A dual genome-methylome map of clonal evolution in grapevine

Grapevine is one of the oldest and most economically important perennial crops, vegetatively propagated for centuries to millennia. This long history of clonal propagation generates substantial intra-varietal diversity, but its molecular basis remains difficult to resolve with short-read sequencing, which misses large structural variation and DNA methylation. Here, we generate a high-quality, phased diploid reference genome for the cultivar Pinot noir and integrate it with Oxford Nanopore sequencing of 23 distinct clones to build a genome-wide map of clonal genetic and DNA methylation variation in Vitis vinifera.

The genome assembly reveals a deep history of ancient inbreeding, with approximately 12% of the genome occurring in extended runs of homozygosity. Across molecular layers, we observe contrasting patterns of clonal divergence. Somatic genetic variation (67,277 SNPs and 4,037 SVs) is dominated by rare variants and strongly depleted from coding regions, consistent with purifying selection. Structural variation among clones is largely associated with repetitive DNA, particularly duplicated regions and centromeric repeats. In contrast, DNA methylation variation is abundant (15,986 CG, 52,158 CHG, and 32,062 CHH methylation polymorphisms) and strongly enriched within gene bodies, highlighting it as an important component of clonal divergence. Notably, CG and CHG methylation patterns alone reconstruct clonal relationships mirroring SNP-based lineages, consistent with their stable retention across mitotic cycles, a congruence absent in CHH methylation.

Together, our results show that clonal identity in grapevine is shaped by the combined contributions of genome and methylome, with stable CG and CHG methylation capturing clonal relationships at near-genetic resolution.