Nitrogen nutrition status of the vine: correlation between N-tester and SPAD chlorophyll indices

Knowledge of the nitrogen nutrition status of the vine is essential for long-term management of its nutrition with the aim of producing high-quality grapes. Measurement of the chlorophyll index is a fast, non-destructive and relatively inexpensive method that provides a good approximation of the nitrogen nutrition status of the vine during the growing season. Several chlorophyll meters are available on the market, each using its own measurement unit. With the aim of popularizing the use of chlorophyll meters, the interpretation thresholds of the SPAD index, measured on the vine at the veraison stage, have been established from correlation with the N-tester index, for which the thresholds are already known

Carryover effects of crop thinning and foliar N fertilisation on grape amino N composition

This article is published in cooperation with Terclim 2022 (XIVth International Terroir Congress and 2nd ClimWine Symposium), 3-8 July 2022, Bordeaux, France.Nitrogen (N) is an essential element for vine development and yield; it is also involved in the winemaking process and significantly affects wine composition. It is therefore essential to control and optimise plant N use to ensure an adequate N composition of the grapes at harvest. An improved understanding of the impact of cultivation practices on plant N metabolism would allow a better orientation of technical choices with the objective of quality and sustainability (i.e., fewer inputs, more efficiency).Our trial focused on the impacts of fertilisation and crop thinning on grape N composition. A wide crop load gradient was set up in a homogeneous plot of Chasselas (Vitis vinifera L.) in an experimental vineyard in Switzerland. Foliar urea was applied at veraison in order to compare it with an unfertilised control. Vine development and grape composition were evaluated over two years, with particular attention to the carryover effects of both fertilisation and crop thinning.Foliar N fertilisation effectively increased the amount of N in grapes at harvest in the same year, but had no impact on grape ripeness or carryover effect on year n + 1. Conversely, crop thinning improved grape maturity by reducing fruit N and C demand. Interestingly, amino N proportions could be distinguished according to crop load, while the global grape N concentration at harvest remained unchanged. Some amino acids were more affected by crop thinning than others. The concentrations of alanine, γ-aminobutyric acid (GABA), serine and threonine were reduced by crop thinning. Crop thinning had a strong carryover effect on year n + 1. The carryover impact of crop thinning on grapes in terms of both maturation index and N composition could be observed at the onset of grape ripening on year n + 1.This experiment highlighted the influence of the previous year’s agricultural practices on grape C and N accumulation before and during the ripening phase. Consequently, the modulation of grape composition at harvest should be considered over two consecutive years. These results will contribute to the improvement of predictive models and sustainable agronomic practices in perennial crops

Oeno One

This review addresses the role of nitrogen (N) in vine balance and grape composition. It offers an integrative approach to managing grapevine N nutrition. Keeping in mind that N excess is just as detrimental to wine quality as N depletion, the control of grapevine N status, and ultimately must N composition, is critical for high-quality grape production. N fertilisation has been intensively used in the past century, despite plants absorbing only 30 to 40 % of applied N. By adapting plant material, soil management and vine balance to environmental conditions, it would be possible for grape growers to improve plant N use efficiency and minimise N input in the vineyard. Vineyard N management is a complex exercise involving a search for a balance between controlling vigour, optimising grape composition, regulating production costs and limiting pollution. The first part of this review describes grapevine N metabolism from root N uptake to vine development and grape ripening, including the formation of grape aroma compounds. The advantages and limits of methods available for measuring plant N status are addressed. The second part focuses on the parameters that influence grapevine N metabolism, distinguishing the impacts of environmental factors from those of vineyard management practices. Areas for further research are also identified

Intensity and timing of defoliation on white cultivar Chasselas under the temperate climate of Switzerland

Aim: The objective of this work is to investigate the effects of early defoliation on cv. Chasselas under the temperate conditions of Switzerland, with particular attention to berry anatomical traits and wine sensory parameters. Methods and results: Defoliation (removal of 6 basal leaves + 6 lateral shoots per shoot) was completed during three developmental stages of grapevine, i.e., pre-flowering, late flowering and bunch closure, and at two intensity levels. The experimentation was performed repeatedly over four years. In addition to vintage effect, pre-flowering defoliation had a consistent impact on vine agronomic behaviour. The yield was highly affected by the technique (more than 30% loss). Earlier and more intense defoliation had more impact on yield, while post-berry-set defoliation had no effect on yield. Intensive defoliation also modified berry skin thickness and had a positive impact inhibiting Botrytis development. Wine composition and sensory analysis were not affected by the practice. However, pre-floral defoliation affected bud fruitfulness and vigour, i.e., trimming and pruning weights. This result noted a carryover effect that could affect vine sustainability under restrictive conditions. Conclusion: In the context of this study, pre-flowering defoliation seems to be an interesting practice to reduce vigour and control the high production potential of the cv. Chasselas. The intensity of early defoliation allows for the modulation of the impact on the yield in order to prevent excessive yield loss. Significance and impact of the study: Pre-flowering defoliation of the white cultivar represents a prophylactic solution to reduce both chemical entrants and bunch-thinning costs

The year-long unprecedented European heat and drought of 1540 - a worst case

The heat waves of 2003 in Western Europe and 2010 in Russia, commonly labelled as rare climatic anomalies outside of previous experience, are often taken as harbingers of more frequent extremes in the global warming-influenced future. However, a recent reconstruction of spring-summer temperatures for WE resulted in the likelihood of significantly higher temperatures in 1540. In order to check the plausibility of this result we investigated the severity of the 1540 drought by putting forward the argument of the known soil desiccation-temperature feedback. Based on more than 300 first-hand documentary weather report sources originating from an area of 2 to 3 million km2, we show that Europe was affected by an unprecedented 11-month-long Megadrought. The estimated number of precipitation days and precipitation amount for Central and Western Europe in 1540 is significantly lower than the 100-year minima of the instrumental measurement period for spring, summer and autumn. This result is supported by independent documentary evidence about extremely low river flows and Europe-wide wild-, forest- and settlement fires. We found that an event of this severity cannot be simulated by state-of-the-art climate models

Retrospective evaluation of whole exome and genome mutation calls in 746 cancer samples

Funder: NCI U24CA211006Abstract: The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) curated consensus somatic mutation calls using whole exome sequencing (WES) and whole genome sequencing (WGS), respectively. Here, as part of the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium, which aggregated whole genome sequencing data from 2,658 cancers across 38 tumour types, we compare WES and WGS side-by-side from 746 TCGA samples, finding that ~80% of mutations overlap in covered exonic regions. We estimate that low variant allele fraction (VAF < 15%) and clonal heterogeneity contribute up to 68% of private WGS mutations and 71% of private WES mutations. We observe that ~30% of private WGS mutations trace to mutations identified by a single variant caller in WES consensus efforts. WGS captures both ~50% more variation in exonic regions and un-observed mutations in loci with variable GC-content. Together, our analysis highlights technological divergences between two reproducible somatic variant detection efforts

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 72 h 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.The authors thank Dr. Roger Pezet for critically reading the manuscript, Mr. Eric Remolif for production of grapevine cuttings and Ms. Sevan Kuyumcuyan for helpful technical assistance. We gratefully acknowledge the Juana de Vega Foundation (Spain) for its financial support.Fundación Juana de VegaPeer reviewe

Nitrogen dilution in excessive canopies of Chasselas and Pinot noir cvs

Aims: The impact of canopy management on the nitrogen (N) content in grapevines was studied. Methods and Results: Two trials were carried out between 2001 and 2010 on Vitis vinifera cvs. Chasselas and Pinot noir. The observed factors of variation were the intensity of lateral shoot removal for the first trial and the severity of shoot trimming for the second trial. The N content was evaluated in parallel by leaf diagnosis, the chlorophyll index and the yeast available N concentration (YAN) found in the musts. When the yields were the same, a significant dilution of N in proportion to the development of the leaf area was revealed. Treatments resulting in excessive leaf area presented N deficiency in the leaves and the musts. Conclusion: The N content in both the vines and grapes was influenced by the canopy management (lateral shoot removal and shoot trimming), and the magnitude of the response appeared to be even greater in the absence of water stress. In addition, the risk of N deficiency was found to increase beyond a maximum value of the leaf-fruit ratio. Significance of the study: Canopy management has a significant influence on the N content in foliage and grapes, and the risk of N deficiency increases under a situation that produces an excessive leaf area

Physiological and histological approaches to study berry shrivel in grapes

Aims: The current work aims to study berry shrivel in grapes (a grape-ripening disorder) in relation to vine water status and climatic conditions using physiological and histological approaches. Methods and results: Measurements of rachis hydraulic conductance on grapevine clusters (Vitis vinifera L.) and observations of the vascular tissues (xylem and phloem) using transmission electron microscopy were conducted on rachises from healthy clusters and clusters having berry shrivel (BS) symptoms during the season. BS intensity was largely dependent on the vine water status: BS was greater in vines without water stress than in vines with moderate to high water stress around veraison time. Preliminary results showed that rachis hydraulic conductance declined sharply after veraison but remained slightly higher in healthy clusters in comparison with clusters presenting BS symptoms. An important degradation of the primary phloem was observed in the rachises of BS clusters, with the appearance of hard, non-functional liber (secondary phloem) and a disorganization of the cell content in the phloem tissue. An alteration of the primary xylem was also observed in the middle of the rachis and in the secondary rachis ramifications. Conclusion: These results suggest that the decrease in sugar and water accumulation in BS berries would primarily be associated with a decline in rachis phloem functionality. Significance and impact of the study: The management of the vine water status plays a key role in berry shrivel development