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lundi, 14 octobre 2013

MASSAL OR CLONAL

MASSAL OR CLONAL SELECTION?

Corrected version


Claude Gilois

Massal selection consists, in the first instance, of visually selecting the best vines from a vineyard, usually over 50 years old, to perpetuate the diversity that has been created over time. The second phase involves the transplant of some genetic material onto young vines.  In contrast, clonal selection consists of producing genetically identical vines in a nursery over a period of time, approximately 20 years, before selling them. A vineyard can be planted with a single or with a mix of several clones. 

 

Jean Michel Cazes, owner of the Chateau Lynch Bage and Ormes du Pez has been using massal selection for the replacement of his vines since 2005. He argues: ‘Old vineyards are the result of observation, adaptation and optimisation of the vines on its terroir. Genetic diversity gives us a better guarantee against disease in adverse conditions and even catastrophic situations that could more easily threaten clonal vineyards. Jean Michel Cazes has a way of perceiving the massal procedure as a sort of Darwinian selection where nature is not in total control, but where human intervention also plays a part as it benefits from ‘a little help from our friend’: the human factor. But, realistically, how much genetic diversity is brought about by massal selection? The answer is practically none, as there is no hybridisation, therefore no crossing of genetic material in old vineyards. The vine evolves by somatic mutations that can produce a marginally better resistance, but certainly not to protect vines from catastrophes such as phylloxera.

 

The qualitative argument for using massal rather than clonal selection seems more admissible on face value, but is it really convincing? It is worth noting that clonal selection has only existed for about a quarter of a century, before that all selection was massal and yet vines have probably never been in a worse shape than now. 

 

Mark Bixler from Kistler Vineyards, which produces some of the best chardonnay in California and indeed in the world, declares: ‘We use the old Wente clones and we can trace their origins to the region of Livermore, 50 kms east of San Francisco about 100 years ago. Flowering is particularly bad and you only get very small berries, in fact it is similar to the disease called millerandage, the skin is very thick, the colour is pale yellow, the berries have an important concentration of minerals, the acidity is high and the fruit very lemony and juicy’; but he adds: ‘I am sure that a hundred years ago it was not like this. It is wrong to oppose clonal selection to massal selection, once you have the desired grape with massal selection you can clone it, this is how the Wente clone came to exist.

 

For the aficionados of clonal selection, there is too much danger in using massal selection, as visual examination does not reveal all, in particular what is going on inside the vine. Even if the vines appear in good health, you cannot exclude the presence of a virus that could be transmitted to the new vineyard’. He adds: ‘even if I do not have the same diversity with clonal selection, I usually plant no less than 8 clones and 10% of the total vineyard is planted with massal selection. This is the way to avoid criticism of standardisation that   is often levelled at clones. The problem is not so much the clones but the types of clones that you choose. If you select prolific clones, then you are never going to get great results. You need to select clones that are not too productive. 

 

And, of course there is viticulture: one cannot conduct viticulture of a young vineyard as one conducts that of an old vineyard.   Young vines are more prolific even if you choose low production clones. You have to control the vigour of vines. We now know that it is possible to achieve small yields with young vines. You have to prune short with less productive techniques, limit fertilisers, and plant grass in between the rows etc.

 

Would the debate between massal or clonal selection not be a false debate?  The real truth is probably about controlling yields, rather than opposing massal to clonal selection, without which high quality is not possible.  

 

 

 

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