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Mildew
Kinds of Mildew Terms modified by Mildew Selected AbstractsIdentification and Mapping of Two New Genes Conferring Resistance to Powdery Mildew from Aegilops tauschii (Coss.) SchmalJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 10 2006Xiao-Li Sun Abstract Two powdery mildew resistance genes were identified from Aegilops tauschii accessions Y201 and Y212 and mapped using two different F2 populations derived from the crosses between susceptible accession Y2272 and Y201, and susceptible accession Y2263 and Y212. Genetic analysis of resistance to powdery mildew indicated that the resistance of Y201 was controlled by a single dominant gene, whereas the resistance of Y212 was controlled by a single recessive gene. We have temporarily designated these genes as PmY201 and PmY212, respectively. By bulk segregation analysis, six microsatellite markers including Xgwm174, cfd26, cfd57, cfd102, Xgwm583 and Xgwm639 were found to be linked to PmY201 with genetic distances of 5.2, 7.7, 9.6, 12.5, 20.2 and 22.1 cM, respectively. Five SSR markers, including cfd57, Xgwm182, cfd7, cfd102, and cfd12, were found to be linked to PmY212 with distances of 5.6, 7.2, 11.5, 14.7, and 18.5 cM, respectively. According to the locations of the linked markers, the two resistance genes were located in the 5DL region. Based on the chromosomal locations and the resistance patterns of the two genes, we propose that PmY201 and PmY212 are two novel powdery mildew resistance genes, and are suitable for marker-assisted selection. (Managing editor: Ya-Qin Han) [source] Introgression of Resistance to Powdery Mildew Conferred by Chromosome 2R by Crossing Wheat Nullisomic 2D with RyeJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 7 2006Diao-Guo An Abstract Using the nullisomic back-cross procedure, four wheat-rye chromosome substitution 2R (2D) lines with different agronomic performance, designated WR02-145-1, WR01-145-2, WR02-145-3, and WR02-145-4, were produced from a cross between 2D nullisomic wheat (Triticum aestivum L. cv. "Xiaoyan 6") and rye (Secale cereale L. cv. "German White"). The chromosomal constitution of 2n=42=21 in WR02-145 lines was confirmed by cytological and molecular cytogenetic methods. Using genomic in situ hybridization on root tip chromosome preparations, a pair of intact rye chromosomes was detected in the WR02-145 lines. PCR using chromosome-specific primers confirmed the presence of 2R chromosomes of rye in these wheat-rye lines, indicating that WR02-145 lines are disomic chromosome substitution lines 2R(2D). The WR02-145 lines are resistant to the powdery mildew (Erysiphe graminis DC. f. sp. tritici E. Marchal) isolates prevalent in northern China and may possess gene(s) for resistance to powdery mildew, which differ from the previously identified Pm7 gene located on chromosome 2RL. The newly developed "Xiaoyan 6"- "German White" 2R (2D) chromosome substitution lines are genetically stable, show desirable agronomic traits, and are expected to be useful in wheat improvement. (Managing editor: Li-Hui Zhao) [source] Lipid Peroxidation and Antioxidant Activities Involved in Resistance Response against Downy Mildew in Opium PoppyJOURNAL OF PHYTOPATHOLOGY, Issue 2 2010Mukesh K. Dubey Abstract The aim of this study was to observe the lipid peroxidation (LP) of cell membranes and antioxidant systems in response to inoculation of Peronospora arborescens causing downy mildew (DM) in opium poppy. Contents of the LP product, malondialdehyde (MDA) and antioxidant glutathione (GSH) were determined in leaves of two opium poppy genotypes, Pps-1 (highly resistant to DM) and Jawahar-16 (highly susceptible to DM) at different time intervals after inoculation (12 h, 24 h, 48 h and 72 h). The provided GSH content corresponded to that of total non-protein sulfhydryl groups. In leaves of Jawahar-16, a significant decrease in concentration of GSH and a persistent increase in concentration of MDA were recorded after inoculation in comparison to leaves of control plants. The continuous decrease in GSH content contributed to damage of cell membranes leading to disease development in Jawahar-16. On the other hand in a resistant genotype (Pps-1), initially at 12 h after inoculation (hai) the level of GSH was found to be high, but a transient and highly significant decrease in content of GSH and increase in content of MDA was observed at 24 hai in comparison to control plants of same genotype and also in comparison to inoculated plants of susceptible genotype (Jawahar-16). These results indicate that generation of GSH and MDA is negatively correlated during the infection process as found in the case of DM-resistant genotype Pps-1 at 24hai, which also suggests an increased need by the host plant for oxidative stress, required for hypersensitive response mediated defense mechanism. [source] Characterization of Reactions to Powdery Mildew (Podosphaera pannosa) in Resistant and Susceptible Rose GenotypesJOURNAL OF PHYTOPATHOLOGY, Issue 5 2007A. Dewitte Abstract Fungal development of powdery mildew Podosphaera pannosa (Wallr.: Fr.) de Bary on rose leaves depends on constitutive or induced resistance mechanisms present in attacked rose genotypes. The relationship between fungal development and plant resistance was investigated microscopically on young greenhouse leaves of four rose genotypes with different levels of resistance: Rosa wichuraiana, R. laevigata anemoides and R. hybrida cultivars ,Excelsa' and ,Gomery'. Induced plant reactions, hydrogen peroxide production and cross sections through infected leaves were examined. The variation in development of the fungus on these rose genotypes depended on the relative presence of normal haustoria, abnormal haustoria, induced cell reactions, papilla formation or physical barriers. Formation of papillae could arrest up to one third of the successful penetrations. Papillae formation was often succeeded by total cell reaction. Abnormal haustoria were detected as rudimentary haustoria, haustoria with abnormal shape or haustoria without extra haustorial matrix. Post-haustorial cell reactions, with and without cell collapse, were detected. In non-collapsed cells, appositions were directed to both cell wall and haustorium. This was followed by accumulation of non-identified, probably antifungal compounds. Both single and multicell reactions occurred. Hydrogen peroxide was detected during papilla formation and induced cell reactions. [source] Leaf Disc Inoculation, a Fast and Precise Test for the Screening of Metalaxyl Tolerance in Sunflower Downy MildewJOURNAL OF PHYTOPATHOLOGY, Issue 6 2001B. Rozynek A new method, based on leaf disc inoculation, was developed for the screening of metalaxyl tolerance in field isolates of Plasmopara halstedii. High-pressure liquid chromatography (HPLC) was used to determine the fungicide concentration in the inoculation medium and in the incubated leaf tissue over the test period. These measurements revealed that the fungicide concentration inside the leaf tissue within 24 h had adjusted to the concentration in the outer medium and remained constant for the time of cultivation over a period of more than 11 days. In contrast to whole seedling tests with application of the fungicide via seed dressing, the leaf disc method allows precise quantification of the effective fungicide concentration at the site of infection and is less space and time consuming. Metalaxyl tolerance of P. halstedii isolates was gradually determined according to the sporulation of the pathogen on sunflower leaf discs in the presence of increasing fungicide concentrations. Isolates collected in South Germany showed no tolerance and sporulation was prohibited when tests were carried out at 0.02 ,g (a.i.)/ml of metalaxyl or more. In contrast, a tolerant French isolate developed sporangia on leaf discs incubated in a metalaxyl solution of 100 ,g (a.i.)/ml. [source] Variation in Resistance of Camelina (Camelina sativa [L.] Crtz.) to Downy Mildew (Peronospora camelinae Gäum.)JOURNAL OF PHYTOPATHOLOGY, Issue 3-4 2001Vollmann Camelina (Camelina sativa) is a potential oilseed crop for both food and non-food utilization cultivated on a limited acreage in Europe and North America. An important low-input feature of camelina is its high level of resistance against plant diseases, which may partly be due to the production of antimicrobially efficient phytoalexins. In Central European countries such as Austria, downy mildew (Peronospora camelinae) is the only disease of camelina which has been found repeatedly, whereas other diseases and pests have been observed only occasionally. Therefore, the genotypic variation of downy mildew incidence was evaluated in two camelina field experiments carried out within a breeding programme. In both experiments, totally resistant breeding lines were identified and a continuous pattern of variation in disease incidence was observed, suggesting a horizontal type of resistance. In bi-parental populations, disease incidence of progeny appeared to be associated with disease scores of the parent genotypes, and transgressive segregation in disease incidence was also found. In 1998, the rate of downy mildew in camelina was lower than in 1999; in the latter growing season, grain yield was significantly affected by the disease, whereas other agronomic characters remained unaffected. Variation der Resistenz von Leindotter (Camelina sativa[L.] Crtz.) gegen Falschen Mehltau (Peronospora camelinae Gäum.) Leindotter (Camelina sativa) ist eine Ölpflanze, die zur Nahrungsmittelherstellung und für andere Zwecke genutzt werden kann und in Europa und Nordamerika auf relativ kleiner Fläche angebaut wird. Ein wichtiges Low-Input-Merkmal des Leindotters ist seine hohe Krankheitsresistenz, die vermutlich teilweise auf die Bildung antimikrobiell wirksamer Phytoalexine zurückgeht. In Österreich und anderen Ländern Mitteleuropas ist Falscher Mehltau (Peronospora camelinae) die einzige regelmäßig anzutreffende Krankheit des Leindotters, andere Krankheiten und Schädlinge werden nur gelegentlich beobachtet. Daher wurde die genotypische Variation der Inzidenz des Falschen Mehltaus im Rahmen eines Leindotter-Züchtungsprogramms in zwei Feldversuchen geprüft. In beiden Versuchen wurden vollständig resistente Zuchtlinien identifiziert, und ein kontinuierliches Variationsmuster der Krankheitsresistenz wurde beobachtet, was auf horizontale Resistenz schließen läßt. In biparentalen Populationen war die Befallshänfigkeit bei den Nachkommen offenbar mit den Boniturwerten der elterlichen Genotypen assoziiert, und bei der Befallshänfigkeit wurde auch eine transgressive Aufspaltung beobachtet. 1998 war der Befall des Leindotters mit Falschem Mehltau geringer als 1999; im letztgenannten Jahr war der Kornertrag infolge der Krankheit deutlich verringert, während andere agronomische Merkmale unbeeinflußt blieben. [source] Utricularia (Lentibulariaceae) , a New Host Plant Genus of Powdery Mildew (Sphaerotheca sp.)JOURNAL OF PHYTOPATHOLOGY, Issue 3-4 2001Lebeda Symptoms of powdery mildew infections were recorded on a group of 15 Utricularia species cultivated in a glasshouse. A white superficial mycelium formed rings around the peduncles and also occurred on both sides of the leaves of several species. The microscopic examination proved that the fungus belonged to the powdery mildews , Erysiphales, only the anamorph was observed. Its morphological characters are typical for powdery mildews from the tribe Cystotheceae. Conidia were able to cause infections on cotyledons of susceptible Cucumis sativus cv. Stela F1. Based on all observations, it is very probable that this fungus belongs to the genus Sphaerotheca. This is the first report of a powdery mildew on Utricularia spp. and the family Lentibulariaceae. Utricularia(Lentibulariaceae) , eine neue Wirtspflanzengattung des Echten Mehltaus (Sphaerothecasp.) Symptome von Infektionen mit dem Echten Mehltau wurden bei einer Gruppe von 15 in einem Gewächshaus gehaltenen Utricularia -Arten festgestellt. Ein weißes oberflächliches Myzel bildete Ringe um die Blütenstandsstiele und trat bei verschiedenen Arten auch auf beiden Seiten der Blätter auf. Mikroskopische Untersuchungen ergaben, daß es sich um einen Echten Mehltaupilz (Erysiphales) handelte; ausschließlich die Anamorph wurde beobachtet. Die morphologischen Merkmale sind typisch für Echte Mehltaupilze vom Stamm Cystotheceae. Die Konidien konnten auch Infektionen auf den Keimblättern anfälliger Pflanzen von Cucumis sativus cv. Stela F1 auslösen. Auf der Grundlage aller Beobachtungen erscheint es als sehr wahrscheinlich, daß dieser Pilz der Gattung Sphaerotheca angehört. Dies ist der erste Bericht über Echten Mehltau an Utricularia spp. und der Familie Lentibulariaceae. [source] A Contribution to the Identity of Rhododendron Powdery Mildew in EuropeJOURNAL OF PHYTOPATHOLOGY, Issue 1 2000A. J. Inman Abstract Rhododendron powdery mildew has caused serious disease on outdoor Rhododendron in Europe since 1981 yet its identity and origins are still uncertain. Light and scanning electron microscope studies continued previous evidence that conidial specimens on outdoor Rhododendron in Europe are morphologically similar. They could all be placed into the newly erected anamorph taxon. Oidium subgenus Pseudoidium. Cleisiothecia of Microsphaera azaleae on deciduous azalea (Rhododendron luteum) and evergreen rhododendron (Rhododendron hybrid and Rhododendron fortunei) are described in detail for the first time in Europe from Bonn, Germany, together with the previously undescribed anamorph. An earlier record of ,M. azaleae' from Belgium was shown to be a new species, here described as Microsphaera digitata sp. nov. The pseudoidium anamorphs associated with both M. azaleae and M. digitata were similar to those examined on outdoor Rhododendron in Europe. They all conformed to the description of Oidium ericinum from Rhododendron and other Ericaceae. These two Microsphaera species are the first rhododendron powdery mildews in Europe for which the teleomorph-anamorph connections have been described. The possible identities of rhododendron powdery mildews in Europe are discussed. Zusammenfassuiig Ein Beitrag zur Identität des Echten Mehltaus an Rhododendron in Europa Seit 1981 ist der Echte Mehllau der Rhododendron cine bedeutende Krankheit an Freiland- Rhododendron in Europa. obwohl dessen Identität und Herkunft noch unsicher ist. Licht-und rasterelektronenmikroskopische Untersuehungen haben frühere Ergebnisse bestätigt,dass es eine morphologischc Similarilät unten den von Freiland- Rhododendron gewonnen Isolaten gibt. Alle Isolate konnten in dem neuen errichtetcn Anamorphe-Taxon Oidium subgenus Pseudoidium zugeordnet werden. Die Kleislothecien von Microsphaera azaleae an Aizaleen (Rhododendron luteum) sowie an immergrünen Rhododendron (Rhododendron-Hybride und Rhododendron fortunei), die in Bonn. Deutschland gesammelt worden waren. werden zum ersten Mai detalliert beschrieben, zusammen mit dem vorher noch nicht beschriebenen Anamorph. Eine frühere Beschreibung von ,M. azaleae' in Belgien konnte als eine neue Art identifiziert werden, hier als Microsphaera digitata sp. nov. beschrieben. Die Pseudoidium-Amimorphe. die mit M. azaleae und M. digitata assoziiert waren. ähnelten den untersuchlen europäischen FrcWand-Rhododendron. Alle konnlen als Oidium ericinum, bekannt von Rhododendron und anderen Ericaceaen. bestimmt werden. Diese Microsphaera -Spezies sind die ersten Echter Mehltau Arten in Europa, wofür die Teleomorph-Anamorph-Vebindungen beschrieben worden sind. Diskuticrt werden auch die möglichen Identilälen von den Echter Mehllau Arten in Europa. [source] Functional variation in a disease resistance gene in populations of Arabidopsis thalianaMOLECULAR ECOLOGY, Issue 22 2008T. H. JORGENSEN Abstract Analyses of functional genetic diversity in natural populations may provide important new insights into gene function and are necessary to understand the evolutionary processes maintaining diversity itself. The importance of including diversity within and between local populations in such studies is often ignored although many of the processes affecting genetic diversity act on this scale. Here we examine the molecular diversity in RPW8 (Recognition of Powdery Mildew), a gene conferring broad-spectrum resistance to powdery mildews in Arabidopsis thaliana stock-center accessions. Our eight UK study populations of the weedy A. thaliana were from locations judged to be subject to a minimum of anthropogenic disturbance and potentially long established. The majority of populations comprised considerable variation both in disease phenotype and RPW8 genotype. Although resistant individuals shared a major RPW8 genotype, no single allele was uniquely associated with resistance. It is concluded that RPW8 is an essential component of resistance to powdery mildews in A. thaliana, but not the only genetic factor involved in this process. No signature of selection was detected at RPW8 with a microsatellite multilocus test using an empirical null model. Unlike many previous studies of this model plant species, we found high levels of genetic diversity and relatively low differentiation (FST = 0.31) between populations at 14 microsatellite markers. This is judged to be due to our sampling being aimed at potentially long established populations and highlights the importance of population choice for studies of genetic diversity within this species. [source] Associations between fungal and abiotic leaf spotting and the presence of mlo alleles in barleyPLANT PATHOLOGY, Issue 6 2007J. C. Makepeace The hypothesis that the increased use of the powdery mildew-resistance gene mlo has caused the increase in spotting diseases of barley over the past 20 years was tested in field trials. Near-isogenic lines with alleles of the Mlo gene for susceptibility or resistance to mildew in two parental backgrounds were trialled at four sites in Scotland and two in Ireland that were prone to spotting diseases, over 3 consecutive years. Mildew was controlled by sprays with quinoxyfen. Disease levels were low in the trials, the two most important diseases being scald caused by Rhynchosporium secalis and ramularia leaf spot caused by Ramularia collo-cygni. There were high levels of abiotic spotting. Lines with mutant mlo alleles consistently developed less Rh. secalis and Ra. collo-cygni, but more abiotic spots. This study indicates that the mlo mildew-resistance gene has not alone been responsible for the rise in spotting diseases over the past 20 years. Possible reasons for the rise are discussed, including the interaction of the mlo gene with the environment. [source] A dynamic simulation model for powdery mildew epidemics on winter wheat,EPPO BULLETIN, Issue 3 2003V. Rossi A system dynamic model for epidemics of Blumeria graminis (powdery mildew) on wheat was elaborated, based on the interaction between stages of the disease cycle, weather conditions and host characteristics. The model simulates the progress of disease severity, expressed as a percentage of powdered leaf area, on individual leaves, with a time step of one day, as a result of two processes: the growth of fungal colonies already present on the leaves and the appearance of new colonies. By means of mathematical equations, air temperature, vapour pressure deficit, rainfall and wind are used to calculate incubation, latency and sporulation periods, the growth of pathogen colonies, infection and spore survival. Effects of host susceptibility to infection, and of leaf position within the plant canopy, are also included. Model validation was carried out by comparing model outputs with the dynamics of epidemics observed on winter wheat grown at several locations in northern Italy (1991,98). Simulations were performed using meteorological data measured in standard meteorological stations. As there was good agreement between model outputs and actual disease severity, the model can be considered a satisfactory simulator of the effect of environmental conditions on the progress of powdery mildew epidemics. [source] UV-B radiation constrains the photosynthesis of Quercus robur through impacts on the abundance of Microsphaera alphitoidesFOREST PATHOLOGY, Issue 5 2000By K. K. Newsham Summary Quercus robur saplings were exposed at an outdoor facility in the UK to supplemental levels of UV-B radiation (280,315 nm) under arrays of cellulose diacetate-filtered fluorescent lamps which also produced UV-A radiation (315,400 nm). Saplings were also exposed to supplemental UV-A radiation under arrays of polyester-filtered lamps and to ambient levels of solar radiation under arrays of unenergized lamps. The UV-B treatment was modulated to maintain a 30% elevation above the ambient level of erythemally weighted UV-B radiation. Naturally occurring infections by oak powdery mildew (Microsphaera alphitoides) were more abundant, and developed more rapidly, on lammas leaves of saplings which were exposed to treatment levels of UV-B radiation than on leaves of saplings exposed to supplemental UV-A or to ambient levels of solar radiation over 12 weeks in summer and autumn 1996. An analysis of leaf photosynthetic capacities revealed that M. alphitoides infection reduced the quantum efficiency of photosystem (PS) II by 14% at moderate irradiance. Although there was no direct effect of UV-B radiation on PSII photochemistry, exposure of saplings to supplemental UV-A radiation under polyester-filtered lamps resulted in a 17.5% decrease in PSII quantum efficiency, compared with saplings exposed to ambient solar radiation. The results from our study suggest that photosynthesis of Q. robur may be constrained by exposure to UV-B radiation in the natural environment through impacts on the abundance of M. alphitoides. [source] Downy mildew (Plasmopara viticola) epidemics on grapevine under climate changeGLOBAL CHANGE BIOLOGY, Issue 7 2006SALINARI FRANCESCA Abstract As climate is a key agro-ecosystem driving force, climate change could have a severe impact on agriculture. Many assessments have been carried out to date on the possible effects of climate change (temperature, precipitation and carbon dioxide concentration changes) on plant physiology. At present however, likely effects on plant pathogens have not been investigated deeply. The aim of this work was to simulate future scenarios of downy mildew (Plasmopara viticola) epidemics on grape under climate change, by combining a disease model to output from two general circulation models (GCMs). Model runs corresponding to the SRES-A2 emissions scenario, characterized by high projections of both population and greenhouse gas emissions from present to 2100, were chosen in order to investigate impacts of worst-case scenarios, among those currently available from IPCC. Three future decades were simulated (2030, 2050, 2080), using as baseline historical series of meteorological data collected from 1955 to 2001 in Acqui Terme, an important grape-growing area in the north-west of Italy. Both GCMs predicted increase of temperature and decrease of precipitation in this region. The simulations obtained by combining the disease model to the two GCM outputs predicted an increase of the disease pressure in each decade: more severe epidemics were a direct consequence of more favourable temperature conditions during the months of May and June. These negative effects of increasing temperatures more than counterbalanced the effects of precipitation reductions, which alone would have diminished disease pressure. Results suggested that, as adaptation response to future climate change, more attention would have to be paid in the management of early downy mildew infections; two more fungicide sprays were necessary under the most negative climate scenario, compared with present management regimes. At the same time, increased knowledge on the effects of climate change on host,pathogen interactions will be necessary to improve current predictions. [source] Approaching risk assessment of complex disease development in horse chestnut trees: a chemical ecologist's perspectiveJOURNAL OF APPLIED ENTOMOLOGY, Issue 5 2008A. B. Johne Abstract The chemo-ecological predispositions were investigated for the development of a complex disease on the basis of an insect,fungus mutualism using the system of horse chestnuts (Aesculus hippocastanum and Aesculus x carnea), the horse chestnut leaf miner (Cameraria ohridella) and the biotrophic powdery mildew (Erysiphe flexuosa). Both C. ohridella and E. flexuosa can appear on the same horse chestnut leaf tissue simultaneously. The olfactory detection of fungal infection by the insect, its ability to discriminate the potentially mutualistic fungus from other fungi and the impact of fungal infection on insect oviposition were examined. Gas chromatography coupled with mass spectroscopic and electroantennographic detection by C. ohridella (GC-MS/EAD) was used to assess the olfactory detection of fungal-infected A. hippocastanum and A. x carnea leaves by C. ohridella. Infection-related compounds, such as benzyl alcohol, dodecane, tridecane and methyl salicylate as well as fungus-related C8 compounds, are perceived by C. ohridella. The discrimination of E. flexuosa from another phytopathogenic fungus, such as Guignardia aesculi, is based primarily on the differing pattern of C8 compounds of these fungi. Oviposition on fungal-infected leaves of A. hippocastanum and leaves treated with fungal-related compounds showed that C. ohridella is able to respond to the modifications in the leaf volatile profiles of horse chestnuts caused by the different fungal infections. Thus, from the perception point of view, the necessary predispositions for the development of a close insect,fungus relation between the biotrophic fungus E. flexuosa and the leaf-mining insect C. ohridella are fulfilled. However, decreased oviposition on infected leaves does not enhance the selective contact between the species. As a consequence, an important predisposition for forming an insect,fungus mutualism is not fulfilled by these two species and, according to this approach, the risk of forming a complex disease can be assessed as low. [source] Evaluation of methods to control Phytonemus pallidus and Anthonomus rubi in organic strawberry productionJOURNAL OF APPLIED ENTOMOLOGY, Issue 8 2007R. Berglund Abstract:, Use of the predatory mite Neoseiulus cucumeris (Oudemans) (Acari, Phytoseiidae) and a fleece cover in combination with pyrethrum application showed potential for control of two important pests in organic production of strawberry (Fragaria × ananassa Duch.), although there were some unexpected interactions between pyrethrum and the release of N. cucumeris that need to be investigated further. Two cultivars, Honeoye and Cavendish, were treated with pyrethrum with or without fleece to control strawberry blossom weevils [Anthonomus rubi Herbst. (Col., Curculionidae)] and N. cucumeris was released to control strawberry mites [Phytonemus pallidus (Banks) (Acari, Tarsonemidae)]. Number of strawberry mites, number of flower buds damaged by the weevil, incidence of grey mould and powdery mildew, and fruit yield were measured in two consecutive fruiting seasons. In Honeoye, the fleece in combination with pyrethrum decreased the proportion of damaged buds by 11,23% and increased yield by 49,91 g per plant. When pyrethrum was used alone it did not influence the number of damaged buds or yield. This indicates that the combined treatment was more effective because of the fleece. In Cavendish, the fleece and pyrethrum treatments were not found to be effective. Almost no P. pallidus was found in Honeoye and the results were not analysable. In plots with Cavendish where N. cucumeris had been released, there were approximately 50% fewer P. pallidus from the end of August onwards in 2003. However, this response did not significantly influence the succeeding year's yield. The number of fruits infected with fungi was very low and no effects were observed for any of the treatments. [source] Effect of the Penicillium chrysogenum antifungal protein (PAF) on barley powdery mildew and wheat leaf rust pathogensJOURNAL OF BASIC MICROBIOLOGY, Issue 6 2008Balázs Barna Abstract The small molecular mass antifungal protein of Penicillium chrysogenum (PAF) inhibited the growths of two obligate biotrophic fungal pathogens, Blumeria graminis f. sp. hordei and Puccinia recondita f.sp. tritici and, hence, mitigated the symptoms of barley powdery mildew and wheat leaf rust infections, respectively. PAF also affected adversely the germination of B. graminis conidia and P. recondita uredospores causing degenerative branching of germ tubes. Since powdery mildews and rusts cause serious economic losses the potential applicability of PAF to control these plant diseases is promising. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Spatio-temporal analysis of plant pests in a greenhouse using a Bayesian approachAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 3 2010Christine Poncet 1The present study aimed to propose a method that can improve our understanding of pest outbreaks and spatio-temporal development in greenhouse crops. 2The experiment was carried out in a greenhouse rose crop grown under integrated pest management (IPM) for 21 months. The main pests observed were powdery mildew, two-spotted spider mites and western flower thrips. A quick visual sampling method was established to provide continuous monitoring of overall crop health. 3A Bayesian inferential approach was then used to analyse temporal and spatial heterogeneity in the occurrence of pests. Interactions between pest dynamics and properties of spatial evolutions were exhibited revealing the influence of biotic and abiotic factors on crop health. 4In the context of IPM, this information could be used to improve monitoring strategies by identifying periods or locations at risk. It could also facilitate the implementation of the whole IPM procedure through the identification of key factors that have a negative impact on overall crop health. [source] Identification and Mapping of Two New Genes Conferring Resistance to Powdery Mildew from Aegilops tauschii (Coss.) SchmalJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 10 2006Xiao-Li Sun Abstract Two powdery mildew resistance genes were identified from Aegilops tauschii accessions Y201 and Y212 and mapped using two different F2 populations derived from the crosses between susceptible accession Y2272 and Y201, and susceptible accession Y2263 and Y212. Genetic analysis of resistance to powdery mildew indicated that the resistance of Y201 was controlled by a single dominant gene, whereas the resistance of Y212 was controlled by a single recessive gene. We have temporarily designated these genes as PmY201 and PmY212, respectively. By bulk segregation analysis, six microsatellite markers including Xgwm174, cfd26, cfd57, cfd102, Xgwm583 and Xgwm639 were found to be linked to PmY201 with genetic distances of 5.2, 7.7, 9.6, 12.5, 20.2 and 22.1 cM, respectively. Five SSR markers, including cfd57, Xgwm182, cfd7, cfd102, and cfd12, were found to be linked to PmY212 with distances of 5.6, 7.2, 11.5, 14.7, and 18.5 cM, respectively. According to the locations of the linked markers, the two resistance genes were located in the 5DL region. Based on the chromosomal locations and the resistance patterns of the two genes, we propose that PmY201 and PmY212 are two novel powdery mildew resistance genes, and are suitable for marker-assisted selection. (Managing editor: Ya-Qin Han) [source] Introgression of Resistance to Powdery Mildew Conferred by Chromosome 2R by Crossing Wheat Nullisomic 2D with RyeJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 7 2006Diao-Guo An Abstract Using the nullisomic back-cross procedure, four wheat-rye chromosome substitution 2R (2D) lines with different agronomic performance, designated WR02-145-1, WR01-145-2, WR02-145-3, and WR02-145-4, were produced from a cross between 2D nullisomic wheat (Triticum aestivum L. cv. "Xiaoyan 6") and rye (Secale cereale L. cv. "German White"). The chromosomal constitution of 2n=42=21 in WR02-145 lines was confirmed by cytological and molecular cytogenetic methods. Using genomic in situ hybridization on root tip chromosome preparations, a pair of intact rye chromosomes was detected in the WR02-145 lines. PCR using chromosome-specific primers confirmed the presence of 2R chromosomes of rye in these wheat-rye lines, indicating that WR02-145 lines are disomic chromosome substitution lines 2R(2D). The WR02-145 lines are resistant to the powdery mildew (Erysiphe graminis DC. f. sp. tritici E. Marchal) isolates prevalent in northern China and may possess gene(s) for resistance to powdery mildew, which differ from the previously identified Pm7 gene located on chromosome 2RL. The newly developed "Xiaoyan 6"- "German White" 2R (2D) chromosome substitution lines are genetically stable, show desirable agronomic traits, and are expected to be useful in wheat improvement. (Managing editor: Li-Hui Zhao) [source] Lipid Peroxidation and Antioxidant Activities Involved in Resistance Response against Downy Mildew in Opium PoppyJOURNAL OF PHYTOPATHOLOGY, Issue 2 2010Mukesh K. Dubey Abstract The aim of this study was to observe the lipid peroxidation (LP) of cell membranes and antioxidant systems in response to inoculation of Peronospora arborescens causing downy mildew (DM) in opium poppy. Contents of the LP product, malondialdehyde (MDA) and antioxidant glutathione (GSH) were determined in leaves of two opium poppy genotypes, Pps-1 (highly resistant to DM) and Jawahar-16 (highly susceptible to DM) at different time intervals after inoculation (12 h, 24 h, 48 h and 72 h). The provided GSH content corresponded to that of total non-protein sulfhydryl groups. In leaves of Jawahar-16, a significant decrease in concentration of GSH and a persistent increase in concentration of MDA were recorded after inoculation in comparison to leaves of control plants. The continuous decrease in GSH content contributed to damage of cell membranes leading to disease development in Jawahar-16. On the other hand in a resistant genotype (Pps-1), initially at 12 h after inoculation (hai) the level of GSH was found to be high, but a transient and highly significant decrease in content of GSH and increase in content of MDA was observed at 24 hai in comparison to control plants of same genotype and also in comparison to inoculated plants of susceptible genotype (Jawahar-16). These results indicate that generation of GSH and MDA is negatively correlated during the infection process as found in the case of DM-resistant genotype Pps-1 at 24hai, which also suggests an increased need by the host plant for oxidative stress, required for hypersensitive response mediated defense mechanism. [source] Differentiation of Two Pathogens of Powdery Mildew Disease in Flowering Dogwood (Cornus florida) by PCR-mediated Method Based on ITS SequencesJOURNAL OF PHYTOPATHOLOGY, Issue 5 2009Ainong Shi Abstract Two fungi, Phyllactinia guttata and Erysiphe pulchra were identified as the pathogens of powdery mildew of flowering dogwood (Cornus florida). The objective of this research was to identify and distinguish the two fungi by developing species-specific primers. The internal transcribed spacer (ITS) universal primers and a series of species-specific primers designed from the ITS regions were used to evaluate and validate the two fungi causing powdery mildew in dogwood. Four primer pairs showed specificity to P. guttata and three to E. pulchra. These species-specific primer pairs can be used as molecular markers to provide diagnostic tools for detection and differentiation of the two powdery mildew pathogens in flowering dogwood. [source] Adaptation of the Forecasting Model DOWNCAST for Determination of Downy Mildew Epidemics of Oilseed Poppy in Tasmania, AustraliaJOURNAL OF PHYTOPATHOLOGY, Issue 4 2008J. B. Scott Abstract Peronospora cristata, causing downy mildew, has become an economically important pathogen of oilseed poppy (Papaver somniferum) since its first record in Tasmania in 1996. DOWNCAST, originally developed for downy mildew of onion, was evaluated for its ability to predict sporulation and infection of poppy by P. cristata. To assess the influence of the parameters within DOWNCAST, two modifications (POPCAST1 and POPCAST2) of the standard DOWNCAST model were also developed and tested. Initial accuracy of determination of sporulation events by DOWNCAST was 75%, while POPCAST1 (but not POPCAST2) was a significantly more accurate predictor of sporulation events (86%) than DOWNCAST (,2 = 5.74, P = 0.025). This increase in accuracy was attributed to increasing both the rainfall threshold inhibitory to sporulation from 0.2 to 3.0 mm, and the relative humidity threshold for induction and development of sporulation from 95% to 96%. While DOWNCAST, POPCAST1 and POPCAST2 had accuracies of infection determination of 65%, 80% and 75%, respectively, chi-squared analysis indicated no significant difference between models. Preliminary field evaluation indicated that POPCAST1 and POPCAST2 were more sensitive in detecting early infection events than DOWNCAST. Field observations indicated that conditions are frequently conducive for downy mildew spread, therefore the ability to predict early season infection events would allow growers to reduce initial infection rates, and thus inoculum loads later in the season. POPCAST1 and POPCAST2 represent a significant step towards the development of a predictive model for downy mildew in poppy crops. [source] Occurrence of Bremia lactucae in Natural Populations of Lactuca serriolaJOURNAL OF PHYTOPATHOLOGY, Issue 7 2004I. Petr, elová Abstract In the period 1996,2001 the natural occurrence of Bremia lactucae (lettuce downy mildew) on Asteraceae plants was studied in the Czech Republic. Lactuca serriola (prickly lettuce) is the most common naturally growing host species of B. lactucae. Infection of plants was recorded during the whole vegetation season with the first occurrence in April and last in November. Bremia lactucae was found on host plants in all developmental stages. High percentages of naturally infected populations of L. serriola were recorded. Host plants exhibited broad variation in phenotypic expression of disease symptoms and degree of infection, however, the intensity of infection was rather low in the majority of populations. Geographic distribution of B. lactucae was studied in the two main parts of Czech Republic, central and southern Moravia, and eastern, northern and central Bohemia. Bremia lactucae was recorded in all these areas. Nevertheless, in the warmest parts of the Czech Republic (southern Moravia) only sporadic occurrence of the pathogen was recorded. Bremia lactucae infection on L. serriola and disease severity was judged also in relation to the type of habitat, and the size and density of host plant populations. However, no substantial differences among various habitats were found; only host plants growing in urban areas were frequently free of infection and the degree of infection was very low. Nevertheless, these plants were commonly infected with powdery mildew (Golovinomyces cichoracearum), which is most aggressive pathogen of this type of habitat. [source] Variation in Resistance of Camelina (Camelina sativa [L.] Crtz.) to Downy Mildew (Peronospora camelinae Gäum.)JOURNAL OF PHYTOPATHOLOGY, Issue 3-4 2001Vollmann Camelina (Camelina sativa) is a potential oilseed crop for both food and non-food utilization cultivated on a limited acreage in Europe and North America. An important low-input feature of camelina is its high level of resistance against plant diseases, which may partly be due to the production of antimicrobially efficient phytoalexins. In Central European countries such as Austria, downy mildew (Peronospora camelinae) is the only disease of camelina which has been found repeatedly, whereas other diseases and pests have been observed only occasionally. Therefore, the genotypic variation of downy mildew incidence was evaluated in two camelina field experiments carried out within a breeding programme. In both experiments, totally resistant breeding lines were identified and a continuous pattern of variation in disease incidence was observed, suggesting a horizontal type of resistance. In bi-parental populations, disease incidence of progeny appeared to be associated with disease scores of the parent genotypes, and transgressive segregation in disease incidence was also found. In 1998, the rate of downy mildew in camelina was lower than in 1999; in the latter growing season, grain yield was significantly affected by the disease, whereas other agronomic characters remained unaffected. Variation der Resistenz von Leindotter (Camelina sativa[L.] Crtz.) gegen Falschen Mehltau (Peronospora camelinae Gäum.) Leindotter (Camelina sativa) ist eine Ölpflanze, die zur Nahrungsmittelherstellung und für andere Zwecke genutzt werden kann und in Europa und Nordamerika auf relativ kleiner Fläche angebaut wird. Ein wichtiges Low-Input-Merkmal des Leindotters ist seine hohe Krankheitsresistenz, die vermutlich teilweise auf die Bildung antimikrobiell wirksamer Phytoalexine zurückgeht. In Österreich und anderen Ländern Mitteleuropas ist Falscher Mehltau (Peronospora camelinae) die einzige regelmäßig anzutreffende Krankheit des Leindotters, andere Krankheiten und Schädlinge werden nur gelegentlich beobachtet. Daher wurde die genotypische Variation der Inzidenz des Falschen Mehltaus im Rahmen eines Leindotter-Züchtungsprogramms in zwei Feldversuchen geprüft. In beiden Versuchen wurden vollständig resistente Zuchtlinien identifiziert, und ein kontinuierliches Variationsmuster der Krankheitsresistenz wurde beobachtet, was auf horizontale Resistenz schließen läßt. In biparentalen Populationen war die Befallshänfigkeit bei den Nachkommen offenbar mit den Boniturwerten der elterlichen Genotypen assoziiert, und bei der Befallshänfigkeit wurde auch eine transgressive Aufspaltung beobachtet. 1998 war der Befall des Leindotters mit Falschem Mehltau geringer als 1999; im letztgenannten Jahr war der Kornertrag infolge der Krankheit deutlich verringert, während andere agronomische Merkmale unbeeinflußt blieben. [source] Utricularia (Lentibulariaceae) , a New Host Plant Genus of Powdery Mildew (Sphaerotheca sp.)JOURNAL OF PHYTOPATHOLOGY, Issue 3-4 2001Lebeda Symptoms of powdery mildew infections were recorded on a group of 15 Utricularia species cultivated in a glasshouse. A white superficial mycelium formed rings around the peduncles and also occurred on both sides of the leaves of several species. The microscopic examination proved that the fungus belonged to the powdery mildews , Erysiphales, only the anamorph was observed. Its morphological characters are typical for powdery mildews from the tribe Cystotheceae. Conidia were able to cause infections on cotyledons of susceptible Cucumis sativus cv. Stela F1. Based on all observations, it is very probable that this fungus belongs to the genus Sphaerotheca. This is the first report of a powdery mildew on Utricularia spp. and the family Lentibulariaceae. Utricularia(Lentibulariaceae) , eine neue Wirtspflanzengattung des Echten Mehltaus (Sphaerothecasp.) Symptome von Infektionen mit dem Echten Mehltau wurden bei einer Gruppe von 15 in einem Gewächshaus gehaltenen Utricularia -Arten festgestellt. Ein weißes oberflächliches Myzel bildete Ringe um die Blütenstandsstiele und trat bei verschiedenen Arten auch auf beiden Seiten der Blätter auf. Mikroskopische Untersuchungen ergaben, daß es sich um einen Echten Mehltaupilz (Erysiphales) handelte; ausschließlich die Anamorph wurde beobachtet. Die morphologischen Merkmale sind typisch für Echte Mehltaupilze vom Stamm Cystotheceae. Die Konidien konnten auch Infektionen auf den Keimblättern anfälliger Pflanzen von Cucumis sativus cv. Stela F1 auslösen. Auf der Grundlage aller Beobachtungen erscheint es als sehr wahrscheinlich, daß dieser Pilz der Gattung Sphaerotheca angehört. Dies ist der erste Bericht über Echten Mehltau an Utricularia spp. und der Familie Lentibulariaceae. [source] Powdery Mildew Resistance in Barley Landraces from MoroccoJOURNAL OF PHYTOPATHOLOGY, Issue 5 2000J. H. Czembor Nineteen barley landraces collected from Morocco were screened for resistance to powdery mildew. The landraces originated from the collection at the Polish Gene Bank, IHAR Radzików, Poland. The fifteen landraces tested showed powdery mildew resistance reactions and 35 single plant lines were selected. Twenty-one of these lines were tested in the seedling stage with 30, four lines with 17 and another 10 lines with 23 differential isolates of powdery mildew, respectively. The isolates were chosen according to their virulence spectra observed on the Pallas isolines differential set. Nine lines (E 1029-1-1, E 1042-2-2, E 1050-1-1, E 1054-5-1, E 1056-2-5, E 1056-3-1, E 1061-1-1, E 1061-1-3 and E 1067-1-2) which originated from seven landraces showed resistance to all prevalent European powdery mildew virulence genes. The most frequent score was 2 and 16 lines showed this reaction for inoculation with most isolates used. The distribution of reaction type indicated that about 77% of all reaction types observed were classified as powdery mildew resistance (scores 0, 1 and 2). In all lines the presence of unknown genes alone or in combinations with specific ones was postulated. Four different resistance alleles (Mlat, Mla6, Mla14 and Mla12) were postulated to be present in 10 tested lines alone or in combination. Alleles Mlat, Mla6 and Mla14 were postulated to be present in four and Mla12 in two tested lines, respectively. The value of barley landraces for diversification of resistance genes for powdery mildew is discussed. Zusammenfassung Neunzehn Gerstenlandrassen aus Marokko wurden auf ihre Resistenz gegenüber dem Echten Mehltau untersucht. Diese Landrassen wurden in der Sammlung der Polish Gene Bank, IHAR, Radzikow, Polen aufbewahrt. Fünfzehn der geprüften Rassen zeigten Echte Mehltau-Resistenz und davon wurden 35 einzelne Pflanzenlinien selektiert. 21 dieser Linien wurden als Sämlinge gegenüber 30, 4 Linien gegenüber 17 und weitere 10 Linien gegenüber 23 differentialen Echten Mehltau-Isolaten geprüft. Diese Isolate wurden an Hand von ihren Virulenzspektren bei dem Pallas-Isoline-Differential-Set ausgewählt. Bei 9 Linien (E 1029-1-1, E 1042-2-2, E 1050-1-1, E 1054-5-1,E1056-2-5, E 10456-3-1, E 1061-1, E 1061-1-3 sowie E 1067-1-2), die von 7 Landrassen stammten, konnte eine Resistenz gegenüber allen bedeutenden europäischen Virulenzgenen festgestellt werden. Am häufigsten wurde die Resistenznote 2 vergeben, 16 Linien zeigten diese Reaktion nach einer Inokulation mit den meisten angewandten Isolaten. Die Verteilung des Reaktionstyps deutete daraufhin, dass ca. 77% der beobachteten Reaktionstypen als Echte Mehltau-Resistenz (die Note 0,1 und 2) eingestuft werden konnten. Das Vorkommen von unbekannten Genen, ob alleine oder in Kombination mit einem spezifischen Gen, wurde in allen Linien postuliert. Ebenfalls postuliert wurde das Vorhandensein von vier unterschiedlichen Resistenzallelen (Mlat, Mla6, Mla14 und Mla12), entweder alleine oder in Kombinationen, in den 10 geprüften Linien. Die Allele Mlat, Mla6 und Mla14 wurden in 4, das Allel Mla12 in 2 der getesteten Linien postuliert. Die Relevanz von Landrassen in der Erweiterung von Resitenzgenen gegenüber dem Echten Mehltau in der Gerste wird diskutiert. [source] A Contribution to the Identity of Rhododendron Powdery Mildew in EuropeJOURNAL OF PHYTOPATHOLOGY, Issue 1 2000A. J. Inman Abstract Rhododendron powdery mildew has caused serious disease on outdoor Rhododendron in Europe since 1981 yet its identity and origins are still uncertain. Light and scanning electron microscope studies continued previous evidence that conidial specimens on outdoor Rhododendron in Europe are morphologically similar. They could all be placed into the newly erected anamorph taxon. Oidium subgenus Pseudoidium. Cleisiothecia of Microsphaera azaleae on deciduous azalea (Rhododendron luteum) and evergreen rhododendron (Rhododendron hybrid and Rhododendron fortunei) are described in detail for the first time in Europe from Bonn, Germany, together with the previously undescribed anamorph. An earlier record of ,M. azaleae' from Belgium was shown to be a new species, here described as Microsphaera digitata sp. nov. The pseudoidium anamorphs associated with both M. azaleae and M. digitata were similar to those examined on outdoor Rhododendron in Europe. They all conformed to the description of Oidium ericinum from Rhododendron and other Ericaceae. These two Microsphaera species are the first rhododendron powdery mildews in Europe for which the teleomorph-anamorph connections have been described. The possible identities of rhododendron powdery mildews in Europe are discussed. Zusammenfassuiig Ein Beitrag zur Identität des Echten Mehltaus an Rhododendron in Europa Seit 1981 ist der Echte Mehllau der Rhododendron cine bedeutende Krankheit an Freiland- Rhododendron in Europa. obwohl dessen Identität und Herkunft noch unsicher ist. Licht-und rasterelektronenmikroskopische Untersuehungen haben frühere Ergebnisse bestätigt,dass es eine morphologischc Similarilät unten den von Freiland- Rhododendron gewonnen Isolaten gibt. Alle Isolate konnten in dem neuen errichtetcn Anamorphe-Taxon Oidium subgenus Pseudoidium zugeordnet werden. Die Kleislothecien von Microsphaera azaleae an Aizaleen (Rhododendron luteum) sowie an immergrünen Rhododendron (Rhododendron-Hybride und Rhododendron fortunei), die in Bonn. Deutschland gesammelt worden waren. werden zum ersten Mai detalliert beschrieben, zusammen mit dem vorher noch nicht beschriebenen Anamorph. Eine frühere Beschreibung von ,M. azaleae' in Belgien konnte als eine neue Art identifiziert werden, hier als Microsphaera digitata sp. nov. beschrieben. Die Pseudoidium-Amimorphe. die mit M. azaleae und M. digitata assoziiert waren. ähnelten den untersuchlen europäischen FrcWand-Rhododendron. Alle konnlen als Oidium ericinum, bekannt von Rhododendron und anderen Ericaceaen. bestimmt werden. Diese Microsphaera -Spezies sind die ersten Echter Mehltau Arten in Europa, wofür die Teleomorph-Anamorph-Vebindungen beschrieben worden sind. Diskuticrt werden auch die möglichen Identilälen von den Echter Mehllau Arten in Europa. [source] Soil properties, but not plant nutrients (N, P, K) interact with chemically induced resistance against powdery mildew in barleyJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 3 2003Joachim Wiese Abstract Chemically induced resistance is a promising method of plant protection against diseases, which can be triggered by systemically acting chemical inducers such as BTH (benzo(1, 2, 3)thiadiazole-carbothioic-acid-S-methylester). BTH is commercially distributed as a 50,% formulation, called Bion®. The uncertain success of Bion® application in controlling infection by powdery mildew is a major obstacle in using induced resistance for plant protection in agriculture. This study aimed to investigate the effect of soil properties, selected macronutrients (N, P, and K), and addition of organic matter on induced resistance and to identify possible factors responsible for the high variability of BTH effect under field conditions. A pot experiment under open-air conditions was set up using the pathosystem Hordeum vulgare cv. Ingrid / Blumeria graminis f. sp. hordei race A6. The different soils strongly affected the resistance of barley plants against powdery mildew after BTH treatment. The infection of barley by powdery mildew was lower than on all other soils when grown on an acid forest soil which was limed up to pH 4.9, even after BTH treatment. A reproducible induction of pathogen resistance by BTH was shown only on a mineral soil (Kleinlinden) with a negligible C content. Application of N, P, and K did not consistently affect the induction of resistance by BTH. The addition of green manure and compost led to an enhanced variability of resistance induction on the soil "Kleinlinden". Possible effects of soil microflora on resistance induction are discussed. Bodeneigenschaften, aber nicht Pflanzennährstoffe (N, P, K) interagieren mit der chemisch induzierten Resistenz gegen Gerstenmehltau in Gerste Chemisch induzierte Resistenz ist eine viel versprechende Methode im Pflanzenschutz, welche durch systemisch wirkende Substanzen wie BTH (Benzo(1, 2, 3)-thiadiazolcarbothion-Säure- S -Methylester) induziert werden kann. BTH ist die wirksame Komponente des kommerziell erhältlichen Produkts Bion®. Allerdings ist die Wirksicherheit von Bion® im Feld gering, wodurch die Anwendung des Produkts im Pflanzenschutz eingeschränkt ist. Das Ziel der vorliegenden Arbeit war es, den Einfluss verschiedener Böden, ausgewählter Makronährstoffe (N, P und K) und des Zusatzes von organischem Material zum Boden auf die induzierte Resistenz zu untersuchen und Faktoren zu identifizieren, die für die unsichere BTH-Wirkung im Feld verantwortlich sind. Dafür wurden Gefäßexperimente unter freilandähnlichen Bedingungen durchgeführt. In diesen wurde das Pathosystem Hordeum vulgare cv. Ingrid / Blumeria graminis f. sp. hordei Stamm A6 verwendet. Es wurde ein starker Einfluss des Bodens auf die Resistenz der Gerste gegen Gerstenmehltau nach BTH-Behandlung ermittelt. Die Mehltauinfektion von Gerste, welche auf einem sauren Waldboden kultiviert wurde, der auf einen pH-Wert von 4, 9 aufgekalkt worden war, war niedriger als auf allen anderen Böden, selbst nach BTH-Behandlung. Eine reproduzierbare Induktion der Pathogenresistenz durch BTH konnte nur auf einem Mineralboden mit vernachlässigbarem C-Gehalt gezeigt werden. Die Ernährung mit N, P und K hatte keinen konsistenten Einfluss auf die Resistenzinduktion mittels BTH. Der Zusatz von Kompost und Gründünger zum Boden ,Kleinlinden" erhöhte die Variabilität der Resistenzinduktion. Der mögliche Einfluss der Bodenmikroflora auf die Resistenzinduktion wird diskutiert. [source] Sugar-beet powdery mildew (Erysiphe betae)MOLECULAR PLANT PATHOLOGY, Issue 3 2002Sally Francis Summary Erysiphe betae causes sugar-beet powdery mildew, a serious fungal foliar disease resulting in sugar yield losses of up to 30%. The fungus occurs world-wide in all regions where sugar beet is grown and it also infects other edible beet crops, e.g. beetroots (garden beets). Unlike other powdery mildews, E. betae has so far received relatively little attention from pathologists and the precise mechanisms by which it infects its host remain unclear. Sources of genetic resistance have been identified in cultivated and wild Beta germplasm and molecular markers developed linked to Pm, the only single major R gene described so far, and also to QTL. Taxonomy:,Erysiphe betae (Vañha) Weltz.,Kingdom Fungi, Subdivision Ascomycotina, Class Pyrenomycetes, Order Erysiphales, Family Erysiphaceae, Genus Erysiphe. Identification:, Superficial persistent mycelium; unbranched erect conidiophores; conidia ripen singly, are hyaline, ovoid, 30,50 µm × 15,20 µm; cleistothecia globose, dark brown/black, 80,120 µm in diameter; mostly 4,8 asci per cleistothecium, mostly 2 or 3 spores per ascus. Host range:, A monophagous parasite specific to Beta species. Disease symptoms:, Infected foliage and inflorescences bear numerous powdery, white colonies. Under favourable environmental conditions the colonies coalesce, host tissue develops chlorosis and usually senesces early. Cleistothecia develop on heavily infected leaves in late summer and are small black/dark brown globose bodies resting on the mycelial surface. Control:, Chemical control and partial genetic resistance. [source] Transient expression of a vacuolar peroxidase increases susceptibility of epidermal barley cells to powdery mildewMOLECULAR PLANT PATHOLOGY, Issue 6 2001Brian Kåre Kristensen summary The expression of genes encoding the peroxidases, Prx7 and Prx8, is induced in barley leaf tissue after inoculation with the barley powdery mildew fungus, Blumeria graminis f.sp. hordei (DC) Speer (Bgh). The role of these peroxidases in general barley defence responses against fungal attack was investigated using a transient expression system. Colonization frequencies of Bgh on cells transfected with Prx7 or Prx8 expression-, mutant- or fusion-DNA constructs were compared to the frequencies on cells expressing a ,-glucuronidase (GUS) control construct. Twice the number of powdery mildew colonies were observed on cells expressing Prx7 as compared to control cells. Introduction of either mutant or truncated versions of Prx7 showed that decreased resistance against Bgh was dependent on the presence of the C-terminal signal peptide required for correct subcellular targeting, but not affected significantly by mutations in the catalytic centre. No impact on Bgh performance was observed after the introduction of Prx8 or mutant constructs. An enhanced accumulation of the apoplastic Prx8 was verified by immunocytology. These results indicate a more complex role of peroxidases in defence responses than was previously suspected. [source] | |||||||||||||||||||||||||||||||