Detection of genetic diversity among clones of cv. Fortana (Vitis vinifera L.) by microsatellite DNA polymorphism analysis

Allelic polymorphism at 6 microsatellite loci was analyzed in 5 clones of cv. Fortana, which had been divided into two morphological groups (CAB 2, CAB 13, CAB 14, and CAB 1, CAB 3, respectively) by discriminant multivariate analysis of leaf traits. Of the 6 microsatellite loci, 5 (VVS 1, VVS2, VVS4, VVMD3, VVMD6) showed polymorphism between clones and one (VVMD7) gave identical DNA profiles. Two genotypic patterns were found: clones CAB 2, CAB 13 and CAB 14 appeared identical and distinct from clones CAB 1 and CAB 3, but all of them shared at least one of the two alleles for each locus, thus showing a certain degree of genetic relatedness. The slight morphological differences of the two Fortana clone groups could thus be related to the diversity of their genotypic profiles. Thus, the two clone groups may have originated not via vegetative propagation of a single individual but from seedlings, parents or siblings of this progenitor. The present investigation supports the assumptions of the polyclonal origin of cv. Fortana and concludes that the strict definition of cultivar, which admits of clonal origin only, is not altogether adequate for the old varieties of unknown origin. The Italian term 'vitigno' and the French 'cepage', which do not imply genetic uniformity, would appear more appropriate than cultivar to indicate a winegrape variety.