Reproductive performance of cabernet sauvignon and merlot (Vitis Vinifera L.) Is Affected When Grafted To Rootstocks

Abstract

Background and Aims: Cabernet Sauvignon and Merlot are Vitis vinifera cultivars known to be susceptible to poor fruitset in cool climates (MJT 19°C-20.9°C). The importance of rootstocks in viticulture is well documented, particularly in relation to yield, salinity and water relations; little is known, however, about how rootstocks affect reproductive performance. This study assessed the reproductive performance of Cabernet Sauvignon and Merlot grafted to rootstocks. Methods and Results: Cabernet Sauvignon and Merlot grafted to rootstocks, Ramsey, 5C Teleki, Schwarzmann and 1103 Paulsen, were assessed for reproductive performance over three consecutive growing seasons. This was measured by assessing the following: bud fruitfulness, flower number per inflorescence, fruitset (%), berry number per bunch, coulure index (CI), and millerandage index (MI). Fruitset was higher when grafted to rootstocks compared to that of ungrafted vines which corresponded to a decrease in MI and CI. For Cabernet Sauvignon, there were no observed differences in fruitset, however, fruitfulness and bunch number were higher when grafted to rootstocks compared to ungrafted vines. Conclusion: Rootstocks affect fruitfulness and fruitset in Cabernet Sauvignon and Merlot, however, reproductive performance differs between cultivars when grafted to the same rootstock. Significance of the Study: Rootstocks may be used as a management tool to manipulate the reproductive performance of Cabernet Sauvignon and Merlot in cool climates. © 2013 Australian Society of Viticulture and Oenology Inc.