Virginia Alonso-Villaverde

The effectiveness of stilbenes in resistant Vitaceae: ultrastructural and biochemical events during Plasmopara viticola infection process

Leaves of different Vitis vinifera L. cultivars, susceptible or resistant to downy mildew, Chasselas, Solaris, IRAC 2091 (cvs. Gamaret x Bronner) and Muscadinia rotundifolia were inoculated with Plasmopara viticola. Samples were then examined by scanning and transmission electron microscopy, by light microscopy and for their ability to synthesise stilbenes. These phytoalexins were strictly analysed at infection sites. In the susceptible Chasselas, P. viticola colonises, at 72h post-infection (hpi), all of the spongy mesophyll with functional haustoria and produces mainly the non toxic piceide. No necrotic zone was observed on Chasselas leaves. The ultrastructural response to downy mildew infection is different in each of the other three resistant grape cultivars. In Solaris, where leaf necrosis are rapidly induced, the infection is restricted to the upper part of the loose spongy mesophyll, and associated with a rapid cell wall disruption and the dispersion of cytoplasmic content along with the production of viniferins. In IRAC 2091, leaf necrosis are quite similar to those observed on Solaris but the infected plant cell, as well as the haustoria, show high electron dense cellular particles without any recognisable organelles, probably related to the effect of the toxic compound pterostilbene, which is synthesised in this grape cultivar. In M. rotundifolia leaf necrosis are much more scarce and smaller than in other cultivars, but pathogen and plant cells are both strongly affected, with concomitant expulsion of cytoplasmic materials through the stomata after P. viticola penetration. In this cultivar, the concentration of all identified stilbenes exceeds 1×10³ μmol mg(-1) FW. The critical role of stilbenes in the resistance of Vitis spp. is discussed.

Impact of clonal variability in Vitis vinifera cabernet franc on grape composition, wine quality, leaf blade stilbene content, and downy mildew resistance

In this study, 10 clones of Vitis vinifera Cabernet franc (not yet commercial) have been phenotyped on precocity, grape composition, and assessment of wine quality made by microvinification in 2008-2010. Additionally, two original criteria have been considered: concentration of 3-isobutyl-2-methoxypyrazine (IBMP) in grapes and wines (the green bell pepper flavor) and resistance of grapevines to downy mildew ( Plasmopara viticola ) by stilbene quantification upon infection. Precocity of veraison varied up to four days at veraison. Berry size and yield were highly variable among clones. However, these variables were not correlated. Tanins and anthocyanins varied among clones in grapes and wines. Variations in grape and wine IBMP were not significant. Some clones showed lower susceptibility for downy mildew on leaves. Lower susceptibility was linked to a higher production of stilbenic phytoalexins involved in downy mildew resistance mechanisms.

Effect of temperature stress on the early vegetative development of Brassica oleracea L.

BackgroundDue to its biennual life cycle Brassica oleracea is especially exposed to seasonal changes in temperature that could limit its growth and fitness. Thermal stress could limit plant growth, leaf development and photosynthesis. We evaluated the performance of two local populations of B. oleracea: one population of cabbage (B. oleracea capitata group) and one population of kale (B. oleracea acephala group) under limiting low and high temperatures.ResultsThere were differences between crops and how they responded to high and low temperature stress. Low temperatures especially affect photosynthesis and fresh weight. Stomatal conductance and the leaf water content were dramatically reduced and plants produce smaller and thicker leaves. Under high temperatures there was a reduction of the weight that could be associated to a general impairment of the photosynthetic activity.ConclusionsAlthough high temperatures significantly reduced the dry weight of seedlings, in general terms, low temperature had a higher impact in B. oleracea physiology than high temperature. Interestingly, our results suggest that the capitata population is less sensitive to changes in air temperature than the acephala population.

Susceptibility to downy mildew in grape clusters: New microscopical and biochemical insights

Grape clusters of different Vitis genotypes, including Vitis vinifera cvs Chasselas and Merlot, and two interspecific grape varieties, Solaris (cvs. Merzling* x (Saperavi severneyi x Muscat ottonel)) and 2091 (cvs. Gamaret x Bronner), are susceptible or resistant to downy mildew. These cultivars were inoculated with Plasmopara viticola at three developmental stages (BBCH stages 53, 69 and 75). Samples were examined by scanning electron microscopy and the synthesis of stilbenes was measured. Microscopical examinations of pedicels, rachis and calyptras showed important differences in stomatal structures within seasonal development. At BBCH 53, successful infections were observed on all tested cultivars and functional stomata were present, while no infections were observed after this stage. At BBCH 69 and 75, cracks were observed around the stomata and guard cells were unstructured or completely collapsed, leading to closed-like stomata. At BBCH 53, significant stilbene accumulation was quantified in 2091 and Solaris; pterostilbene and δ-viniferin were produced in large amounts. In the susceptible varieties, only piceid and resveratrol were induced. At the other two stages, the concentration of all measured stilbenes was undetectable. The critical roles of seasonal development and stilbenes in the resistance of grape clusters towards downy mildew are discussed.

Relationship Between Susceptibility to Botrytis Bunch Rot and Grape Cluster Morphology in the Vitis vinifera L. Cultivar Albariño

ABSTRACT The grapevine (Vitis vinifera L.) cultivar Albariño is well adapted to damp climatic conditions in northwestern Spain and is of great economic importance in the area. The damp, mild conditions of this region are, however, also optimum for the development of fungi such as Botrytis cinerea that attack grapevines. Different ‘Albariño’ clones were found to vary in susceptibility to infection. Morphological differences in the clusters, berries, and rachises of these clones were then sought and their relationship with this susceptibility examined. One of the 14 clones studied—with the shortest pedicels and the smallest berries—was clearly more resistant to this fungus.

Stilbenes: Biomarkers of Grapevine Resistance to Disease of High Relevance for Agronomy, Oenology and Human Health

Stilbenic phytoalexins are key defence molecules implicated in the resistance of grapevine cultivars to three major fungal pathogens, Botrytis cinerea (grey mould of grape), Plamopara viticola (downy mildew) and Erysiphe necator (powdery mildew). HPLC analysis of stilbenes is an efficient method to evaluate the ability of the vine plants to inhibit the development of fungal pathogens. Resistant grapevine varieties react very rapidly to infections by producing high concentrations of the most toxic stilbenes, δ-viniferin and pterostilbene, at the sites of infection. Monitoring of such stress biomarkers is also of great interest for evaluating the efficiency of priming molecules at inducing the grapevines’ natural defence responses. In addition, these compounds have various beneficial effects on human health, acting as anti-oxidants and also as potential chemopreventive agents. The diversity of stilbenes is intriguing, and new holistic analytical approaches, such as metabolomics, that are widely used for wine classification also have great potential for the comprehensive study of responses of Vitaceae to biotic and abiotic stress.

Quantification of Stilbenes in Vitis Genotypes with Different Levels of Resistance to Plasmopara viticola Infection

Stilbenic phytoalexins have been associated with disease resistance. In Vitis spp., stilbene synthesis can be induced by UV irradiation, treatment with a variety of substance extracts, and inoculation with Botrytis cinerea or Plasmopara viticola. The aim of the present work was to examine the relationship between stilbene production and the level of resistance of different Vitis genotypes to P. viticola. The ability of different grapevine genotypes (Vitis vinifera L. cvs. Tempranillo, Touriga Nacional, Pinot noir, and Cabernet Sauvignon and Vitis riparia cv. Gloire de Montpellier) to resist Plasmopara viticola infection was assessed via their potential to accumulate toxic stilbenic phytoalexins. Leaf discs taken from plants belonging to these genotypes were inoculated with P. viticola sporangia and disease severity was determined five days later. Stilbene production was quantified in similar leaf material at 6, 24, 48, and 72 hr postinoculation. After P. viticola infection, the resistant genotype V. riparia showed high production of the phytotoxic stilbenes ɛ- and δ-viniferin, which limited the development of the pathogen and prevented it from producing spores. Indeed, this genotype was associated with the lowest sporulation values. No relationship was observed, however, between resistance and these compounds in the V. vinifera genotypes. Further study is required to define the role of stilbenic phytoalexins in resistance to P. viticola.

Grapevine (Vitis vinifera L.): Old Varieties are Reflected in Works of Art

Grapevine (Vitis viniferaL.): Old Varieties Are Reflected in Works of Art. The northwest of the Iberian Peninsula is home to a number of ancient grapevine varieties now in danger of extinction, regarding which the literature contains only a few references, dating from the 19th century. In this region, baroque religious art, which is commonly ornamented with grapevine motifs, achieved great importance. This work reports the ampelographic comparison of the leaves of 19 old grapevine varieties from this region with those represented on 42 baroque altarpieces. Many of the latter were found to be ampelographically correct representations of grapevine leaves; in some cases they showed such similarity to these old varieties that their cultivation at the time when the corresponding sculptures were made can be confirmed. A larger study may therefore help determine when other varieties were cultivated in the past.

Works of Art and Crop History: Grapevine Varieties and the Baroque Altarpieces

Works of Art and Crop History: Grapevine Varieties and the Baroque AltarpiecesThis study compares the ampelographic characterization of adult leaves and clusters from real grapevine varieties with those present in Solomonic columns of Baroque altarpieces. In a previous preliminary work, the authors concluded that sculpted grapevine leaves in Baroque altarpieces were represented with botanical accuracy and may represent real varieties. Grapevines are a very important decorative feature of these art works, in particular as ornamentation on Solomonic columns. The present work examines more of these carved leaves and includes also the clusters. Six real grapevine varieties were identified on as many altarpieces, enriching their cultural value and pointing to their existence in the wine-growing zone by the 17th century. Further varieties may be identifiable on Baroque altarpieces in other winemaking areas using the same methods. These results encourage other researchers to use unconventional sources for the study of the evolution of agriculture and crop history.Obras de arte e historia de las especies cultivadas: El caso de las variedades de vid y los retablos BarrocosEl presente trabajo compara a nivel ampelográfico las hojas adultas y los racimos de variedades de vid reales con aquellos que aparecen representados en las columnas salomónicas de ciertos retablos barrocos. En un trabajo preliminar publicado anteriormente los autores habían concluido que las hojas esculpidas en estos retablos barrocos están representadas con una gran precisión botánica y por lo tanto podrían estar representando a variedades reales. La vid es un elemento decorativo muy importante en este tipo de obras de arte, en particular como decoración de las columnas de estilo salomónico. El presente trabajo examina un mayor número de retablos e incluye el estudio de los racimos. Seis variedades reales de vid han sido identificadas en otros tantos retablos lo que les aporta nuevos valores culturales y permite demostrar su existencia en la zona vitícola en el siglo XVII. Otras variedades podrían ser también identificadas en retablos barrocos localizados en otras zonas vitícolas diferentes siguiendo la misma metodología. Estos resultados podrían abrir las puertas para que otros investigadores utilicen fuentes de información menos convencionales en el estudio de la evolución de la agricultura y la historia de los diferentes cultivos.

Synonymy of two ancient grapevine cultivars (Vitis vinifera L.) - Cascón and Corbillón - from the D.O. Rías Baixas Ribeira do Ulla Subzone (Galicia, Spain).

In 1986, the Spanish CSIC began a project to find, describe, and recover ancient grapevine cultivars in the regions of Galicia and Asturias. Almost 100 such cultivars have been found, all of which now form part of the grapevine collection at the Misión Biológica de Galicia (CSIC). Until now, the red cultivars “Cascón” and “Corbillón,” two of the most ancient cultivars of the Ribeira do Ulla subzone Protected Designation of Origen (P. D. O.) Rías Baixas, remained undescribed. An ampelographic and molecular analysis of these cultivars showed them to in fact be one and the same.