Javier Tardáguila

Grapevine Yield and Leaf Area Estimation Using Supervised Classification Methodology on RGB Images Taken under Field Conditions

The aim of this research was to implement a methodology through the generation of a supervised classifier based on the Mahalanobis distance to characterize the grapevine canopy and assess leaf area and yield using RGB images. The method automatically processes sets of images, and calculates the areas (number of pixels) corresponding to seven different classes (Grapes, Wood, Background, and four classes of Leaf, of increasing leaf age). Each one is initialized by the user, who selects a set of representative pixels for every class in order to induce the clustering around them. The proposed methodology was evaluated with 70 grapevine (V. vinifera L. cv. Tempranillo) images, acquired in a commercial vineyard located in La Rioja (Spain), after several defoliation and de-fruiting events on 10 vines, with a conventional RGB camera and no artificial illumination. The segmentation results showed a performance of 92% for leaves and 98% for clusters, and allowed to assess the grapevine’s leaf area and yield with R2 values of 0.81 (p < 0.001) and 0.73 (p = 0.002), respectively. This methodology, which operates with a simple image acquisition setup and guarantees the right number and kind of pixel classes, has shown to be suitable and robust enough to provide valuable information for vineyard management.

Solar ultraviolet radiation is necessary to enhance grapevine fruit ripening transcriptional and phenolic responses

BackgroundUltraviolet (UV) radiation modulates secondary metabolism in the skin of Vitis vinifera L. berries, which affects the final composition of both grapes and wines. The expression of several phenylpropanoid biosynthesis-related genes is regulated by UV radiation in grape berries. However, the complete portion of transcriptome and ripening processes influenced by solar UV radiation in grapes remains unknown.ResultsWhole genome arrays were used to identify the berry skin transcriptome modulated by the UV radiation received naturally in a mid-altitude Tempranillo vineyard. UV radiation-blocking and transmitting filters were used to generate the experimental conditions. The expression of 121 genes was significantly altered by solar UV radiation. Functional enrichment analysis of altered transcripts mainly pointed out that secondary metabolism-related transcripts were induced by UV radiation including VvFLS1, VvGT5 and VvGT6 flavonol biosynthetic genes and monoterpenoid biosynthetic genes. Berry skin phenolic composition was also analysed to search for correlation with gene expression changes and UV-increased flavonols accumulation was the most evident impact. Among regulatory genes, novel UV radiation-responsive transcription factors including VvMYB24 and three bHLH, together with known grapevine UV-responsive genes such as VvMYBF1, were identified. A transcriptomic meta-analysis revealed that genes up-regulated by UV radiation in the berry skin were also enriched in homologs of Arabidopsis UVR8 UV-B photoreceptor-dependent UV-B -responsive genes. Indeed, a search of the grapevine reference genomic sequence identified UV-B signalling pathway homologs and among them, VvHY5-1, VvHY5-2 and VvRUP were up-regulated by UV radiation in the berry skin.ConclusionsResults suggest that the UV-B radiation-specific signalling pathway is activated in the skin of grapes grown at mid-altitudes. The biosynthesis and accumulation of secondary metabolites, which are appreciated in winemaking and potentially confer cross-tolerance, were almost specifically triggered. This draws attention to viticultural practices that increase solar UV radiation on vineyards as they may improve grape features.

Assessment of the spatial variability of anthocyanins in grapes using a fluorescence sensor: relationships with vine vigour and yield

The use of new, rapid and non-invasive sensors in the field allows the collection of many observations which are necessary to assess the spatial variability of berry composition. The aim of this work was to study the spatial variability in anthocyanin content in grapes and to quantify its relationship with the vigour and yield in a commercial vineyard. The study was conducted in a Tempranillo (Vitis vinifera L.) vineyard (Navarra, Spain). A new, hand-held, non-destructive fluorescence-based proximal sensor was used for monitoring the anthocyanin content in grapes at veraison and harvest. Yield, vine vigour, spectral (normalized difference vegetation index and plant cell density) and chlorophyll (SPAD and simple chlorophyll fluorescence ratio) parameters were measured. Yield variability within the vineyard was the largest of all the parameters. Fluorescence-based anthocyanin indices were less variable at harvest than at veraison. The vigour parameters (main shoot length, total shoot length and shoot pruning weight) were positively correlated to yield; the chlorophyll and the spectral indices were negatively correlated with berry anthocyanin production. The correlations between vigour, yield and anthocyanin content in grapes varied substantially in time and space across the vineyard.

Variations of soil properties affect the vegetative growth and yield components of “Tempranillo” grapevines

To obtain the best must quality, winegrowers must harvest uniform batches of grapes, thus they might define sub-units of the vineyard and treat them as separate management units for cultivation and harvest. The objectives of this work were to determine if there were variations of soil properties that could be arranged into different units of relative uniformity and separated from each other by discrete boundaries, and if there was a significant relationship between those units and the vegetative development and yield components of the grapevines. A soil index that is a linear combination of four soil characteristics was constructed and an interpolation method allowed the definition of soil areas with relative uniformity. These areas were significantly correlated with the vine growth that, in turn, had a significant correlation with the yield components of the vines. This methodology might prove useful to define areas within vineyards where the vegetative development and yields warrant a differentiated management within the vineyard.

Phenolic composition of Tempranillo wines following early defoliation of the vines.

BACKGROUND Early defoliation is a viticultural practice aimed at crop control. So far, the impact of early leaf removal on the monomeric phenolic composition of wines has not been explored. This study examines the effects of early defoliation on the phenolic profile and content in Tempranillo wines. The influence of the defoliation method (manual vs mechanical) and the timing of leaf removal (pre-bloom vs fruit set) was investigated. RESULTS Over two consecutive seasons, 2007 and 2008, the monomeric phenolic composition in Tempranillo wines was studied by high-performance liquid chromatography with photodiode array detection, and 22 compounds were identified and quantified. Overall, early defoliation led to wines more intensely coloured, of higher alcohol content and with larger concentrations of hydroxycinnamic acids, flavonols and anthocyanins (in 2008 only for mechanical treatments). In the absence of fungal infection, resveratrol was found to increase in wines corresponding to early defoliation treatments. The method of leaf removal seemed to be more critical than the timing of intervention, and larger effects on wine phenolic composition were observed for mechanical treatments. CONCLUSION Early defoliation proved to be an effective technique for improving the phenolic composition of Tempranillo wines, by favouring the accumulation of hydroxycinnamics, flavonols and anthocyanins. This is an important achievement, as wine quality is often described by its colour and phenolic attributes.

Impact of Prebloom and Fruit Set Basal Leaf Removal on the Flavonol and Anthocyanin Composition of Tempranillo Grapes

The influence of timing and method of basal defoliation on the profile and content of anthocyanins and flavonols in Tempranillo grapes was investigated. Basal leaf removal was manually and mechanically performed at two phenological stages, prebloom and fruit set. Phenolic composition was determined in grape extracts by HPLC-UV-Vis and 13 anthocyanin and flavonol compounds were identified and quantified. Regardless of the timing and method of defoliation, basal leaf removal led to more ripened fruit in terms of higher soluble solids and reduced acidity and favored the accumulation of flavonols and anthocyanins, which was related to the increase in total leaf area per yield observed in defoliated vines. For anthocyanins, there was a significant relationship between their concentrations and the larger relative skin mass observed in berries of defoliated vines. In general, the enhancement in flavonols and anthocyanins observed in berries from basal-defoliated vines tended to be greater when defoliation was conducted mechanically; yet overall, no evident differences between prebloom and fruit-set defoliation were found.

An open database of grape harvest dates for climate research: Data description and quality assessment

V. Daux, I. Garcia de Cortazar-Atauri, P. Yiou, I. Chuine, E. Garnier, E. Le Roy Ladurie, O. Mestre, and J. Tardaguila LSCE/IPSL, laboratoire CEA/CNRS/UVSQ, UMR8212, Gif/Yvette, France Université Versailles-Saint Quentin en Yvelines, Versailles, France INRA-Agroclim, Avignon, France CEFE, UMR5175, Montpellier, France CRHQ UMR CNRS Université de Caen, Caen, France Institut Universitaire de France, Paris, France Collège de France, Paris, France Météo-France, Toulouse, France Universidad de la Rioja, Logroño, Spain

Early leaf removal impact on volatile composition of Tempranillo wines

BACKGROUND Early defoliation is a very innovative technique in viticulture used for yield management. The effects of early leaf removal performed manually and mechanically at two different phenological stages, pre-bloom and fruit set, on the volatile composition of Tempranillo (Vitis vinifera L.) wines were studied. Volatiles were identified and quantified by gas chromatography. RESULTS Early leaf removal only modified the total concentrations of C₆ compounds and acetates, whereas total alcohols, esters, volatile acids and terpenes remained generally unaffected. Early defoliation induced a significant reduction in C₆ compounds and increased the concentrations of acetates in Tempranillo wines. An effect of timing (pre-bloom vs fruit set) alone was observed for all acetates analysed. Regarding the method of defoliation (manual vs mechanical), significant differences in some ethyl ester (ethyl-2-methylbutyrate and ethyl octanoate) and volatile acid concentrations were observed among treatments. Ethyl octanoate, 2-phenylethyl acetate, 3-methylbutyl acetate and hexanoic acid, with OAV (odour activity value) > 1 and mainly fruity and floral odour descriptors, showed higher levels after early defoliation treatments compared with non-defoliated vines. Principal component analysis illustrated the difference in wines from defoliated and non-defoliated treatments based on their volatile composition. CONCLUSION It can be concluded that early leaf removal significantly modified the wine aroma compounds, increasing or decreasing several of these compounds.

Evaluation of the aroma descriptors variability in Spanish grape cultivars by a quantitative descriptive analysis

Aroma descriptors variability was evaluated by quantitative descriptive analysis (QDA) in Spanish cultivars. Abariño, Mencía and Godello cultivars were evaluated by three expert panels by using monovarietal wines. The frequency and intensity of aroma descriptors was evaluated and geometric mean (GM) was calculated. The largest differences between cultivars were shown by principal component analysis (PCA). Albariño cultivar was characterised by Ripe fruit, Apple and Fruit descriptors; Mencía cultivar was Balsamic and Red fruit, while Citric, Grass, Pineapple, Toasting, Tropical, Dry grass, Pear, Melon and Floral were the attributes of the Godello cultivar. According to GM obtained of aroma attributes from, a positive correlation was found between Albariño and Godello cultivars. The QDA and PCA have contributing to define the aroma of different Spanish grape cultivars (Albariño, Mencía and Godello) by analysis of the monovarietal wines. The results obtained suggest that QDA is a good tool to evaluate the sensory variability of a product, when the tasting panel is good trained.

Using an Automatic Resistivity Profiler Soil Sensor On-The-Go in Precision Viticulture

Spatial information on vineyard soil properties can be useful in precision viticulture. In this paper a combination of high resolution soil spatial information of soil electrical resistivity (ER) and ancillary topographic attributes, such as elevation and slope, were integrated to assess the spatial variability patterns of vegetative growth and yield of a commercial vineyard (Vitis vinifera L. cv. Tempranillo) located in the wine-producing region of La Rioja, Spain. High resolution continuous geoelectrical mapping was accomplished by an Automatic Resistivity Profiler (ARP) on-the-go sensor with an on-board GPS system; rolling electrodes enabled ER to be measured for a depth of investigation approximately up to 0.5, 1 and 2 m. Regression analysis and cluster analysis algorithm were used to jointly process soil resistivity data, landscape attributes and grapevine variables. ER showed a structured variability that matched well with trunk circumference spatial pattern and yield. Based on resistivity and a simple terrain attribute uniform management units were delineated. Once a spatial relationship to target variables is found, the integration of point measurement with continuous soil resistivity mapping is a useful technique to identify within-plots areas of vineyard with similar status.