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The correct identification of plant variety is very important, particularly in viticulture, an agricultural sector characterised by a wide number of varieties. Moreover, the correct variety identification is necessary for the recovery and characterization of autochthonous accessions and for the preservation of ampelographic biodiversity.
In viticulture the variety, also called 'vitigno', is a group of plants obtained by vegetative propagation from a single plant coming from a seed (seedling). Inside the variety, a clone is a group of homogeneous plants obtained by vegetative propagation from a single plant that differs from the others of the same variety in some morphologic, phenological or productive characteristics due to somatic mutations.
The correct identification of a grapevine variety is difficult because of the high number of varieties, the presence of many synonymous and homonymous and the wide variability of the different accessions due to the high polymorphism expressed by this specie.
A rapid and objective method for grapevine variety identification is necessary in modern grapevine and wine marketing and for the identification of the numerous synonymous and homonymous inside the activity of recovery and characterization of autochthonous grapevine accessions. New opportunity in this area arrived with the development of DNA molecular markers. Among these, actually, the 'microsatellite' are the most useful in the identification of a grapevine variety.
A microsatellite, or Simple Sequence Repeats (SSR) or Sequence Tagged Microsatellite Sites (STMS) is a DNA sequence constituted by a sequence of 1 to 6 nucleotide repeated a tandem 5 to 100 times (like (GA)n; (GATA)n).
The polymorphism of a microsatellite is in the number of the repeats of the short unit, and it appears as different alleles that differ in sequence length. This type of polymorphism is easily detected by amplification of the DNA fragment by PCR and by measurement of its length by high resolution electrophoresis. The polymorphism of a number of microsatellite loci (microsatellite profile) unequivocally identifies a specific variety. Moreover, the co-dominant heredity of microsatellites allows discrimination between homozygosis and heterozygosis, to analyse the parentage and the phylogenies. In addition, the major part of primers developed to amplify many microsatellite loci in Vitis vinifera allows amplification of the same loci in other species of the same genus and of the same family.
The scientific Institutions of the European project GENRES CT96 No 81 “European network for grapevine genetic resources conservation and characterization”, with the aim of suggesting a standard procedure in the identification of grapevine varieties, choose 6 microsatellite loci amongst over than 300 loci characterised in grapevine on the basis of their polymorphism: VVS2, VVMD5, VVMD7, VVM27, VrZAG62 e VrZAG79.