Vine and Berry Responses to Severe Water Stress in Different Stages in cv. Syrah (Vitis vinifera L.)
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This experiment was carried out during the 2009 growing season in order to evaluate the ecophysiology and quality characteristics of cv. Syrah (Vitis vinifera L.) grafted onto SO4 in the ECOTRON vineyard in Montpellier SupAgro/INRA in France. The aim of this study was to analyse the effect of sudden and severe water stress (SWS) on the ecophysiological changes, volume losses and shrivellings in grape berries. Also possibilities of existence of recovery, and its possible relationship with SWS and final grapes composition at different phenological stages in cv. Syrah were studied. Three water regime levels; Control (only very mild water stress) and 2 severe water stress levels, SWS1 and SWS2 were established depending on the Ψpd. Stressed periods were started at the BV, MM and EM phenological stages. A randomized block design was used. The experimental plots consisted of 54 vines totally. All data analyses were performed with MSTAT-C Statistical Software (Michigan State University) and LSD tests were done for significant differences of measured traits between groups. Minimum Ψpd values in BV were -0.28MPa, -1.79MPa, -2.16MPa¸ in MM were -0.14MPa; -1.58MPa, -2.72MPa, in EM were -0.16MPa; -2.37MPa, -2.76MPa for Control, SWS1 and SWS2 respectively. Notice that such low predawn total leaf water potential are really exceptional, and at that level the regulation of the osmotic potential is critical. In the berry volume a limited recovery determined after about 13.00- 26.00% volume loss for SWS1 and SWS2 respectively along stressed periods. At harvest; berry volume (cm3 ), 100- berry weight (g), total soluble solids (°Brix), pH, total acidity (g tartaric acid L-1 ), Tartaric acid (g L-1 ), K (g L-1 ), TPI and Anthocyanins (mg L-1 ) were analysed. Berry volume loss rate (%) and mg sugar per 1g berry were calculated. SWS had a negative effect on the sugar per 1g berry, 100 berry weight, berry volume, TSS and positive effect on the anthocyanin concentrations and TPI at three phenological stages. This can open new ways for irrigation monitoring in combination with too high berry sugar content due to the climate change.