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Dive into the research topics where Maria P. Diago is active.

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Featured researches published by Maria P. Diago.


Precision Agriculture | 2012

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

Javier Baluja; Maria P. Diago; P. Goovaerts; Javier Tardáguila

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.


Journal of the Science of Food and Agriculture | 2012

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

Maria P. Diago; Belén Ayestarán; Zenaida Guadalupe; Álvaro Garrido; Javier Tardáguila

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.


American Journal of Enology and Viticulture | 2012

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

Maria P. Diago; Belén Ayestarán; Zenaida Guadalupe; Stefano Poni; Javier Tardáguila

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.


Journal of the Science of Food and Agriculture | 2012

Early leaf removal impact on volatile composition of Tempranillo wines

Mar Vilanova; Maria P. Diago; Zlatina Asenova Genisheva; J. M. Oliveira; Javier Tardáguila

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.


PLOS ONE | 2015

Support Vector Machine and Artificial Neural Network Models for the Classification of Grapevine Varieties Using a Portable NIR Spectrophotometer

Salvador Gutiérrez; Javier Tardáguila; Juan Fernández-Novales; Maria P. Diago

The identification of different grapevine varieties, currently attended using visual ampelometry, DNA analysis and very recently, by hyperspectral analysis under laboratory conditions, is an issue of great importance in the wine industry. This work presents support vector machine and artificial neural network’s modelling for grapevine varietal classification from in-field leaf spectroscopy. Modelling was attempted at two scales: site-specific and a global scale. Spectral measurements were obtained on the near-infrared (NIR) spectral range between 1600 to 2400 nm under field conditions in a non-destructive way using a portable spectrophotometer. For the site specific approach, spectra were collected from the adaxial side of 400 individual leaves of 20 grapevine (Vitis vinifera L.) varieties one week after veraison. For the global model, two additional sets of spectra were collected one week before harvest from two different vineyards in another vintage, each one consisting on 48 measurement from individual leaves of six varieties. Several combinations of spectra scatter correction and smoothing filtering were studied. For the training of the models, support vector machines and artificial neural networks were employed using the pre-processed spectra as input and the varieties as the classes of the models. The results from the pre-processing study showed that there was no influence whether using scatter correction or not. Also, a second-degree derivative with a window size of 5 Savitzky-Golay filtering yielded the highest outcomes. For the site-specific model, with 20 classes, the best results from the classifiers thrown an overall score of 87.25% of correctly classified samples. These results were compared under the same conditions with a model trained using partial least squares discriminant analysis, which showed a worse performance in every case. For the global model, a 6-class dataset involving samples from three different vineyards, two years and leaves monitored at post-veraison and harvest was also built up, reaching a 77.08% of correctly classified samples. The outcomes obtained demonstrate the capability of using a reliable method for fast, in-field, non-destructive grapevine varietal classification that could be very useful in viticulture and wine industry, either global or site-specific.


Journal of the Science of Food and Agriculture | 2015

Assessment of cluster yield components by image analysis

Maria P. Diago; Javier Tardáguila; Nuria Aleixos; Borja Millan; José Manuel Prats-Montalbán; Sergio Cubero; José Blasco

BACKGROUND Berry weight, berry number and cluster weight are key parameters for yield estimation for wine and tablegrape industry. Current yield prediction methods are destructive, labour-demanding and time-consuming. In this work, a new methodology, based on image analysis was developed to determine cluster yield components in a fast and inexpensive way. RESULTS Clusters of seven different red varieties of grapevine (Vitis vinifera L.) were photographed under laboratory conditions and their cluster yield components manually determined after image acquisition. Two algorithms based on the Canny and the logarithmic image processing approaches were tested to find the contours of the berries in the images prior to berry detection performed by means of the Hough Transform. Results were obtained in two ways: by analysing either a single image of the cluster or using four images per cluster from different orientations. The best results (R(2) between 69% and 95% in berry detection and between 65% and 97% in cluster weight estimation) were achieved using four images and the Canny algorithm. The models capability based on image analysis to predict berry weight was 84%. CONCLUSION The new and low-cost methodology presented here enabled the assessment of cluster yield components, saving time and providing inexpensive information in comparison with current manual methods.


Journal of Horticultural Science & Biotechnology | 2016

Thermal imaging to detect spatial and temporal variation in the water status of grapevine (Vitis vinifera L.)

Olga M. Grant; H. Ochagavía; Javier Baluja; Maria P. Diago; Javier Tardáguila

ABSTRACT Thermal imaging can detect variation in stomatal conductance and therefore spatial variation in the water status of grapevine. Temporal variation can also be assessed, using indices that relate canopy temperature to reference temperatures, but, as yet, there is no standard approach to obtain these reference values. Also, the potential of above-canopy imaging is uncertain for vine rows with mainly vertically oriented leaves. Thermal images of the side (vertical leaves) and top (horizontal leaves) of ‘Tempranillo’ (Vitis vinifera L.) grapevine rows were captured on different dates and in different plots in a vineyard in the Rioja, Spain. Reference temperatures were determined separately (i) as the temperature of artificial leaves placed in the grapevine canopy, or (ii) by calculation from the leaf energy budget. With respect to imaging the side of grapevine rows, the two approaches exhibited similar potential to indicate variation in stomatal conductance or stem water potential within a single date and time of day. Over different dates (implying temporal as well as spatial variability) and both sides of the grapevines, the use of the artificial surfaces resulted in stronger correlations between thermal indices and physiological variables than the application of energy budget models. The use of such reference surfaces would allow a standardised approach to thermography. Imaging the top of rows produced some highly significant correlations between thermal indices and physiological variables. Modified artificial leaves could be developed to standardise the determination of reference temperatures, at the same spatial resolution as the leaves of interest. That imaging the top of grapevine canopies provides useful information on water status suggests that aerial imaging could be used to assess spatial variation in water status across entire vineyards.


Journal of the Science of Food and Agriculture | 2015

Effects of UV exclusion on the physiology and phenolic composition of leaves and berries of Vitis vinifera cv. Graciano

María-Ángeles Del-Castillo-Alonso; Maria P. Diago; Laura Monforte; Javier Tardáguila; Javier Martínez-Abaigar; Encarnación Núñez-Olivera

BACKGROUND Ultraviolet (UV) radiation induces adaptive responses that can be used for plant production improvement. The aim of this study was to assess the effect of solar UV exclusion on the physiology and phenolic compounds of leaves and berry skins of Vitis vinifera L. cv. Graciano under field conditions. Phenolic compounds were analyzed globally and individually in both the vacuolar fraction and, for the first time in grapevine, the cell wall-bound fraction. These different locations may represent diverse modalities of phenolic response to and protection against UV. RESULTS UV exclusion led to a decrease in Fv /Fm in leaves, revealing that solar UV is needed for adequate photoprotection. Only p-caffeoyl-tartaric acid from the soluble fraction of leaves and myricetin-3-O-glucoside from the soluble fraction of berry skins were significantly higher in the presence of UV radiation, and thus they could play a role in UV protection. Other hydroxycinnamic acids, flavonols, flavanols and stilbenes did not respond to UV exclusion. CONCLUSION UV exclusion led to subtle changes in leaves and berry skins of Graciano cultivar, which would be well adapted to current UV levels. This may help support decision-making on viticultural practices modifying UV exposure of leaves and berries, which could improve grape and wine quality.


American Journal of Enology and Viticulture | 2016

Assessment of Vineyard Canopy Porosity Using Machine Vision

Maria P. Diago; Mark Krasnow; Marijan Bubola; Borja Millan; Javier Tardáguila

Canopy porosity is an important viticultural factor because canopy gaps favor fruit exposure and air circulation, both of which benefit fruit quality and health. Point quadrat analysis (PQA) is standard for assessing canopy gaps but has limited utility because the method is laborious and time consuming. A new, objective, noninvasive, image-based method was developed and compared with PQA to assess the percent canopy gaps in vineyards with diverse viticultural conditions and grape varieties in New Zealand, Croatia, and Spain. The determination coefficient (R2) of the regressions between the percent gaps using both methods exceeded 0.90 (p < 0.05) at each site, and R2 of the global regression was 0.93 (p < 0.05). The time of day and side of the canopy photographed did not significantly affect the performance of the algorithm. With this new image-based assessment method, canopy management may be optimized to configure a desired amount of canopy gaps and thereby improve fruit quality and health.


Journal of the Science of Food and Agriculture | 2017

Non-destructive assessment of grapevine water status in the field using a portable NIR spectrophotometer

Javier Tardáguila; Juan Fernández-Novales; Salvador Gutiérrez; Maria P. Diago

BACKGROUND Until now, the majority of methods employed to assess grapevine water status have been destructive, time-intensive, costly and provide information of a limited number of samples, thus the ability of revealing within-field water status variability is reduced. The goal of this work was to evaluate the capability of non-invasive, portable near infrared (NIR) spectroscopy acquired in the field, to assess the grapevine water status in diverse varieties, grown under different environmental conditions, in a fast and reliable way. The research was conducted 2 weeks before harvest in 2012, in two commercial vineyards, planted with eight different varieties. Spectral measurements were acquired in the field on the adaxial and abaxial sides of 160 individual leaves (20 leaves per variety) using a commercially available handheld spectrophotometer (1600-2400 nm). RESULTS Principal component analysis (PCA) and modified partial least squares (MPLS) were used to interpret the spectra and to develop reliable prediction models for stem water potential (Ψs ) (cross-validation correlation coefficient (rcv ) ranged from 0.77 to 0.93, and standard error of cross validation (SECV) ranged from 0.10 to 0.23), and leaf relative water content (RWC) (rcv ranged from 0.66 to 0.81, and SECV between 1.93 and 3.20). The performance differences between models built from abaxial and adaxial-acquired spectra is also discussed. CONCLUSIONS The capability of non-invasive NIR spectroscopy to reliably assess the grapevine water status under field conditions was proved. This technique can be a suitable and promising tool to appraise within-field variability of plant water status, helpful to define optimised irrigation strategies in the wine industry.

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Stefano Poni

Catholic University of the Sacred Heart

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