Phylogenomic insights into the origin of the Norton grape

Societal Impact Statement Challenges in viticulture such as disease resistance have renewed interest in underutilized cultivars. The Norton grape, one of the earliest popular North American grape cultivars, holds the potential to produce exceptional wine while being resistant to pests and disease. Yet, the ancestry of the Norton grape is controversial. Here, we use novel genomic approaches to investigate the possible parentage of the Norton cultivar. We suggest the Norton grape is a complex 3‐generation hybrid involving two North American grape species and the European V. vinifera. This hypothesis supports potential future breeding efforts and conservation of this important historical grape cultivar. Summary The Norton grape (Vitis aestivalis ‘Norton’) has been celebrated for being the first American grape valued in viticulture. It was established sometime around the 1820s near Richmond, Virginia. There has been a renewed interest in the Norton grape for its pest and disease resistance as well as its wine quality. Novel genomic methodologies can help determine the complex and controversial origin of the Norton grape. Here, 1,013 nuclear loci and whole plastid genomes were sequenced from plant collections representing V. aestivalis ‘Norton’ and its close wild relatives from North America and Eurasia. Nuclear and plastome phylogenomic inferences, phylogenetic networks, and Single Nucleotide Polymorphisms were used to determine potential hybrid origin and contributors. We identified three parental species of Norton, V. aestivalis, Vitis labrusca, and Vitis vinifera. Norton is hypothesized to be a 3‐generation hybrid, with the first generation cross (F1) involving the Bland grape as the maternal parent and V. aestivalis as an accidental pollen donor. The breeder hybridized the F1 with V. vinifera to improve taste, and the F2 was then crossed with V. aestivalis as the maternal parent to improve resistance, producing F3, i.e. the Norton grape. The Bland grape was likely derived from [(V. labrusca x V. vinifera) V. labrusca]. Our findings based on phylogenomics are consistent with historical hypotheses regarding the origin of the cultivar. Norton represents a pattern consistent with other popular grape cultivars, where a cultivar was developed via hybridization, including backcrossing with wild species, creating a disease‐resistant cultivar.