Development of a standard set of microsatellite reference alleles for identification of grape cultivars. Theoretical and Applied Genetics

10 partners in seven countries analyzed 46 grape cultivars at six loci (VVMD5, VVMD7, VVMD27, VVS2, VrZAG62, VrZAG79) in order to investigate the comparability of microsatellite profiles obtained in different laboratories, No effort was made to standardize equipment or protocols. Although some partners obtained very similar results, in other cases different absolute allele sizes and sometimes different relative allele sizes were obtained. A strategy for data comparison by means of reference to the alleles detected in well known cultivars was proposed. For each marker, each allele was designated by a code based on the name of the reference cultivar carrying that allele. Thirty-three cultivars, representing from 13 to 23 alleles per marker, were chosen as references. After the raw data obtained by the different partners were coded, more than 97% of the data were in agreement. Minor discrepancies were attributed to errors; suboptimal amplification and visualization; and mis-scoring of heterozygous versus homozygous allele pairs. We have shown that coded microsatellite data produced in different laboratories with different protocols and conditions can be compared and that it is suitable for the identification and SSR allele characterization of cultivars. It is proposed that the six markers employed here, already widely used, be adopted as a minimal standard marker set for future grapevine cultivar analyses and that additional cultivars be characterized by means of the coded reference alleles presented here. Complete database is available at hppt://www.genres.de/eccdb/vitis/.