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.

The BioMart Community Portal (www.biomart.org) is a community-driven effort to provide a unified interface to biomedical databases that are distributed worldwide. The portal provides access to numerous database projects supported by 30 scientific organizations. It includes over 800 different biological datasets spanning genomics, proteomics, model organisms, cancer data, ontology information and more. All resources available through the portal are independently administered and funded by their host organizations. The BioMart data federation technology provides a unified interface to all the available data. The latest version of the portal comes with many new databases that have been created by our ever-growing community. It also comes with better support and extensibility for data analysis and visualization tools. A new addition to our toolbox, the enrichment analysis tool is now accessible through graphical and web service interface. The BioMart community portal averages over one million requests per day. Building on this level of service and the wealth of information that has become available, the BioMart Community Portal has introduced a new, more scalable and cheaper alternative to the large data stores maintained by specialized organizations.

The genome of potato, a major global food crop, was recently sequenced. The work presented here details the integration of the potato reference genome (DM) with a new sequence-tagged site marker−based linkage map and other physical and genetic maps of potato and the closely related species tomato. Primary anchoring of the DM genome assembly was accomplished by the use of a diploid segregating population, which was genotyped with several types of molecular genetic markers to construct a new ~936 cM linkage map comprising 2469 marker loci. In silico anchoring approaches used genetic and physical maps from the diploid potato genotype RH89-039-16 (RH) and tomato. This combined approach has allowed 951 superscaffolds to be ordered into pseudomolecules corresponding to the 12 potato chromosomes. These pseudomolecules represent 674 Mb (~93%) of the 723 Mb genome assembly and 37,482 (~96%) of the 39,031 predicted genes. The superscaffold order and orientation within the pseudomolecules are closely collinear with independently constructed high density linkage maps. Comparisons between marker distribution and physical location reveal regions of greater and lesser recombination, as well as regions exhibiting significant segregation distortion. The work presented here has led to a greatly improved ordering of the potato reference genome superscaffolds into chromosomal “pseudomolecules”.

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Characterization of nearly 1,000 cultivated potato accessions with simple sequence repeats (SSRs; also referred to as microsatellites) has allowed the identification of a reference set of SSR markers for accurate and efficient genotyping. In addition, 31 SSRs are reported here for a potato genetic map, including new map locations for 24 of them. A first criterion for this proposed reference set was ubiquity of the SSRs in the eight landrace cultivar groups of the potato, Solanum tuberosum. All SSRs tested in the present study displayed the same allele phenotypes and allele size range in the diverse germplasm set as in the advanced potato cultivar germplasm in which they were originally discovered. Thirteen of 13 SSR products from all cultivar groups are shown to cross-hybridize with the corresponding SSR product of the source cultivar to ascertain sequence homology. Other important SSR selection criteria are quality of amplification products, locus complexity, polymorphic index content, and well-dispersed location on a potato genetic map. Screening of 156 SSRs allowed the identification of a highly informative and userfriendly set comprising 18 SSR markers for use in characterization of potato genetic resources. In addition, we have identified true-and pseudo-multiplexing SSRs for even greater efficiency.

The fingerprinting of 742 potato landraces with 51 simple sequence repeat (SSR, or microsatellite) markers resulted in improving a previously constructed potato genetic identity kit. All SSR marker loci were assayed with a collection of highly diverse landraces of all species of cultivated potato with ploidies ranging from diploid to pentaploid. Loci number, amplification reproducibility, and polymorphic information content were recorded. Out of 148 SSR markers of which 30 are new, we identified 58 new SSR marker locations on at least one of three potato genetic linkage maps. These results permitted the selection of a new potato genetic identity kit based on 24 SSR markers with two per chromosome separated by at least 10 cM, single locus, high polymorphic information content, and high quality of amplicons as determined by clarity and reproducibility. The comparison of a similarity matrix of 742 landraces obtained with the 24 SSR markers of the new kit and with the entire dataset of 51 SSR markers showed a high correlation (r = 0.94) by a Mantel test and even higher correlations (r = 0.99) regarding topological comparisons of major branches of a neighbor joining tree. This new potato genetic identity kit is able to discriminate 93.5% of the 742 landraces compared to 98.8% with 51 SSR markers. In addition, we made a marker-specific set of allele size standards that conveniently and unambiguously provide accurate sizing of all alleles of the 24 SSR markers across laboratories and platforms. The new potato genetic identity kit will be of particular utility to standardize the choice and allele sizing of microsatellites in potato and aid in collaborative projects by allowing cumulative analysis of independently generated data.

Microsatellites, or simple sequence repeats (SSRs) are very useful molecular markers for a number of plant species. They are commonly used in cultivar identification, plant variety protection, as anchor markers in genetic mapping, and in marker-assisted breeding. Early development of SSRs was hampered by the high cost of library screening and clone sequencing. Currently, large public SSR datasets exist for many crop species, but the number of publicly available, mapped SSRs for potato is relatively low (approximately 100). We have utilized a database mining approach to identify SSR-containing sequences in The Institute For Genomic Research Potato Gene Index database (http://www.tigr.org), focusing on sequences with size polymorphisms present in this dataset. Ninety-four primer pairs flanking SSR sequences were synthesized and used to amplify potato DNA. This study rendered 61 useful SSRs that were located in pre-existing genetic maps, fingerprinted in a set of 30 cultivars from South America, North America, and Europe or a combination thereof. The high proportion of success (65%) of expressed sequence tag-derived SSRs obtained in this work validates the use of transcribed sequences as a source of markers. These markers will be useful for genetic mapping, taxonomic studies, marker-assisted selection, and cultivar identification.

A genetic linkage map of cassava has been constructed with 132 RFLPs, 30 RAPDs, 3 microsatellites, and 3 isoenzyme markers segregating from the heterozygous female parent of an intraspecific cross. The F cross was made between 'TMS 30572' and 'CM 2177-2', elite cassava cultivars from Nigeria and Colombia, respectively. The map consists of 20 linkage groups spanning 931.6 cM or an estimated 60% of the cassava genome. Average marker density is 1 per 7.9 cM. Since the mapping population is an F cross between heterozygous parents, with unique alleles segregating from either parent, a second map was constructed from the segregation of 107 RFLPs, 50 RAPDs, 1 microsatellite, and 1 isoenzyme marker from the male parent. Comparison of intervals in the maleand female-derived maps, bounded by markers heterozygous in both parents, revealed significantly less meiotic recombination in the gametes of the female than in the male parent. Six pairs of duplicated loci were detected by low-copy genomic and cDNA sequences used as probes. Efforts are underway to saturate the cassava map with additional markers, to join the male-and female-derived maps, and to elucidate genome organization in cassava.