Impact of water status on vine physiology, grape ripening and terroir expression. Cornelis (Kees) van Leeuwen

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1 Impact of water status on vine physiology, grape ripening and terroir expression Cornelis (Kees) van Leeuwen 1

2 Water relations are highly important in viticulture Crop quantity Water deficit reduces yield Crop quality potential Best quality is generally obtained when vines experience water deficit «Terroir» effect can in large part be explained by vine water status Many factors affect vine water status Climate Rainfall Reference Evapo Transpiration (ET ) Soil Texture Depth Coarse elements Plant material Variety Root-stock Rooting depth Training system Leaf area Irrigation Water relations have to be studied in the Soil Plant Atmosphere continuum 2

3 Effect on photosynthesis Water deficit provokes stomatal closure and, hence, a reduction of photosynthesis Evolution du potentiel tige du Cabernet franc sur trois sols à Saint- Emilion (21), 28/6/21 5/7/21 12/7/21 19/7/21 26/7/21 2/8/21 9/8/21 16/8/21 23/8/21 3/8/21 -,2 Potentiel tige (Mpa) -,4 -,6 -,8-1, -1,2-1,4-1,6-1,8-2, Graves Sable avec nappe Argile Photosynthèse (µmol m -2 s -1 ) Niveau de photosynthèse mesuré sur 3 sols à Saint-Emilion le 31 août 21 (cépage Cabernet franc) Van Leeuwen and Destrac 21, unpublished data Graves Sable avec nappe Argile Photosynthesis and water deficit are correlated 14 A R 2 12 =, ,8-1,6-1,4-1,2-1 -,8 -,6 -,4 -,2 Potentiel tige (MPa) Photosynthèse (micromole m -2 s -2 ) Van Leeuwen and Destrac 21, unpublished data 3

4 Consequences of reduced photosynthesis Water deficit = lower yields In extreme situations, lower sugar production can adversely affect quality potential Shoot growth cessation and water deficit are highly correlated Correlation between shoot growth cessation and minimum stem water potential (Merlot, 2) 3 R 2 =, , -1,5-1, -,5, Stem water potential (MPa) Shoot growth cessation (day of the year) Trégoat et al., 22 JISVV 4

5 Impact of shoot growth cessation Under water deficit shoot growth stops before veraison No competition between shoot growth and grape ripening -> Better quality potential Water deficit has no impact on precocity of veraison Correlation between precociousness of veraison and minimum pre-dawn leaf water potential (Merlot, ) , -,8 -,6 -,4 -,2, Pre-dawn leaf water potential (MPa) Date of veraiso (day of the yea Trégoat et al., 22 JISVV 5

6 Berry growth and water deficit are highly correlated Correlation between berry weight and minimum stem water potential (Merlot, 2) R 2 =,7578 2, 1,8 1,6 1,4 1,2 Berry weight (g) -2, -1,5-1, -,5, Stem water potential (MPa) 1, Trégoat et al., 22 JISVV Smaller berries under water deficit Reduced yield Increased quality (in red wine production) 6

7 Berry sugar content and water deficit are highly correlated, but this correlation is not linear Correlation between berry sugar content and minimum stem water potential (Merlot, 2) R 2 27 =, , -1,5-1, -,5, Stem water potential (MPa) Berry sugar content (g) Trégoat et al., 22 JISVV Berry malic acid content and water deficit are highly correlated Correlation between berry malic acid content and minimum stem water potential (Merlot, 2) R 2 =, Malic acid (meq/l) -2, -1,5-1, -,5, Stem water potential (MPa) Trégoat et al., 22 JISVV 7

8 Water deficit has no impact on berry tartrate Correlation between berry tartrate content and minimum predawn leaf water potential (Merlot, ) Tartrate (meq/l) -1, -,8 -,6 -,4 -,2, Pre-dawn leaf water potential (MPa) 5 Trégoat et al., 22 JISVV Berry anthocyanin content and water deficit are highly correlated Correlation between berry anthocyanin content and minimum stem water potential (Merlot, 2) R 2 =,7799-2, -1,5-1, -,5, Stem water potential (MPa) Anthocyanin (g/kg) Trégoat et al., 22 JISVV 8

9 Similar correlation obtained with a different data set (Merlot, Saint- Emilion, 24-27) Van Leeuwen et al., 29 JISVV Quality potential of red table wine is correlated with the intensity of water deficit (Agiorgitiko, Greece) H98 Global tasting mark (-2) H97 P98 y = -2,98x + 3,331 R 2 =,997, p =.1 P97 A98 A97 4 -,7 -,6 -,5 -,4 -,3 -,2 -,1 Predawn leaf water potential (MPa) Koundouras et al., 22, JAFC 9

10 Vintage quality in Bordeaux is correlated with the intensity of water deficit stress Note qualité millésime R 2 = ,1,2,3,4,5,6,7,8,9 1 Indice de stress hydrique moyen entre véraison et récolte Van Leeuwen et al., 29 JISVV The paradox of the effect of water deficit stress in viticulture Despite its limiting effect on vine photosynthesis, water deficit improves quality in red table wine production This can be explained by the beneficial effect on berry size and shoot growth cessation 1

11 When the intensity of water deficit increases, shoot growth is reduced before photosynthesis FTSW Pellegrino et al., 26 Europ. J. Agronomy Effect of water deficit on aroma precursors in Sauvignon blanc : study in Graves and Pessac- Léognan (Bordeaux) Two different soils 2 sandy-gravelly soils (GS et SG; low SWHC) 2 limestone soils (LSB et LHB; medium SWHC) Two contrastng vintages 1998 very dry 1999 very rainy 11

12 Highest aroma precursor level was obtained in a situation of mild water deficit stress P-4MMP et P-4MMPOH (ng eq thiol/l) P-4MMP et P-4MMPOH (ng eq thiol/l) P-4MMP P-4MMPOH P-3MH SG GS LSB LHB 5 P-4MMP P-4MMPOH P-3MH P-3MH (ng eq thiol/l) P-3MH (ng eq thiol/l) 1998: highest levels of aroma precursors on limestone soils 1999: highest levels of aroma precursors on gravelly soils Peyrot des Gachons et al., 25, JSFA SG GS LSB LHB Evolution of 4MMP precursor during grape ripening in 1998 Limestone soils p-4mmp (ng eq / L) SG GS LSB LHB 2 Gravelly soils Date de récolte Août Septembre Octobre Peyrot des Gachons et al., 25, JSFA 12

13 Importance of soil water holding capacity (SWHC) SWHC of viticultural soil: 5 35 mm Depends on: Soil texture Fraction of coarse elements Rooting depth Soil type Vine age Huge impact on resistance of vines to water deficit stress Vines are sensitive to water stress when SWHC is low (<15 mm) Vines are resistant to water stress when SWHC is high (> 25 mm) This effect is often underrated When SWHC is high, vines experience little water deficits, even if rainfall is low Water balance for a vineyard with 35 mm Soil Water Holding Capacity in a year with no rainfall from budbreak to harvest (ETP Mérignac 21) (Crop coefficient k =,6) Water balance (mm) % SWHC = 14 mm 5 1-avr avr 21-avr 1-mai 11-mai 21-mai 31-mai 1-juin 2-juin 3-juin 1-juil 2-juil 3-juil 9-août 19-août 29-août 8-sept 18-sept 28-sept 13

14 Conclusion Water deficit is necessary for the production of high quality red wines Quality losses can occur: When water deficit is too low When water deficit is too severe Quality losses because of too little water deficit often remain unnoticed Soil water can compensate for dry climatic conditions Soil with low SWHC are good soils in wet climates (Bordeaux) Soils with at least medium SWHC are good soils in dry climates (Languedoc, Douro) 14