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lundi, 12 novembre 2012

TECHNICAL DATA: THE GENETIC OF THE VINE

HOW TO REINFORCE THE GENETIC DIVERSITY  OF THE VINE AND MAKE IT MORE RESISTANT

Hybridization, Genetically Modified Organisms and

Marker Assisted Selection


 

 Hybridization

This is the oldest means and the one that has been used since agriculture was born to improve quality and quantity. By crossing various plants, we also cross the genetic make up and improve their resistance and adaptability to their environment.

Hybridization has played a major role in improving plant diversity and resistance before phylloxera devastated vineyards but since then habridization has been largely confined to research institutes. Much of this research is indebted to Alain Bouquet of the French INRA[1]. In 1974 he initiated a program and started crossing Vitis vinifera plants with Muscadinia rotondifolia, an American vitis that possesses genes resistant to phylloxera, mildew, odium and to a small worm (nematodes) responsible for many diseases of the vine. From his first crossing, he subsequently crossed known Vitis vinifera cultivars such as merlot, cabernet, grenache and the newly created varieties that kept the resistance conferred by the Muscadinia rotondifolia. However, the INRA did not authorise these to be used as new cultivars (apart from experimental trials) arguing that they only possess a monogenetic resistance (only one gene is resistant) that pests could overcome and preferred to wait to develop polygenetic plants (many genes of resistance) to ensure that they would be more resistant to pest infestations. This decision was not consensual in the profession and generated criticism from eminent university professors and various viticultural authorities. 

Today, the INRA has developed 6 grape varieties (five reds and one white) by hybridization, which exhibit polygenic resistance to pest infestation, and experimental trials are currently being carried out in four different locations in France. If the results are conclusive the new varieties could be authorised in 2016. It usually rquires 20-25 years to develop a new variety that is agronomically interesting and shows interesting organoleptic qualities. 

Paradoxically, the use of new resistant cultivars is more developed in some countries. Switzerland, a small grape growing country of great diversity (more than 60 different cultivars) has successfully introduced a hybrid cultivar, Gamaret, obtained by crossing the Vitis viniferas plant with Vitis amurensis from Asian origin. This new grape variety is, today, the most widely planted variety in Switzerland. Three additional grape varieties have since been successfully created, solaris, souvignier gris and muscaris.

The German Frieburg Institute has also been very active in this area of research and seven white new varieties as well as seven red varieties have been created with suggestive names such as Cabernet Cortis, Cabernet Carol, Cabernet Carbon, Prior, Monarch and Baron. They are now listed or will be listed in the catalogue of approved cultivars for quality wine production.

Altogether, in the world today, more than 3000 hectares of these new varieties are being cultivated in 25 different countries in the European Union and also in South Africa, Chile, Australia, and New Zealand etc[i].   In Europe they are all classified as AOP (Appellation d’Origine Protégée) and as Vitis vinifera on the basis of the morphological characteristics. 

It is probably worth mentioning that these cultivars are new and that hybridization techniques involve the transformation of a known cultivar into a different one. This is, of course, problematic when it comes to worldwide known varieties that have contributed to the reputation of regions such as Bordeaux, Burgundy and some other prestigious ones.

 

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Francois Baco practising hybridiztion. He invented the hydrid, Maurice Baco 22A recommended for the production of Armagnac  Maurice Baco 22A is part of the AOC registered grape varieties.  

Genetically modified organisms (GMO)

 

A genetically modified organism is an organism whose genetic materiel has been modified by human intervention. It is worth noting that the American definition also includes modifications that occurred naturally or artificially. The technique involves inserting a small fraction of the DNA of a micro-organism (usually, but not always, a bacteria or a virus) called a transgene into another living organism to modify its genetic characteristics.  So far, for vines, research has essentially consisted in making the plant more resistant.  This type of technology applied to vines came to the fore when an experimental GMO vineyard, set up by the INRA of Colmar to test the resistance of genetically modified vines to fanleaf virus, was destroyed by an anti-GMO activist as indeed were most of GMO cultures in France.   Interestingly enough, a few days before the vineyard was destroyed, the court of Strasbourg cancelled the authorisation of the culture of the experimental vineyard given by the French Ministry of Agriculture, as it did not conform to the European directive 2001/18 that regulates the usage of GMO.

 

This begs the question as to why such potentially useful technology is facing such a huge resistance. The history of its development will cast some light on the subject. 

In 1972 the first experiment of transferring genetic material from one organism to another took place. Confronted with such a powerful technique, the scientists decided to put a moratorium on it, a moratorium that would only be lifted in 1977. In 1980, the Supreme Court of the United States authorised the patentability of living matter, providing it was truly “man-made” (judgement confirmed in 1987). In 1992 the European Union also admitted the principle of patentability of living organisms. In 1998 the Organisation for Economic Co-operation and Development, OECD, established the principle of ‘substantial equivalence’ stipulating that if a new food or food component is found to be substantially equivalent to an existing food or food component, it can be treated in the same manner with respect to safety. This exempted all genetically modified organisms from toxicity tests and any labelling regulations.  As soon as genetic engineering was perceived as a huge potential market worth hundreds of billions of pounds, scientific and ethnic norms were replaced by norms based on the immediate interest of any commercial business: maximisation of profit.  This where the difficulty lies as this powerful technology was introduced in many countries before any political control (democratic control) could be exerted.    Europe, largely, but narrowly, escaped after “a ‘war’ against the genetically modified organisms” described by a journalist from Le Monde, Hervé Kempf, in his book ‘La guerre des OGM’.

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While the technology could be a useful tool for genetic improvement, the opacity in which it was introduced, the control of large transnational industries on such sensitive issues as food production, combined with non-existent evaluations on long term basis, have resulted in a poor acceptability which renders this technology unlikely for the improvement of the genetics of the vine, at least in Europe.

 

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Marker Assisted Selection (MAS) combined with genomic selection

 

This technique, also called Gene Chips or Microarrays technology consists in examining the genetic variations that have occurred over time during the process of domestication of the vine by identifying thousands of markers called SNP (Single Nucleotides Polymorphism) present in the genetic heritage of the vine. Marker Assisted Selection (MAS) is an indirect selection process where a trait of interest is selected, not based on the trait itself, but on a marker linked to it. To do this, rather than identifying genes that are responsible for the major traits of the vine (such as resistance to diseases, flowering, berry size, colour, taste etc), markers, which are tightly linked to genes are used instead as they are easier and more cost-effective to identify.   The markers obtained are then submitted to powerful computer software, to classify genes that are similar or to classify them according to their sequence (hence their function) and to see if the variations are associated with a particular trait of the vine. This technique which consists in genotyping (albeit indirect analyses of the gene) is now becoming cheaper and much quicker that phenotyping (i.e. waiting 3 years to assess the characteristics of the plant   as with conventional hybridization). So it is now quite conceivable that it will be possible to maintain the organoleptic characteristics of certain cultivars (who wants to see the Pinot Noir and Chardonnay characteristics disappear from Burgundy) while modifying the genetic structure of the plant to make it resistant to pests. This, of course, implies obtaining markers from the great majority of known wild and domesticated varieties, selecting those traits that are wanted, hybridising on the basis of the MAS technology as many times as needed to achieve the desired traits in the plant, so expect 5-10 years before seeing the new technology bearing its fruits. But the technology is promising… 

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MAS technology applied to fish

[1] INRA: Institut National de la Recherche Agronomique.



[i] CEPAGES RESISTANTS AUX MALADIES CRYPTOGAMIQUES. Cahier de l’Observatoire viticole n°25.

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