Ecotypic differentiation under farmers' selection: Molecular insights into the domestication of Pachyrhizus Rich. ex DC. (Fabaceae) in the Peruvian Andes.

Understanding the distribution of crop genetic diversity in relation to environmental factors can give insights into the eco-evolutionary processes involved in plant domestication. Yam beans (Pachyrhizus Rich. ex DC.) are leguminous crops native to South and Central America that are grown for their tuberous roots but are seed-propagated. Using a landscape genetic approach, we examined correlations between environmental factors and phylogeographic patterns of genetic diversity in Pachyrhizus landrace populations. Molecular analyses based on chloroplast DNA sequencing and a new set of nuclear microsatellite markers revealed two distinct lineages, with strong genetic differentiation between Andean landraces (lineage A) and Amazonian landraces (lineage B). The comparison of different evolutionary scenarios for the diversification history of yam beans in the Andes using approximate Bayesian computation suggests that Pachyrhizus ahipa and Pachyrhizus tuberosus share a progenitor-derivative relationship, with environmental factors playing an important role in driving selection for divergent ecotypes. The new molecular data call for a revision of the taxonomy of Pachyrhizus but are congruent with paleoclimatic and archeological evidence, and suggest that selection for determinate growth was part of ecophysiological adaptations associated with the diversification of the P. tuberosus-P. ahipa complex during the Mid-Holocene.

Isolation of novel stilbenoids from the roots of Cyrtopodium paniculatum (Orchidaceae).

Four new stilbenoids, named cyrtopodinone (1), cyrtopodinol (2), and coeludols A and B (3-4) were isolated from the roots of Cyrtopodium paniculatum, together with 21 known stilbenoids derivatives (5-25). Their structures were elucidated by comprehensive spectroscopic analysis including extensive 1D and 2D-NMR techniques. The cytotoxic activities of the isolated compounds were tested on human glioblastoma U-87MG cell line with fluorescence-based image cytometry. Only four compounds (18, 19, 22 and 25) displayed moderate cytotoxicity with IC50 values of 45.2, 39.9, 58.2 and 48.0µM, respectively.

Chemical Constituents from the Aerial Parts of Cyrtopodium paniculatum.

We report the first phytochemical study of the neotropical orchid Cyrtopodium paniculatum. Eight new compounds, including one phenanthrene 1, one 9,10-dihydro-phenanthrene 2, one hydroxybenzylphenanthrene 3, two biphenanthrenes 4-5, and three 9,10 dihydrophenanthrofurans 6-8, together with 28 known phenolic compounds, mostly stilbenoids, were isolated from the CH2Cl2 extract of its leaves and pseudobulbs. The structures of the new compounds were established on the basis of extensive spectroscopic methods.

Microsatellite markers for the yam bean Pachyrhizus (Fabaceae).

PREMISE OF THE STUDY: Microsatellite loci were developed for the understudied root crop yam bean (Pachyrhizus spp.) to investigate intraspecific diversity and interspecific relationships within the genus Pachyrhizus. • METHODS AND RESULTS: Seventeen nuclear simple sequence repeat (SSR) markers with perfect di- and trinucleotide repeats were developed from 454 pyrosequencing of SSR-enriched genomic libraries. Loci were characterized in P. ahipa and wild and cultivated populations of four closely related species. All loci successfully cross-amplified and showed high levels of polymorphism, with number of alleles ranging from three to 12 and expected heterozygosity ranging from 0.095 to 0.831 across the genus. • CONCLUSIONS: By enabling rapid assessment of genetic diversity in three native neotropical crops, P. ahipa, P. erosus, and P. tuberosus, and two wild relatives, P. ferrugineus and P. panamensis, these markers will allow exploration of the genetic diversity and evolutionary history of the genus Pachyrhizus.