Crop yield response to water - Cra

Figure 3Plasticity of flowering of grapevine varieties in southeastern Australia. Plasticity is calculated asthe slopes of the lines relating date of flowering of each variety and the environmental meandate of flowering (inset). Adapted from Sadras et al. (2009).Cab SauvignonRieslingSemillonShirazMerlotChardonnayCabernet Franc0.6 0.8 1.0 1.2Plasticity of floweringDate of flowering of individual varietySlope > 1 (above-average plasticity)Slope = 1 (average plasticity)Slope < 1 (below-average plasticity)Environmental mean date of floweringRiesling. The actual timing of occurrence of critical phenological stages, total season lengthand phenological plasticity are critical traits in the quest to match varieties and environmentsincluding the fine-tuning of irrigation management.Grapevine development and warming trendsPhenology is temperature driven; therefore warming trends recorded since the middle ofthe twentieth century are reflected in grapevine phenological shifts of great significance forvine management and winemaking (Duchene et al., 2010). Several studies have assessed therates of change associated with phenological variables in both the northern and SouthernHemisphere (Wolfe et al., 2005 and Duchene and Schneider, 2005). Not surprisingly, vinesdevelop faster in warmer conditions but the actual rates need consideration. Two importantaspects of these responses are the differential sensitivity of particular phenological phases,and the potential decoupling of berry attributes. For example faster sugar accumulation thatis not fully compensated by early harvest means higher sugar content in berries and higheralcohol potential, as suggested for Riesling in Alsace and for Cabernet Sauvignon and Shiraz inAustralia (Petrie and Sadras, 2008 and Duchene and Schneider, 2005).Response to wATER deficitsOverview: rainfall patterns and development of water deficitRainfall pattern and soil-water storage capacity are major drivers of the temporal pattern ofwater supply and water deficit in rainfed systems, as illustrated by comparison of winter- andsummer-rainfall viticultural regions. Aschmann (1973) highlighted the concentration of rainfall inthe winter half-year as the most distinctive element of the Mediterranean climate, and proposed65 percent of annual rainfall in this period as a boundary in his definition. Grapevines are grown inMediterranean-type climates in southern Europe, California, and parts of South Africa, Chile andAustralia. Winter rainfall often ensures soil water storage that allows for early growth, whereas apattern of terminal drought is typical of rainfed vines in Mediterranean environments. Temporarywater deficits are common in temperate, summer rainfall regions of western and central Europewhere vineyards are established in shallow soils or soils with low water-holding capacity. In thesegrapevine 465