Browsing by Subject "Weinrebe"

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Epidemiologie des Esca-Erregers Phaeomoniella chlamydospora und eine neue Bekämpfungsmöglichkeit mittels eines Wundverschlusses aus elektrogesponnenen Polymeren
(2018) Molnar, Melanie; Vögele, Ralf
Esca disease has become a global thread for viticulture over the last decades. It is caused by a complex of at least three different wood-inhabitating fungi Phaeomoniella chlamydospora (Pch), Phaeoacremonium aleophilum (Pal), und Fomitiporia mediterranea (Fmed). For all these fungi wounds in wood are seen as the main entrance way, especially pruning wounds, which are caused by winter pruning. Currently, there are no effective control mechanisms available Therefore, it was the main aim of this project to test a new wound closure made of electrospun fibers, which shall be applied on the pruning wounds to build a physical barrier against invading spores. For evaluating the effectiveness of this treatment the epidemiology of the fungus Pch was investigated, as this fungus is one of the first of this complex invading the vine. For this purpose new molecular techniques have been developed to identify and differentiate Pch reliably. For epidemiologic studies the focus was placed on the occurrence of spores of Pch in the vineyards during the year. Spore traps were placed in vineyards of the Julius Kühn-Intitute which were showing severe symptoms of Esca and in vineyards which were free of foliar symptoms. Traps were analyzed during the whole three year project period on a weekly basis. In this study a new method was developed using a Pch- specific Nested-PCR (polymerase chain reaction) to analyze the spore traps instead of the usual method, in which the trapped spores are spread on media and counting germinated spores. The new Nested-PCR turned out to be a very fast, reliable and sensitive method. It was the first time Pch could be detected in a German vineyard year round. Spores of this fungus could be detected over the whole trial period. Furthermore, a collection of 16 Pch strains with origins from Germany, Italy and South Africa was analyzed using a set of 17 RAMS (random amplified microsatellites) primer to link each one with a unique haplotype. By using this method some polymorphisms formed a pattern which could be interpreted as length polymorphisms. Further analyses of the sequences showed that there are in fact length polymorphisms which are based on repeats of the same sequence. The combination of RAMS primers and the sequence analysis resulted in a finer differentiation of isolates. Primers were developed flanking these repetitive sequences to detect polymorphisms directly without a previous RAMS-analysis. In the end ten haplotypes and two clusters each containing three isolates were found. However, it was not possible to link haplotypes to their geographical origin to gain knowledge of the spread of the fungus. Markers found using the RAMS-analysis were used to differentiate the fungal spores trapped in the spore traps. Furthermore, spores were also compared with strains found in vines of the same vineyard to verify, if the spores were possibly released by fungi in the plants or if they had a different source. This direct analysis was successful in first trials and proofed the existence of different strains in the traps. For an exact classification more markers and primer pairs have to be developed suitable for analyzing spore traps. The epidemiologic survey of this pathogen clearly shows the necessity of a good working wound closure which has to be applied directly after pruning, as the spores are present all year round and especially at the time of winter pruning. For this purpose, different electrospun fibermats made of different fibers of lactic acid were tested under laboratory conditions and in greenhouses for their impermeableness against spores of Pch. During these tightness tests in the greenhouse the new developed Nested-PCR was used to exclude, within the scope of its detection limits, an already exiting infection of the tested plants and to confirm that the a new infection was caused by the applied strain of Pch. Furthermore the degradation and aging of the materials was tested under laboratory and field conditions. Fiber mats with an added amount of glycolic acid turned out to be less stable. Among the different materials fiber mats based on pure lactic acid turned out to be principally suitable to build an applicable and efficient wound closure. First trials in the vineyard confirmed this positive result. However, the long term effect of this treatment on the incidence of Esca disease in vineyards has to be proven.
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.
Grapevine Trunk Diseases : Epidemiologie und Molekulardiagnose wichtiger Esca-Erreger während der Pflanzguterzeugung
(2018) Haag, Nicolai; Vögele, Ralf
Esca is one of the most important grapevine trunk diseases (GTDs) worldwide. In Europe, the wood-inhabiting fungi Phaeomoniella chlamydospora (Pch), Phaeoacremonium aleophilum (Pch) and Fomitiporia mediterranea (Fmed) are considered the main causal agents of this disease. Even young vineyards and planting material can be affected by pathogens of Esca. So far, control possibilities were mainly limited to prophylactic measures, such as prevention of overly large pruning wounds, minimizing stress of affected grapevines and elimination of dead wood. By now, biological control is basically possible; its efficacy however, still remains to be fully proven under practical conditions. According to previous studies in Germany investigating the infection status of planting material, Pch is considered the most important causal agent for an early infection in grapevine nursery propagation. Based on this, the objective of the present study was to comprehensively assess the occurrence of Pch and other GTD-pathogens in grapevine wood and potential inoculum sources and to visually evaluate Esca-associated symptoms in rootstocks and scions during the propagation process including indoor working steps and the outdoor rooting phase. The results should then be used to point up possible control measures. For this purpose, from 2014 to 2016 visual ratings of Esca-associated wood symptoms were conducted on grapevine material collected from three different nurseries over the entire propagation process as well as from planting material ready for sale. Further assessments on pathogen occurrence by nested PCR and traditional culturing methods focused on rootstock material, which is more affected from experience, and were at first limited to the detection of Pch. For each year, a strong increase of wood symptoms, both in rootstocks and scions, was observed in the course of the production process. Compared to that, PCR- and culture-based detection rates of Pch in rootstock wood were considerably lower revealing a marked discrepancy between symptom incidence and the actual presence of the pathogen. Interestingly, a previously unconsidered fungus, Caophora luteo-olivacea (Clo), which is suspected to be a further GTD-pathogen, was frequently isolated from symptomatic rootstocks. Based on this observation, a multiplex nested PCR method was subsequently developed to specifically detect Pch, Clo as well as species of the Esca-relevant genus Phaeoacremonium (Pm). By using this method, Pch and Pm spp. were detected in ~9% and ~15% of tested rootstocks, respectively (average of all nurseries and years of observation), whereas detection rates of Clo were comparatively high at ~78%. This way, it was possible to harmonize previously observed discrepancies between symptom and pathogen incidence to a great extent. Regarding the occurrence of pathogens and expression of wood symptoms significant differences between nurseries were noticed at single sampling dates, in general however, infestation situations were quite similar. Further investigations were conducted to identify potential inoculum sources in the propagation process. Herefore, sampling was done from various hydration tanks, callusing media and nursery soil. In addition, spore traps were installed in nursery fields in order to monitor airborne inoculum. Samples were subsequently analysed by multiplex nested PCR and/or fungal isolation. PCR-based detections of Pch, Pm spp. and Clo were obtained from hydration tanks as well as from callusing media and air with Clo being the most common species in every respect. Furthermore, viable inoculum of Pch and Pm spp. were found in rootstock wood only, whereas Clo could be additionally isolated from hydration tanks, callusing media and nursery soil. However, isolation rates of Pch, Clo and Pm spp. respectively corresponded to only ~9%, ~9% and ~2% of the detection frequencies when using multiplex nested PCR. The present study allowed for a comprehensive and in part previously unknown insight into the infestation situations of planting material regarding Pch and further Esca-associated pathogens. It provides specific information on potential inoculum sources in grapevine nursery propagation and emphasizes the possible role of pre-infected planting in the development and spread of Esca. With respect to a targeted control of Esca and associated diseases, the obtained results provide an important basis to verify efficacy and practicabilty of existing or yet to be developed control measures.
Mechanisms of frost adaptation and freeze damage in grapevine buds
(2002) Badulescu Valle, Radu Virgil; Blaich, Rolf
Mechanisms of frost hardening in compound (latent) buds of the grapevine cultivar ?Bacchus? were tested with different methods during three winters. The investigated parameters were LTE/HTE (low temperature exotherm/high temperature exotherm), water content, starch, sugar- and anions combination and bud histology. Water content from wood and buds was determined regularly every 2 weeks from March 1998 until Mai 2000. The lowest water content in wood and buds (about 40 %) was found between November and February. In general shoot sections and buds from the apical shoot area contained less water than in the basal area. Sugars and anions were analyzed with HPLC. The highest concentrations of soluble sugars were found in basal buds of the shoot, the lowest concentration in buds of the apical shoot area. Sucrose was the predominant soluble sugar, it was accompanied by glucose, fructose, sucrose, raffinose, and also stacchyose which was hitherto not described for grapevine buds. The concentration of soluble sugars increased during autumn and reached its maximum (around 150 mg/g dry matter) in November/December until the beginning of January then it decreased again to around 30 mg/g at bud burst. The predominant anion was sulphate while chloride could be detected only in traces. The anions reached their maximum at the beginning of January and in mid April. To evaluate the exotherm measuring method, model experiments were carried out with water drops (1µl) on filter paper and with small plant parts (leaf, stems, flower parts). Both the plant parts and the destilled water on the cellulose fiber freeze mainly between ?8 and ?15°C (an influence of the low osmotic value of the plant sap could not be found). After the first freezing the specimen were thawed and freezing repeated. The freezing points of the first and the second freezing cycle were significantly correlated. This shows that freezing does not occur at random, but is determined by ice nucleation sites characteristic for each sample. These sites even survive the physical destruction of the cells by the ice cristals. Further model experiments were carried out to get indications on possible barriers to ice cristal growth in plant tissue. Exotherm analysis was used to determine the freezing point of grapevine buds which is accompanied by a transient temperature rise called exotherm. The grapevine buds show 2 or more exotherms, one or two HTEs (high temperature exotherms) between ? 5 °C and ?10°C and the LTE (low temperature exotherm, sometimes more than one ) between ?10°C and ?25°C depending on the frost adaption of the buds. The HTEs are assumed to indicate the freezing of surface water or apoplastic water in the subtending tissue (bud pad), whereas the LTE (or LTEs) seem to be caused by freezing of the primary (and secondary) buds (shoot primordiy of the compound bud). The temperature minimum of the LTEs (down to ? 25 °C) is reached in January/February and is not influenced by humidity which, however, changes the THE values occuring usually around ? 10 ° and ? 4 °C, which are influenced by water in the bud scales. The LTEs of the buds in the lower area of the shoot were higher as compared to the buds in the middle and upper area of the shoot. The LTE analysis clearly shows the frost adaptation of the latent buds which usually reaches a maximum by the end of January but a clear relation to the changing air temperatures could not be established. Histological and cytological analyses were used to test for frost damage in bud parts and for changes during the cold adaptation. A modified staining method was developed to differentiate the cells. During automn and winter the buds contained a lot of starch grains which dissolved at bud burst. A permeability barrier between bud pad and shoot primordia could not be found, however it could be directly shown, that a HTE causes no cell damage in the buds, while after the appearence of the LTE(s) a disintegration of protoplasts in primary and secondary buds could be found. This is a direct evidence that LTEs indicates the death of the eyes in the complex grapevine bud. If after the appearance of the HTE the buds were held one day at this temperature before further cooling, no LTEs would appear. This and similar observations during the frost storage of grapevine cuttings is discussed in terms of the (harmless) ice formation in the bud base at moderate minus temperatures which would result in a freeze drying effect due to the lower water potential of the bud pad (in comparison to the non frozen eyes) and a further increase of the frost resistance of the growing points. If frost adapted grapevine shoots from the field were kept at 20°C deacclimation occurred after about 10 days. Accidentally wetted buds showed exotherms above ?4°C. In these buds and the watering water ice nucleating bacteria (Pseudomonas fluorescens) could be found.
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.
Nutritional and climatic effects on berry shrivel of grapevines in Southern Germany
(2012) Bachteler, Kristina; Wünsche, Jens Norbert
Berry shrivel (BS) is one of the economically most important physiological disorders in grapevine, but it is also one of the least studied ones. At the beginning of the ripening process, berries stop accumulating sugars and lose their turgescence. The must weight remains low, the berries taste sour and bitter. During the last ten years, several studies were conducted to narrow eliciting factors. As a result, an unbalanced ratio of K and Mg in the soil was considered likely to induce BS. To verify this hypothesis, two fertilization trials with two different varieties each, one via the soil and one foliar fertilization trial, were initiated. Within two years, no effect on the incidence of BS was evident. In the foliar fertilization trials, Mg, K and Ca fertilizers were tested with their effect on BS. For the first year, no significant differences could be observed. In the second year, more berries were affected by BS in the plots treated with Ca fertilizer. The plots with Mg fertilizer showed significantly less berries affected by BS than the untreated control in one variety. Extensive analysis of concentrations of Ca, Mg and K in berries illustrate that berries affected by BS show significantly higher concentrations of Ca compared to healthy berries. The loss of quality of wines made of berries affected by BS was demonstrated by must and wine analysis as well as by a consumer preference analysis. Phenolic compounds (in particular resveratrol) that are often used as indicators of abiotic stress were analysed as well. It was supposed that BS is caused or increased by abiotic stress so that the concentration of resveratrol in berries affected by BS is increased as well. However, in all varieties analysed, the concentration of resveratrol was higher in healthy berries than in affected ones. A direct connection between weather condition at bloom and especially at ripening was examined. Observations at monitoring sites and reports from other countries seem to show that cool and wet weather at these phenological stages might increase the risk of BS. It was only possible to statistically prove a connection between the precipitation at bloom and the incidence of BS.
Plasmopara viticola, the downy mildew of grapevine : phenotypic and molecular characterization of single sporangium strains infecting hosts with different resistance levels
(2015) Gómez Zeledón, José Javier; Spring, Otmar
The downy mildew of grapevine, Plasmopara viticola, is one of the most important pathogens in viticulture. Its genetic diversity had been assessed in some previous studies using molecular markers, but the diversity of the infection behavior has not yet been addressed adequately. Therefore, the development of a fast, reliable and uncomplicated assay to screen for pathogen phenotypes on host with different resistance levels was a major task of this work. A leaf disc test was proposed, evaluating sporulation and necrosis produced by the pathogen on Vitis plants with different susceptibility. Using this bioassay, interesting strains were assessed and kept for future studies. The urgent need to work with genetic homogeneous inoculum was shown, because the assays revealed a high phenotypic diversity in isolates collected from the field as a bulk sample. Hence, a cloning technique to obtain single sporangium strains was found useful to avoid working with mixed genotypes. The leaf disc bioassay also allowed screening for fungicide resistance in P. viticola populations. Isolates resistant to dimethomorph and metalaxyl, two important fungicides for oomycetes control, were detected. Higher resistance was associated with fields were the fungicide application was high as well. Some strains were even resistant to doses where the fungicide exhibits phytotoxic activity to grapevine. The approach of characterizing P. viticola pathotypes on different host plants of Vitis vinifera cultivars and Vitis species from North America and Asia revealed a broad spectrum of fully susceptible to completely resistant reactions. This information is of direct practical value in future plant breeding programs, but also provides the chance to select specific host-pathogen combinations to study the mechanisms of resistance or susceptibility. Fluorescence microscopy revealed how the infection progress of highly and lowly virulent strains advance in tolerant and susceptible hosts, and which points of the infection are interesting for future studies. On the molecular level, effectors were investigated to trace their possible involvement in the infection process. It was found that RXLR 1, NLP 1, Elicitin like 2, Glucanase inhibitor 2 and 4 , and 1,3-ß Glucanase 2 are candidates which are upregulated in the earliest infection stages. Following the here established methodology and suggested strategy it should be possible in the future to get a better insight in the mechanisms of infection and resistance of grapevine downy mildew.
Profiling of physiological responses and quality aspects in Vitis vinifera L. as influenced by aspects of N application
(2019) Lang, Carina Paola; Zörb, Christian
Viticulture and the vinification of vines (Vitis vinifera L.) to wine is an important branch in agriculture world-wide. Berry quality and the associated wine quality are the driving factors here. Nitrogen (N) is the most important plant nutrient for the grapevine. In addition to its influence on vegetative and generative growth, it determines significantly the metabolite composition and the oenological parameters of the grape berry. Nitrogen is present in various forms, such as nitrate, ammonium or amino acid, in the individual plant organs and is used differently by the grapevine. Grapevines are believed to have the ability to assimilate N in various forms, which in turn may affect the quality of berries and the resulting wine. For a better understanding of the effects of N on berry and wine quality, knowledge of which N-form can be assimilated by the vine and the way that this affects oenological parameters and quality-giving metabolites is essential. To this end, several investigations were carried out at various test levels, starting with hydroponic experiments, a pot experiment and a further field experiment, and on the matured wine. The various N-forms of nitrate, ammonium, urea and the amino acids arginine and glutamine were applied, following which the plant-physiological reactions of the grapevine and quality-determining parameters in berry and wine were measured. Furthermore, a metabolite profile with a focus on phenolic components was prepared and a sensory analysis of the wine was performed. The grapevines in the hydroponics and pot experiments were treated with 4 mM total N. The grapevines in the field experiment were fertilized with 60 kg N ha-1, calculated in relation to the block size. The rootstocks SO4 and RU140 showed similar patterns of N assimilation with respect to the N-form but differed significantly with regard to the level of growth and N content among all N-forms. The N-sensitive rootstock SO4 reacted more strongly than the rootstock RU140 and, therefore, SO4 was used for further experiments. This suggests that grapevines are able to assimilate the amino acids glutamine and arginine, as also shown by the enzymatic nitrate reductase activity and the increased abundance of the transcripts of nitrate reductase and nitrite reductase. Nevertheless, the N-forms NO3- and NH4+ were preferentially assimilated. The assimilation under urea treatment was significantly reduced. In addition to the N-form, the amount of N applied had an influence on N assimilation in the grapevine. With increasing amounts, the vegetative and generative growth increased up to a threshold. However, if this threshold was exceeded, both were significantly reduced. If the grapevine is overfertilized, the sink : source ratio changes, which will lead to a change in the biomass production and furthermore to a saturation and storage of N. In addition, competition for assimilates occurs, this alters the N distribution and N availability within the plant and the berries. The N-form has no influence on berry yield. The oenological and chemical parameters of the must and the wine are of enormous importance for product quality. The key components include pH and acidity, which contribute significantly to the organoleptic properties of wine. Both factors are influenced by the N-form and the amount of N offered. As the amount of N increases, the pH increases and the acidity decreases. The N-forms NO3- and urea and, the zero application (without additional N) show the highest influences. The must weight is a defining factor reflecting the berrys maturity and thus the time of harvest. As the amount of N increases, the must weight decreases. On the one hand, an increased N amount leads to lower acidity in the berry, indicating that more sugar is being stored and that the berry is in an advanced stage of maturity. On the other hand, an increased N amount leads to a decreasing must weight, which leads further to a maturation delay. The total phenolic content increases with increasing N amount, but is highest following zero N application. Tentative phenols measured in the metabolite profile are markedly down-regulated after urea treatment and are upregulated with NO3- following NH4+ treatment. This result might arise from reduced N assimilation in the root and thus reduced N availability for the berries. The influence of N on the aroma and sensory aspects of wine is controversial. The individual aroma attributes show both an increase and a decrease in their intensity attributable to N, mainly urea and NO3-. A marked influence between N-treated vines and the zero application is also apparent. However, these contrasting results clearly show that aroma and thus the sensory characteristics of wine can be influenced both positively and negatively. The results of the aroma and sensory evaluation in the agroforestry system underline once again the controversial influence of N on the sensory features of wine; no significant influence was measured. In summary, N has a significant influence on the vegetative and generative growth of the grapevine. The influence of N can be both positive and negative and is in part directly or indirectly linked to wine quality and should therefore not be ignored.
Untersuchungen zur Abundanz der Reblaus (Dactylosphaera vitifolii Shimer) und zur Nodositätenbildung in Abhängigkeit von Umweltfaktoren
(2000) Kopf, Andreas; Blaich, Rolf
The aim of the examinations was to investigate the abundance of Phylloxera (Dactylosphaera vitifolii Shimer), the occurrence of different biotypes of Phylloxera, the reaction of rootstocks to the infestation by Phylloxera and the influence of abiotic environmental conditions on the interaction between insect and plant. To investigate this interaction galls on rootlets (nodosities) and leaf galls were examined. The abundance of Phylloxera and the issue of the holocyclical reproduction in the wine region palatinate were evaluated in a field monitoring. In a special field trial the occurrence of different stages of Phylloxera and their damages on the rootstock were registered. With a dual aseptical in vitro system Phylloxera of different origins were examined on their aggressiveness to different varieties of rootstocks. In pot trials the influence of the type of soil and the effect of N-fertilization on the development of nodosities were investigated. The results of the examination show that Phylloxera can be found in nearly every part of the palatinate and that the improper cultivation of grafted rootstocks promotes the spreading of Phylloxera. Through shoots of rootstocks ? as they can be found in vineyards run wild - a holocyclical development of Phylloxera is made possible under appropriate climatical circumstances. Fitness, population dynamics of Phylloxera and the number of nodosities caused by the insects are correlating with their adaptation to a host rootstock. Pot studies have demonstrated that Phylloxera populations develop better in clay soil than sandy soil. High densities of Phylloxera in combination with a lack of N-supply increase a growth depression on grafted roots. It could also be proved that N-fertilization reduces the Phylloxera populations and the development of nodosities up to 98 %.
Untersuchungen zur Grünfäule (Penicillium spec.) an Weintrauben
(2008) Walter, Ruth; Buchenauer, Heinrich
Since the end of the 90th increasing problems with the occurrence of secondary bunch rot pathogens could be observed in German vine growing regions. Thereby blue mould, caused by Penicillium species, plays a mayor role. Already small amounts of infected bunches can lead to economical losses by off-flavors in the wine, so that infected bunches have to be discarded before harvest. Only little was known about the pathogen on grapes. So questions about the causing species in German vineyards, the biology and epidemiology, the impact of cultivation methods on disease development, the competition with Botrytis cinerea and possible preventing strategies were investigated.
Untersuchungen zur physikalischen Kartierung des Genoms der Weinrebe
(2000) Böhm, Andreas; Blaich, Rolf
In this study research on physical mapping of the grapevine genome was done and a method for preparation of high molecular weight DNA from Vitis-protoplasts was established. In the first part of the project the usefulness of megarestriction-fragments for physical mapping in different grapevine-varieties was analyzed. Hybridization experiments with a probe for repetitive DNA showed that most of the restriction fragments were only about 200 Kb in length with a maximum of 400 Kb. Due to the distance of 300 Kb/cM in the genome of Vitis most fragments only cover a distance of less than 1 cM. For this reason physical mapping with megarestriction-fragments would be less successful. As an alternative strategy for physical mapping a genomic BAC-library was constructed for the variety 'Vidal blanc' which is less sensitive to fungal pathogens. 800 BAC-clones with an average insert size of about 49 Kb have been randomly picked and analyzed. After transforming the complete ligation-mixture 30000 single BACs are expected. They represent more than 3-fold genomesize of Vitis and each single-copy sequence would be contained in the library with a probability of 95 For a first screening of the partial library specific probes for genes from the metabolism of plants or for genes with correlation to pathogen resistance have been developed. The amplification of partial sequences from these Vitis-genes was done with specific oligonucleotides. The PCR-products have been cloned and sequenced. A special probe specific for chloroplast-DNA was used to detect BACs with inserts from the genome of chloroplasts. As a first result of colony-hybridization experiments eight clones with inserts of chloroplast-DNA could be identified. One BAC-clone contains a gene similar to an osmotin-like protein.
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.