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Abstract

Somatic variation is a natural source of diversity that has long been exploited
to improve traditional grapevine wine cultivars and adapt them to changing
environmental conditions and market demands. Somatic variation is also a
source of novel traits such as grape color variation enabling cultivar innovation
and diversification of products. To understand the mutational mechanisms
generating somatic variation in grape color, we compared the Tempranillo
Blanco white berry somatic variant with its black berry ancestor, Tempranillo
Tinto. By whole-genome resequencing and structural variation analysis we
identified that complex genome rearrangements involving three chromosomes
and hemizygous deletion of 1.7% of the genome resulted in the loss of the
grape color locus functional allele in Tempranillo Blanco. We showed that this
complex genome reshuffling has additional consequences affecting production
in Tempranillo Blanco. Similar structural variation analyses in Grenache grape
color somatic variants identified more simple deletion events as the causal
mutations. To assist future intra-varietal studies in Tempranillo, the third most
widely grown wine cultivar in the world, we are now using long-read
sequencing PacBio and Nanopore technologies to build a haplotype-resolved
genome assembly and to annotate it. These genomic tools will be exploited to
search for causal mutations in improved Tempranillo somatic variants
identified in clonal selection programs.