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”.

Summary: The characterization of natural recessive resistance genes and virus‐resistant mutants of Arabidopsis have implicated translation initiation factors of the 4E family [eIF4E and eIF(iso)4E] as susceptibility factors required for virus multiplication and resistance expression. To date, viruses controlled by these genes mainly belong to the family Potyviridae. Melon necrotic spot virus (MNSV) belongs to the family Tombusviridae (genus Carmovirus) and is an uncapped and non‐polyadenylated RNA virus. In melon, nsv‐mediated resistance is a natural source of recessive resistance against all strains of MNSV except MNSV‐264. Analyses of chimeras between non‐resistance‐breaking and resistance‐breaking strains have shown that the avirulence determinant maps to the 3′‐untranslated region (3′‐UTR) of the viral genome. Using a combination of positional cloning and microsynteny analysis between Arabidopsis thaliana and melon, we genetically and physically delimited the nsv locus to a single bacterial artificial chromosome clone and identified the melon eukaryotic translation initiation factor 4E (Cm‐eIF4E) as a candidate gene. Complementation analysis using a biolistic transient expression assay, confirmed Cm‐eIF4E as the product of nsv. A single amino acid change at position 228 of the protein led to the resistance to MNSV. Protein expression and cap‐binding analysis showed that Cm‐eIF4E encoded by a resistant plant was not affected in it's cap‐binding activity. The Agrobacterium‐mediated transient expression of the susceptibility allele of Cm‐eIF4E in Nicotiana benthamiana enhanced MNSV‐264 accumulation. Based on these results, a model to explain melon resistance to MNSV is proposed. These data, and data from other authors, suggest that translation initiation factors of the eIF4E family are universal determinants of plant susceptibility to RNA viruses.

The majority of disease resistance (R) genes identified to date in plants encode a nucleotide-binding site (NBS) and leucine-rich repeat (LRR) domain containing protein. Additional domains such as coiled-coil (CC) and TOLL/interleukin-1 receptor (TIR) domains can also be present. In the recently sequenced Solanum tuberosum group phureja genome we used HMM models and manual curation to annotate 435 NBS-encoding R gene homologs and 142 NBS-derived genes that lack the NBS domain. Highly similar homologs for most previously documented Solanaceae R genes were identified. A surprising ∼41% (179) of the 435 NBS-encoding genes are pseudogenes primarily caused by premature stop codons or frameshift mutations. Alignment of 81.80% of the 577 homologs to S. tuberosum group phureja pseudomolecules revealed non-random distribution of the R-genes; 362 of 470 genes were found in high density clusters on 11 chromosomes.

Potato is a member of the Solanaceae, a plant family that includes several other economically important species, such as tomato, eggplant, petunia, tobacco and pepper. The Potato Genome Sequencing Consortium (PGSC) aims to elucidate the complete genome sequence of potato, the third most important food crop in the world. The PGSC is a collaboration between 13 research groups from China, India, Poland, Russia, the Netherlands, Ireland, Argentina, Brazil, Chile, Peru, USA, New Zealand and the UK. The potato genome consists of 12 chromosomes and has a (haploid) length of approximately 840 million base pairs, making it a medium-sized plant genome. The sequencing project builds on a diploid potato genomic bacterial artificial chromosome (BAC) clone library of 78000 clones, which has been fingerprinted and aligned into ~7000 physical map contigs. In addition, the BAC-ends have been sequenced and are publicly available. Approximately 30000 BACs are anchored to the Ultra High Density genetic map of potato, composed of 10000 unique AFLP^TM markers. From this integrated genetic-physical map, between 50 to 150 seed BACs have currently been identified for every chromosome. Fluorescent in situ hybridization experiments on selected BAC clones confirm these anchor points. The seed clones provide the starting point for a BAC-by-BAC sequencing strategy. This strategy is being complemented by whole genome shotgun sequencing approaches using both 454 GS FLX and Illumina GA2 instruments. Assembly and annotation of the sequence data will be performed using publicly available and tailor-made tools. The availability of the annotated data will help to characterize germplasm collections based on allelic variance and to assist potato breeders to more fully exploit the genetic potential of potato. La papa es un miembro de las Solanaceae, una familia de plantas que incluye varias otras especies económicamente importantes, tales como tomate, berenjena, petunia, tabaco y ají o chili. El consorcio de secuenciación del genoma de la papa (PGSC) tiene por objeto dilucidar la secuencia completa del genoma de la papa, el tercer cultivo alimentario más importante del mundo. El PGSC es una colaboración entre 13 grupos de investigación procedentes de China, India, Polonia, Rusia, los Países Bajos, Irlanda, Argentina, Brasil, Chile, Perú, EE.UU., Nueva Zelanda y el Reino Unido. El genoma de la papa consiste de 12 cromosomas y tiene una longitud (haploide) de aproximadamente 840 millones de pares de bases, por lo que es una planta con un genoma de tamaño mediano. El proyecto de secuenciación se basa en una biblioteca de 78000 clones de cromosoma artificial bacteriano genomico de papa diploide (BAC), del que se ha obtenido la huella genética y alineado en 7000 ~ contigs de mapa físico. Además, los extremos terminales BAC se han secuenciado y están a disposición del público. Aproximadamente 30000 BACS están anclados al mapa genético de ultra alta densidad de la papa, compuesto de 10000 marcadores AFLP^TM únicos. De esta mapa genético-físico integrado, entre 50 a 150 semillas BACs han sido identificadas para cada cromosoma. Experimentos de hibridación in situ fluorescente en clones BAC selectos confirman estos puntos de anclaje. La clones semilla proveen el punto de partida para la estrategia de secuenciación de BAC a BAC. Esta estrategia se complementa con los enfoques de secuenciación escopeta del genoma completo usando los instrumentos 454 GS FLX e Illumina GA2. El ensamblaje y anotación de los datos de la secuencia será realizados mediante herramientas publicas disponibles y hechas a la medida. La disponibilidad de los datos anotados ayudarán a caracterizar las colecciones de germoplasma basándose en variación alélica y ayudará a los fitomejoradores de papa a explotar más plenamente el potencial genético de la papa.

We screened 429 individuals from 31 diploid Ipomoea trifida accessions from different countries of Central and South America for 2n pollen production. Almost 20% of this population was found to produce 2n pollen in different frequencies. The production of 2n pollen is not an isolated incident but a common phenomenon in this taxon. Pollen diameter was measured in normal and 2n pollen-producing clones. The diameter of 2n pollen is 30% larger than that of normal pollen, making it very easy to detect 2n pollen producers and measure their frequency. Production of 2n pollen was confirmed by the finding of dyads and triads in anther samples at the tetrad stage of meiosis. Furthermore, Ax individuals were found among progenies of 4x × 2x crosses, providing direct evidence of 2n pollen production in the diploid male parent. The occurrence of 2n pollen in 2× I. trifida provides a clue to understanding how polyploidization and gene flow between different ploidy levels can occur in nature. These findings are discussed in relation to the origin of the polyploid series in this species and of the cultivated sweet potato, I. batatas.