Reproductive Development in Grape (Vitis vinifera L.): Responses to Seasonal Water Deficits

Abstract

The sensitivity of reproductive development to water deficits was investigated in Vitis vinifera L. cv. Cabernet franc by altering the supply of irrigation water in a drip-irrigated vineyard in Napa Valley, California. Midday leaf water potentials indicated that significant water deficits were imposed when water was withheld before or after veraison. When water was supplied at a rate 2x the standard production practice, fruit growth, cluster initiation, and differentiation of buds were increased. The data showed that yield increases of 30% to 40% can be obtained by increasing irrigation above the standard practice. Vine water status decreased until veraison in all treatments, but treatment differences did not occur until after fruit set. Water deficits imposed before or after veraison inhibited yield, fruit expansion, and bud development, but early deficits were more inhibitory. All water deficits depressed development of second crop. Yield component analysis indicated that the greatest amount of variation in yield was explained by variation in berries per cluster.