The Genome Assembly of Vitis vinifera cv. Shiraz

Abstract

Background and Aims. Shiraz (Syrah) is a dark-skinned cultivar of the wine grape Vitis vinifera that forms the basis of some of the world's most iconic wines. Worldwide, Shiraz is the fourth most planted grapevine cultivar; however, it represents the most planted cultivar in Australia. Given the importance of Shiraz to worldwide wine production, this study aimed to produce a reference genome for this cultivar while investigating the unique genetic variants and ancestral origins of this iconic variety. Methods and Results. Long-read ONT data were selected to produce a highly contiguous genome assembly for Shiraz. Phylogenetic reconstruction using high-quality genome assemblies for wine grape cultivars provided further support of a kinship between Shiraz and Pinot Noir. Harnessing long-read data, transposable element insertions potentially affecting gene function were characterized in Shiraz and assessed relative to other cultivars. This revealed a heterogenous landscape of transposon insertion points across cultivars and uncovered a specific combination of allelic variants at the VviTPS24 terpene synthase locus. Conclusions. This establishment of a Shiraz genome provides a detailed view of the genetics that underpin this cultivar, including the discovery of a specific combination of VviTPS24 variants, which when combined with appropriate environmental triggers may allow Shiraz to produce high levels of rotundone, the aroma compound responsible for the distinctive peppery characteristics of this cultivar. Significance of the Study. The availability of a reference genome for Shiraz expands the pool of genomes available for wine grapes while providing a foundation resource for whole-genome studies involving this iconic cultivar, including intracultivar variant identification and transcriptomic studies using a matching reference genome.