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Loren H Rieseberg - One of the best experts on this subject based on the ideXlab platform.

  • skim sequencing reveals the likely origin of the enigmatic endangered sunflower Helianthus schweinitzii
    Genes, 2019
    Co-Authors: Justin E Anderson, Edward E. Schilling, Michael B Kantar, Dan G Bock, Kunsiri Chaw Grubbs, Loren H Rieseberg
    Abstract:

    Resolving the origin of endangered taxa is an essential component of conservation. This information can be used to guide efforts of bolstering genetic diversity, and also enables species recovery and future evolutionary studies. Here, we used low-coverage whole genome sequencing to clarify the origin of Helianthus schweinitzii, an endangered tetraploid sunflower that is endemic to the Piedmont Plateau in the eastern United States. We surveyed four accessions representing four populations of H. schweinitzii and 38 accessions of six purported parental species. Using de novo approaches, we assembled 87,004 bp of the chloroplast genome and 6770 bp of the nuclear 35S rDNA. Phylogenetic reconstructions based on the chloroplast genome revealed no reciprocal monophyly of taxa. In contrast, nuclear rDNA data strongly supported the currently accepted sections of the genus Helianthus. Information from combined cpDNA and rDNA provided evidence that H. schweinitzii is likely an allo-tetraploid that formed as a result of hybridization between the diploids Helianthus giganteus and Helianthus microcephalus.

  • Phenotypic selection on leaf ecophysiological traits in Helianthus
    New Phytologist, 2009
    Co-Authors: Lisa A. Donovan, Loren H Rieseberg, F. Ludwig, David M. Rosenthal, Susan A. Dudley
    Abstract:

    Summary • Habitats that differ in soil resource availability are expected to differ for selection on resource-related plant traits.  Here, we examined spatial and temporal variation in phenotypic selection on leaf ecophysiological traits for 10 Helianthus populations, including two species of hybrid origin, Helianthus anomalus and Helianthus deserticola, and artificial hybrids of their ancestral parents. Leaf traits assessed were leaf size, succulence, nitrogen (N) concentration and water-use efficiency (WUE).  Biomass and leaf traits of artificial hybrids indicate that the actively moving dune habitat of H. anomalus was more growth limiting, with lower N availability but higher relative water availability than the stabilized dune habitat of H. deserticola. Habitats differed for direct selection on leaf N and WUE, but not size or succulence, for the artificial hybrids. However, within the H. anomalus habitat, direct selection on WUE also differed among populations. Across years, direct selection on leaf traits did not differ.  Leaf N was the only trait for which direct selection differed between habitats but not within the H. anomalus habitat, suggesting that nutrient limitation is an important selective force driving adaptation of H. anomalus to the active dune habitat.

  • Genetic Architecture of Leaf Ecophysiological Traits in Helianthus
    Journal of Heredity, 2007
    Co-Authors: Larry C. Brouillette, Loren H Rieseberg, Christian Lexer, David M. Rosenthal, Russell L. Malmberg, Lisa A. Donovan
    Abstract:

    Studies of the genetic architecture of ecologically important traits shed light on the evolution of those traits in natural populations. Studies of genetic architecture of complex traits are important because they can predict whether a phenotypic transition involved major leaps or occurred more smoothly (Burke et al. 2002). Also, alleles with large effects will fix more rapidly than will those of very small effect (Barton and Keightley 2002). An historical illustration of genetic architecture is the study by Beadle (1972) examining the inheritance of maize domestication traits. Using a primitive landrace of maize and a teosinte accession, Beadle observed the segregation of the maize and teosinte phenotypes at a 1:500 ratio, indicating that 4 or 5 genes of major effect were responsible for the bulk of changes from teosinte to maize (Beadle 1972). This demonstrated that the phenotypic transition from wild progenitor to primitive maize likely occurred in major leaps. This contrasts with sunflower, where domestication appears to have involved many small quantitative trait loci (QTLs), suggesting a smoother and more gradual transition to the domesticated form (Burke et al. 2002). Phenotypic differences between wild sunflower species (Helianthus) also seem to be controlled by a large number of loci, each with a relatively small contribution to the phenotype (Kim and Rieseberg 1999; Rieseberg et al. 2003; Lexer et al. 2005). Two Helianthus species that have been the targets of previous genetic study, Helianthus annuus and Helianthus petiolaris, are of particular interest because they hybridized to form 3 stable, ancient, diploid hybrid species Helianthus anomalus, Helianthus deserticola, and Helianthus paradoxus (Rieseberg et al. 1990; Rieseberg 1991), which occupy extreme habitats compared with the parents: active sand dunes, dry desert floors, and brackish salt marshes, respectively. The range of phenotypes observed in the hybrid species is also more extreme than those of the parental species (Schwarzbach et al. 2001; Rosenthal et al. 2002). Evolution of the hybrid sunflower species appears to have occurred quickly (Buerkle CA and Rieseberg LH, in review; Ungerer et al. 1998), and 2 of the hybrid species may have multiple origins (H. anomalus, Schwarzbach and Rieseberg 2002 and H. deserticola, Gross et al. 2003). Additionally, phenotypes of the stable hybrid species are present in populations of early hybrids between H. annuus and H. petiolaris (Rosenthal, Rieseberg, and Donovan 2005). If the preadaptive phenotypic differences important for colonizing the extreme habitats of the hybrid species are controlled by multiple genes of small effect, then the rate of fixation of individual QTL alleles is likely to be slow and the sizes of parental chromosomal blocks in the hybrid species should be smaller than when loci of large effect control the phenotype (Barton and Keightley 2002). It seems paradoxical that most of the QTLs in Helianthus tend to be of small effect, but the hybrid species genomes seem to have stabilized relatively quickly (Buerkle and Rieseberg, in review; Ungerer et al. 1998). It may be the case, however, that variation in some of the traits that are important to the survival of early-generation hybrids in Helianthus are controlled by large-effect QTLs. Also, we know that pollen sterility QTLs, which also affect hybrid genomic composition (Rieseberg et al. 1996; Karrenberg et al. forthcoming), are controlled by major QTLs (Lai et al. 2005). Here, we examine leaf ecophysiological traits, some of which greatly affect fitness of plants in the wild. Leaf nitrogen is likely to be ecologically important because it roughly estimates investment in nitrogen-rich photosynthetic enzymes, with investment per unit leaf area influencing photosynthetic capacity (Field and Mooney 1986). Foliar nitrogen is positively transgressive in the hybrid sunflower species H. anomalus (Rosenthal et al. 2002) and has been shown to impact survival in its native habitat (Ludwig et al. 2004). Despite being an important physiological trait, leaf nitrogen has only recently received attention in QTL analyses (Ishimaru et al. 2001; Hall et al. 2005; Takai et al. 2006; Weih et al. 2006). Other leaf chemistry traits measured in this study assess important aspects of plant physiology that are related to nitrogen allocation. Leaf carbon is a rough assessment of investment in carbon-rich structural molecules such as cellulose and correlates with construction cost of leaves (Nagel et al. 2002). Carbon isotopic ratio (δ13C) is often used as a proxy for water-use efficiency in C3 plants (Farquhar et al. 1989; Ehleringer et al. 1992). Differences in leaf nitrogen isotopic composition (δ15N) for plants grown under similar conditions imply differences in nitrogen uptake or use (Evans 2001). Photosynthetic nitrogen use efficiency (PNUE) is the instantaneous rate of photosynthesis per unit leaf nitrogen and may be under selection in nutrient-poor or water-limited habitats (Field and Mooney 1986; Fredeen et al. 1991; Wright et al. 2002). Here we report the results of QTL analyses for these ecologically important, physiologically based leaf traits.

  • adaptive introgression of herbivore resistance traits in the weedy sunflower Helianthus annuus
    The American Naturalist, 2006
    Co-Authors: Kenneth D Whitney, Rebecca A Randell, Loren H Rieseberg
    Abstract:

    Abstract: The role of hybridization in adaptive evolution is contentious. While many cases of adaptive trait introgression have been proposed, the relevant traits have rarely been identified, resulting in a lack of clear examples of this process. Here, we examine a purported case of adaptive introgression in which the annual sunflower Helianthus annuus annuus has captured alleles from a congener (Helianthus debilis) to form a stabilized hybrid, Helianthus annuus texanus. We tested the hypotheses that herbivore resistance traits have introgressed from H. debilis to H. annuus and have increased adaptation in the latter. In two common gardens, fitness (estimated by seed production) was on average 55% higher in H. a. texanus than in H. a. annuus. For H. a. texanus, three damage traits (of seven tested) differed significantly from the H. a. annuus parent in one or both sites and were shifted in the direction of the more resistant H. debilis. Natural selection favored H. a. \documentclass{aastex} \usepackage{am...

  • Reconstructing the Origin of Helianthus deserticola: Survival and Selection on the Desert Floor
    The American Naturalist, 2004
    Co-Authors: Briana L. Gross, Nolan C. Kane, Christian Lexer, F. Ludwig, David M. Rosenthal, Lisa A. Donovan, Loren H Rieseberg
    Abstract:

    Abstract: The diploid hybrid species Helianthus deserticola inhabits the desert floor, an extreme environment relative to its parental species Helianthus annuus and Helianthus petiolaris. Adaptation to the desert floor may have occurred via selection acting on transgressive, or extreme, traits in early hybrids between the parental species. We explored this possibility through a field experiment in the hybrid species’ native habitat using H. deserticola, H. annuus, H. petiolaris, and two populations of early‐generation (BC2) hybrids between the parental species, which served as proxies for the ancestral genotype of the ancient hybrid species. Character expression was evaluated for each genotypic class. Helianthus deserticola was negatively transgressive for stem diameter, leaf area, and flowering date, and the latter two traits are likely to be advantageous in a desert environment. The BC2 hybrids contained a range of variation that overlapped these transgressive trait means, and an analysis of phenotypic ...

Hugh D. Wilson - One of the best experts on this subject based on the ideXlab platform.

Andrea Cavallini - One of the best experts on this subject based on the ideXlab platform.

  • Analysis of transposons and repeat composition of the sunflower (Helianthus annuus L.) genome
    Theoretical and Applied Genetics, 2010
    Co-Authors: Andrea Cavallini, Tommaso Giordani, Lucia Natali, Andrea Zuccolo, Irena Jurman, Veronica Ferrillo, Nicola Vitacolonna, Vania Sarri, Federica Cattonaro, Marilena Ceccarelli
    Abstract:

    A sample-sequencing strategy combined with slot–blot hybridization and FISH was used to study the composition of the repetitive component of the sunflower genome. One thousand six hundred thirty-eight sequences for a total of 954,517 bp were analyzed. The fraction of sequences that can be classified as repetitive using computational and hybridization approaches amounts to 62% in total. Almost two thirds remain as yet uncharacterized in nature. Of those characterized, most belong to the gypsy superfamily of LTR-retrotransposons. Unlike in other species, where single families can account for large fractions of the genome, it appears that no transposon family has been amplified to very high levels in sunflower. All other known classes of transposable elements were also found. One family of unknown nature (contig 61) was the most repeated in the sunflower genome. The evolution of the repetitive component in the Helianthus genus and in other Asteraceae was studied by comparative analysis of the hybridization of total genomic DNAs from these species to the sunflower small-insert library and compared to gene-based phylogeny. Very little similarity is observed between Helianthus species and two related Asteraceae species outside of the genus. Most repetitive elements are similar in annual and perennial Helianthus species indicating that sequence amplification largely predates such divergence. Gypsy -like elements are more represented in the annuals than in the perennials, while copia -like elements are similarly represented, attesting a different amplification history of the two superfamilies of LTR-retrotransposons in the Helianthus genus.

  • Genetic variability in sunflower (Helianthus annuus L.) and in the Helianthus genus as assessed by retrotransposon-based molecular markers
    Theoretical and Applied Genetics, 2009
    Co-Authors: M. Vukich, Alan H. Schulman, Tommaso Giordani, L. Natali, Ruslan Kalendar, Andrea Cavallini
    Abstract:

    The inter-retrotransposon amplified polymorphism (IRAP) protocol was applied for the first time within the genus Helianthus to assess intraspecific variability based on retrotransposon sequences among 36 wild accessions and 26 cultivars of Helianthus annuus L., and interspecific variability among 39 species of Helianthus. Two groups of LTRs, one belonging to a Copia-like retroelement and the other to a putative retrotransposon of unknown nature (SURE) have been isolated, sequenced and primers were designed to obtain IRAP fingerprints. The number of polymorphic bands in H. annuus wild accessions is as high as in Helianthus species. If we assume that a polymorphic band can be related to a retrotransposon insertion, this result suggests that retrotransposon activity continued after Helianthus speciation. Calculation of similarity indices from binary matrices (Shannon’s and Jaccard’s indices) show that variability is reduced among domesticated H. annuus. On the contrary, similarity indices among Helianthus species were as large as those observed among wild H. annuus accessions, probably related to their scattered geographic distribution. Principal component analysis of IRAP fingerprints allows the distinction between perennial and annual Helianthus species especially when the SURE element is concerned.

  • Transgenic Sunflower (Helianthus annuus)
    Transgenic Crops I, 2000
    Co-Authors: Claudio Pugliesi, Marco Fambrini, Andrea Cavallini
    Abstract:

    The genus Helianthus (Asteraceae) includes about 100 species (Watson 1929), the majority of which are native to North America. The genus provides two food plants, H. annuus, the sunflower, and H. tuberosus, the topinambour or Jerusalem artichoke. Several varieties of H. annuus, as well as other species of the genus, are sometimes cultivated as ornamentals (Rogers et al. 1982).

  • Genomic alterations in the interspecific hybrid Helianthus annuus×Helianthus tuberosus
    Theoretical and Applied Genetics, 1998
    Co-Authors: Lucia Natali, Tommaso Giordani, Enza Polizzi, Claudio Pugliesi, Marco Fambrini, Andrea Cavallini
    Abstract:

    The genome of a Helianthus annuus (2n=34) ×Helianthus tuberosus (2n=102) hybrid was studied at cytological, biochemical and molecular levels and compared to those of the parental species. Cytophotometric analyses showed that the hybrid has a 4C DNA content higher than expected and with a larger variability than in the parents. This high variability is probably not related to chromosome-number variations since the hybrid always had 2n=68 chromosomes. Moreover, hybrid interphase nuclei showed lower heterochromatin condensation than the parental ones. Thermal denaturation of genomic DNAs indicated that quantitative variation of some DNA families occurred in the hybrids compared to parents. Finally, molecular analyses of DNAs restricted with different enzymes, after Southern blotting and hybridization with HR probes, showed restriction patterns in the hybrid different from those observed in parents. These results indicate that interspecific hybridization between H. annuus and H. tuberosus may determine quantitative variation of some DNA families and differential DNA methylations that probably modify the nuclear structure. These phenomena are probable responses to a “genomic shock” following the interspecific cross.

Michael B Kantar - One of the best experts on this subject based on the ideXlab platform.

  • skim sequencing reveals the likely origin of the enigmatic endangered sunflower Helianthus schweinitzii
    Genes, 2019
    Co-Authors: Justin E Anderson, Edward E. Schilling, Michael B Kantar, Dan G Bock, Kunsiri Chaw Grubbs, Loren H Rieseberg
    Abstract:

    Resolving the origin of endangered taxa is an essential component of conservation. This information can be used to guide efforts of bolstering genetic diversity, and also enables species recovery and future evolutionary studies. Here, we used low-coverage whole genome sequencing to clarify the origin of Helianthus schweinitzii, an endangered tetraploid sunflower that is endemic to the Piedmont Plateau in the eastern United States. We surveyed four accessions representing four populations of H. schweinitzii and 38 accessions of six purported parental species. Using de novo approaches, we assembled 87,004 bp of the chloroplast genome and 6770 bp of the nuclear 35S rDNA. Phylogenetic reconstructions based on the chloroplast genome revealed no reciprocal monophyly of taxa. In contrast, nuclear rDNA data strongly supported the currently accepted sections of the genus Helianthus. Information from combined cpDNA and rDNA provided evidence that H. schweinitzii is likely an allo-tetraploid that formed as a result of hybridization between the diploids Helianthus giganteus and Helianthus microcephalus.

  • ecogeography and utility to plant breeding of the crop wild relatives of sunflower Helianthus annuus l
    Frontiers in Plant Science, 2015
    Co-Authors: Michael B Kantar, Chrystian C Sosa, Colin K Khoury, Nora P Castanedaalvarez, Harold A Achicanoy, Vivian Bernau
    Abstract:

    Crop wild relatives (CWR) are a rich source of genetic diversity for crop improvement. Combining ecogeographic and phylogenetic techniques can inform both conservation and breeding. Geographic occurrence, bioclimatic, and biophysical data were used to predict species distributions, range overlap and niche occupancy in 36 taxa closely related to sunflower (Helianthus annuus L.). Taxa lacking comprehensive ex situ conservation were identified. The predicted distributions for 36 Helianthus taxa identified substantial range overlap, range asymmetry and niche conservatism. Specific taxa (e.g., Helianthus deblis Nutt., Helianthus anomalus Blake, and Helianthus divaricatus L.) were identified as targets for traits of interest, particularly for abiotic stress tolerance, and adaptation to extreme soil properties. The combination of techniques demonstrates the potential for publicly available ecogeographic and phylogenetic data to facilitate the identification of possible sources of abiotic stress traits for plant breeding programs. Much of the primary genepool (wild H. annuus) occurs in extreme environments indicating that introgression of targeted traits may be relatively straightforward. Sister taxa in Helianthus have greater range overlap than more distantly related taxa within the genus. This adds to a growing body of literature suggesting that in plants (unlike some animal groups), geographic isolation may not be necessary for speciation.

  • Breaking tuber dormancy in Helianthus tuberosus L. and interspecific hybrids of Helianthus Annuus L. × Helianthus tuberosus
    Hortscience, 2012
    Co-Authors: Michael B Kantar, Kevin Betts, Brent S. Hulke, Robert M. Stupar, Donald L. Wyse
    Abstract:

    Tubers of Helianthus tuberosus L. are dormant after production in the late fall until the next spring. In the wild, tuber dormancy is broken after exposure to winter cold, resulting in sprouting and shoot development in the spring when conditions are favorable. The dormancy period typically limits H. tuberosus populations to one growth cycle per year. An efficient method for breaking tuber dormancy is needed to have an additional growth cycle per year in a breeding program, which could take place in winter inthenurseryorthegreenhouse allowingforincreased breedingefficiency.Theobjective of thisresearch was to compare chemicaland cold temperature treatments for artificially breaking tuber dormancy in 12 genotypes of H. tuberosus and interspecific hybrids of Helianthus annuus L. 3 H. tuberosus. Five cold exposures (2, 4, 6, 8, 10 weeks at 2 8C), three plant hormones (ethylene, cytokinin, and gibberellic acid), and one untreated control were examined. Gibberellic acid was the best chemical treatment, initiating plant growthwithin6.5to11.5daysinthemajorityofgenotypestested.Thebestcoldtreatment was exposure to 2 8C for 8 weeks, where plant growth began 63.6 to 67.5 days after treatment initiation. Although longer cold treatments shortened the time to emergence while in the greenhouse, the penalty of the long cold treatment per se was too long to be useful. The gibberellic acid treatment strategy described here may not need further optimization, because it is short enough to allow for two growth cycles of H. tuberosus per year.

T J Gulya - One of the best experts on this subject based on the ideXlab platform.