|E. Rühl, H. Konrad, B. Lindner, E. Bleser
Clonal selection in Germany commenced at the end of the 19th century.
The major cause was the low performance of vineyards at the time.
Infections by GFLV, ArMV or GLRaV1 were the main reason for reduced fruit-set and low production.
As virus infections, the major cause for the degeneration of grapevines, had not been identified and consequently no direct tests existed for them, early clonal selection focussed on visual assessment of appearance and performance.
By the mid 1950s high performing clonal propagation material of most traditional varieties was available.
Since the early 1970s only clonal material has been planted.
With the large scale introduction of clones the problem of diminishing genetic resources within traditional varieties arises, as vineyard, planted with unselected or mass-selected propagation material, disappear fast.
To assess the need for preserving the genetic range of traditional varieties, a trial was established in 1988 with Pinot noir types of different origin.
The material was virus-tested, grafted to 5C rootstock and established on a uniform site at the department’s vineyard.
Data were collected between 1993 and 1998. Average yield of clones ranged from 657 to 1623 gm-2, juice acidity from 9.4 to 13.6 g L-1, sugar level from 20.7 to 22.0° Brix and botrytis infection from 2 to 26 % infected berries.
These data demonstrate the importance of genetic variation within traditional varieties.
This genetic variation is the source of clonal selection and therefore has to be preserved and protected for future generations.
To prevent gene erosion, German breeders, in particular Geisenheim, try to maintain the genetic range within varieties by selecting a large number of different clones of each variety.
The task of clonal selection in the future has to be the development of a large range of superior clones with a wide genetic width and the preservation of genetic variability between and within varieties.
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