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Aims: To study the impact of soil-type, grapevine variety and rootstock on grape yield and wine quality in prestigious estates located in the Bordeaux area (France). Methods and results: High-resolution soil maps (scale: 1/3000th) were created for seven prestigious red wine-producing estates in Bordeaux, covering a total area of approximately 400 ha. Soil-type, rootstocks and grapevine varieties were recorded for each vineyard block. A Quality Index was created by considering the destination of the grapes produced in each block, whether they were integrated in the first, the second or the third quality wine produced by the estate. Quality Index was averaged over five vintages. Yield was also measured for each vineyard block and averaged over five vintages. PEYROSOL (gravelly soil) was the most frequent soil-type in these estates (45% of the total mapped area). Soils with temporary waterlogging (REDOXISOL), heavy clay soils (PLANOSOL) and sandy-gravelly soils (BRUNISOL) covered around 10% of the mapped area each. Highest quality was obtained on PLANOSOLS, ARENOSOLS (sandy soils), BRUNISOLS and PEYROSOLS. Quality was low on COLLUVIOSOLS (deep soils on colluvium), LUVISOLS (leached acidic soils) and REDUCTISOLS (soils with permanent waterlogging). Cabernet-Sauvignon was the dominant grapevine variety (59% of the mapped area), followed by Merlot (32%), Cabernet franc (8%) and Petit Verdot (1%). On average, the Quality Index was higher for Cabernet-Sauvignon and Merlot compared with Cabernet franc and Petit Verdot. Riparia Gloire de Montpellier (RGM) was by far the most used rootstock. It covered 45% of the mapped area. Including 3309C and 420A, these three rootstocks covered 75% of the total acreage planted in these estates. Highest quality wine was produced with 420A, RGM, 3309C and Gravesac. Highest yields were obtained with 161-49C, 101-14 MG, RGM, SO4 and 420A. Conclusions: Soil, grapevine variety and rootstock have a major impact on yield and wine quality in prestigious Bordeaux wine producing estates. Significance and impact of the study: Assessment of a Quality Index by soil-type, cultivar and rootstock can indicate which combinations of soiltype, cultivar and rootstock would best optimise quality performance in Bordeaux vineyards.

Aims: The impact of water deficit stress on vine shoot growth, berry weight, grape composition and overall vintage quality was investigated in Bordeaux vineyards. Methods for assessing water deficit stress were compared. Methods and results: Vine water status was assessed on three soil types during four vintages by means of stem water potential and carbon isotope discrimination measured on grape sugar. Regional water deficit was compared for a range of over 30 vintages by means of water balance modelling. It was shown that water deficit stress anticipated shoot growth slackening, limited berry weight and enhanced berry anthocyanin content. Berry sugar content was greatest when water deficit was mild. It was shown that stem water potential measurements and carbon isotope discrimination are accurate tools for assessing vine water status at plot scale. Seasonal water deficit at a regional scale can be correctly estimated by water balance models. Vintage quality in Bordeaux is determined by the intensity of water deficit stress rather than by the level of the temperatures. Conclusions: Vine phenology and grape ripening are highly dependent on water uptake conditions. Mild water deficit stress enhances grape quality for the production of red wines. Vine water status can accurately be assessed by means of stem water potential or carbon isotope discrimination measured on grape sugars. Quality losses through severe water stress can be avoided through the use of drought-adapted plant material, appropriate canopy management, yield reduction or the implementation of deficit irrigation. Significance and impact of the study: This study shows the key role of water deficits in the production of quality grapes for red wine production. Methods for assessing vine water status are compared and discussed. Among many existing methods, the accuracy of stem water potential, carbon isotope discrimination measured on grape sugar and water balance modelling are emphasized.

Aims: It is well known that vine nitrogen deficiency can negatively impact on aroma in white wines. Soil nitrogen fertilization enhances aroma expression, but it also increases vine vigour and susceptibility to grey rot. The aim of this work was to investigate the impact of foliar nitrogen as well as foliar nitrogen and sulphur applications on aromatic expression, vigour and susceptibility to grey rot of Vitis vinifera L. cv. Sauvignon blanc. Methods and results: The impact of foliar nitrogen (N) and sulphur (S) application on aromatic expression of Vitis vinifera L. cv. Sauvignon blanc has been investigated. On a plot where vine nitrogen status is naturally low and water availability not limiting, foliar nitrogen and sulphur fertilization (10 kg/ha of N and 5 kg/ha of S) increased yeast available nitrogen content. Vine vigour and maturity level of grapes were not modified compared to the control. The wines produced from N+S vines contained more volatile thiols and glutathione. These results were confirmed by a tasting of wines produced with grapes from the experimental plots. Foliar nitrogen fertilization alone (10 kg/ha of N) also increased Sauvignon blanc aromatic expression, but less so than the N + S treatment. Conclusions: Foliar N and foliar N + S applications can enhance aromatic expression in Vitis vinifera L. cv. Sauvignon blanc wines without increasing vine vigour and infestation by grey rot. Significance and impact of the study: Vine nitrogen deficiency can negatively impact on grape aroma potential. Soil nitrogen application can increase vine nitrogen status, but it has several drawbacks: it increases vigour and enhances Botrytis susceptibility. This study shows that foliar N and foliar N + S applications can improve vine nitrogen status and enhance aroma expression in Sauvignon blanc wines without the negative impact on vigour and Botrytis susceptibility. Although this study was carried out on Sauvignon blanc vines, it is likely that foliar N or foliar N + S applications will have similar effects on other grapevine varieties containing volatile thiols (Colombard, Riesling, Petit Manseng and Sémillon).

Vine water and nitrogen uptake can be assessed by means of physiological indicators in field conditions. In this study, pre-dawn leaf water potential (ψB) and stem water potential (ψT) were used to indicate vine water status of Vitis vinifera L cv. Merlot. Carbon isotope composition of grape sugar (ΔC13) was used as an integrative indicator of vine water deficit during the ripening period. Must assimilable nitrogen and leaf blade colour intensity, were used to assess vine nitrogen status. All of the three indicators of vine water status allowed a clear differentiation of vine water uptake conditions in the ten experimental plots. The indicators of vine nitrogen status showed more ambiguous results. Must assimilable nitrogen content did not only vary with vine nitrogen uptake, but also with yield. Leaf colour was more easy to interpret. Vine development and berry composition were more influenced by water uptake conditions than by vine nitrogen status. In 2000, which was a dry vintage in Bordeaux, water stress induced early growth slackening and a small berry size. Grapes contained more sugar, anthocyanin and total phenolics and less malic acid when water availability was low. On plots where water uptake conditions were similar, low vine nitrogen status increased berry potential.

Carbon isotope discrimination in primary products of photosynthesis varies with plant water uptake conditions. This property was used to show that the 13C/12C ratio (called ΔC13) in grape sugars and tartrate measured at ripeness can be a valuable indicator of vine water deficit. Correlation between ΔC13 in grape sugar and minimum pre-dawn leaf water potential is excellent (R2 = 0,81; n = 36). A statistically significant effect of soil and vintage is pointed out. When measured on a great number of plots of an estate, ΔC13 varies with the soil type. This proves ΔC13 can be a valuable tool in « terroir » studies. ΔC13 measured on phenolic compounds in wine is also significantly correlated to minimum pre-dawn leaf water potential as well as to ΔC13 in grape sugar. ΔC13 is actually the only tool capable to assess global vine water uptake conditions between veraison and harvest at a low cost, without the installation of heavy equipment in the vineyard.

Vine leaf area is an important viticultural parameter. Because its assessment is difficult, leaf area is not frequently taken into account. In this survey, several techniques of vine leaf area estimation are compared for their accuracy and rapidity. Leaf area is highly correlated with leaf blade fresh or dry weight. This method is destructive, because all the leaves have to be removed, and thus it can only be applied after harvest. Leaf area can also be estimated by the measurement of the lenght of two upper lateral veins. This method is precise, but very time consuming. Sample size reduction to one leaf out of four measured does not affect the quality of the estimation, though sample reduction to one leaf out of ten does. For accurate assessment, samples must be taken from multiple shoots. The third method utilizes the correlation between leaf area and shoot length. This technique combines precision and rapidity, though a standard curve should be established for each cultivar and stage of vine development. The percentage of light extinction through the vegetation can be measured by means of an L.A.I. 2000 device. Values are closely correlated to leaf area index and vine leaf area can be deduced when vine density is known. This method is very rapid (only one to two minutes per vine) but it does not distinguish between the primary and secondary leaf area. Moreover, the L.A.I. 2000 device is very expensive. Digital photographs were taken of the vines studied. Assessment of the percentage of leaf surface area, after binarisation of the image, does not lead to an accurate estimation of vine leaf area. The choice of a technique for vine leaf area estimation among the ones tested, will depend on: a) required precision, b) time availability, c) the need to dispose separately of primary and secondary leaf area, d) the possibility to invest in equipment and e) the possibility to remove leaves.

Vine water status is an important factor in grape quality. High tannin and anthocyanin content in red grape berries are related to moderate vine water deficits. Hence, a simple and sensitive indicator is required to determine vine water status and especially water constraint. Pressure chamber allows a quick and easy to practice determination of water status in the vineyard. Three applications of pressure chamber are known: predawn leaf water potential (ΨB), leaf water potential (ΨF) and stem water potential (ΨT). Only ΨB and ΨF are widely used on vines. In this survey ΨB, ΨF, ΨT and transpiration flow were measured on mature leaves to determine non-irrigated vine water status in field grown vines during the growing season. In California as well as in France, stem Ψ was the most discriminating indicator for both moderate and severe water deficits. In every plot surveyed ΨT was much better correlated to leaf transpiration than ΨF. Moreover, ΨT revealed nascent water deficit earlier than ΨB did. Among the three application of pressure chamber, ΨT was the only one to indicate short term water deficit after a rainfall. Hence, ΨT appears to be a useful indicator for grapevine management in both non-irrigated and irrigated vineyards.

Continuous measurement of micro variations in the diameter of woody organs provides an early detection of mild water deficits in field grown vines. Trunk diameter variations gives more reliable data than cane diameter variations. Water deficit induces trunk shrinkage and increases the Daily Contraction Amplitude / Potential Evapo Transpiration ratio ( DCA / PET). This does not occur on irrigated control vines. Moreover, micromorphometry appears to be an accurate technique for detecting short-term water deficits, because the measurements are continuous. Major constraints in the use of micromorphometry on field grown vines include the positioning of sensor needles on the trunk and the need to maintain fragile equipment permanently in the vineyard. Additionally, this method does not quantify water deficits.