Investigations into the origin of ‘Norton’ grape using SSR markers
‘Norton’ produces excellent wine in some regions where Vitis vinifera is diffi cult to grow. The high-quality and pest resistance of ‘Norton’ make it attractive to generate hybrids of similar parentage, producing cultivars with traits distinct from ‘Norton’ but with similar adaptation. ‘Norton’ is frequently described as V. aestivalis, but was initially declared a hybrid between an American grape (‘Bland’) and V. vinifera (‘Miller’s Burgundy’, a synonym for ‘Pinot Meunier’). To try to identify the parents of ‘Norton’, simple sequence repeat (SSR) markers were compared across V. vinifera cultivars and accessions derived from American species. The precise parentage could not be identifi ed using available data. Allele frequencies were compared among 181 Euvitis of North American origin and 354 V. vinifera cultivars for which there were data at 13 loci. At least one allele found in ‘Norton’ at all 13 loci was also present among the vinifera cultivars, while at 6 loci the other allele in ‘Norton’ did not occur among the vinifera cultivars, suggesting these alleles may derive from a non-vinifera parent. Allelic frequency distributions for different Vitis series indicated that the putative non-vinifera ‘Norton’ alleles were common within the aestivales. These data are consistent with ‘Norton’ being a hybrid with ancestry including V. aestivalis and V. vinifera. ‘Norton’ alleles for locus VVMD36 are rare and may offer the best opportunity for identifying ‘Norton’ parents. Interestingly, ‘Enfariné noir’, a vinifera cultivar which has similarities in synonymy, morphology, and origin with ‘Pinot Meunier’, shares the rare as well as most common alleles with the presumed ‘Norton’ vinifera parent.