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Quinoa (Chenopodium quinoa Willd.) is an important seed crop throughout the Andean region of South America. It is important as a regional food security crop for millions of impoverished rural inhabitants of the Andean Altiplano (high plains). Efforts to improve the crop have led to an increased focus on genetic research. We report the identifi cation of 14,178 putative single nucleotide polymorphisms (SNPs) using a genomic reduction protocol as well as the development of 511 functional SNP assays. The SNP assays are based on KASPar genotyping chemistry and were detected using the Fluidigm dynamic array platform. A diversity screen of 113 quinoa accessions showed that the minor allele frequency (MAF) of the SNPs ranged from 0.02 to 0.50, with an average MAF of 0.28. Structure analysis of the quinoa diversity panel uncovered the two major subgroups corresponding to the Andean and coastal quinoa ecotypes. Linkage mapping of the SNPs in two recombinant inbred line populations produced an integrated linkage map consisting of 29 linkage groups with 20 large linkage groups, spanning 1404 cM with a marker density of 3.1 cM per SNP marker. The SNPs identifi ed here represent important genomic tools needed in emerging plant breeding programs for advanced genetic analysis of agronomic traits in quinoa.

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Potato tubers (Solanum tuberosum L. cv Bintje and Désirée) were stored for 12 months under three different storage conditions: 4 °C, 20 °C with sprout inhibitor and 20 °C without sprout inhibitor. Independent of the storage conditions, our results show that the increase of membrane permeability, as revealed by electrolyte leakage, is not correlated with the lipid saturation status. Moreover, there is no simple correlation between cold sweetening and membrane permeability or lipid saturation status. During storage at 20 °C without sprout inhibitor, the increase in membrane permeability is inversely correlated to sucrose accumulation, but this is not the case when tubers were stored with sprout inhibitors. Lipoxygenase (LOX) is often proposed as responsible for peroxidative damage to membrane lipids. The gradual peroxidation resulting in double bond index decrease is regarded as a cause of senescence sweetening. Our results revealed that the role of LOX in aging and senescence of potato tubers is far from clear. LOX activity and gene expression are not correlated with the fatty acids composition of the membrane. Moreover, LOX activity and fatty acid hydroperoxide content are low in older tubers, whatever the storage conditions or the varieties. On the basis of our results, the correlation between sugar accumulation (low temperature and senescence sweetening) and peroxidative damage occurring during storage of potato tubers is discussed.

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A cDNA clone encoding a soluble inorganic pyrophosphatase (EC 3.6.1 .l) of potato (Solanum tuberosum 1.) was isolated by screening a developing tuber library with a heterologous probe. The central domain of the encoded polypeptide is nearly identical at the sequence leve1 with its Arabidopsis homolog (J.J. Kieber and E.R.Signer [1991] Plant MOI Biol 16: [345][346][347][348]. Computer-assisted analysis of the potato, Arabidopsis, and Escherichia coli soluble pyrophosphatases indicated a remarkably conserved organization of the hydrophobic protein domains. The enzymatic function of the potato protein could be deduced from the presence of amino acid residues highly conserved in soluble pyrophosphatases and was confirmed by its capacity to complement a thermosensitive pyrophosphatase mutation i n E. coli. The potato polypeptide was purified from complemented bacterial cells and its pyrophosphatase activity was shown to be strictly dependent on Mg2+ and strongly inhibited by Ca2+. The subcellular location of the potato pyrophosphatase is unknown. Structure analysis of the N-terminal protein domain failed to recognize typical transit peptides and the calculated molecular m a s of the polypeptide (24 kD) is significantly inferior to the values reported for the plastidic (alkaline) or mitochondrial pyrophosphatases in plants (28-42 kD). Two unlinked loci could be mapped by restriction fragment length polymorphism analysis in the potato genome using the full-length cDNA as probe.Inorganic pyrophosphatases (EC 3.6.1.1) are ubiquitous enzymes catalyzing the hydrolysis of PPi into two Pi's. PPi hydrolysis is highly exergonic (AG" = -33.5 kJ mol-l) and provides a thermodynamic driving force to a range of anabolic processes. Most notably, the synthesis of biological polymers produces PPi either during the activation of monomers (e.g. ADP-Glc synthesis prior to starch elongation, amino acid activation into amino acyl-tRNA prior to polypeptide elongation) or during the elongation of the polymers (eg. DNA and RNA synthesis, polyisoprene [rubber] synthesis). According to the Kornberg (1962) model, the energy "wasted" by PPi hydrolysis is needed for making these processes thermodynamically irreversible. Hence, the first and most ubiquitous function of inorganic pyrophosphatases is presumably to drive anabolism.

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A preliminary study of the genetic diversity of Bolivian oca (Oxalis tuberosa Mol.) varieties maintained in situ and ex situ through the utilization of ISSR molecular markers Marie Malice AE Nicolas Martin AE Audrey Pissard AE Jorge A. Rojas-Beltran AE Antionio Gandarillas AE Pierre Bertin AE Jean-Pierre Baudoin Abstract ISSR molecular markers have been used to investigate genetic diversity of oca (Oxalis tuberosa Mol.), an Andean neglected tuber crop species. Sampling procedure allowed a preliminary study of the genetic diversity at the intra-and intervarietal levels. Twenty tuber lots conserved in situ in the microcentre of Candelaria and ex situ in the Toralapa Centre (Bolivia) were identified. Four ISSR primers amplified a total of 25 fragments of which 17 (68%) were polymorphic. These experiments show that the structure of oca varieties is mainly based upon vernacular names with a greater differentiation among tuber lots than within them, supporting agromorphological data. ISSR technique enlightened the existence of heterogeneous varieties in oca and divergence between in situ and ex situ conservation strategies. These observations are potentially linked to the different ways of management of tubers in these two conservation systems.