Hidden Rice Diversity in the Guianas

Co-conserving Indigenous and local knowledge systems with seeds

Indigenous and local knowledge (ILK) holders have deep ecological, horticultural, and practical knowledge of plants, but this knowledge is not routinely considered and supported along with seed collections conserved ex situ. In this opinion, conceived collaboratively by a team of botanists, ecologists, ethnobiologists, and practitioners in biodiversity and ILK systems conservation, we propose seven actions towards the co-conservation of seeds and associated knowledge to overcome obstacles and encourage ex situ conservation institutions to support knowledge holders in multiple ways. Success depends on simultaneous changes in conservation practices, new collaborative relationships, and shifts in policy to share and conserve biocultural diversity. Failure to act will witness the continued erosion of ILK and depreciation of ex situ plant collections.

Retrieval of long DNA reads from herbarium specimens

High-throughput sequencing of herbarium specimens' DNA with short-read platforms has helped explore many biological questions. Here, for the first time, we investigate the potential of using herbarium specimens as a resource for long-read DNA sequencing technologies. We use target capture of 48 low-copy nuclear loci in 12 herbarium specimens of Silene as a basis for long-read sequencing using SMRT PacBio Sequel. The samples were collected between 1932 and 2019. A simple optimization of size selection protocol enabled the retrieval of both long DNA fragments (>1 kb) and long on-target reads for nine of them. The limited sampling size does not enable statistical evaluation of the influence of specimen age to the DNA fragmentation, but our results confirm that younger samples, that is, collected after 1990, are less fragmented and have better sequencing success than specimens collected before this date. Specimens collected between 1990 and 2019 yield between 167 and 3403 on-target reads > 1 kb. They enabled recovering between 34 loci and 48 (i.e. all loci recovered). Three samples from specimens collected before 1990 did not yield on-target reads > 1 kb. The four other samples collected before this date yielded up to 144 reads and recovered up to 25 loci. Young herbarium specimens seem promising for long-read sequencing. However, older ones have partly failed. Further exploration would be necessary to statistically test and understand the potential of older material in the quest for long reads. We would encourage greatly expanding the sampling size and comparing different taxonomic groups.

The evolution of the hypotetraploid Catolobus pendulus genome - the poorly known sister species of Capsella

The establishment of Arabidopsis as the most important plant model has also brought other crucifer species into the spotlight of comparative research. While the genus Capsella has become a prominent crucifer model system, its closest relative has been overlooked. The unispecific genus Catolobus is native to temperate Eurasian woodlands, from eastern Europe to the Russian Far East. Here, we analyzed chromosome number, genome structure, intraspecific genetic variation, and habitat suitability of Catolobus pendulus throughout its range. Unexpectedly, all analyzed populations were hypotetraploid (2n = 30, ~330 Mb). Comparative cytogenomic analysis revealed that the Catolobus genome arose by a whole-genome duplication in a diploid genome resembling Ancestral Crucifer Karyotype (ACK, n = 8). In contrast to the much younger Capsella allotetraploid genomes, the presumably autotetraploid Catolobus genome (2n = 32) arose early after the Catolobus/Capsella divergence. Since its origin, the tetraploid Catolobus genome has undergone chromosomal rediploidization, including a reduction in chromosome number from 2n = 32 to 2n = 30. Diploidization occurred through end-to-end chromosome fusion and other chromosomal rearrangements affecting a total of six of 16 ancestral chromosomes. The hypotetraploid Catolobus cytotype expanded toward its present range, accompanied by some longitudinal genetic differentiation. The sister relationship between Catolobus and Capsella allows comparative studies of tetraploid genomes of contrasting ages and different degrees of genome diploidization.

Target Capture Reveals the Complex Origin of Vietnamese Ginseng

The global market of the medicinal plant ginseng is worth billions of dollars. Many ginseng species are threatened in the wild and effective sustainable development initiatives are necessary to preserve biodiversity at species and genetic level whilst meeting the demand for medicinal produce. This is also the case of Panax vietnamensis Ha & Grushv., an endemic and threatened ginseng species in Vietnam that is locally cultivated at different scales and has been the object of national breeding programs. To investigate the genetic diversity within cultivated and wild populations of P. vietnamensis we captured 353 nuclear markers using the Angiosperm-353 probe set. Genetic diversity and population structure were evaluated for 319 individuals of Vietnamese ginseng across its area of distribution and from wild and a varying range of cultivated areas. In total, 319 individuals were sampled. After filtering, 1,181 SNPs were recovered. From the population statistics, we observe high genetic diversity and high genetic flow between populations. This is also supported by the STRUCTURE analysis. The intense gene flow between populations and very low genetic differentiation is observed regardless of the populations' wild or cultivated status. High levels of admixture from two ancestral populations exist in both wild and cultivated samples. The high gene flow between populations can be attributed to ancient and on-going practices of cultivation, which exist in a continuum from understorey, untended breeding to irrigated farm cultivation and to trade and exchange activities. These results highlight the importance of partnering with indigenous peoples and local communities and taking their knowledge into account for biodiversity conservation and sustainable development of plants of high cultural value.

The legacy of traditional rice cultivation by descendants of Indian contract laborers in Suriname

BACKGROUND

Some 35,000 indentured laborers from India were recruited to work on plantations in Suriname between 1868 and 1916. It is likely that most were familiar with farming before they were shipped to this former Dutch colony in the Caribbean. Around 1900, those who did not return received a piece of land where most of them started growing rice as a staple crop. Agronomists characterized their traditional landraces as inferior and infested with weedy rice and started to 'purify' these landraces. No research has been done on whether these ancient rice varieties still exist. We aimed to document the rice varieties (both landraces and more modern cultivars) grown currently or in the recent past by (descendants of) Hindustani smallholders in Suriname, their origin, morphological and agronomic characters, local uses and cultural and spiritual relevance. Given the rapid decline in small-scale rice cultivation in the past 40 years, we wanted to know why people continued or abandoned rice farming and what aspects of traditional practices still survived.

METHODS

We interviewed 26 (former) small-scale Hindustani farmers and asked about the varieties they cultivated and traditional agricultural practices. We collected seed samples, local names and associated information, and compared these to information from agricultural reports from the colonial period. We also interviewed 11 Maroons, one Javanese farmer, and three persons of mixed ethnicity, who were somehow involved in the cultivation of East Indian rice varieties.

RESULTS AND DISCUSSION

Hindustani smallholders in Suriname largely lost their traditional rice landraces. Most of the interviewed farmers grew modern cultivars, developed after 2000. Some cultivars from the 1950s were still planted for fodder, but these were heavily mixed with weedy rice and other weeds. Maroon farmers in the interior, however, still actively cultivated varieties with names like 'coolie rice', which probably descend from landraces introduced by the Indian contract laborers, although this needs to be confirmed by molecular research. Although traditional cultivation practices seem to have been lost, smallholders still retain pleasant memories of the manual planting, harvesting, and processing of rice, as well as the gender-based practices and beliefs associated with the cultivation of the crop. The oral history of former rice farmers and traditional rice varieties (possibly obtained from Maroon fields) could play a role in museum settings as living vehicles for memories of the descendants of Asian contract labourers in Suriname and Guyana.

Relative performance of customized and universal probe sets in target enrichment: A case study in subtribe Malinae

PREMISE

Custom probe design for target enrichment in phylogenetics is tedious and often hinders broader phylogenetic synthesis. The universal angiosperm probe set Angiosperms353 may be the solution. Here, we test the relative performance of Angiosperms353 on the Rosaceae subtribe Malinae in comparison with custom probes that we specifically designed for this clade. We then address the impact of bioinformatically altering the performance of Angiosperms353 by replacing the original probe sequences with orthologs extracted from the Malus domestica genome.

METHODS

To evaluate the relative performance of these probe sets, we compared the enrichment efficiency, locus recovery, alignment length, proportion of parsimony-informative sites, proportion of potential paralogs, the topology and support of the resulting species trees, and the gene tree discordance.

RESULTS

Locus recovery was highest for our custom Malinae probe set, and replacing the original Angiosperms353 sequences with a Malus representative improved the locus recovery relative to Angiosperms353. The proportion of parsimony-informative sites was similar between all probe sets, while the gene tree discordance was lower in the case of the custom probes.

DISCUSSION

A custom probe set benefits from data completeness and can be tailored toward the specificities of the project of choice; however, Angiosperms353 was equally as phylogenetically informative as the custom probes. We therefore recommend using both a custom probe set and Angiosperms353 to facilitate large-scale systematic studies, where financially possible.

New targets acquired: Improving locus recovery from the Angiosperms353 probe set

PREMISE

Universal target enrichment kits maximize utility across wide evolutionary breadth while minimizing the number of baits required to create a cost-efficient kit. The Angiosperms353 kit has been successfully used to capture loci throughout the angiosperms, but the default target reference file includes sequence information from only 6-18 taxa per locus. Consequently, reads sequenced from on-target DNA molecules may fail to map to references, resulting in fewer on-target reads for assembly, and reducing locus recovery.

METHODS

We expanded the Angiosperms353 target file, incorporating sequences from 566 transcriptomes to produce a 'mega353' target file, with each locus represented by 17-373 taxa. This mega353 file is a drop-in replacement for the original Angiosperms353 file in HybPiper analyses. We provide tools to subsample the file based on user-selected taxon groups, and to incorporate other transcriptome or protein-coding gene data sets.

RESULTS

Compared to the default Angiosperms353 file, the mega353 file increased the percentage of on-target reads by an average of 32%, increased locus recovery at 75% length by 49%, and increased the total length of the concatenated loci by 29%.

DISCUSSION

Increasing the phylogenetic density of the target reference file results in improved recovery of target capture loci. The mega353 file and associated scripts are available at: https://github.com/chrisjackson-pellicle/NewTargets.

Lineage-specific vs. universal: A comparison of the Compositae1061 and Angiosperms353 enrichment panels in the sunflower family

PREMISE

Phylogenetic studies in the Compositae are challenging due to the sheer size of the family and the challenges they pose for molecular tools, ranging from the genomic impact of polyploid events to their very conserved plastid genomes. The search for better molecular tools for phylogenetic studies led to the development of the family-specific Compositae1061 probe set, as well as the universal Angiosperms353 probe set designed for all flowering plants. In this study, we evaluate the extent to which data generated using the family-specific kit and those obtained with the universal kit can be merged for downstream analyses.

METHODS

We used comparative methods to verify the presence of shared loci between probe sets. Using two sets of eight samples sequenced with Compositae1061 and Angiosperms353, we ran phylogenetic analyses with and without loci flagged as paralogs, a gene tree discordance analysis, and a complementary phylogenetic analysis mixing samples from both sample sets.

RESULTS

Our results show that the Compositae1061 kit provides an average of 721 loci, with 9-46% of them presenting paralogs, while the Angiosperms353 set yields an average of 287 loci, which are less affected by paralogy. Analyses mixing samples from both sets showed that the presence of 30 shared loci in the probe sets allows the combination of data generated in different ways.

DISCUSSION

Combining data generated using different probe sets opens up the possibility of collaborative efforts and shared data within the synantherological community.

A Comprehensive Phylogenomic Platform for Exploring the Angiosperm Tree of Life

The tree of life is the fundamental biological roadmap for navigating the evolution and properties of life on Earth, and yet remains largely unknown. Even angiosperms (flowering plants) are fraught with data gaps, despite their critical role in sustaining terrestrial life. Today, high-throughput sequencing promises to significantly deepen our understanding of evolutionary relationships. Here, we describe a comprehensive phylogenomic platform for exploring the angiosperm tree of life, comprising a set of open tools and data based on the 353 nuclear genes targeted by the universal Angiosperms353 sequence capture probes. The primary goals of this article are to (i) document our methods, (ii) describe our first data release, and (iii) present a novel open data portal, the Kew Tree of Life Explorer (https://treeoflife.kew.org). We aim to generate novel target sequence capture data for all genera of flowering plants, exploiting natural history collections such as herbarium specimens, and augment it with mined public data. Our first data release, described here, is the most extensive nuclear phylogenomic data set for angiosperms to date, comprising 3099 samples validated by DNA barcode and phylogenetic tests, representing all 64 orders, 404 families (96\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}$\%$\end{document}) and 2333 genera (17\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}$\%$\end{document}). A “first pass” angiosperm tree of life was inferred from the data, which totaled 824,878 sequences, 489,086,049 base pairs, and 532,260 alignment columns, for interactive presentation in the Kew Tree of Life Explorer. This species tree was generated using methods that were rigorous, yet tractable at our scale of operation. Despite limitations pertaining to taxon and gene sampling, gene recovery, models of sequence evolution and paralogy, the tree strongly supports existing taxonomy, while challenging numerous hypothesized relationships among orders and placing many genera for the first time. The validated data set, species tree and all intermediates are openly accessible via the Kew Tree of Life Explorer and will be updated as further data become available. This major milestone toward a complete tree of life for all flowering plant species opens doors to a highly integrated future for angiosperm phylogenomics through the systematic sequencing of standardized nuclear markers. Our approach has the potential to serve as a much-needed bridge between the growing movement to sequence the genomes of all life on Earth and the vast phylogenomic potential of the world’s natural history collections. [Angiosperms; Angiosperms353; genomics; herbariomics; museomics; nuclear phylogenomics; open access; target sequence capture; tree of life.]

Traditional rice landraces in Lei-Qiong area of South China tolerate salt stress with strong antioxidant activity

Salt stress, causing serious loss on crop productions, is one of the most important environmental stresses throughout the world. The aim of this study is to select salt-tolerant traditional rice resources collected from Lei-Qiong area of South China and investigate their physiological performances and biochemical regulations during salt stress response, together with two well-known international varieties, Nona Bokra (salt-tolerant sample) and IR29 (salt-sensitive sample). After comprehensive analyses, we discovered that two Lei-Qiong traditional salt-tolerant rice samples showed less growth inhibition by salt stress during both germination and seedling stage, in comparison with other rice samples. Moreover, there were less chlorosis symptoms in these two kinds of salt tolerant rice under salt stress, corresponding to their better water-holding capacity. We measured malondialdehyde and proline contents, and activities of CAT and POD of seedlings treated with 100 mM NaCl for 5 dand 10 d, respectively. Interestingly, less cellular membrane damage and stronger antioxidant enzyme system were found in the two Lei-Qiong rice samples. Our study suggests that traditional rice landrace growing onshore of Lei-Qiong area in China possesses good salt-tolerant capacity, which could be attributed to their efficient antioxidant enzyme system.

Reconstructing the Complex Evolutionary History of the Papuasian Schefflera Radiation Through Herbariomics

With its large proportion of endemic taxa, complex geological past, and location at the confluence of the highly diverse Malesian and Australian floristic regions, Papuasia - the floristic region comprising the Bismarck Archipelago, New Guinea, and the Solomon Islands - represents an ideal natural experiment in plant biogeography. However, scattered knowledge of its flora and limited representation in herbaria have hindered our understanding of the drivers of its diversity. Focusing on the woody angiosperm genus Schefflera (Araliaceae), we ask whether its morphologically defined infrageneric groupings are monophyletic, when these lineages diverged, and where (within Papuasia or elsewhere) they diversified. To address these questions, we use a high-throughput sequencing approach (Hyb-Seq) which combines target capture (with an angiosperm-wide bait kit targeting 353 single-copy nuclear loci) and genome shotgun sequencing (which allows retrieval of regions in high-copy number, e.g., organellar DNA) of historical herbarium collections. To reconstruct the evolutionary history of the genus we reconstruct molecular phylogenies with Bayesian inference, maximum likelihood, and pseudo-coalescent approaches, and co-estimate divergence times and ancestral areas in a Bayesian framework. We find strong support for most infrageneric morphological groupings, as currently circumscribed, and we show the efficacy of the Angiosperms-353 probe kit in resolving both deep and shallow phylogenetic relationships. We infer a sequence of colonization to explain the present-day distribution of Schefflera in Papuasia: from the Sunda Shelf, Schefflera arrived to the Woodlark plate (present-day eastern New Guinea) in the late Oligocene (when most of New Guinea was submerged) and, subsequently (throughout the Miocene), it migrated westwards (to the Maoke and Bird's Head Plates and thereon) and further diversified, in agreement with previous reconstructions.