Agriculture Reference
In-Depth Information
diverse techniques and methods by which to
identify grapes. These include:
ence is necessary to correctly identify cultivars
on the basis of physical parameters alone (and
not all researchers have that experience or the
time and means to acquire it), and it is very easy
to make mistakes. Furthermore, grapevine
morphological features such as leaves and
bunches can be greatly affected by the environ-
ment. For example, the size of grape bunches
and berries can differ based on water access
and the availability of minerals in the soil, as
well as the yields of the grapevines.
Also, morphological identifi cation can be
applied only when berries and leaves are fully
visible, so ampelographic recognition can take
place only at certain times of the year. The onus
is then on nursery personnel to work accurately
and correctly: only several years after a vineyard
is planted are mistakes noticed. Everyone knows
of producers who thought they were growing
Cabernet Franc or Merlot or Albariño only to
realize their vines were Carmenère or Savagnin
instead. Nursery mistakes such as these are
more frequent than is commonly believed.
To increase precision, ampelometric meth-
ods were added to ampelographic observation.
Ampelometric methods possess the advantage
of being less subjective than ampelographic
characteristics, as they are measurable. In 1983,
the Offi ce International de la Vigne et du Vin
(OIV) published the
Code des caractéres descrip-
tifs des variétés et espèces de Vitis
(Code of the
Descriptive Characters of the Varieties and Spe-
cies of
Vitis
) in French, English, Spanish, and
German. In it, they presented the codifi cation
of 128 ampelographic descriptive characters
(later reduced to a more manageable eighty-
four), a method adopted by other international
organizations, including the International
Board for Plant Genetic Resource (IBPGR) and
the International Union for the Protection of
New Varieties of Plants (UPOV).
•
Ampelographic descriptions and ampelomet-
rics: the former describe the morphological
characteristics of grapevines; the latter
consist in measurements of organs and are
less subjective than ampelographic methods.
•
Biochemical methods, such as isoenzyme
analysis or aromatic molecule precursor
analysis, that reveal the presence or absence
of specifi c enzymes and of some metabolites
in each variety.
•
Biomolecular methods, which reveal DNA
sequences specifi c to single varieties.
The use of all three methods together allows for
more accurate variety identifi cation. Ampelogra-
phers and geneticists cannot function to their full
potential working alone; in fact, the identifi cation
of grape varieties is very much a team effort.
AMPELOGRAPHY
Ampelography is the fi rst step toward charac-
terization of a grape variety and of fundamental
importance for subsequent genetic testing.
Grapevines are classifi ed based on the appear-
ance of their leaves, shoots, berries, bunch
appearance, and color, and by viticultural
parameters such as date of fl owering or har-
vest. The data compiled is tremendously spe-
cifi c and precise; for example, within the cate-
gory of leaves, everything from single
indentations to color of the veins is considered.
Another example is the shoot tip, the color of
which can be a very useful descriptor in the
spring: for instance, the white tip of Merlot dis-
tinguishes it from Cabernet Franc or Cabernet
Sauvignon, with which it is often confused.
These ampelographic characteristics are classi-
fi ed by qualitative, quantitative, and alternative
characteristics, and may be either present or
absent. By compiling this data, a reasonably
accurate but not infallible identifi cation of a
variety may be made. However, diffi culties
abound. For one, an immense level of experi-
CHEMICAL ANALYSIS: ISOENZYMES,
SECONDARY METABOLITES
Until DNA testing became routinely available in
the twenty-fi rst century, biochemical methods
