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Is Chara corallina a suitable model plant for studying cell-failure mechanisms in fruit skins?
Get PDFThe freshwater alga, Chara corallina, is often used as a model system in studies of cell-wall mechanics. Chara has a unique and very simple architecture, in which a number of node cells form the interface between two giant internode cells. Given this architecture, when investigating a specimen comprising a single internode cell, a tensile test stresses just its cell walls. However, when investigating a specimen comprising two internode cells and their intervening node, the stress is imposed on both the cellulosic cell wall components but also on the (in-series) pectin middle lamellae between the cells comprising the node. This setup should allow comparative study of the properties of the cellulose of the cell walls in the absence of middle lamellae and also of the pectin layers of the middle lamellae in the node. Such information would be of particular interest in the case of fruit skins that in tension typically fail along the middle lamellae causing separation of adjacent cells. The objectives were to establish whether the mechanical properties of the pectin middle lamellae between the Chara node cells may be inferred by comparing tensile properties of an internode cell and of a node.
Chara cell walls are composed of cellulose and de-esterified pectins as indexed by staining with calcofluorwhite and LM19. Staining with 2F4 indicates the presence of homogalacturonans crosslinked by Ca. Compared with internodes, nodes had lower stiffness, lower maximum force at failure and lower maximum strain. For the internode+node+internode samples, failure in the internode was more frequent than failure in the node. Lowering the medium pH had no effect on stiffness, maximum force at fracture or maximum strain of either internodes or nodes but it did increase the frequency of node vs. internode failure. Incubation in EGTA extracted Ca and decreased stiffness, maximum force at fracture and maximum strain of both internode and node samples. There was little effect of EGTA on the frequency of node vs. internode failure. Incubating internodes and nodes in pectinase decreased stiffness, maximum force at failure and maximum strain.
The pectin components of Chara cells are almost identical to those of fruit skin cells. The tensile properties of both internodes and nodes are affected by pectins. This makes it difficult to infer those of the interfacing middle lamellae
Aus den Arbeitsgemeinschaften der Gesellschaft für Pflanzenzüchtung (GPZ):: Tagung der Gesellschaft für Pflanzenzüchtung, AG 17 Arznei- und Gewürzpflanzen 2021
Get PDFColorado potato beetle (CPB – Leptinotarsa decemlineata (Say, 1824)) in Germany – Control strategies from 1936 to the present day
Get PDFDie Geschichte des Kartoffelkäfers (Coleoptera, Chrysomelidae, Leptinotarsa decemlineata (Say, 1824)) in Deutschland ist ein Lehrbeispiel für die unkontrollierte Ausbreitung eines Schaderregers, der ohne regelmäßige Gegenmaßnahmen schwere Ertragsminderungen an einer unserer wichtigsten Nahrungspflanzen verursachen würde. Das Fehlen wirksamer Feinde und seine enorme Anpassungsfähigkeit an Pflanzenschutzmittel machen ihn zu einem starken Gegner, der auch die zukünftigen Generationen immer wieder herausfordern wird. Von seinem Auftreten im Jahr 1936 bis in die Gegenwart wird die historische Bekämpfung des Kartoffelkäfers nachgezeichnet. Die intensive und ausschließliche Anwendung von Insektiziden hat in der Vergangenheit immer zu Resistenzen gegen die verwendeten Wirkstoffe geführt. Vorbeugende Maßnahmen wie 500 m Abstand zu Vorjahresflächen einhalten, Kartoffeldurchwuchs vermeiden, Vorkeimen und Nutzung früher Sorten reichen nicht aus, um den Kartoffelkäfer langfristig zu regulieren. Neue Ergebnisse im Ökologischen Landbau zeigen die hohe Wirksamkeit biologischer Pflanzenschutzmittel von Spinosad und Neem auf. Zukünftig können Resistenzeigenschaften von Wildarten (z. B. Leptin-Glykoalkaloide) im Rahmen klassischer Züchtungsverfahren genutzt werden, um widerstandsfähige Kartoffelsorten zu züchten und damit zu einem integrierten Pflanzenschutzkonzept gegen Kartoffelkäfer beizutragen. In Gärten und auf kleinen Anbauflächen ist auch das Absammeln per Hand weiterhin eine wirksame Maßnahme.The history of the Colorado Potato Beetle (CPB) (Coleoptera, Chrysomelidae, Leptinotarsa decemlineata (Say, 1824)) in Germany is an object lesson in the uncontrolled spread of a pest that, without regular control measures, would cause severe yield reductions in one of our most important food crops. Its lack of natural and effective enemies and its tremendous adaptability to pesticides make it a potent adversary that will continue to challenge future generations. Historical pest control of the CPB is traced from its appearance in 1936 to the present. In the past, the intensive and exclusive use of insecticides has always led to resistance to the active substances used. Preventive measures such as keeping a distance of 500 m from the previous year\u27s fields, avoiding potato overgrowth, pre-sprouting and using early varieties are not sufficient to control the Colorado Potato Beetle in the long term. New results in organic farming show the high efficacy of biological control agents of spinosad and neem. In the future, resistance properties of wild species (e.g. leptin glycoalkaloids) can be used within classical breeding methods to breed resistant potato varieties and thus contribute to an integrated pest management concept against Colorado Potato beetle. In gardens and on small fields, hand collection also remains an effective control measure
Physiological changes induced by either pre- or post-veraison deficit irrigation in \u27Merlot\u27 vines grafted on two different rootstocks
Get PDFReduced summer precipitations and higher evapotranspiration due to elevated temperatures are expected to enhance the impact of water deficit in modern viticulture. We investigated the effect of the timing of deficit irrigation on vine growth, water relations, yield and grape composition in \u27Merlot\u27 vines grafted on 1103P or SO4. In both years we did not measure any differences between rootstocks in stem water potential (SWP). Vegetative growth was decreased by the restriction of irrigation between fruit set and veraison. Stomatal conductance (gs) was affected by irrigation, but not by the rootstock. During the pre-veraison period there was a clear inverse relationship between gs and SWP. The leaf non photochemical quenching readily responded to the stress imposed on 1103P rootstock. Vines subjected to water deficit between fruit set and veraison produced smaller berries than well irrigated ones, whereas deficit applied after veraison determined about 10 % differences in berry weight. The highest and lowest values of pH and TA were measured in berries from pre-veraison deficit irrigated vines grafted on both 1103P and SO4, respectively
Erinea in the \u27Ansonica\u27 grapevine cultivar: trichome complement, histological effects and analysis of chlorophyll fluorescence in affected leaves
Get PDFGrapevine leaves are usually characterized by trichomes, specialized epidermal cells. They are interesting in ampelography and also important for the plant ecological responses in biotic and abiotic interactions. In nature, the trichome development is a genetic trait but it can be modified by pests as eriophyid mites. Colomerus vitis is quite common and its economic value is sometime substantial. Here, we studied the leaf erineum induced by C. vitis on \u27Ansonica\u27 (\u27Inzolia\u27), an important grapevine cultivar characterized by a low level of leaf trichome coating. To date, the interaction between C. vitis and grape has been investigated in few pedo-climatic conditions and no data are reported in \u27Ansonica\u27. Therefore, our objectives were: (1) the analysis, in a Tuscan environment, of the morphology and histology of trichomes in \u27Ansonica\u27 leaves unaffected or affected by C. vitis; (2) evaluation, in mature leaves, of the effects of the mite both on pigment content and chlorophyll a fluorescence parameters. \u27Ansonica\u27 was devoid of glandular trichomes but it has been established the presence of few simple trichomes strictly associated with the veins. In the erineal sectors, a dense proliferation of simple trichomes in the abaxial epidermis and the development of hyperplasia in the adaxial surface were observed. Moreover, the leaf sections in the erineal regions were thicker due to an abnormal development of the lacunar parenchyma, and trichome proliferation was also extended to interveinal regions. Leaves with erinea showed a deficient content of carotenoids, in comparison to unaffected leaves. In \u27Ansonica\u27 leaves, C. vitis induced a decrease in the steady-state operational efficiency of photosystem II associated to a reduction in photochemical quenching and an increase in non-photochemical quenching values. In leaves with erinea, the reduction of photosystem II efficiency was extended to foliar areas not directly affected by galls. The collected results highlight that \u27Ansonica\u27 is susceptible to attacks by C. vitis and in the case of widespread leaf attacks the productive damage should not be underestimated
Phenotypic key factors, genetic regions and genes associated to cluster architecture in grapevine (Vitis vinifera)
No full textWeltweit rangieren domestizierte Reben (Vitis vinifera) unter den meistangebauten Obstkulturen. Die geernteten Trauben werden geschätzt als nahrhaftes Obst, für die Herstellung von Traubensaft und für die Vinifikation begehrter Weine. Vitis vinifera Sorten dominieren den globalen Weinbau, jedoch sind diese Sorten hoch anfällig gegenüber pilzlichen Schaderregern und müssen intensiv mit Fungiziden behandelt werden. Der Anbau pilzresistenter Sorten reduziert den Fungizideinsatz um 60 %. Grauschimmel, verursacht durch Botrytis cinerea, ist ein Hauptpathogen im Weinbau und nimmt eine gesonderte Stellung in der Resistenzzüchtung ein. Für dieses Pathogen sind derzeit keine aktiven zellulären Resistenzmechanismen bekannt. Deshalb zielt die Resistenzzüchtung auf das Einkreuzen physikalischer Eigenschaften ab, die den Infektionsmechanismus des Pathogens behindern. Lockere Traubenarchitektur hat hierbei eine zentrale Rolle. Um genetische Ursachen für lockere Traubenarchitektur zu identifizieren wurden F1 Individuen aus der Kreuzung (‘Calardis Musqué’ × ‘Villard Blanc’) und somatische Varianten der Sorte ‘Pinot Noir’ mit signifikanten Unterschieden in der Traubenkompaktheit untersucht.
Die phänotypischen Untersuchungen dieser Arbeit zeigen, dass sechs von 20 erfassten Untermerkmalen der Traubenachitektur eine herausragende Rolle für den Grad der Traubenkompaktheit spielen. Traubengewicht, Beerenanzahl, Beerenvolumen, Rachislänge, Schulterlänge und Pedicellänge sind für die Züchtung des komplexen Merkmals Lockerbeerigkeit von vorrangiger Bedeutung. Dies gilt sowohl für 149 phänotypisch diverse F1 Individuen der Kreuzugspopulation, als auch für lockere und kompakte ‘Pinot Noir’ Klone aus fünf Selektionslinien.
Die genetischen Untersuchungen identifizieren acht Regionen des Referenzgenoms für Reben auf denen merkmalsgekoppelte quantitative Loci für bis zu vier Faktoren der Traubenarchitektur gemeinsam lokalisiert sind. Darüber hinaus können molekulare Marker mit starker Kopplung zu Faktoren der Traubenarchitektur benannt werden. Mit der Kombination aus drei der ermittelten molekularen Marker können 29 % der unerwünschten kompakten Genotypen in der Kreuzungspopulation (‘Calardis Musqué’ × ‘Villard Blanc’) selektionieret werden.
Expressionsstudien an mehreren Standorten zeigen, dass die differentielle Genexpression von 15 Kandidatengenen stabil mit Traubenarchitekturparametern von ‘Pinot Noir’ Klonen korreliert. In weiteren Studien mit, in Bezug auf Traubenarchitektur, stark unterschiedlichen Individuen aus diversem genetischem Hintergrund ergibt sich, dass das Transkriptionsfaktor kodierende Gen PRE6 und weitere sechs Gene mit Bezug zu Auxinmetabolismus, Zellwandlockerung und Strigolaktonen zwischen lockeren und kompakten Individuen differentiell exprimiert sind. Diese Gene können dazu geeignet sein um molekulare Marker für Traubenarchitektur zu entwickeln. Diese Marker können dann zur MAS von optimiertem Zuchtmaterial mit physikalischer Resilienz gegen Botrytis cinerea eingesetzt werden.Cultivated grapevine (Vitis vinifera) is one of the most widely grown fruit crops in the world and held in high regard for its nourishing fruits, sweet juices and iconic wines. Global viticulture predominantly utilizes Vitis vinifera varieties, because they convey sensory attributes corresponding to the current consumer ideal of product quality. However, they are also highly susceptible to fungal pathogens, and therefore require intense applications of plant protection products with adverse side effects. Newly bred varieties with resistances against fungal pathogens reduce the necessity for fungicide application by 60%. For grey mold, a severe threat in viticulture, an active resistance mechanism is still not feasible. Therefore, grapevine-breeding aims at introducing fungi-static physical properties. The central hub of these physical barriers is a loosely clustered variety. The enhanced available space between the berries provides the framework for the effective formation of a firm berry surface and waxy cover and is restricting the time-span with favorable moisture conditions for fungal infections.
The experimental design of this thesis draws on different sources of natural variance: Firstly, the F1 generation of the cross (‘Calardis Musqué’ × ‘Villard Blanc’) and secondly, somatic variants of the variety ‘Pinot Noir’ showing significantly different cluster compactness. The phenotypic assessment in both sources of natural variation identified six main drivers for cluster compactness. Cluster weight, berry number, berry volume, rachis length, shoulder length and pedicel length are main drivers of cluster compactness.
The genetic approach exposed eight overlapping regions with up to four quantitative trait loci for important architecture sub-traits that are physically co-located on the grapevine reference genome. In addition, several molecular markers with strong linkage to these cluster architecture sub-traits could be proposed. It was possible to exploit three of these markers for MAS against unwanted compactly clustered individuals. So, the number of undesirable compact clustered genotypes could be reduced by 29 % without selecting a single false positive in the investigated population. The gene expression of 15 candidate genes consistently correlates to cluster architecture variations of ‘Pinot Noir’ clones in a multi environmental experiment. The transcription factor gene PRE6 and six genes related to auxin metabolism, cell wall loosening, brassinosteroids and strigolactones showed differential expression in a further extended set of phenotypically divergent individuals from a genetically diverse background. The genetic approach and the gene expression experiments provide multiple lines of evidence for the reported candidate genes. Thus, the candidate genes presented here may have the capacity to be successfully involved in marker development with the aim of selecting cluster architecture traits in MAS enabling breeders to identify optimized breeding material with physical resilience to fungal pathogens such as Botrytis cinerea