The evolution of Ampelography throughout history.
Ampelography comes from the Greek ampelos , which means vine, therefore, the term can be considered in a general way as ´ ”description of the vine”, a science that has evolved throughout history in parallel with advances in the techniques of characterization and identification.
In the origins , the description consisted of adjectives in a particular way the morphological aspects of the plant that were appreciated with the naked eye. Later on, these characters were narrowed down to be described using a more or less standardized language for the results of said observations. Although there was less and less subjectivity, it was still present in each ampelograph, so that the characterizations could not be extrapolated from one observer to another.
To try to solve these problems of subjectivity and lack of standardization in morphological characterization, the “ List of OIV (International Office for Vine and Wine) descriptors for vine varieties and Vitis species” and the “Guidelines for the execution of the examination of the distinction, homogeneity and stability ”of the International Union for the Protection of New Varieties of Plants (UPOV), where the characterization is carried out through a set of morphological descriptors, assigning them a specific and pre-established level of expression in said lists. It is carried out on the different organs of the vine and at the right moment of observation and development of the organ to be described. It is made in the top, young leaf, adult leaf, tendril, branch, bunch, berry and vine.
In a first degree of specialization of classical ampelography, its comparison emerged by means of isoenzymes, a now obsolete biochemical technique, which required a laborious interpretation.
The study of markers based on DNA analysis represented a significant leap in ampelography. They have several advantages: they are more objective, they do not depend on environmental conditions, they require less time for analysis and interpretation, allowing an easier comparison. The most important molecular markers are those based on the PCR technique (Polymerase Chain Reaction) and are currently used.
In the 90s the technique of RAPDs (Random Amplified Polymorphic DNAs) was used, which uses regions of random sequence within the genome. Its main advantage is that no prior knowledge of the genome is required, but the analysis of the obtained profiles can be complex and subjective.
In the mid-90s microsatellites appeared : STMS (Sequence Marked Microsatellite Sites), or SSR (Simple Sequence Repeats). For each marker, two alleles are obtained, represented by numbers corresponding to their approximate molecular size. The microsatellites have advantages over the previous markers: they are reproducible, rapidity of analysis, and the possibility of elaboration of comparison databases. The OIV has included, among its descriptors, six used internationally: VVMD5, VVMD7, VVMD27, VVS2, ssrVrZAG62 and ssrVrZAG79. Because these markers, for certain studies, may be scarce, a total of 20 microsatellites are usually used.
Currently, a new type of DNA marker has been incorporated : SNPs (single nucleotide polymorphism). Despite having the advantages of microsatellites, it is necessary to use more markers, however, the results are easier to analyze and reproduce.
In short, DNA markers are the most useful and agile tool in the characterization of vine varieties, however, they must be complemented with a morphological study , which allows to complete the characterization.