What does the word “hybrids” mean to you…and rootstock? Surely, you’ve thought of something bad, haven’t you? Whatever one’s position, the fact is that viticulture today thrives on hybrids. How did hybrids come about and what do they represent?
The emergence of hybrids and the metamorphosis of viticulture
The golden age of direct producer hybrids, HDP
So the chemicals sprayed on the plant had no effect, because the insect found refuge in the soil. However, researchers at the time noticed that American Vitis vines tolerated the lice, so they thought of solutions with their ‘involvement’. So that’s pretty much where the era of using hybrids in viticulture started.
Direct producer hybrids, HDP – they don’t need to be grafted, they grow on their own roots, very resistant to phylloxera. HDP have arisen by natural or artificial cross-pollination of different grape species. At most, crosses have used offspring up to the 4th generation. That is why there are up to 50% Vitis Vinifera in the gene pool of direct producer hybrids.
The first attempts were to hybridise the American variety Vitis Labrusca with noble varieties. Gradually, it became clear that the use of direct producer hybrids does not guarantee a quality wine, because of the watery structure, with no chance of lasting over time. Moreover, HDP can damage the nervous system due to an extremely high ethanol content, or high concentrations of malvidin diglucoside. Today, direct producer hybrids are banned from commercial consumer production in the EU, but unfortunately they are still found in people’s backyards. Have you heard of strawberry/Isabella? Well, this is one of the banned hybrids, there are others like Othello, Noah, Jacques Clinton and Herbemont, etc.
Which hybrids can be planted or from which wines can be produced? The answer is clear – Interspecific hybrids bred to be resistant to extreme temperatures, various cryptogamic diseases (diseases caused by grey rot, mange, mealybug, etc.) and insect pests such as phylloxera. Moreover, by creating disease-resistant interspecific hybrids, winegrowers have been given the opportunity to avoid the overuse of pesticides containing heavy metals. Interspecific hybrids contain 75-80% Vitis Vinifera in their genes. But most importantly, thanks to such hybrids, today we have a viticulture that can develop. Here I refer to rootstocks.
What is a rootstock?
In 1869, a researcher named Laliman was keen to highlight the importance of grafting European varieties onto a rootstock of American varieties (they are also called wild varieties). This new practice has shaken up the wine industry around the world. Some took up the challenge early on, while others implemented the practice later. In the same vein, the first rootstocks were created by selection using Vitis Rupestris and Vitis Riparia, then hybridisation was used. This time another American variety was used – Vitis Berlandieri crossed with either Vitis Rupestris or Vitis Riparia.
The first rootstocks used worldwide were created by Labrusca x Riparia selection. The best known and most used in Europe were Vitis Riparia with reference to Riparia Gloire. From the frost-resistant Vitis Rupestris, Rupestris du Lot was obtained. It was widespread in the Mediterranean, South America, California and Bulgaria. However, the rootstock was vulnerable to phylloxera. Today it is no longer used because it is overtaken by other hybrid rootstocks such as 140 Ruggeri and 1103 P.
Sounds pretty complicated, doesn’t it? Rootstock is a theme that cannot be neglected by a winemaker who wants to produce exceptional wines. But it’s quite a complex and interesting subject. Note that it’s not only the climatic conditions, soil, temperatures and slopes that contribute to a quality wine, but also the suitability of a rootstock. In the literature, the compatibility between variety and rootstock is called “affinity”.
So how is the rootstock used? Let’s say we want to plant a parcel of Cabernet Sauvignon that will grow healthy and produce high-quality grapes. What do we need? First of all, we need to know everything about that plot. I mean climate, wind, exposure, slope inclination. Including research, even laboratory research, on everything from temperature, humidity, minerals, Ph, limestone levels and soil structure. Taking these factors into account, a rootstock should be chosen that is compatible not only with the natural factors but also with the graft variety. Thus, in order to save the vineyard from the killer insect, the root should be represented by a rootstock compatible with the graft, i.e. the Cabernet Sauvignon stem. How and when does the process of joining them take place?
Obviously there are several methods, the most popular being the Omega method and it refers to cuttings. Here you can see a video that clearly explains how grafting of cuttings and their production takes place. Another method would be directly in the vineyard. See here for another explanatory video.
How is it possible for two different species to live together? Basically, by grafting, we are forcing them to put up with each other all their lives, even if sometimes it won’t be an easy life, because they will both want to give birth to their own children and go their separate ways. So the intervention of the winegrower will be necessary this time too, especially to obtain good results that will be reflected in the quality of the wine.
How many kinds of rootstocks are there and how do they differ?
I will not mention all the existing root stocks. They are used depending on the terroir of a wine-growing region. In the Republic of Moldova, depending on the micro-climate and the affinity for a particular variety, the rootstocks Riparia 101-14, Kober 5 BB, SO4, Ruggeri 140 are used.
- Berlandieri x Riparia crosses produced Kober 5BB, SO4, 420A, 5 C and Christmasel-2 rootstocks. High vigour rootstocks which are also transmitted to noble grafted varieties. Resistant to chlorosis. Chlorosis also occurs if there is a large amount of limestone in the soil which the plant cannot tolerate. As a result, the leaves turn yellow.
- Berlandieri x Riparia Kober 5 BB – bred in Austria by clonal selection from Berlandieri x Riparia Teleki seeds. This rootstock grows vigorously, phylloxera resistant, drought and frost tolerant. It tolerates excess moisture. Roots thrive in all soil types. It tolerates soils that do not exceed 20% limestone. Has an affinity for all types of noble varieties. In Moldova it was introduced in 1946.
- SO4 – created in Germany by clonal selection Berlandieri x Riparia Teleki 5 A. Other experts believe that the rootstock originates from Berlandieri x Teleky 4 A. Drought tolerant, accepts soil limestone concentration of 17%. Cuttings are vigorous and hardy. Shoots grow vertically, which helps to tie them to the trellis. Sensitive to harmful salts in the soil.
- Crăciunel 2- created in Romania in 1935 by clonal selection Berlandieri x Riparia Kober 5 BB. Vigorous growth. Resistant to phylloxera, drought and excess moisture.
Resulting rootstocks between Riparia x Rupestris: 101-14, 3309 C.
- Riparia x Rupestris: 101-14 MGT – variety bred in 1882 in France. Portaltoi closer to the variety Riparia than to Rupestris. Resistant to phylloxera, lower temperatures and less heat and humidity. Does not tolerate soils with a limestone content above 9%. It has an affinity for most European varieties.
There are other rootstocks resulting from these varieties, such as Riparia x Rupestris 3309 C which unfortunately is less resistant to extreme temperatures and forms shoots from the stump head which is costly to remove, so is not so widely used by winemakers.
Berlandieri x Rupestris crosses have resulted in rootstocks: 1103 P, 110 R, 140 Ruggeri (140 Ru), etc.
110 R and 140 Ru give the must a more acidic taste and a lower Ph. 140 Ru has more vigorous wood and 110 R is widespread in the Mediterranean, resistant to chlorosis and heat.
1103 P is planted on clay soils. The roots do not need to grow too hard. Resistant to heat and humidity.
How to choose a rootstock?
First of all, its resistance to phylloxera and other diseases will be taken into account;
the degree of affinity, in other words, the ability of the noble varieties (graft) to live and develop with a rootstock;
The type of soil and the level of limestone that the varieties involved can withstand. For example, Riesling, Traminer, Silvaner varieties are more sensitive to limestone chlorosis. Most varieties in the Pinot family are resistant to chlorosis. Excess limestone in the soil blocks soluble iron and limits the plant’s access to the elements needed for growth. Recently, the Fercal rootstock has been developed, making it the most resistant to chlorosis. It can also withstand high temperatures and humidity. It produces quality wines with a high ageing potential. Perfect for dry climates with calcareous soils;
Acid soils are usually soaked with heavy metals, which does not allow root development. However, a new rootstock resistant to such soils has been developed – Gravesac;
Other environmental conditions such as temperature extremes (cold and drought), soil moisture. The resistance of rootstock varieties to excess moisture is determined by the way the root system develops. Varieties with a strong root system have been found to be more resistant to drought and soil moisture. They can also resist mineral content, including heavy metals;
Growing season. The relationship between graft and rootstock determines the start of the bud break and flowering period;
Often, on the more vigorous rootstock, the graft acquires similar traits. Vine growers in warm regions do not prefer this property, because the vine develops foliage and high productivity. A very vigorous root and plant are suitable for temperate continental climates, regions with mineral-poor soils. Of note, the rootstock is responsible for mineral uptake from the soil.
The most used rootstocks in Moldova
For example, Codru region, with heat and relative humidity, hot summers, unstable springs and cold winters, Sauvignon Blanc grafted on different rootstocks will have different results. Research observations over a period of 5 years have shown that on Ruggeri 140, compared to other rootstocks, most of the Sauvignon Blanc plant’s meshes could not withstand frost. The most productive rootstocks proved to be those with a high carbohydrate content in the must. Such as, for example, 101-14 and Kobber 5 BB. However, the most appreciation was given to wines whose plants developed on SO4 and Kobber 5 BB.
Merlot from warm areas with sandy soils becomes a very vigorous plant on SO4, as opposed to growing on its own roots. But this unintentionally accelerates an excess of nitrogen that is contraindicated in viticulture. Merlot on SO4 gives a rich harvest in Mediterranean regions, but lowers yields. The plant is rich in leaves. Merlot must has a lower alcohol level. Therefore, the SO4 rootstock is recommended for continental climates, with relative humidity, on soils with a higher clay content, or on soils poor in minerals. Merlot also gives outstanding results on 101-14 rootstock, where the climate is continental, on soils with a heavier structure. Similarly, Pinot Noir is compatible with the 101-14 rootstock, as the soils are calcareous, with relative humidity.
In the case of Syrah, it gives exceptional results on 101-14 and 140 Ru, but only on certain soils. Rather, the results also depend on the region chosen. Depending on the soil and climate conditions, the appropriate rootstock will be chosen. Cabernet Sauvignon from regions with continental climates appreciate the 101-14 rootstock. It is cold-resistant. New selection varieties (Viorica, Riton, Alb de Onițcani, etc.) have an affinity for Kober 5 BB.
If the root is a rootstock with soil type requirements, do we still take into account the preferences of the noble variety?
In my rootstock research, I asked myself the question, “If root is a very picky rootstock in a particular soil type, why do people fret that noble varieties have preferences for this or that soil?” The answer is quite complex. Through the rootstock, the plant feeds itself. Let’s say we have a few rows of the Chardonnay variety planted in poor soils on a rootstock that is sensitive to limestone. In this case, this Chardonnay will not present a quality wine. The reason is that the variety, itself, prefers chalky, chalky medium soils. Therefore, the rootstock should be chosen carefully taking into account the existing terroir.
In conclusion, thanks to hybrids and rootstocks, we are not only managing to keep phylloxera under control, but we are also developing viticulture despite the existing challenges. Basically, depending on the rootstock, the root can grow anywhere, but it depends on the ability of the graft to adapt, to accumulate the minerals needed to produce quality wines. It should be noted that if the rootstock has not been chosen correctly, including the wrong affinity, then absolutely nothing can be done. Why? Because the plant has undergone a morphological change, it has adapted by living alongside the rootstock. The only solution is to start again!
Selective bibliography
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