`Pinot noir' and `Riesling' Grapevines Respond to Water Stress Duration and Soil Water-holding Capacity

Abstract

Glasshouse-grown `Pinot noir' and `Riesling' grapevines (Vitis vinifera L.) were subjected to one of four water stress durations [no water deficit (control); and water deficits imposed postbloom, lag phase, and veraison] in combination with three soil water-holding capacities (0%, 26%, and 52% gravel, by volume). Vines subjected to increasing water stress duration had less cumulative lateral shoot length and lower shoot count, leaf size, and berry weights than those not stressed. Soluble solids concentration (SSC) during maturation and pH at harvest also increased with increasing water stress duration, but titratable acidity was not affected. Transpiration and stomatal conductance also were reduced with increased water stress duration, but soil water increased, reflecting the larger leaf surface on vines with veraison-imposed deficits. Reducing water-holding capacity (by increasing the percentage of gravel in the soil) tended to increase berry weight and SSC but reduced lateral shoot growth. The 52% gravel treatments increased transpiration rate and stomatal conductance for `Riesling' but reduced them slightly in `Pinot noir'. Percentage of soil moisture was reduced linearly with reduced water-holding capacity. These results indicate that early irrigation deficits may advance fruit maturity of wine grapes with concomitant reductions in vegetative growth. Differential responses of these cultivars to soil water-holding capacity also should help to identify suitable wine grape cultivars as the wine grape industry expands into areas with low water-holding capacity soils.