Potato (Solanum tuberosum L.) is the world's most important non-grain food crop and is central to global food security. It is clonally propagated, highly heterozygous, autotetraploid, and suffers acute inbreeding depression. Here we use a homozygous doubled-monoploid potato clone to sequence and assemble 86% of the 844-megabase genome. We predict 39,031 protein-coding genes and present evidence for at least two genome duplication events indicative of a palaeopolyploid origin. As the first genome sequence of an asterid, the potato genome reveals 2,642 genes specific to this large angiosperm clade. We also sequenced a heterozygous diploid clone and show that gene presence/absence variants and other potentially deleterious mutations occur frequently and are a likely cause of inbreeding depression. Gene family expansion, tissue-specific expression and recruitment of genes to new pathways contributed to the evolution of tuber development. The potato genome sequence provides a platform for genetic improvement of this vital crop.

5 7Carrot (Daucus carota subsp. carota L.; 2n = 2x = 18) is a globally important root crop whose production has quadrupled between 1976 and 2013 (FAO Statistics; see URLs), outpacing the overall rate of increase in vegetable production and world population growth (FAO Statistics; see URLs) through development of high-value products for fresh consumption, juices, and natural pigments and cultivars adapted to warmer production regions 1 .The first documented colors for domesticated carrot root were yellow and purple in Central Asia approximately 1,100 years ago 2,3 , with orange carrots not reliably reported until the sixteenth century in Europe 4,5 . The popularity of orange carrots is fortuitous for modern consumers because the orange pigmentation results from high quantities of alpha-and beta-carotene, making carrots the richest source of provitamin A in the US diet 6 . Carrot breeding has substantially increased nutritional value, with a 50% average increase in carotene content in the United States as compared to 40 years ago 6 . Lycopene and lutein in red and yellow carrots, respectively, are also nutritionally important carotenoids, making carrot a model system to study storage root development and carotenoid accumulation.Carrot is the most important crop in the Apiaceae family, which includes numerous other vegetables, herbs, spices, and medicinal plants that enhance the epicurean experience 7 , including celery, parsnip, arracacha, parsley, fennel, coriander, and cumin. The Apiaceae family belongs to the euasterid II clade, which includes important crops such as lettuce and sunflower 8 . Genome sequences of euasterid I species have been reported, but only two genomes 9,10 have been published among the other euasterid II species.Here we report a high-quality genome assembly of a doubledhaploid orange carrot, characterization of the mechanism controlling carotenoid accumulation in storage roots, and the resequencing of 35 accessions spanning the genetic diversity of the Daucus genus. Our comprehensive genomic analyses provide insights into the evolution of the asterids and several gene families. These results will facilitate biological discovery and crop improvement in carrot and other crops.A high-quality carrot genome assembly provides new insights into carotenoid accumulation and asterid genome evolution We report a high-quality chromosome-scale assembly and analysis of the carrot (Daucus carota) genome, the first sequenced genome to include a comparative evolutionary analysis among members of the euasterid II clade. We characterized two new polyploidization events, both occurring after the divergence of carrot from members of the Asterales order, clarifying the evolutionary scenario before and after radiation of the two main asterid clades. Large- and small-scale lineage-specific duplications have contributed to the expansion of gene families, including those with roles in flowering time, defense response, flavor, and pigment accumulation. We identified a candidate gene, DCAR_032551, that conditions caro...

Centromeres in most higher eukaryotes are composed of long arrays of satellite repeats. By contrast, most newly formed centromeres (neocentromeres) do not contain satellite repeats and instead include DNA sequences representative of the genome. An unknown question in centromere evolution is how satellite repeat-based centromeres evolve from neocentromeres. We conducted a genome-wide characterization of sequences associated with CENH3 nucleosomes in potato (Solanum tuberosum). Five potato centromeres (Cen4, Cen6, Cen10, Cen11, and Cen12) consisted primarily of single-or low-copy DNA sequences. No satellite repeats were identified in these five centromeres. At least one transcribed gene was associated with CENH3 nucleosomes. Thus, these five centromeres structurally resemble neocentromeres. By contrast, six potato centromeres (Cen1, Cen2, Cen3, Cen5, Cen7, and Cen8) contained megabase-sized satellite repeat arrays that are unique to individual centromeres. The satellite repeat arrays likely span the entire functional cores of these six centromeres. At least four of the centromeric repeats were amplified from retrotransposon-related sequences and were not detected in Solanum species closely related to potato. The presence of two distinct types of centromeres, coupled with the boom-and-bust cycles of centromeric satellite repeats in Solanum species, suggests that repeat-based centromeres can rapidly evolve from neocentromeres by de novo amplification and insertion of satellite repeats in the CENH3 domains.

Potato (Solanum tuberosum) has the densest genetic linkage map and one of the earliest established cytogenetic maps among all plant species. However, there has been limited effort to integrate these maps. Here, we report fluorescence in situ hybridization (FISH) mapping of 30 genetic marker-anchored bacterial artificial chromosome (BAC) clones on the pachytene chromosome 6 of potato. The FISH mapping results allowed us to define the genetic positions of the centromere and the pericentromeric heterochromatin and to relate chromatin structure to the distribution of recombination along the chromosome. A drastic reduction of recombination was associated with the pericentromeric heterochromatin that accounts for 28% of the physical length of the pachytene chromosome. The pachytene chromosomes 6 of potato and tomato (S. lycopersicum) share a similar morphology. However, distinct differences of heterochromatin distribution were observed between the two chromosomes. FISH mapping of several potato BACs on tomato pachytene chromosome 6 revealed an overall colinearity between the two chromosomes. A chromosome inversion was observed in the euchromatic region of the short arms. These results show that the potato and tomato genomes contain more chromosomal rearrangements than those reported previously on the basis of comparative genetic linkage mapping.