Rootstocks of prestigious Bordeaux vineyards: implications on quality and yield

Rootstocks have been used in most of the vineyards for over a century. This may seem to be a long period, but it represents only three successive plantations. Moreover, during this period of time, production objectives have changed. This study shows the implications on quality and yield of rootstocks used in prestigious red-wine producing vineyards in the Bordeaux area. It has been carried out on 400 hectares localized in five main appellations of the Bordeaux vineyard. In total, 15 different rootstocks are used. A quality index is created by weighing the destination of grapes of each plot (first wine, second wine, third wine) by the economic valuation of each wine produced in these properties. First quality is rated 4, second quality 1.5 and third quality 0.
The first results show that two rootstocks, Riparia Gloire de Montpellier (RGM) and 420A, cover 67% of the planted area. Including 3309C, 101-14 MG and SO4, 94% of the total acreage is represented. The highest quality is produced with 420A, RGM and 3309C (average quality index > 2.5). The highest yields are obtained with 161-49C, 101-14 MG, 5BB, RGM and SO4. The quality of the production with RGM and 3309C increases year after year linearly. Surprisingly, the quality of the wine produced by plots grafted on SO4 decreases after 35 years. In terms of age class, SO4 gives the best results during the period 0-30 years, 3309C for the period 30-40 years and RGM in plots of over 40 years old. Yield decreases with age, but more rapidly for some rootstocks (SO4) than for others (RGM).
Some results confirm what is already widely admitted: RGM is a high quality potential root-stock and wine quality increases with vine age. Other results are more surprising: 101-14 MG appears as the most vigourous rootstock of the list and RGM as a dryness tolerant rootstock. These last two points need to be studied on a larger scale to confirm these results.