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Further evidence that calcium, magnesium and seaweed mixtures reduce grapevine leaf stripe symptoms and increase grape yields
Full text linkSummary. Grapevine leaf stripe disease (GLSD) is the most important syndrome of the esca disease complex. GLSD foliar symptoms are associated with grapevine yield losses and decline in vigour of host plants. Relationship between incidence and severity of GLSD symptoms and reductions grape quantity and quality has been demonstrated. In 2010–2012, foliar applications of mixtures of fertilizers based on calcium, magnesium and seaweed reduced symptom expression and increased yield quantity and quality. In the present study, mixture applications were carried out in 2013-2015 in different vineyards located in Abruzzo and Emilia-Romagna Regions (north-central Italy). These treatments reduced GLSD symptom incidence and severity, and applications of seaweed without calcium and magnesium was not effective. This confirmed involvement of the nutrients in the reduction of leaf symptom expression. Mechanical properties and absorbance difference measurements demonstrated increased berry quality from vines treated with the mixture. In trials carried out in 2015, the efficacy of the mixture applied in
tank mix with other pest and disease control products was not reduced. We conclude that applications of calcium, magnesium and seaweed mixtures are effective for reducing the impacts of GLSD in vineyards
Understanding the control strategies effective against the esca leaf stripe symptom: the edge hypothesis
Full text linkA peculiar symptom that may develop in grapevines affected by wood pathogens involved in the esca complex of diseases is the leaf stripe symptom, which also gives the name to the Grapevine Leaf Stripe Disease. Multiple studies have revealed strong links between fungal presence, wood symptomatology and expression of the
leaf stripe symptom. However, numerous other factors have been shown to play roles in symptom onset, incidence, severity and yearly fluctuation of this disease. While the factors triggering the leaf stripe symptom are still under investigation, three control strategies have been proven effective for substantially reducing its expression, namely trunk surgery, and applications of sodium arsenite or a fertilizer mixture. These control strategies are examined here, including their (putative or confirmed) modes of action, and how they may influence the leaf stripe symptom development. In this article, we also propose the ‘edge’ hypothesis to tentatively explain symptoms onset, keeping in consideration past knowledge and recent advances in the understanding of the esca leaf stripe symptom. Ultimately, it is our intention to offer food-for-thought and and stimulate and stimulate debate within the phytopathological community
Effect of Different Foliar Fertilizer Applications on Esca Disease of Grapevine: Symptom Expression and Nutrient Content in the Leaf and Composition of the Berry
No full textAbstract: Esca disease, the most common grapevine wood disease in Europe, causes yield losses correlated with the foliar symptoms’ expression. In two vineyards located in the Abruzzo Region of Italy, each of which were investigated for esca symptoms after 1994, different applications of macro- and microelements were performed in two consecutive growing seasons. The main aim of the work consisted of verifying the effects of the fertilizer applications on the foliar symptoms’ expression, in order to deepen knowledge of the nature of the symptom, which is still unclear. For each treatment, in each year, the leaf content of macro- and microelements and the composition of berries and musts were assessed. The effects of these applications on vegetative growth and yield quantity were also verified. The trials were carried out on symptomatic, asymptomatic and apparently healthy vines. All applications, in particular those with microelements, increased the foliar symptoms’ expression, and a greater vegetative growth was detected only in vines treated with NPK fertilizers. The symptoms’ increase was always associated in the leaf with a decrease of calcium, and to a lesser extent, magnesium, reinforcing the hypothesis of the plant’s hypersensitive reaction in the development of foliar symptoms, given the role of calcium in the defense response. The vineyards
were in nutritional balance regardless of the fertilizer applications. The general increase in foliar symptoms and the decrease in sugars in the musts of asymptomatic treated vines underlined the importance of the vegetative-productive balance, in Esca infected vineyards especially, in order to limit the symptoms’ expression and the decrease in yield
Rainfall and temperature influence expression of foliar symptoms of grapevine leaf stripe disease (esca complex) in vineyards
Full text linkSummary. Two vineyards in the Abruzzo Region, central Italy, affected by grapevine leaf stripe disease (GLSD), were monitored for incidence and severity of foliar symptoms of the disease for 21 consecutive years (1994 to 2014). Each year, rainfall and temperature were recorded. Correlations between symptom incidence or severity and rainfall or temperature of different periods of the year or single months were assessed. July rainfall and temperature were highly correlated with incidence and severity of leaf symptoms. The vineyards were characterized by high longevity, vigour and yields, and a particular dynamic of GLSD. In the period following 2005, the year of peak vine mortality, there was a decrease of the expression of foliar symptoms, which was not correlated with both of the climate parameters. Greater mortality occurred for vines showing severe symptoms at the first appearance of GLSD than for vines with low severity
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Mixture of calcium, magnesium and seaweed affects leaf phytoalexin contents and grape ripening on vines with grapevine leaf stripe disease
Full text linkSummary. Grapevine leaf stripe disease (GLSD) is a tracheomycosis caused by Phaeomoniella chlamydospora and Phaeoacremonium minimum. Impacts on yields of grapes were correlated with the incidence and severity of GLSD symptoms on vine canopies. In 2012 and 2013, vines in two vineyards were treated with nine applications of a mixture of leaf fertilizers containing calcium, magnesium and seaweed extracts. At different growth stages, leaves were sampled from treated and control plots of healthy, GLSD-asymptomatic, or GLSD-symptomatic vines and contents were measured of the phytoalexins trans-resveratrol, trans-ε-viniferin, trans-δ-viniferin and trans-pterostilbene.
Grape ripening was also monitored from veraison to harvest during both vintages. The treatments caused significant reductions in canopy symptom expression. Increased phytoalexin contents were measured from ‘fruit set’ to ‘berries developing colour’ stages. Trans-resveratrol peak was recorded in asymptomatic diseased vines at the ‘berries pea-sized’ stage, and trans-ε-viniferin and trans-δ-viniferin increased at the ‘berries beginning to touch’ stage, compared to the contents recorded in untreated asymptomatic vines. From ‘berries developing colour’ to harvest, all treated vines had lower amounts of phytoalexins than the control ones. At harvest, treated healthy and symptomatic vines produced berries with similar amounts of total sugars compared to untreated vines. Treated asymptomatic vines produced berries with greater amounts of total sugars compared to the untreated vines These results indicate that increased phytoalexin content recorded from ‘fruit set’ to ‘berries beginning to touch’ in asymptomatic vines treated with the mineral/seaweed mixture may reduce symptoms of GLSD
First Results of Management of Powdery Mildew in Grapevine Using Sulphur, Silicate and Equisetum arvense Formulations
No full textThe management of grapevine from diseases is now particularly focused on the development of environmentally friendly strategies. Although sulphur is not in itself a toxic substance, its extensive use in powdery mildew, in organic vineyards especially, may cause environmental problems and plant phytotoxicity and affect the health and safety of viticultural workers. The activity of sulphur applied at doses reduced up to 50% in tank mixtures with silicates or Equisetum arvense-based products was assessed on powdery mildew in grapevine. Two-year trials were carried out applying the products every 7–10 days in the period of greatest risk for disease infections, in two organic vineyards in the Abruzzo region, Italy. In both vineyards throughout all trial years, at harvest, disease incidence and severity on leaves and bunches in the silicon + sulphur treatments were generally significantly lower compared to both the sulphur at full dose and to the control. In all trials, in both vineyards, a strong activity of silicon + sulphur mixtures towards disease on leaves was observed. This effect could be decisive in lowering the potential inoculum in the following season. In the Ari vineyard, vines treated with the mixtures always increased yield quantity and quality, given the higher contents of soluble solids and lower levels of total acidity. In the Cellino vineyard, probably due to the young age of the vines, increases in yield quantity were observed, with lesser effects on quality. The promising activity of the mixtures needs further studies to confirm these positive results. Furthermore, in both vineyards, the source of primary inoculum of the pathogen was observed as chasmothecia on the leaves
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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