Volume 50 Number 4 Article 39
Year 1996 Month 10
Title: Clone Selection of Grape Vine Varieties in Germany
Authors: H. Schoffling and G. Stellmach
Abstract:
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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