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Fruit Varieties Journal
(Fruit Var J)

American Pomological Society

Volume 50 Number 4 Article 39 Pages: 235-247
Year 1996 Month 10
Title: Clone Selection of Grape Vine Varieties in Germany
Authors: H. Schoffling and G. Stellmach
In Germany, clonal selection based on plant performance is a 200 year-old tradition. The present program, 'Systematic preservation-breeding' of varieties is a legally established system and is based on careful individual plant selection with subsequent biometrical tests on descendants (clones). First characteristics of about 10,000 vines were observed for five years. Thereafter the number of individual vines per clone was approximately 100 in every test. Must density, total acidity and ph-value were determined with sample of berries and yield determined from number of bunches, number of berries per bunch as well as their average weight. Statistical evaluation of the initial results in the individual vine selection consisted of the four field method. The main procedure for systematic maintenance of clonal varieties consisted of a complex series of observations and repeated tests. These resulted in A-, B- and C-clones. Basic propagation material came from C-clones. Certified plants came from Basic plants. Besides freedom from leaf-roll disease and ringspot diseases, such as yellow mosaic, virological tests were required on the mother stock plants. Plants were also tested for nepo-viruses, the corky bark pathogen, Rupestris stem pitting and Kober stem grooving. Optimum growth clones were selected which had less vigorous growth but satisfactory yield and quality. For example, a favorable starting position was to select Aclones with up to 20% less growth but good yield levels. Differences in bunch rot resistance among clones was greatest in 'Auxerrois' and least in Pinot noir. A trial with 11 A-clones of Riesling, showed that between the years 1991-1993 the range in portion of fallen bunches, amounted to 190%, and ranged between 9 and 26 kg/acre. Frost resistance clones produced yield decreases of only 25% in frost years; sensitive clones decreased 56%. Investigations into chlorosis-resistance among clones suggested that differences of up to 30% were produced among the 13 Riesling clones. Other resistances may also be worth investigating such as resistance to stem atrophy. When berries were smaller (e.g. clone Weinsberg 29) must density and wine quality increased. The size of the grape yield was determined primarily by the number of bunches. The number of berries per bunch and the individual berry weight were mostly affected by fruit set. Sensory wine assessments from clones growing under the same cultivation conditions produced maximum differences in the nose, in the taste, in harmony and in quality of up to 40%. This demonstrates that some clones produced better wines.

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