind, zeigten in Feldversuchen auf C. sativa eine mittlere Hypovirulenz bzw. Virulenz. Ausserdem waren sie dsRNA positiv bzw. negativ. Die unvollständige Ausbreitung des CHV 1 innerhalb einer vc-Typs könnte das überwiegen pigmentierter Isolate in oberflächlichen Krebsen erklären. [source] Seasonal resin canal formation and necroses expansion in resinous stem canker-affected Chamaecyparis obtusaFOREST PATHOLOGY, Issue 4-5 2002T. YAMADA Summary The season of disease development on the basis of two major internal symptoms, resin canal formation and necrotic lesion expansion in phloem, were anatomically determined in Chamaecyparis obtusa (Hinoki cypress) affected by resinous stem canker. Newly formed resin canals were mostly observed at first from July to August in samples of the canker-affected C. obtusa phloem. This result indicates the occurrence of stimuli causing resin canal formation and the beginning of the formation from May to July of the same year. This and the beginning of resin exudation observed in May or June indicated that resin, exuded at least before August, originated from resin canals formed in the previous year(s). The expansion of phloem necrotic lesions began in June and continued until October, and was conspicuous in the August samples. Stimuli causing necrotic lesion development were also suggested to occur from May to August of the same year. It is hypothesized that excess resin production induces lesion development and that expansion of necrotic lesion induces both resin exudation from previously formed resin canals and new resin canal formation. The causal agent of the disease could be activated in the late spring or summer season. Résumé Formation saisonnière de canaux résinifères et extension des nécroses chez Chamaecyparis obtusa atteint par le chancre résineux du tronc Chez Chamaecyparis obtusa affecté par le chancre résineux du tronc, la saison de développement de la maladie a été déterminée anatomiquement en se basant sur deux symptômes internes majeurs: la formation de canaux résinifères et l'extension des nécroses au niveau du phloème. Des canaux résinifères récemment formés ont surtout été observés à partir de juillet et en août dans le phloème de C. obtusa atteint par la maladie. Ce résultat montre l'existence de stimuli de la formation de canaux résinifères, ceux-ci commençant à se former en mai jusqu'en juillet. Jointe au fait que l'exsudation de résine a lieu en mai ou juin, cette observation montre que la résine (au moins celle exsudée avant août) provient des canaux formés au cours de la ou des années précédentes. L'extension de la nécrose du phloème débutait en juin, était forte en août et se poursuivait jusqu'en octobre. Il est suggéré que les stimuli du développement de la nécrose ont lieu entre mai et août de la même année. Il est supposé, d'une part que la production excessive de résine induit le développement des lésions, et d'autre part que l'extension des nécroses induit l'exsudation de résine à partir des canaux antérieurement formés ainsi que la formation de nouveaux canaux. L'agent causal de la maladie pourrait être activéà la fin du printemps ou en été. Zusammenfassung Saisonale Harzkanalbildung und Entwicklung der Nekrosen bei Chamaecyparis obtusa mit ,HarzigemStammkrebs' Bei Chamaecyparis obtusa mit Befall durch den ,Harzigen Stammkrebs' wurde die Phänologie der Krankheitsentwicklung anhand der Harzkanalbildung und der Ausbreitung der Nekrosen im Phloem anatomisch erfasst. Im krebsbefallenen Phloem wurden neu gebildete Harzkanäle zuerst im Juli und August beobachtet. Dies weist darauf hin, dass die Stimulation für die Harzkanalbildung und die Entwicklung der Harzkanäle in der Zeit von Mai bis Juli des laufenden Jahres erfolgt. Diese Beobachtung und der Beginn des Harzflusses, welcher im Mai und Juni auftritt, deuten darauf hin, dass der Harzfluss vor dem August aus Harzkanälen stammt, die bereits im Vorjahr oder noch früher angelegt worden waren. Die Expansion der Phloem-Nekrosen begann im Juni und hielt bis Oktober an, im August war sie besonders stark ausgeprägt. Der Reiz für die Ausdehnung der Nekrosen dürfte somit von Mai bis August des laufenden Jahres vorhanden sein. Es wird die Hypothese aufgestellt, dass die stark gesteigerte Harzproduktion die Nekrosenentwicklung fördert und dass die Expansion der Nekrosen sowohl den Harzfluss aus den früher gebildeten Harzkanälen anregt als auch die Bildung neuer Harzkanäle induziert. Der ursächliche Faktor für diese Krankheit dürfte im späten Frühjahr oder im Sommer aktiv sein. [source] Systemic induced resistance in Monterey pineFOREST PATHOLOGY, Issue 2 2001Bonello The pathogenic fungus Fusarium circinatum causes pitch canker of pines. This study shows that Monterey pine (Pinus radiata), one of the most economically important pine species in the world and the main host in California, responds to infection by Fusarium circinatum in a manner consistent with systemic induced resistance. Repeated mechanical inoculations of the same trees in the field produced progressively smaller lesions over a period of 2 years, with mean lesion length decreasing significantly from 2.89 ± 0.42 cm to 1.04 ± 0.17 cm. In the greenhouse, predisposing inoculations with the pathogen induced a significant lesion length reduction, from 5.5 ± 0.21 cm in control trees to 4.46 ± 0.36 cm in predisposed trees over a period of 6 weeks. Under constant environmental conditions in a growth chamber, predisposing inoculations also induced a significant reduction in lesion size, from 3.01 ± 0.15 cm to 2.55 ± 0.18 cm over a period of 4 weeks. This is the first unequivocal report of systemic induced resistance in a conifer. Résistance systémique induite chez le Pinus radiata Fusarium circinatum est l'agent causal du ,pitch canker' des pins. Le Pinus radiata est l'un des pins les plus importants économiquement dans le monde, et le principal hôte de la maladie en Californie. Cette étude montre que P. radiata réagit régulièrement à l'infection de Fusarium circinatum d'une façon qui peut être de la résistance systémique induite. Des inoculations mécaniques répétées sur de mêmes arbres en nature ont produit progressivement des lésions dont la taille diminuait au cours d'une période de deux ans; la longueur des lésions diminuait significativement de 2.89 ± 0.42 cm à 1.04 ± 0.17 cm. En serre, des inoculations de pré-conditionnement avec le parasite ont entraîné une réduction significative de la longueur des lésions, de 5.5 ± 0.21 cm chez les témoins à 4.46 ± 0.36 cm chez les arbres pré-conditionnés, au cours d'une période de six semaines. En conditions environnementales constantes en chambre climatique, les inoculations de pré-conditionnement ont aussi induit une réduction significative de la taille des lésions, de 3.01 ± 0.15 cm à 2.55 ± 0.18 cm, en une période de 4 semaines. Ceci est la première mention non équivoque d'une résistance systémique induite chez un conifère. Induzierte systemische Resistenz in Monterey-Kiefer Der pathogene Pilz Fusarium circinatum verursacht einen Krebs an Kiefern (pitch canker). Die vorliegende Untersuchung zeigt, dass die Monterey-Kiefer (Pinus radiata), eine der ökonomisch wichtigsten Kiefernarten der Welt und Hauptwirt in Kalifornien, auf Infektionen durch Fusarium circinatum mit induzierter systemischer Resistenz reagiert. Wiederholte mechanische Inokulationen der gleichen Bäume im Feld führten zu zunehmend kleineren Läsionen über einen Beobachtungszeitraum von zwei Jahren. Die Länge der Läsionen nahm von 2.89 ± 0.42 cm auf 1.04 ± 0.17 cm signifikant ab. Im Gewächshaus bewirkten prädisponierende Inokulationen mit dem Pathogen eine signifikante Reduktion der Läsionslänge von 5.5 ± 0.21 cm in den Kontrollen auf 4.46 ± 0.36 cm in den prädisponierten Pflanzen über einen Beobachtungszeitraum von sechs Wochen. Prädisponierende Inokulationen bewirkten auch unter konstanten Umweltbedingungen in einer Klimakammer eine signifikante Abnahme der Läsionsgrösse von 3.01 ± 0.15 cm auf 2.55 ± 0.18 über eine Periode von vier Wochen. Es handelt sich hier um den ersten eindeutigen Nachweis von induzierter systemischer Resistenz bei einer Konifere. [source] Genetic variability of the ,bark canker resistance' character in several natural provenances of Cupressus sempervirensFOREST PATHOLOGY, Issue 2 2000A. Santini Summary Several Aegean (Greece) and Anatolian (Turkey) cypress provenances were studied for resistance variability to bark canker, a disease caused by the fungal pathogen Seiridium cardinale. The investigation also examined whether the low disease rate within the natural area of cypress was due to genetic or geographic-climatic reasons. Results demonstrated strong variability for the ,bark canker resistance' character, in particular for trees within families. As trees from the provenances studied were not found to have genetic superiority for bark canker resistance, the above-mentioned low disease rate could be due to geographic-climatic barriers that inhibit the development of the fungus or its ability to infect the host. Several half-sib progenies exhibited high resistance, suggesting that this character is totally inherited through the maternal line. Should this finding be confirmed by further research, it would facilitate the task of genetic improvement for resistance, allowing progenies of resistant trees to be obtained. [source] Season-long mating disruption of citrus leafminer, Phyllocnistis citrella Stainton, with an emulsified wax formulation of pheromoneJOURNAL OF APPLIED ENTOMOLOGY, Issue 6 2010L. L. Stelinski Abstract The citrus leafminer, Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae), is a major worldwide pest of citrus. Larval feeding by this insect facilitates proliferation of citrus bacterial canker, Xanthomonas axonopodis pv. citri. Herein, we describe a season-long disruption trial of P. citrella with a newly developed, emulsified wax dispenser of pheromone (SPLAT-CLMTM). A formulation containing a 3 : 1 blend of (Z,Z,E)-7,11,13-hexadecatrienal:(Z,Z)-7,11-hexadecadienal at a 0.2% loading rate of active ingredient by weight and deployed twice per season (24 weeks total) at 490 g of formulation/ha caused season-long disruption of male moth catch in pheromone traps as well as reduced leaf infestation. Analysis of pheromone release from dispensers by gas chromatography revealed that effective disruption of P. citrella occurred at a deployment rate of 126 ,g of (Z,Z,E)-7,11,13-hexadecatrienal/ha/h. Direct observation of moth behaviour in the field suggested that disruption by this formulation occurred by a non-competitive mechanism. A formulation of the 3 : 1 attractive blend at a 0.02% pheromone loading rate caused only 2,6 weeks of disruption per deployment and did not reduce leaf infestation during mid and end of the season evaluations. A formulation containing 0.2% of (Z,Z)-7,11-hexadecadienal alone and deployed at 490 g/ha caused 6,7 weeks of moth disruption to pheromone traps and did not prevent leaf infestation, while an identical formulation loaded with 0.02% (w/w) of (Z,Z)-7,11-hexadecadienal alone had no effect on P. citrella orientation to pheromone traps. The SPLAT formulation evaluated herein appears to be an excellent release device for (Z,Z,E)-7,11,13-hexadecatrienal given that approximately 100 days of steady release occurred following an initial brief (ca. 7 days) burst of higher release. The advantages of SPLAT as a formulation for P. citrella disruption include low cost of manufacturing, biodegradable and weather resistant characteristics, and flowability allowing machine application. Mating disruption should be an effective alternative to insecticides for management of P. citrella and may reduce the incidence of citrus canker. [source] Potential of Trichoderma harzianum and T. atroviride to Control Botryosphaeria berengeriana f. sp. piricola, the Cause of Apple Ring RotJOURNAL OF PHYTOPATHOLOGY, Issue 4-5 2002G. KEXIANG Abstract Trichoderma harzianum T88 and T. atroviride T95 were tested for their efficacy in controlling apple ring rot (caused by Botryosphaeria berengeriana f. sp. piricola) in vitro and in the field. Isolates of T88 and T95 produced both volatile and non-volatile antibiotics that suppressed mycelial growth of the pathogen. Light and scanning electron microscopy showed that mycoparasitism by Trichoderma spp. of B. berengeriana f. sp. piricola resulted in penetration and disruption of hyphal cells, and thinning of cytoplasm of the pathogen. The culture filtrates of T88 and T95 in Czapek's liquid medium suppressed conidial germination of the pathogen, and the germination level was negatively correlated with the duration of culture of Trichoderma. In inoculation tests, 32 days after simultaneous inoculation or preinoculation with B. berengeriana f. sp. piricola and Trichoderma spp., the incidence of infected apple shoots was reduced, respectively, by 65.3,76.4% and 62.5,76.4%, and the index of infection reduced by 36.9,38.9 and 40.7,44.4, The effect of inoculating B. berengeriana f. sp. piricola 3 days after the antagonists were inoculated was greater (81.4,88.8%) than simultaneous inoculation (72.2,77.8%). Re-isolation from inoculated apple shoots demonstrated that the pathogen had been suppressed by Trichoderma. The ability to re-isolate the pathogen from apple after co-inoculation and pre-inoculation with Trichoderma spp. was reduced by 27.0,42.3% and 22.2,47.1%, respectively. The biocontrol field trial suggested that the B. berengeriana f. sp. piricola canker on apple shoots and stems and rotting fruit had been efficiently controlled by the application of spore suspensions of T. harzianum T88 and T. atroviride T95. The efficacy of control by Trichoderma is thus similar to that of routine chemical control. [source] Physiological and Biochemical Characteristics of Iranian Strains of Xanthomonas axonopodis pv. citri, the Causal Agent of Citrus bacterial Canker DiseaseJOURNAL OF PHYTOPATHOLOGY, Issue 2 2001M. Mohammadi Twenty-four strains of Xanthomonas axonopodis pv. citri (Xac), the causal agent of bacterial canker of citrus, isolated from Mexican lime (Citrus aurantifolia) and lemon (Citrus limon) in southern Iran, were characterized phenotypically. Strains were all pathogenic on C. aurantifolia. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis analysis revealed slight differences in soluble protein profiles among the strains. Based on host range specificity and phenotypic characteristics, representative strains were differentiated into two groups of Asiatic (A) and atypical Asiatic (aA) forms. DNA fingerprinting analysis using EcoRI as the restriction endonuclease showed a negligible difference in restriction pattern between the two groups. On the basis of isozymic analysis, the two groups were distinct with respect to superoxide dismutase (SOD) and esterase (EST) banding patterns. Plasmid DNA profile analysis showed that the bacterial strains were different from each other in terms of plasmid number and molecular weight. Phage typing study revealed that most of group A strains were susceptible to Cp1 and/or Cp2 and some were resistant to both phage types including the strain in aA group. Bacteriocin production test indicated that there was a variation among Xac strains using different indicators for each bacteriocin producer. It is concluded that the Iranian strains of Xac are heterogeneous and constitute a subgroup(s) within the pathotype A. Physiologische und biochemische Merkmale iranischer Stämme von Xanthomonas axonopodis pv. citri, dem Erreger des bakteriellen Zitruskrebses Vierundzwanzig Stämme von Xanthomonas axonopodis pv. citri, dem Erreger des bakteriellen Zitruskrebses, wurden von mexikanischen Sauren Limetten (Citrus aurantifolia) und Zitronen (Citrus limon) im Südiran isoliert und phänotypisch charakterisiert. Alle Stämme waren für C. aurantifolia pathogen. Eine SDS-PAGE-Analyse zeigte, daß zwischen den Stämmen geringfügige Unterschiede bei den Profilen der löslichen Proteine bestanden. Auf Grundlage der Spezifität des Wirtsspektrums und phänotypischer Merkmale wurden repräsentative Stämme in die zwei Gruppen asiatische (A) und atypische asiatische (aA) Formen eingeteilt. Eine Analyse mit DNA-Fingerabdrücken, wobei EcoRI als Restriktionsendonuclease diente, zeigte einen vernachlässigbar kleinen Unterschied bei den Restriktionsmustern der beiden Gruppen. Die Isoenzymanalyse ergab Unterschiede zwischen beiden Gruppen bezüglich der Bandenmuster von Superoxiddismutase (SOD) und Esterase (EST). Eine Analyse der Plasmid-DNA-Profile zeigte, daß die Bakterienstämme unterschiedliche Plasmidzahlen und verschiedene Molekülmassen aufwiesen. Eine Phagentypisierung ergab, daß die meisten Stämme der Gruppe A anfällig für Cp1 und/oder Cp2 waren; einige waren resistent gegen beide Phagentypen, darunter der Stamm in der aA-Gruppe. Ein Test der Bacteriocinproduktion ergab, daß die Xac -Stämme variierten; hier wurden verschiedene Indikatoren für jeden Bakteriocinbildner verwendet. Es wird gefolgert, daß die iranischen Stämme von Xac heterogen sind und eine oder mehrere Untergruppen innerhalb des Pathotyps A bilden. [source] Occurrence of Pseudomonas avellanae (Psallidas) Janse et al. and related pseudomonads on wild Corylus avellana trees and genetic relationships with strains isolated from cultivated hazelnutsJOURNAL OF PHYTOPATHOLOGY, Issue 9-10 2000M. Scortichini Surveys in submediterranean forests of central Italy were carried out during 1996,98 to verify the possible presence of bacterial canker caused by Pseudomonas avellanae in wild hazelnut trees (Corylus avellana L.). Wilted twigs were noticed several times especially in summer. In other cases, wild C. avellana trees growing near to hazelnut orchards appeared completely wilted. Isolates that were pathogenic to C. avellana, showing a different degree of virulence, were obtained in both situations. Biochemical, physiological and nutritional tests as well as the comparison of whole-cell protein profiles, revealed the presence of 16 isolates identical to P. avellanae reference strains that had previously been isolated in the same area and five deviating isolates. Repetitive-PCR genomic fingerprinting performed by using BOX (Box elements), ERIC (Enterobacterial Repetitive Interkingdom Consensus) and REP (Repetitive Extragenic Palindromic) primer sets and analysed by means of upgma, revealed the existence of two main groups of pseudomonads pathogenic to C. avellana. Group A includes P. avellanae strains isolated in northern Greece and central Italy as well as the isolates obtained from the wild C. avellana trees grown near the cultivated hazelnut orchards. Group B includes strains previously isolated in northern, southern and other areas of central Italy as well as the isolates obtained from C. avellana wild trees showing twig dieback. Control measures should be taken to avoid the spread of bacterial canker of hazelnut in the forests of central Italy. [source] The stem canker (blackleg) fungus, Leptosphaeria maculans, enters the genomic eraMOLECULAR PLANT PATHOLOGY, Issue 3 2005T. ROUXEL SUMMARY Leptosphaeria maculans is the most ubiquitous pathogen of Brassica crops, and mainly oilseed brassicas (oilseed rape, canola), causing the devastating ,stem canker' or ,blackleg'. This review summarizes our current knowledge on the pathogen, from taxonomic issues to specific life traits. It mainly illustrates the importance of formal genetics approaches on the pathogen side to dissect the interaction with the host plants. In addition, this review presents the main current research topics on L. maculans and focuses on the L. maculans genome initiative recently begun, including its main research issues. Taxonomy:,Leptosphaeria maculans (Desm.) Ces. & de Not. (anamorph Phoma lingam Tode ex Fr.). Kingdom Fungi, Phylum Ascomycota, Class Dothideomycetes (Loculoascomycetes), Order Pleosporales, Genus Leptosphaeria, Species maculans. Host range:, cultivated Brassicas such as Brassica napus (oilseed rape, canola), B. rapa, B. juncea, B. oleracea, etc., along with numerous wild crucifers species. Arabidopsis thaliana was recently reported to be a potential host for L. maculans. Primary disease symptoms are greyish-green collapse of cotyledon or leaf tissue, without a visible margin, bearing tiny black spots (pycnidia). The fungus then develops an endophytic symptomless growth for many months. Secondary symptoms, at the end of the growing season, are dry necroses of the crown tissues with occasional blackening (stem canker or blackleg) causing lodging of the plants. Pseudothecia differentiate on leftover residues. Seedling damping-off and premature ripening are also reported under certain environmental conditions. Useful websites:,Leptosphaeria maculans sequencing project at Genoscope: http://www.genoscope.cns.fr/externe/English/Projets/Projet_DM/organisme_DM.html; the SECURE site: http://www.secure.rothamsted.ac.uk/ the ,Blackleg' group at the University of Melbourne: http://www.botany.unimelb.edu.au/blackleg/overview.htm [source] Xanthomonas axonopodis pv. citri: factors affecting successful eradication of citrus cankerMOLECULAR PLANT PATHOLOGY, Issue 1 2004James H. Graham SUMMARY Taxonomic status:, Bacteria, Proteobacteria, gamma subdivision, Xanthomodales, Xanthomonas group, axonopodis DNA homology group, X. axonopodis pv. citri (Hasse) Vauterin et al. Microbiological properties:, Gram negative, slender, rod-shaped, aerobic, motile by a single polar flagellum, produces slow growing, non-mucoid colonies in culture, ecologically obligate plant parasite. Host range:, Causal agent of Asiatic citrus canker on most Citrus spp. and close relatives of Citrus in the family Rutaceae. Disease symptoms:, Distinctively raised, necrotic lesions on fruits, stems and leaves. Epidemiology:, Bacteria exude from lesions during wet weather and are disseminated by splash dispersal at short range, windblown rain at medium to long range and human assisted movement at all ranges. Crop loss:, Severe infections cause defoliation, blemished fruit, premature fruit drop, die-back of twigs and general debilitation of the tree. Distribution:, Citrus canker is not present in all subtropical to tropical regions of citriculture in the world, so considerable regulatory efforts are expended to prevent the introduction and spread of X. axonopodis pv. citri into areas in the Americas, Australia and elsewhere, with climates conducive to the disease. Importance:, Limited strategies exist for suppression of citrus canker on more susceptible cultivars. Blemished fruit are unmarketable and exposed fruit are restricted in market access. The economic impact of loss of markets is much greater than that from yield and quality reductions of the crop. Useful websites:,http://doacs.state.fl.us/canker , http://www.apsnet.org/education/lessonsplantpath/citruscanker/top.htm , http://www.apsnet.org/online/feature/citruscanker/ , http://www.plantmanagementnetwork.org/pub/php/review/citruscanker/ , http://www.abecitrus.com.br/fundecitrus.html , http://www.biotech.ufl.edu/PlantContainment/canker.htm , http://www.aphis.usda.gov/oa/ccanker/ . [source] Xanthomonas citri: breaking the surfaceMOLECULAR PLANT PATHOLOGY, Issue 3 2003Asha M. Brunings SUMMARY Taxonomy: Bacteria; Proteobacteria, Gammaproteobacteria; Xanthomonadales; Xanthomonadaceae, Xanthomonas. Microbiological properties: Gram-negative, obligately aerobic, straight rods, motile by a single polar flagellum, yellow pigment. Related species:X. campestris , X. axonopodis , X. oryzae , X. albilineans . Host range: Affects Rutaceous plants, primarily Citrus spp., Fortunella spp., and Poncirus spp., world-wide. Quarantined pathogen in many countries. Economically important hosts are cultivated orange, grapefruit, lime, lemon, pomelo and citrus rootstock. Disease symptoms: On leaves, first appearance is as oily looking, 2,10 mm, similarly sized, circular spots, usually on the abaxial surface. On leaves, stems, thorns and fruit, circular lesions become raised and blister-like, growing into white or yellow spongy pustules. These pustules then darken and thicken into a light tan to brown corky canker, which is rough to the touch. On stems, pustules may coalesce to split the epidermis along the stem length, and occasionally girdling of young stems may occur. Older lesions on leaves and fruit tend to have more elevated margins and are at times surrounded by a yellow chlorotic halo (that may disappear) and a sunken centre. Sunken craters are especially noticeable on fruit, but the lesions do not penetrate far into the rind. Defoliation and premature abscission of affected fruit occurs on heavily infected trees. Useful websites: First report of Inonotus rickii causing canker and decay on Hevea brasiliensis in ChinaPLANT PATHOLOGY, Issue 4 2010Y. C. Dai No abstract is available for this article. [source] Dual control of avirulence in Leptosphaeria maculans towards a Brassica napus cultivar with ,sylvestris -derived' resistance suggests involvement of two resistance genesPLANT PATHOLOGY, Issue 2 2009A. P. Van de Wouw Blackleg disease (phoma stem canker) of Brassica napus (canola, oilseed rape) is caused by the fungus Leptosphaeria maculans. In some regions of Australia, resistance in oilseed rape cultivars derived from B. rapa subs. sylvestris (e.g. cv. Surpass 400) became ineffective within three years of commercial release. The genetic control of avirulence in L. maculans towards cv. Surpass 400 is described. When Australian field isolates were screened on this cultivar, three phenotypic classes were observed; virulent, intermediate and avirulent. Analysis of crosses between fungal isolates varying in their ability to infect cv. Surpass 400 demonstrated the presence of two unlinked avirulence genes, AvrLm1 and AvrLmS. Complementation of isolates (genotype avrLm1) with a functional copy of AvrLm1, and genotyping of field isolates using a molecular marker for AvrLm1 showed that virulence towards Rlm1 is necessary, but not sufficient, for expression of a virulent phenotype on cv. Surpass 400. Taken together, these data strongly suggest that cv. Surpass 400, with ,sylvestris -derived' resistance, contains at least two resistance genes, one of which is Rlm1. [source] Quantitative resistance to symptomless growth of Leptosphaeria maculans (phoma stem canker) in Brassica napus (oilseed rape)PLANT PATHOLOGY, Issue 2 2009Y. J. Huang Quantitative resistance to Leptosphaeria maculans in Brassica napus was investigated in field and controlled environments using cultivars Darmor (with quantitative resistance) and Eurol (without quantitative resistance). In field experiments, numbers of phoma leaf spot lesions in autumn/winter and severity of stem canker the following summer were assessed in three growing seasons. There were no differences between Darmor and Eurol in number of leaf lesions in autumn/winter. However, stem cankers were less severe on Darmor than Eurol at harvest the following summer. In controlled-environment experiments, development of leaf lesions at different temperatures (5,25°C) and wetness durations (12,72 h) was investigated using ascospore inoculum; symptomless growth of L. maculans along leaf petioles towards the stem was quantified using quantitative PCR and visualized using GFP-expressing L. maculans; growth of L. maculans within stem tissues was investigated using GFP-expressing L. maculans. There were more leaf lesions on Darmor than Eurol, although there was no difference between Darmor and Eurol in L. maculans incubation period. There were no differences between Darmor and Eurol in either distance grown by L. maculans along leaf petioles towards the stem or quantity of L. maculans DNA in leaf petioles, but L. maculans colonized stem tissues less extensively on Darmor than Eurol. It was concluded that quantitative resistance to L. maculans operates during colonization of B. napus stems by the pathogen. [source] Resistance to Leptosphaeria maculans (phoma stem canker) in Brassica napus (oilseed rape) induced by L. biglobosa and chemical defence activators in field and controlled environmentsPLANT PATHOLOGY, Issue 3 2006S. Y. Liu Effects of pretreatment of Brassica napus leaves with ascospores of Leptosphaeria biglobosa or chemical defence activators [acibenzolar- S -methyl (ASM) or menadione sodium bisulphite (MSB)] on infection by ascospores of Leptosphaeria maculans (phoma stem canker) and development of disease were studied in controlled-environment (phoma leaf spot) and field (phoma leaf spot and stem canker) experiments. In controlled-environment experiments, pretreatment of oilseed rape leaves (cv. Madrigal) with L. biglobosa, ASM or MSB delayed the appearance of L. maculans phoma leaf spot lesions. These pretreatments also decreased the phoma leaf spot lesion area in both pretreated leaves (local effect) and untreated leaves (systemic effect). In winter oilseed rape field experiments in the 2002/03 and 2003/04 growing seasons, pretreatment with L. biglobosa or ASM in October/November decreased not only the number of phoma leaf spot lesions per leaf caused by L. maculans in autumn/winter, but also the severity of phoma stem canker in the subsequent spring/summer. Effects were greater in 2002/03 (when natural L. maculans ascospore release began in September 2002) than in 2003/04 (when ascospore release began in December following a period of dry weather in August/September 2003). These results suggest that pretreatment with biological or chemical defence activators can induce local and systemic resistance to L. maculans, with both short-term effects on the development of phoma leaf spotting and long-term effects on the development of stem canker 8 months later. [source] Molecular analysis of the major Phytophthora species on cocoaPLANT PATHOLOGY, Issue 2 2004A. 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] First report of walnut canker caused by Fusarium incarnatum in ArgentinaPLANT PATHOLOGY, Issue 2 2004S. Seta No abstract is available for this article. [source] Menadione sodium bisulphite: a novel plant defence activator which enhances local and systemic resistance to infection by Leptosphaeria maculans in oilseed rapePLANT PATHOLOGY, Issue 4 2003A. A. Borges Pretreatment of the first true leaves of oilseed rape plants (Brassica napus cv. Bristol) with menadione sodium bisulphite (MSB) locally and systemically induced resistance, as shown by reduced lesion size and number, to infection by the fungal pathogen Leptosphaeria maculans, the causal agent of stem canker. Using a known systemic activator of salicylic acid-dependent PR-1 induction, acibenzolar- S -methyl (BTH; S -methylbenzo[1,2,3]thiadiazole-7-carbothiate) as a comparison, real-time PCR expression analysis of genes encoding a pathogenesis-related protein 1 (PR-1) and an ascorbate peroxidase (APX) demonstrated a systemic enhancement of APX expression in MSB-pretreated plants, with no effect on PR-1 expression, suggesting augmented reactive oxygen species production in MSB-pretreated plants. The results demonstrate MSB to be an effective resistance activator in oilseed rape, and potentially useful for the control of stem canker. [source] Seasonal changes in susceptibility of Quercus suber to Botryosphaeria stevensii and Phytophthora cinnamomiPLANT PATHOLOGY, Issue 3 2002J. Luque Monthly inoculations of both intact plants and excised shoots of Quercus suber with the pathogenic species Botryosphaeria stevensii and Phytophthora cinnamomi were performed to investigate seasonal changes in susceptibility of this forest tree species in relation to environmental parameters and plant water status. Infection symptoms were mainly detected on seedlings inoculated from spring to autumn (April through October) with either pathogen. Mean canker sizes also showed a seasonal pattern, the higher values being recorded in the same period as above. Lesion lengths were significantly (P < 0·001) related to environmental minimum temperature. Mean daily minimum temperatures within the range of 5,12°C clearly inhibited lesion development of P. cinnamomi, whereas B. stevensii showed a less pronounced decrease in canker expansion at the same temperature range. In excised shoots of Q. suber inoculated monthly with B. stevensii, a negative linear relationship was found between the studied range of plant relative water content (81,91%) and canker length. In contrast, the lesions caused by P. cinnamomi were not significantly (P = 0·32) related to any seasonal change in water content. Some control measures for the diseases caused by both pathogens are discussed on the basis of the seasonal changes in host susceptibility observed in this study. [source] Epidemiology and management of Leptosphaeria maculans (phoma stem canker) on oilseed rape in Australia, Canada and EuropePLANT PATHOLOGY, Issue 1 2001J. S. West Phoma stem canker (blackleg), caused by Leptosphaeria maculans, is an important disease on oilseed rape (canola, rapeseed, Brassica napus, Brassica juncea, Brassica rapa) causing seedling death, lodging or early senescence in Australia, Canada and Europe, but not in China. The two forms of L. maculans (A group and B group) that occur on oilseed rape are now considered to be separate species. The epidemiology and severity of phoma stem canker differs between continents due to differences in the pathogen population structure, oilseed rape species and cultivars grown, climate and agricultural practices. Epidemics are most severe in Australia, where only the A group occurs, and can be damaging in Canada and western Europe, where both A and B groups occur, although their proportions vary within regions and throughout the year. Epidemics are slight in China, where the A group has not been found. Dry climates (Australia, western Canada) lengthen the persistence of infected debris and may synchronize the release of airborne ascospores (after rain) with seedling emergence. L. maculans spreads from cotyledon and leaf infections down petioles to reach the stem, with infections on cotyledons and leaves early in the season producing the most damaging stem cankers at the stem base (crown). Development of both crown cankers and phoma stem lesions higher up stems is most rapid in regions with high temperatures from flowering to harvest, such as Australia and Canada. Breeding for resistance (genetic, disease escape or tolerance), stubble management, crop rotation and fungicide seed treatments are important strategies for control of phoma stem canker in all areas. Fungicide spray treatments are justified only in regions such as western Europe where high yields are obtained, and accurate forecasts of epidemic severity are needed to optimize their use. [source] Effects of stem canker (Leptosphaeria maculans) and light leaf spot (Pyrenopeziza brassicae) on yield of winter oilseed rape (Brassica napus) in southern EnglandPLANT PATHOLOGY, Issue 4 2000Y. Zhou The relationships between yield loss and incidence or severity of stem canker and light leaf spot in winter oilseed rape were analysed by correlation and regression analyses, using data from experiments at Rothamsted, England in 1992/93, 1994/95 and 1995/96. Growth stages (GS) 6,3/6,4 and 4,0/4,5 were identified as the critical points for relating percentage yield loss to stem canker and light leaf spot (on stems), respectively. Critical point (CP) and area under disease progress curve (AUDPC) models relating percentage yield loss to combined incidence or severity of stem canker and light leaf spot (stems) in each experiment were constructed by linear regression. There were no differences in the CP models for incidence between 1992/93, 1994/95 and 1995/96 experiments, or in the AUDPC models for incidence between 1992/93 and 1994/95 experiments. Therefore, a general CP model relating percentage yield loss (,Y) to combined incidence of stem canker (Si) at GS 6,3/6,4 and light leaf spot (stems) (Li) at GS 4,0/4,5 was constructed using data from the three experiments: ,Y = 0·85 + 0·079Si + 0·065Li (R2 = 43·7%, P < 0·001, 92 df). A general AUDPC model relating ,Y to the AUDPC of combined incidence of stem canker (Sia) from GS 5·7 to GS 6·5 and light leaf spot (stems) (Lia) from GS 4·0 to GS 6·3 was constructed using data from the 1992/93 and 1994/95 experiments: ,Y = 0·07 + 0·00096Sia + 0·0026Lia (R2 = 43·6%, P < 0·001, 68 df). These two general yield-loss models were tested with data from Rothamsted in 1993/94 and Boxworth in 1992/93. The predictive accuracy of the CP model based on combined incidence of stem canker and light leaf spot (stems) was better than that of the AUDPC model. Yield losses predicted by summing the estimates from individual models for incidence of stem canker alone (GS 6,3/6,4) and light leaf spot alone (on leaves at GS 3,3) were greater than observed yield losses in experiments at Rothamsted in 1992/93, 1993/94, 1994/95 and 1995/96 and at Boxworth in 1992/93. [source] Analysis of leaf appearance, leaf death and phoma leaf spot, caused by Leptosphaeria maculans, on oilseed rape (Brassica napus) cultivarsANNALS OF APPLIED BIOLOGY, Issue 1 2010S.J. Powers Development of phoma leaf spot (caused by Leptosphaeria maculans) on winter oilseed rape (canola, Brassica napus) was assessed in two experiments at Rothamsted in successive years (2003,04 and 2004,05 growing seasons). Both experiments compared oilseed rape cultivars Eurol, Darmor, Canberra and Lipton, which differ in their resistance to L. maculans. Data were analysed to describe disease development in terms of increasing numbers of leaves affected over thermal time from sowing. The cultivars showed similar patterns of leaf spot development in the 2003,04 experiment when inoculum concentration was relatively low (up to 133 ascospores m,3 air), Darmor developing 5.3 diseased leaves per plant by 5 May 2004, Canberra 6.6, Eurol 6.8 and Lipton 7.5. Inoculum concentration was up to sevenfold greater in 2004,05, with Eurol and Darmor developing 2.4 diseased leaves per plant by 16 February 2005, whereas Lipton and Canberra developed 2.8 and 3.0 diseased leaves, respectively. Based on three defined periods of crop development, a piece-wise linear statistical model was applied to the progress of the leaf spot disease (cumulative diseased leaves) in relation to appearance (,birth') and death of leaves for individual plants of each cultivar. Estimates of the thermal time from sowing until appearance of the first leaf or death of the first leaf, the rate of increase in number of diseased leaves and the area under the disease progress line (AUDPL) for the first time period were made. In 2004,05, Canberra (1025 leaves ×°C days) and Lipton (879) had greater AUDPL values than Eurol (427) and Darmor (598). For Darmor and Lipton, the severity of leaf spotting could be related to the severity of stem canker at harvest. Eurol had less leaf spotting but severe stem canker, whereas Canberra had more leaf spotting but less severe canker. [source] Effects of temperature and rainfall on date of release of ascospores of Leptosphaeria maculans (phoma stem canker) from winter oilseed rape (Brassica napus) debris in the UKANNALS OF APPLIED BIOLOGY, Issue 1 2007Y.J. Huang Abstract Data from a controlled environment experiment investigating effects of temperature on maturation of Leptosphaeria maculans pseudothecia were used to derive equations describing the times until 30% or 50% of pseudothecia were mature as a function of temperature. A wetness sensor was developed to estimate the oilseed rape debris wetness and operated with debris exposed in natural conditions in 2000 and 2001. The maturation of L. maculans pseudothecia on debris and concentrations of airborne L. maculans ascospores were observed from 1999 to 2004. There were considerable differences between years, with the first mature pseudothecia observed in September in most years. There were linear relationships between the first date when 10% of maximum ascospore release was observed and the dates when 30% or 50% of pseudothecia were mature. By summing the daily temperature-dependent rate of pseudothecial maturation for days after 1 August with rainfall >0.5 mm, the dates when 30% or 50% of pseudothecia were mature were predicted. There was good agreement between predicted and observed dates when 30% or 50% of pseudothecia were mature. These equations for predicting the timing of L. maculans ascospore release could be incorporated into schemes for forecasting, in autumn, the severity of phoma stem canker epidemics in the following spring/summer in the UK. [source]
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