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The Origin Of Grapevine Cultivars
Prof Chris Orffer* & Charles Visser, Vititec
Grapevine cultivars are vegetatively propagated to ensure that the unique characteristics of each cultivar are retained. New cultivars can only be created by means of sexual reproduction, either by spontaneous or intentional hybridisation.
Upon the release of new cultivars, there are often doubts concerning the parents of the cultivar. Until fairly recently the relationship between cultivars was mostly derived from leaf morphology. A fair amount of speculation was involved in trying to determine the origin of grape cultivars.
Few newly created grapevine cultivars could improve on the so-called noble cultivars such as inter alia Chenin blanc, Sauvignon blanc, Chardonnay, Pinot noir, Cabernet Sauvignon and Shiraz. An exception was the Riesling/Sylvaner hybrid from Dr Müller of Thurgau, Switzerland which at one time exceeded the plantings of Riesling in Germany. At a later stage its lineage was questioned by certain researchers because its traits practically agreed with Riesling only and not Sylvaner. Recent DNA analysis revealed the parents to be Riesling and Madeleine Royale.
The use of PCR (Polymerase chain reaction) and micro-satellite markers revolutionised grapevine identification and parent analysis. Bowers and Meredith (1997) succeeded in identifying the parents of the classic Bordeaux cultivar, Cabernet Sauvignon.
Cabernet Sauvignon was found to be the descendant of two other Bordeaux cultivars, namely Cabernet franc and Sauvignon blanc. Bowers et al (1999) also established that Chardonnay and Gamay noir, as well as 14 other French grapevine cultivars, were the descendants of the famous Burgundy cultivar Pinot noir and the practically unknown Gouais blanc.
The authors also showed that the famous Rhône valley cultivar, Shiraz, descended from Dureza of Ardèche and Mondeuse blanche of Savoy in south-eastern France. This repudiates earlier claims that Shiraz originated in the Middle East.
The parents of many cultivars will probably never be determined because they no longer exist. Pinot noir, for example, is considered to be a very old cultivar and might well have existed in the first century. Columella describes a cultivar in De Re Rustica which could possibly have been Pinot noir (Viala & Vermorel, 1901). The name Pinot was first documented in the fourteenth century. Until now no parents have been traced for this economically important cultivar.
In the past knowledge of grapevine genetics was very limited in South Africa. Studies of hybrids and their parents mostly involved the details of their leaves, bunches and wine. With regard to Pinotage, for example, the flavour and darkly coloured wines were queried, since none of the parents, namely Cinsaut and Pinot noir, had similar characteristics. In 2007 the parents of Pinotage were confirmed by means of a PCR analysis by ENTAV (Etablissement National Technique pour l'Amélioration de la Viticulture), France.
Successful local hybrids, namely Pinotage, Chenel, Weldra, Therona, Nouvelle and Roobernet, were developed by means of open air hybridisation in vineyards and not under controlled hothouse conditions.
Auto pollination in Vitis vinifera may take place freely while the operator is engaged in hybridisation. Errors may also occur in the collection of pollen, grape seeds and labelling.
The Department of Viticulture and Oenology at Stellenbosch University did not have specialist personnel for the dedicated creation of hybrids and the evaluation thereof. Hybridisation at the Department of Viticulture and Oenology therefore took place alongside other obligations such as under- and post-graduate student teaching, consultation to producers and winemakers, research, supervision of experiment farms such as Elsenburg, Welgevallen, Robertson, Lutzville, as well as vineyards at Groot Constantia, KWV, SEAC (Stellenbosch - Elsenburg Agricultural College), trials in the districts of Constantia, Stellenbosch, Paarl, Robertson, Worcester, Montagu, Barrydale, Riebeek-Kasteel, Riebeek-West and Tulbagh.
The objective of the Department of Viticulture and Oenology was not genetic research, but to establish fairly big populations of hybrid seedlings each year, with a goal of approximately 1 000 per annum. This was initiated on a small scale by Prof Orffer in 1949, with a two-year hiatus during his doctoral studies at the University of California. The work continued until his retirement at the end of 1986.
Final judging of seedlings was based on strict criteria. Tolerance to botrytis and sour rot were important traits. Low yields and poor vigour were not tolerated at all. Sunburn tolerance and resistance to wind were likewise important characteristics. Wine quality had to be acceptable for the low to medium price categories.
Based on the above criteria Pinotage should have been eliminated from a cultivation point of view. At Welgevallen, in years with a strong southeaster, extremely low yields were obtained due to canes being ravaged by the wind.
As with Pinotage there were doubts concerning the parentage of Therona, Nouvelle and Roobernet. Therona is a hybridisation of Cape Riesling (Crouchen blanc) and Chenin blanc, but this has not yet been confirmed by PCR. In Nouvelle the petiole sinus is fairly open, which might point towards Sémillon. On the other hand, certain leaf and berry traits refer to Ugni blanc. Initially the parents of Nouvelle were thought to be Sémillon and Cape Riesling. With PCR it was confirmed in 2007 by ENTAV, France that it is indeed Cape Riesling and Ugni blanc.
Initially the parents of Roobernet were said to be Cabernet Sauvignon and Pontac. There were indications, however, that Pontac was probably not one of the parents. Given the popularity of the old Constantia wines, numerous hybrids of Cabernet Sauvignon and Pontac were created over many years. Due to the inferior wine quality of Alicante Bouschet, it was never used as a hybrid parent.
After 20 years' observation Roobernet proved the best of all coloured juice hybrids, with yield and vigour often exceeding that of Cabernet Sauvignon. Morphologically the leaves of Roobernet hardly resemble Alicante Bouschet and are often confused with Cabernet Sauvignon. The big bunches and high yield are indicative of Alicante Bouschet, however. In 2007 the parents of Roobernet were confirmed by ENTAV as being Cabernet Sauvignon and Alicante Bouschet. Pollen from Alicante Bouschet must have crept in somehow.
Controlled creation of hybrids is fairly new. Indications are that Bouschet in France created the first hybrids from Aramon and Teinturier (Pontac).
The development of the classical noble cultivars as we know them today from age-old wild cultivars is truly exceptional, in view of the fact that up to now very few successful hybrids have been created artificially by man.
Domestication of the grape is probably linked to the discovery of wine. During the domestication process the biology of the grape underwent remarkable changes to produce a higher sugar content for improved fermentation, as well as bigger and more constant yields. A decisive factor in the process has been the change in berry and bunch sizes and the change from wild, dioecious plants to hermaphrodite cultivated plants. It is not known whether the changes occurred over a long period through sexual hybridisations and natural or human selections or quickly by means of mutations, selections and vegetative reproduction (This et al, 2006).
REFERENCES
Bowers, J.E., Meredith, C.E. (1997). The parentage of a classic wine grape, Cabernet Sauvignon. Nature Genetics, 16: 84 - 87.
* Prof Chris Orffer was professor in Viticulture at Stellenbosch University from 1963 to 1986. He passed away in March 2008.
Between 1958 and 1964 Prof Orffer created several grapevine hybrids, six of which were granted cultivar status, viz. Chenel, Weldra, Roobernet, Therona, Grachen and Nouvelle. He also created numerous rootstock hybrids, the best known being US 2-1 and US 8-7.
Shortly before his death Prof Orffer requested Vititec to investigate the parents of some of the hybrids, because he suspected some of the parents to have been indicated incorrectly. This article is based on a document that was sent to Vititec in February 2008 by Prof Orffer, after he received the results of the DNA parentage analysis.
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