Carotenoids play essential biological roles in plants, and genes involved in the carotenoid biosynthesis pathway are evolutionarily conserved. Orange sweetpotato is an important source of β-carotene, a precursor of vitamin A. In spite of this, only a few research studies have focussed on the molecular aspects of carotenoid genes regarding their specific sequence and structure. In this study, we used published carotenoid gene sequences from Ipomoea and other species for "exon-primed intron-crossing" approaches. Fifteen pairs of primers representing six carotenoid genes were designed for different introns, eleven of which amplified scorable and reproducible alleles. The sequence of PCR products showed high homology to the original ones. Moreover, the structure and sequence of the introns and exons from five carotenoid structural genes were partially defined. Intron length polymorphism and intron single nucleotide polymorphisms were detected in amplified sequences. Marker dosages and allelic segregations were analysed in a mapping population. The developed markers were evaluated in a set of Ipomoeas batatas accessions so as to analyse genetic diversity and conservation applicability. Using CG strategy combined with EPIC-PCR technique, we developed carotenoid gene markers in sweetpotato. We reported the first set of polymorphic Candidate Gene markers for I. batatas, and demonstrated transferability in seven wild Ipomoea species. We described the sequence and structure of carotenoid genes and introduced new information about genomic constitution and allele dosage.
History and environment shape crop biodiversity, particularly in areas with vulnerable human communities and ecosystems. Tracing crop biodiversity over time helps understand how rural societies cope with anthropogenic or climatic changes. Exceptionally well preserved ancient DNA of quinoa (Chenopodium quinoa Willd.) from the cold and arid Andes of Argentina has allowed us to track changes and continuities in quinoa diversity over 18 centuries, by coupling genotyping of 157 ancient and modern seeds by 24 SSR markers with cluster and coalescence analyses. Cluster analyses revealed clear population patterns separating modern and ancient quinoas. Coalescence-based analyses revealed that genetic drift within a single population cannot explain genetic differentiation among ancient and modern quinoas. The hypothesis of a genetic bottleneck related to the Spanish Conquest also does not seem to apply at a local scale. Instead, the most likely scenario is the replacement of preexisting quinoa gene pools with new ones of lower genetic diversity. This process occurred at least twice in the last 18 centuries: first, between the 6th and 12th centuries—a time of agricultural intensification well before the Inka and Spanish conquests—and then between the 13th century and today—a period marked by farming marginalization in the late 19th century likely due to a severe multidecadal drought. While these processes of local gene pool replacement do not imply losses of genetic diversity at the metapopulation scale, they support the view that gene pool replacement linked to social and environmental changes can result from opposite agricultural trajectories.
KeywordsIpomoea batatas; morphological descriptors; skin and flesh colour; sweetpotato. Correspondence M.M. Manifesto, Instituto de Recursos Biológicos CIRN-INTA-Argentina, N Repetto y Los Reseros s/n., AbstractThe knowledge about the distribution of descriptors of a collection constitutes a useful tool for the management of genetic resources. The object of this work was to evaluate the composition and morphological characterisation of the 'in vitro' collection kept at the Gene Bank of the Biological Resources Institute (IRB), INTA Castelar, Argentina, to establish conservation criteria and make available useful data for breeding programmes. This collection, comprising 310 sweetpotato clones, includes landraces, worldwide clones, commercial varieties and breeding material. The descriptors, which presented the highest correlation values, were leaf lobe types, the shape of central leaf lobes and general leaf outline. Cluster analyses showed eight major groups with an average similarity of 0.42 (SE ± 0.005). About 76% of the clones presented unique morphology, whereas 34% of them were distributed in 22 groups that could not be distinguished with this technique. Worldwide germplasm formed a separate group with values of diversity higher than those of the Argentinean clones and no duplicates. A projection of the phenotypic variation among cultivars was obtained through Principal Coordinate Analysis (PCoorA), which confirmed the results obtained by UPGMA analysis, predominant skin colour, secondary skin colour, number of leaf lobes, general leaf outline, petiole pigmentation and predominant colour of vine were the variables that made the highest contribution. Collection composition in reference to flesh and skin colour was also analysed.
Characterization and genotype identification are essential for rational conservation, management and genetic diversity evaluation. In this work, simple sequence repeat (SSR) markers were used to identify 57 accessions of sweet potato kept at the 'in vitro' Gene Bank of INTA, Argentina. This collection includes primitive materials from primary zones of dispersion, commercial varieties, breeding clones and foreign materials from different parts of the world (Africa, Asia and USA). Average similarity between the materials evaluated was 0.367. Grouping analysis revealed six clusters and a strong association with skin colour of storage roots. The set of selected SSR markers allowed us to verify identity, detect duplicates and estimate the genetic similarity of the materials analysed. This characterization complements morphological data and provides tools to estimate the variation of diversity between local and foreign germplasm groups.
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