No abstract

No abstract

Background and Aims Previous research has investigated widely the effects of irrigation application in red winegrape cultivars; however, white grape cultivars have been the subject of a lesser number of field trials. An experiment was undertaken for three seasons in a drip‐irrigated, cv. Muscat of Alexandria/161‐49C vineyard to define the most sustainable irrigation strategy for white winegrapes in eastern Spain. Methods and Results The treatments were as follows: (i) Control, irrigated at 100% of estimated crop evapotranspiration (ETc) for the entire season; (ii) sustained deficit irrigation (SDI), irrigated at 50% of Control; (iii) early deficit (ED), where pre‐veraison irrigation was withheld, followed by 100% ETc; and (iv) late deficit (LD), irrigated as for the Control until veraison and thereafter at 25% ETc until harvest. Yield in ED and LD was reduced 25 and 15%, respectively, compared with that of Control. Yield under SDI did not differ significantly from that of the Control and was similar to that of the ED and LD treatments. All the deficit irrigation treatments had some carry‐over effects because of a significant decrease in shoot fruitfulness and in bunch mass due to smaller berries. The ED treatment, however, led to a greater reduction in berry growth compared with that of LD. Full irrigation increased pruning mass and leaf area mainly due to larger secondary shoots, and besides delayed grape ripening. Conclusions The SDI treatment resulted in the greatest water use efficiency, ensuring the high yield potential of the cultivar, providing that a threshold value of water stress integral of 35 MPa day during the periods from anthesis to veraison and from veraison to harvest was not surpassed. In addition, it favoured an improved grape composition, particularly in terms of grape sugar accumulation. Significance of the Study Sustained deficit irrigation at 50% of ETc should be applied where water is scarce or expensive, paying attention to possible carry‐over effects if water withholding has to be continued for more than three seasons.

Background and Aims: Climate change is advancing grape ripening, decoupling berry technological and phenolic composition and negatively impacting wine quality. The aim for this study was to test the usefulness of late leaf removal (LLR) under different watering regimes to delay harvest in two Spanish red cultivars in a semiarid and temperate-warm climate. The effects on vine physiology, yield, grape and wine composition were investigated. Methods and Results:In two trials carried out in eastern Spain with Bobal and Tempranillo cultivars, vines were partially defoliated above the cluster zone shortly before veraison under rainfed and deficit irrigation conditions during two seasons. Grape ripening rate was significantly affected by the watering regime and canopy management in both cultivars. Vine water status and photosynthesis was improved by irrigation and LLR. However, the treatments harvested later, did not have an overall positive effect on grape nor on wine composition. The resultant leaf area-tofruit ratios of the defoliated treatments appeared to be limiting for both sugars and anthocyanins accumulation. As a consequence, LLR negatively affected wine colour intensity. In addition, yield was constrained by LLR in Tempranillo due to reductions in cluster and berry mass. Conclusions:A reduction in grape sugars accumulation provoked by LLR did not necessarily implies a better coupling between berry technological and phenolic maturity. The effectiveness of the LLR technique seems to depend on its final impacts on leaf area-to-fruit ratio and vine water status, the vine photosynthetic compensation capacity of the cultivar and the environmental conditions.Significance of the Study: Under low vigour vine conditions, severe defoliation cannot be recommended as a strategy to balance grape sugars and phenolic composition, highlighting the importance of applying defoliation at the right time and intensity.