Genome sequencing and transcriptome analyses provide insights into the origin and domestication of water caltrop (Trapa spp., Lythraceae)

Humans have domesticated diverse species from across the plant kingdom; however, our current understanding of plant domestication is largely founded on major cereal crops. Here, we examine the evolutionary processes and genetic basis underlying the domestication of water caltrop (Trapa spp., Lythraceae), a traditional, yet presently underutilized non-cereal crop that sustained early Chinese agriculturalists. We generated a chromosome-level genome assembly of tetraploid T. natans, and then divided the allotetraploid genome into two subgenomes. Based on resequencing data from 57 accessions, representing cultivated diploid T. natans, wild T. natans (2x and 4x) and diploid T. incisa, we showed that water caltrop was likely first domesticated in the Yangtze River Valley as early as 6300 yr BP, and experienced a second improvement c. 800 years ago. We also provided strong support for an allotetraploid origin of T. natans within the past 230 000–310 000 years. By integrating selective sweep and transcriptome profiling analyses, we identified a number of genes potentially selected and/or differentially expressed during domestication, some of which likely contributed not only to larger fruit sizes but also to a more vigorous root system, facilitating nutrient uptake, environmental stress response and underwater photosynthesis. Our results shed light on the evolutionary and domestication history of water caltrop, one of the earliest domesticated crops in China. This study has implications for genomic-assisted breeding of this presently underutilized aquatic plant, and improves our general understanding of plant domestication. © 2021 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Introgressive Hybridization of Senecio hercynicus and S. ovatus (Compositae, Senecioneae) along an altitudinal gradient in Harz National Park (Saxony-Anhalt, Germany)

Introgressive hybridization of Senecio hercynicus and S. ovatus (Compositae, Senecioneae) was studied in a hybrid zone on the southern slopes of Mt Brocken (Harz Mountains, Germany). A total of 415 plants representing 10 stands along an altitudinal gradient were investigated using multivariate statistical analyses of morphological characters and molecular markers (random amplified polymorphic DNA[RAPD]). Both types of traits detected pure S. hercynicus stands on the summit plateau, pure S. ovatus stands at the lowest elevations, and hybrid swarms at intermediate elevations. While morphological and molecular patterns coincided, some individuals in hybrid stands combined morphological patterns typical of S. ovatus with RAPD patterns typical of S. hercynicus, and vice versa. In general, introgression was symmetrical within stands, though one stand combined S. ovatus characters with the glandular hair typical for S. hercynicus, and two stands combined a S. hercynicus typical RAPD genotype with morphological characters shifted towards S. ovatus. Because pure stands of S. hercynicus occurred only on the summit plateau of Mt Brocken, and markers typical for S. ovatus were detectable in stands up to 1040 m a.s.l., future fusion or assimilation of the rare form, S. hercynicus, by the more widespread S. ovatus appears possible at Mt Brocken

Nuclear and chloroplast DNA-based phylogenies of Chrysanthemoides Tourn. ex Medik. (Calenduleae; Asteraceae) reveal extensive incongruence and generic paraphyly, but support the recognition of infraspecific taxa in C. monilifera

The small genus Chrysanthemoides comprises two species within which a number of infraspecific taxa have been recognized, some of which are invasive aliens in Australia and New Zealand. Here we investigate the relationships of the species and infraspecific taxa using both chloroplast and nuclear non-coding DNA sequence data. Results of the analyses of the plastid and nuclear data sets are incongruent, and neither Chrysanthemoides nor Osteospermum is resolved as monophyletic, although there is some support for the recognition of infraspecific taxa. Analyses of the separate and combined data sets resolve two clades within Chrysanthemoides (which include some species of Osteospermum), and these appear to have a geographic basis, one being restricted to the mainly winter rainfall region, the other the eastern bi-seasonal rainfall area. Our results suggest that there is evidence of past or ongoing hybridization within and possibly between these two lineages