Riparia x Rupestris

24 October, 2006

Rupestris x Riparia, the most popular of the crosses due to the favourable characteristics displayed by both vines.

Initially, hybrids derived from these ‘parents’ were expected to lead to high quality rootstocks and consequently, were used in all the prime viticultural areas of the world.

Rupestris is a drought tolerant vine also known as Rupestris St George, Rupestris du Lot or Ruperstris-Monticola. This extremely vigorous vine has a long growing season and displays excellent phylloxera resistance.

In contrast, Riparia Gloire du Montpellier can withstand wet feet and is one of the oldest rootstocks used against phylloxera in France. Low vigour, lower yields of quality fruit and early ripening are hallmarks of this rootstock.

Quality and vigour issues

The Rupestris – Riparia hybrids we are about to take a look at display low to moderate vigour, in keeping with viticultural belief that low vigour and quality go together. However, if growers go too far in encouraging low vigour, then this trait will work against them as the pressure placed on the vine to produce an economic quantity will become untenable and this in turn will put undue stresses on the vine

Rupestris – Riparia crosses are:

• Are ideal for New Zealand conditions (cool climate viticulture) although we need to remember that in Marlborough, all vines need some irrigation at certain times of the year as these crosses have relatively low drought tolerance.
• Deliver moderate yields. These crosses confer low to moderate vigour to scions and low vigour in some Marlborough areas can become a problem.
• Give excellent phylloxera resistance
• It has been proven that Rupestris – Riparia crosses can improve fruit set in varieties such as Gewürztraminer and Merlot are good examples.

In the past there have been some incompatibility problems with Rupestris – Riparia crosses in that they have failed to graft well. Newer varieties have eliminated this incompatibility and the vines should grow together and keep going for decades.

In Marlborough the most commonly found rootstocks are:

• 3309 C, also known as 3309 Couderc. This cross was made in 1881 when George Couderc planted 18 seeds in a row of the nursery where he had added lime. Of the five that did not show chlorosis (iron deficiency caused by soils high in lime), 3309 C became the most successful. Combining high phylloxera tolerance with medium lime tolerance, this rootstock is ideal for less drought prone soils. Rooting and grafting are easy and use of this rootstock is widespread in NZ. Bud burst in similar soil is a few days earlier.
• 3306 C. This is also one of the Couderc selections and is very similar to 3309C. Bud burst is around 1 week later then 3309C but maturity occurs at the same time. The vegetative cycle lies in between 3309C and 101-14.

3306C is slightly more vigorous but similar in yield.

Schwarzmann is a cross displaying high tolerance to both phylloxera and nematodes but only moderate vigour. It can withstand a fair amount of water and is therefore suited to some of wetter areas that are found in some parts of Marlborough.

In Marlborough rootstock trials it has consistently one of the lowest pruning weights with a slightly higher yield compared to 101-14.

Bud burst is early and the vegetative cycle is a little shorter compared to the other crosses

• 101 –14 Millardet et de Grasset is a lower vigour, early maturing rootstock developed by Professor Millardet and the Marquis de Grasset in the early 1880’s. 

The rootstock has high phylloxera tolerance but moderate nematode tolerance and has a shallow root system. After SO4/5C, 101-14 would be the most widely rootstock used in Marlborough since the early 1990’s.

101-14 has been very successfully used in different NZ wine growing regions. However, we have also encountered a number of problems associated with this rootstock.

The first problem has been associated with Grass grub. High failure rates during plant development and death of mature vines grafted on 101-14 have been noticed in the last few years. (D. Mundy Hort Research 2003).

The second problem is not the fault of the rootstock but more the lack of understanding on the growers’ part. 101-14 was seen as a “universal” rootstock that would grow well under all circumstances hence the reason as being one of the most widely planted rootstocks. 101-14 does not like prolonged wet feet and is under these circumstances very susceptible to root rots which will result in death of the vine.

Acknowledgement: Additional material for this article was taken from The Oxford Companion to Wine (new edition), edited by Jancis Robinson, Oxford, 1999.