Browsing by Subject "Plasmopara viticola"

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    Epidemiologische Aspekte der Falschen Mehltauinfektion durch Plasmopara viticola an Vitis
    (2007) Keil, Sven; Spring, Otmar
    The obligate biotrophic oomycete Plasmopara viticola (Berk. & Curt.) Berl. & de Toni causes downy mildew on grapevine. Plasmopara viticola is one of the economically most important pathogens in viticulture, with severe losses in yield of up to 70%. Existing prognosis models for plant protection in viticulture only allow yes/no statements on possible infection events in the vineyard. On the basis of these models, the severity of infections remain uncertain, although this represents a crucial point for an efficient application of fungicides. At low infestation severity, the application of protective fungicides at the end of the incubation period usually is sufficient. The low level of infestation can be tolerated and only further propagation of the pathogen must be prevented. In contrast, at high infestation severity curative fungicides have to be applied as soon as possible, because otherwise too much host tissue would be destroyed. Based on epidemiological studies and field experiments a prognostic concept has been designed, which enables the user to evaluate the relevance of infection events of grapevine downy mildew. This work has been carried out in the context of the research project ?Optimierung der Peronospora-Bekämpfung im Rebschutz auf der Basis eines erweiterten Prognosemodells (Forschungsvorhaben des Bundesministeriums für Ernährung, Landwirtschaft und Verbraucherschutz Nr. 514-33.54/01HS048)?. The developed concept was then integrated into the existing prognosis model and should support both consultants and winegrowers in using plant protection agents only in case of an expected increase of infestation frequency and severity. In this way, an effective and more economical use of fungicides is possible, which contributes to economic savings and reduces pesticide contamination of the environment. In the present study, aspects of sporangiogenesis, infestation of host tissue and hibernation, spreading of sporangia, interaction between vine leaves and sporangia as well as the climatic conditions during infection were analysed and evaluated with respect to the impact on epidemiology. The results improve existing literature data and deliver new insight to the epidemiology and biology of Plasmopara viticola.
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    Molekulare und biochemische Charakterisierung von NEP1 - ähnlichen Proteinen (NLPs) aus Plasmopara viticola
    (2017) Schumacher, Stefan; Vögele, Ralf
    Plasmopara viticola, the causal agent of grapevine downy mildew is one of the most important diseases in viticulture and leads to significant losses in crop in years with beneficial weather conditions. The molecular processes during the interaction between this pathogen and vine are yet poorly understood. Adopted pathogens achieve an infection by avoidance or suppression of plant innate immunity. This suppression takes place through pathogen secreted effector molecules, which can modulate plant defense mechanisms in all kinds of ways. One of these effector families are the necrosis and ethylene inducing peptide 1 – like proteins (NLP). These proteins occur in a vast variety of microorganisms and can on the one hand act as virulence factors and on the other hand induce a broad spectrum of defense responses in plants. In necrotrophic or hemibiotrophic pathogens these proteins are formed when the organism starts to feed from dead plant material. Beside these cytotoxic proteins many non-cytotoxic NLPs are known from hemibiotrophic or biotrophic microorganisms. However, the particular function of these NLPs is so far unknown. To date NLPs from Hyaloperonospora arabidopsidis, causal agent of downy mildew on the model plant Arabidopsis thaliana, are the only known example for these proteins from an obligate biotroph plant pathogen. These NLPs are not able to induce necrosis and their roll during infection by the pathogen is so far unknown. During this work two NLPs of complete size as well as one truncated version were identified in the genome of the obligate biotrophic oomycete Plasmopara viticola. During further experiments these proteins had been characterized by the use of molecular biological and biochemical techniques. The studies revealed a high degree of conservation of the corresponding genes isolated from several resistant and susceptible grapevine cultivars. Gene expression analysis showed high PvNLP expression during early time points of infection and even before first contact with host plant material, respectively. Necrosis-inducing activity of PvNLPs was neither observed in the model plant Nicotiana benthamiana nor in different susceptible and resistant Vitis species. To further investigate the reasons for the non-cytotoxic character of these proteins several experiments were conducted to clarify the relevance of different structural regions, their affinity to form homo- and hetero oligomers, as well as their subcellular localization. The crucial component for the lack of cytotoxicity was not identified. Neither the presence of a signal peptide nor a Nterminal region from another NLP with cytotoxic characteristics were able to form a necrosis inducing fusion protein with one of the identified NLPs from P. viticola. Formation of homodimers was observed for PvNLPs in vitro, but apparently does not occur during expression in planta. Furthermore PvNLPs are localized in the cytoplasm of N. benthamiana cells and show a possible association with the plant cell nucleus. This pattern of subcellular localization was also observed for a NLP with necrosis-inducing activity. The ability to induce plant innate immunity in Vitis could not be attested, suggesting a possible lack of the corresponding receptor in this plant genus. The results of this work further suggest a different role of non-cytotoxic NLPs which in P. viticola may fulfill a function during early infection stages ranging from zoospore release until the successful penetration of the host plant Vitis vinifera.
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    Weinblattmetabolite als Resistenzmarker für eine Plasmopara viticola Widerstandsfähigkeit
    (2024) Grünwald, Maike; Vögele, Ralf
    Downy mildew of grapevine is one of the most important diseases of the European grapevine Vitis vinifera LINNÉ supsp. vinifera. It is caused by the obligate biotrophic oomycete Plasmopara viticola Berl. & De Toni. American grapevines are largely resistant to downy mildew and may contribute in to the protection of susceptible vines against P. viticola. Therefore, this work deals with the metabolite profiling of resistance markers (RM) from volatile secondary metabolites of susceptible and resistant grapevines. 10 genotypes with different resistance to P. viticola were analysed. 3 different Vitis species (V. vinifera, V. riparia, V. labrusca) and some hybrid vines were analysed. The constitutive markers of 3 developmental stages (BBCH6, BBCH8, BBCH9) were determined. In addition, induced markers were analysed. Furthermore, the relationship between leaf position and the occurrence of RM was investigated. The used metabolomic methods were also applied to identify markers for leaf position. For metabolite profiling the grape leaves were analysed using GC-MS and were evaluated using non-targeted and targeted analytical methods. The comparison of the metabolite profiles showed that the developmental stage has the strongest influence on the metabolite profile and the influence of the leaf position is so small that it can be neglected. A total of 41 constitutive RMs were identified. The metabolites identified came from the substance classes of green leaf volatiles (GLV), norisoprenoids, benzoate derivatives, monoterpenoids, a furan and a sesquiterpene. It was elaborated, that GLV, norisoprenoids, benzoate derivatives and 2-ethylfuran were almost exclusively present in higher concentrations in resistant genotypes. Monoterpenoids and the sesquiterpene calacorene were mainly detected in higher concentrations in the susceptible genotypes of V. vinifera. Furthermore, it could be shown, that monoterpenoids were detected in significantly increased concentrations at the developmental stage BBCH6 in the susceptible V. vinifera. calacorene was never detected in BBCH6. It was only found in significantly increased concentrations in the later developmental stages of V. vinifera. GLVs are RM in the resistant genotypes such as V. labrusca and occur here exclusively at the later developmental stages, mainly at BBCH9. For the constitutive RMs from the classes of norisoprenoids, benzoate derivatives and furan, no dependence of the developmental stages and their occurrence was observed. 3 other metabolites were identified as RMs that showed a strong correlation with the developmental stage. They appeared initially in BBCH6 in significantly increased concentrations in susceptible V. vinifera, but in BBCH9 they showed significantly increased concentrations in the resistant V. labrusca genotypes. These RMs with changing correlation were geranyl acetone, terpineol, and (Z)-3-hexenal. The correlation between occurrence of the constitutive RMs and the developmental stages has not been described before. It is a new finding of this work that monoterpenoids occur as RMs in grapevines mainly at BBCH6 and GLV as well as sesquiterpenes were found as RMs mainly at BBCH9. Norisoprenoids, benzoate derivatives and furan occurred as RMs at all developmental stages tested. Furthermore, terpenoids occurred species-specifically more frequently in V. vinifera as constitutive RMs, whereas the furan 2-ethylfuran never appeared as a RM in V. vinifera. Benzoate derivatives and GLVs were most frequently detected as RMs in V. labrusca genotypes. Norisoprenoids appeared most frequently, but not exclusively, as RMs in V. riparia. The correlation between the occurrence of norisoprenoids as RMs and species specificity to V. riparia is a new finding of this work. Nevertheless, it should be briefly mentioned, that this species specificity refers exclusively to the classification as a constitutive RM. Monoterpenes are also part of the metabolite profile of V. labrusca as well as norisoprenoids are important flavour compounds in quality wines. 24 induced RMs were determined. Most of the induced RMs occurred in the fungus-resistant cultivar Regent and only six induced RMs in the resistant V. labrusca hybrid Blue Isabella and in V. riparia. For all RMs identified, it was searched for reports on bioactivity in publications. For 2-ethylfuran, an isomer mix of (Z)- and (E)-ocimene as well as cyclocitral, an inhibitory effect on P. viticola has already been published. Still, 20 compounds have been associated here for the first time with a resistance response to P. viticola infection. These are theaspirane, (E)-damascone, (E)-damascenone, dihydroedulan I, megastigmatrienone, sulcatone, carvomenthenal A, nonanol , (Z)-3-hexenyl acetate, p-cymenene, p-cymene, limonene, alloocimene, myrcene, citronellol, hotrienol, (Z)-rose oxide, geranium oxide and calacorene.