Differences in canopy development and plant water status between winegrape cultivars grown in a warm area

Abstract

There is an increasing interest by the wine industry to know the performance of new winegrape cultivars in traditional areas to find out which cultivars could better complement the traditional wines. In warm areas, isohydric cultivars and high yields are sought in order to save water and to delay maturity. In 2016, from early after budbreak until 12 July, leaf area development and plant water status of seven cultivars (Barbera, Graciano, Malbec, Nero Amaro, Petit Verdot, Tempranillo and Touriga nacional) were studied under the same environmental conditions. Differences in shoot growth rate and shoot length arose shortly after budbreak even when atmospheric demand was still mild. Touriga nacional, Barbera, Tempranillo and Malbec had the fastest growth rate and in turn, the longest shoots. There was a highly significant relationship between midday stem water potential and leaf area and VPD when all seasonal data where pooled together. When this relationship was calculated for each cultivar VPD was always non-significant while leaf area was highly significant and it turned differences between cultivars. When we established a relationship with all cultivars for each measurement date, none resulted significant regardless differences in leaf area an leaf water potentials between cultivars. This may indicate that i) the daily range of the data for both stem water potential and leaf area is not wide enough for the relationship to be significant ii) enough soil water content to satisfy ambient demand for the surface area of any cultivar.