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Mechanistic modeling constitutes a powerful tool to unravel complex biological phenomena. This study describes the construction of a mechanistic, dynamic model for grapevine plant growth and canopy biomass (vigor). To parametrize and validate the model, the progeny from a cross of Ramsey (Vitis champinii) × Riparia Gloire (V. riparia) was evaluated. Plants with different vigor were grown in a greenhouse during the summer of 2014 and 2015. One set of plants was grafted with Cabernet Sauvignon. Shoot growth rate (b), leaf area (LA), dry biomass, whole plant and root specific hydraulic conductance (kH and Lpr), stomatal conductance (gs), and water potential (Ψ) were measured. Partitioning indices and specific leaf area (SLA) were calculated. The model includes an empirical fit of a purported seasonal pattern of bioactive GAs based on published seasonal evolutionary levels and reference values. The model provided a good fit of the experimental data, with R = 0.85. Simulation of single trait variations defined the individual effect of each variable on vigor determination. The model predicts, with acceptable accuracy, the vigor of a young plant through the measurement of Lpr and SLA. The model also permits further understanding of the functional traits that govern vigor, and, ultimately, could be considered useful for growers, breeders and those studying climate change.

A correct selection of salt-tolerant plants should consider the relative effects of the various existing tolerance mechanisms. When toxic ions, like Na+, reach the leaves, they affect the photosynthetic apparatus, reducing plant growth and performance. Leaf concentration of toxic ions depends on exclusion efficiencies at root level, or compartmentation in organs other than leaves. On the other hand, flow within the plant depends on leaf area, transpiration rate, and soil ion concentrations. From this perspective, in a feedback process, leaf area may be, simultaneously, cause and consequence of salt toxicity. To unravel how this feedback process influences salinity damage in grapevines, a dynamic model of Na+ toxicity was developed. The theoretical model proposed a way to estimate plant exclusion and compartmentation efficiencies. Parametrization was based on a 60-days trial with potted cv. Malbec vines (Vitis vinifera L.), own-rooted and grafted onto 101-14Mgt, 1103P and Cereza, under three soil NaCl levels (0, 50 and 100 mM). The model simulated different grapevine rootstock responses to different salinity levels. These simulations evidenced the key role of Na+ exclusion in long-term tolerance. Stomatal adjustment, compartmentation and rootstock conferred vigor showed relatively minor effects. [ABSTRACT FROM AUTHOR]

Plants have evolved an array of specific photoreceptors to acclimate to the light environment. By sensing light signals, photoreceptors modulate plant morphology, carbon- and water-physiology, crop yield and quality of harvestable organs, among other responses. Many cultural practices and crop management decisions alter light quantity and quality perceived by plants cultivated in the field. Under full sunlight, phytochromes perceive high red to far red ratios (R:FR; 1.1), whereas overhead or lateral low R:FR (below 1.1) are sensed in the presence of plant shade or neighboring plants, respectively. Grapevine is one of the most important fruit crops in the world. To date, studies on grapevine response to light focused on different Photosynthetic Active Radiation (PAR) levels; however, limited data exist about its response to light quality. In this study we aimed to investigate morphological, biochemical, and hydraulic responses of Vitis vinifera to variations in R:FR. Therefore, we irradiated Syrah and Torrontés Riojano plants, grown in a glasshouse, with lateral FR light (low lateral R:FR treatment), while others, that were kept as controls, were not irradiated (ambient lateral R:FR treatment). In response to the low lateral R:FR treatment, grapevine plants did not display any of the SAS morphological markers (i.e. stem length, petiole length and angle, number of lateral shoots) in any of the cultivars assessed, despite an increase in gibberelins and auxin concentrations in leaf tissues. Low lateral R:FR did not affect dry matter partitioning, water-related traits (stomata density and index, wood anatomy), or water-related physiology (plant conductance, transpiration rate, stem hydraulic conductivity, stomatal conductance). None of the Vitis vinifera varieties assessed displayed the classical morphological and hydraulic responses associated to SAS induced by phytochromes. We discuss these results in the context of natural grapevine environment and agronomical relevance. [ABSTRACT FROM AUTHOR]

The purpose of this study was to assess the survival to NaCl in 28 genotypes of the genus Vitis for identifying their degree of salt tolerance. The evaluation included 11 American rootstocks and 17 varieties from Vitis vinifera. Young vines of each genotype were drip-irrigated with a solution of 100 mM of NaCl during 66 days. The day in which 25% of the population had died (1st sample quartile) was calculated, allowing to classify the genotypes according to their salinity tolerance. Three groups of tolerance could be established. First, a sensitive group in which 25% died before the day 30 (3309 Couderc, 161-49 Couderc, Fercal, Freedom, 1103 Paulsen, 99 Richter, SO4, Torrontés Sanjuanino). Second, a moderately tolerant group in which 25% died between the days 30 and 60 (Cereza, Colombard, Criolla Blanca, Criolla Ballista, Palomino, 110 Richter, 140 Ruggeri, Syrah, Torrontés Riojano). Finally, the tolerant group in which 75% survived more than 60 days (101-14 Millardet-Grasset, 196-17 Castel, Criolla Chica, Criolla Sanjuanina, Moscatel de Alejandría, Pedro Giménez). Even in the most tolerant genotypes when the vines grew under salinity, the membranes integrity decreased 17% and the total chlorophyll content decreased 52%. [ABSTRACT FROM AUTHOR]

The goal of the work was to develop grape quality standards based on physical and chemical attributes that may allow to predict wine quality. A treatments Network was installed in Mendoza (North, East and Uco Valley), San Juan (Valle de Zonda), La Rioja (Chilecito), Catamarca and Salta (Calchaqui Valleys), (Argentina). Different crop loads were tested (30 and 50% shoot thinning, 30 and 50% cluster thinning and control) on Malbec and Syrah. During harvest, grapes were analyzed (berry size, sugar concentration, pH, anthocyanins, catechins, tannins, and total phenols) and wine was made with them. The corresponding wines were also analyzed (alcohol, dry matter, color intensity, shade, anthocyanins, catechins, tannins, total phenols, and polymeric color) and evaluated by a panel of wine tasters. By PCA (Principal Component Analysis) two indexes were generated. These indexes summarized the attributes that better explained the observed variability (80%). The indexes were denominated Phenolic richness (RF, associated to anthocyanins, tannins, catechins, total phenols and concentration) and Oxidative threat (PO, associated to pH and hue). There were no differences in RF between varieties or crop levels. Wines with high RF and low PO were considered the most valuable. Cold climate zones had higher RF than hot ones. In Malbec, cold climate zones and low crop level promoted low PO. Predictors of RF and PO in wine were developed for each cultivar. In order to select the most predictive variables, step wise Multiple Linear Regression was used. The adjustment functions RFpred (Malbec R² = 80%; Syrah R² = 62%) and POpred (Malbec R² = 80%; Syrah R² = 62%) were defined. The indexes, translated to quality standards, showed agreement between grapes and wines. The methodology may be valid for other red cultivars, but needs to be adjusted for each case. The standards will allow associations between prices and qualities and also permit achieving a more transparent market. [ABSTRACT FROM AUTHOR]

The goal was to evaluate what maceration time allows a better expression of colour and concentration of Cabernet Sauvignon (CS) and Malbec (M) wines from Mendoza, Argentina. From two 20 000 L industrial winemaking, an experiment (n = 3) was performed to evaluate three times of maceration: 5, 10 and 20 days. This was made extracting 60 L of wine each time. In the wines total phenols, total condensed tanins, gelatin index, colour density, hue, copigmentation and polimeric colour were mesured with VIS and UV espectro-photometric techniques. The wines were also sensory evaluated by an experts panel. 10 and 20 days CS wines were similar and greater in anthocyans, polymeric colour and tanins than that of 5 days. Also provoked bigger concentration and softness and moderated astringency, dryness and roughness. 20 days CS wines had more total phenols and astringent tanins than 10 days CS wines. 10 days M wines reached bigger contents of colour density, total phenols, anthocyanins, polimeric colour and tanins than 5 and 20 days ones. 10 days M provoked sensations of concentration and softness similar to that of 10 and 20 days CS wines. In contrast their dryness, rougness and astringency were smaller than that of CS wines. 5 days M wines resulted poor in attributes and 20 days M intermediate between that of 5 and 10 days. Considering both varieties and all maceration times, the loss of copigmented anthocyans was followed by a proportional increse in polymerised anthocyans. Total phenols and tanins positively correlated with sensations of roughness, astringency, dryness, softness and concentration. Also dryness negatively correlated with gelatine not precipitable tanins. [ABSTRACT FROM AUTHOR]

Cavitation is a physiological dysfunction that takes place in the xylem of water stressed plants. It leads to a loss of hydraulic conductance (kL) as the vessels are filled with air. This impacts water supply, water potential (ΨL) and canopy hydration. Stomatal clossure is an effective response upon diminishing momentary or seasonal foliar hydraulic contents. Depending on each type of plant, stomata may close preventing catastrophic cavitations. This research intended to understand how stomatal control acts upon cavitation events in two contrasting grapevine varieties, Syrah and Grenache. A mechanistic was developed model based on the water and vapour fluxes, kL, stomata conductance (gs), and the vulnerability to cavitation of the xylematic tissue. The theoretical model explains how plants respond to drought and avoid catastrophic cavitation. Water stressed grapevines couple their gs with their kL in order to avoid embolism. It is not stomatal closure, by istself, the controlling mechanism. Grapevines under mild water stress, do not need to completely close their stomata in order to avoid cavitation, therefore, photosynthesis is not completely impeded, and the cost in terms of carbon assimilation is less than expected for other species. [ABSTRACT FROM AUTHOR]

In arid regions under irrigation, vineyards often face water deficit and salinity. As these stressors often occur simultaneously, it is difficult to assess their individual relative severity. The aim of this work was to independently study the physiological responses of grapevine to salinity and water deficit, in order to understand and compare their effects. A pot trial was designed, grafting Cabernet Sauvignon onto 1103P and 101-14 Mgt. Three treatments were evaluated: saline irrigation (Salino; 80 mM ClNa and field capacity), water stress (EH; 0,4 faction of soil transpirable water and 2 mM NaCl) and a control (T; without any stress factors, field capacity and 2mM NaCl). After 54 days, Salino showed smaller effect on leaf area (AF) and shoot length than EH. AF diminished 53% for Salino, while for EH, AF was reduced in a 78% with respect to T. Shoot length diminished 68% for Salino and 83% for EH. Total biomass did not show any difference between both stresses, falling 52% for both situations. However, regarding the biomass partitioning, Salino had higher canopy dry weight while EH showed higher root dry weight. Midday leaf water potential was -1,3 MPa for Salino and EH and -0,9 MPa for T. Although stomatal conductance was similarly reduced for both stress treatments (-41% compared to T), with no differences between rootstocks; an interaction was found between the type of stress and rootstock for net photosynthesis. Finally, 1103P showed a higher Na+ exclusion power than 101-14Mgt (accumulating 21% less Na+ in the plant). Even though the behavior of the Cabernet sauvignon scion was similar for both rootstocks, the higher exclusion that 1103P showed may indicate possible better performances upon salinity. [ABSTRACT FROM AUTHOR]

Grapes cultivated in warm zones have high sugar content and low acidity. The wines made with such grapes are more prone to fast evolution during maturation. Oxidation rate is pH-dependant. The purpose of this study was to compare oxidation risk in three different Malbec wines (pH levels 3.34; 4.14 y 4.33). Wines were made at the Experimental Winery, Enology I and II Chairs, of Agricultural Faculty, grapes were cultivated in the East (wine pH 4.14), North (wine pH 4.33) and South (wine pH 3.34) of Mendoza, Argentina. Assays were made in triplicate. The oxidation risk was determined by Singleton and Kramling test. Absorbance at 420 nm, absorbance at 520 nm and color density were measured. Statistical analysis was performed using ANOVA, Tukey test at the 95% confidence level. Higher pH wine registered a bigger color density increase than lower pH wines. High color density increase is related to high oxidation risk. Red wine oxidation risk can be evaluated by the modified Singleton and Kramling test. Absorbance at 520 nm must be registered and color density must be calculated. The test period might be shortened up to four days. [ABSTRACT FROM AUTHOR]

Vigor control in grapevine may become especially important under climate change. A better understanding of gene-phenotype relationships is required in order to exploit plant genomics for breeding purposes. This research aims to use quantitative trait loci (QTLs) for vigor identified in the progeny from a cross of Ramsey (Vitis champinii) × Riparia Gloire (V. riparia). Genes located 700 kb up and downstream from each QTL position were interrogated for functional enrichment through ShinyGO online tool, based on the gene ontology annotation of Vitis vinifera PN40024. Key biological processes like phloem and xylem development, cell cycle, response to hormones, amino acid transport, tissue development, sugar metabolism, nitrogen transport, and stress/immune responses, showed functional enrichment. Integral response to light and auxin might be required for fine molecular tuning of vegetative growth in Vitis. Fifty out of 1318 candidate genes were prioritized, reducing their amount to a manageable number of candidates genes for further directed breeding strategies. [ABSTRACT FROM AUTHOR]