Water Deficit Effect on Ratio of Seed to Berry Fresh Weight and Berry Weight Uniformity in Winegrape cv. Merlot

Abstract

The objective of this research was to investigate the effect of vine water deficit on berry tissue components and berry weight uniformity at maturity. Field-grown grapevines cv. Merlot (<i>Vitis vinifera</i> L.) were differentially irrigated over six consecutive years to maintain a high or low level of vine water stress from fruit set until harvest and clusters were sampled at maturity in the third and fifth year. Detached berries were individually weighed to assess weight uniformity within each irrigation regime and to obtain a sample of similar weight berries from each level of irrigation. Vine water deficit was associated with up to a 27% increase in the proportion of seed to total berry fresh weight regardless of berry size. Berry weight within each irrigation regime was distributed normally and water deficit did not affect berry weight uniformity at maturity. Results have implications for winemaking because a greater ratio of seed to total berry fresh weight alters the proportion of seed-derived relative to skin-derived compounds present during fermentation.