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Polyploidy is common among grasses (Poaceae) and poses challenges for conventional breeding. Genome editing technology circumvents crossing and selfing, enabling targeted modifications to multiple gene copies in a single generation while maintaining the heterozygous context of many polyploid genomes. Bahiagrass (Paspalum notatum Flüggé; 2n=4x=40) is an apomictic, tetraploid C4 species that is widely grown in the southeastern United States as forage in beef cattle production and utility turf. The chlorophyll biosynthesis gene magnesium chelatase (MgCh) was selected as a rapid readout target for establishing genome editing in tetraploid bahiagrass. Vectors containing sgRNAs, Cas9 and nptII were delivered to callus cultures by biolistics. Edited plants were characterized through PCR-based assays and DNA sequencing, and mutagenesis frequencies as high as 99% of Illumina reads were observed. Sequencing of wild type (WT) bahiagrass revealed a high level of sequence variation in MgCh likely due to the presence of at least two copies with possibly eight different alleles, including pseudogenes. MgCh mutants exhibited visible chlorophyll depletion with up to 82% reductions in leaf greenness. Two lines displayed progression of editing over time which was linked to somatic editing. Apomictic progeny of a chimeric MgCh editing event were obtained and allowed identification of uniformly edited progeny plants among a range of chlorophyll depletion phenotypes. Sanger sequencing of a highly edited mutant revealed elevated frequency of a WT allele, probably due to frequent homology-directed repair (HDR). To our knowledge these experiments comprise the first report of genome editing applied in perennial, warm-season turf or forage grasses. This technology will accelerate bahiagrass cultivar development. [ABSTRACT FROM AUTHOR]

Current and past climatic changes can shift plant climatic niches, which may cause spatial overlap or separation between related taxa. The former often leads to hybridization and introgression, which may generate novel variation and influence the adaptive capacity of plants. An additional mechanism facilitating adaptations to novel environments and an important evolutionary driver in plants is polyploidy as the result of whole genome duplication. Artemisia tridentata (big sagebrush) is a landscape-dominating foundational shrub in the western United States which occupies distinct ecological niches, exhibiting diploid and tetraploid cytotypes. Tetraploids have a large impact on the species' landscape dominance as they occupy a preponderance of the arid spectrum of A. tridentata range. Three distinct subspecies are recognized, which co-occur in ecotones - the transition zone between two or more distinct ecological niches - allowing for hybridization and introgression. Here we assess the genomic distinctiveness and extent of hybridization among subspecies at different ploidies under both contemporary and predicted future climates. We sampled five transects throughout the western United States where a subspecies overlap was predicted using subspecies-specific climate niche models. Along each transect, we sampled multiple plots representing the parental and the potential hybrid habitats. We performed reduced representation sequencing and processed the data using a ploidy-informed genotyping approach. Population genomic analyses revealed distinct diploid subspecies and at least two distinct tetraploid gene pools, indicating independent origins of the tetraploid populations. We detected low levels of hybridization (2.5%) between the diploid subspecies, while we found evidence for increased admixture between ploidy levels (18%), indicating hybridization has an important role in the formation of tetraploids. Our analyses highlight the importance of subspecies cooccurrence within these ecotones to maintain gene exchange and potential formation of tetraploid populations. Genomic confirmations of subspecies in the ecotones support the subspecies overlap predicted by the contemporary climate niche models. However, future mid-century projections of subspecies niches predict a substantial loss in range and subspecies overlap. Thus, reductions in hybridization potential could affect new recruitment of genetically variable tetraploids that are vital to this species' ecological role. Our results underscore the importance of ecotone conservation and restoration. [ABSTRACT FROM AUTHOR]

In plant species, variation in levels of clonality, ploidy and interspecific hybridization can interact to influence geographic patterns of genetic diversity. These factors commonly vary in plants that specialize on saline habitats (halophytes) and may play a role in how they adapt to salinity variation across their range. One such halophyte is the turfgrass and emerging genomic model system seashore paspalum (Paspalum vaginatum Swartz). To investigate how clonal propagation, ploidy variation, and interspecific hybridization vary across ecotypes and local salinity levels in wild P. vaginatum, we employed genotyping‐by‐sequencing, cpDNA sequencing and flow cytometry in 218 accessions representing > 170 wild collections from throughout the coastal southern United States plus USDA germplasm. We found that the two morphologically distinct ecotypes of P. vaginatum differ in their adaptive strategies. The fine‐textured ecotype is diploid and appears to reproduce in the wild both sexually and by clonal propagation; in contrast, the coarse‐textured ecotype consists largely of clonally‐propagating triploid and diploid genotypes. The coarse‐textured ecotype appears to be derived from hybridization between fine‐textured P. vaginatum and an unidentified Paspalum species. These clonally propagating hybrid genotypes are more broadly distributed than clonal fine‐textured genotypes and may represent a transition to a more generalist adaptive strategy. Additionally, the triploid genotypes vary in whether they carry one or two copies of the P. vaginatum subgenome, indicating multiple evolutionary origins. This variation in subgenome composition shows associations with local ocean salinity levels across the sampled populations and may play a role in local adaptation. [ABSTRACT FROM AUTHOR]

Apomixis in crucifer (Brassicaceae) species is rare, reported in just four genera (Boechera, Draba, Erysimum, and Parrya), and one intergeneric hybrid (Raphanobrassica). It is well studied only in Boechera, where it is widespread among 100+ recognized species. However, its occurrence in related genera of the tribe Boechereae has not been documented previously. Here we analyzed genome evolution, mode of reproduction, and fertility of the monospecific Boechereae genus Phoenicaulis (P. cheiranthoides), endemic to the northwestern United States. We discovered that the species encompasses diploid (2n = 2x = 14), triploid (2n = 3x = 21), and tetraploid (2n = 4x = 28) populations. Comparative chromosome painting analyses revealed that the three karyotypes are essentially structurally identical, differing only in the presence of a largely heterochromatic chromosome (Het) in the triploid and tetraploid cytotypes. The genome structure of Phoenicaulis appeared identical to that of Boechera species previously analyzed, suggesting genomic stasis despite the morphological and molecular divergence of the two genera. This genome colinearity extended to the presence and structure of the Het chromosomes, which are closely associated with apomictic reproduction in Boechera. Interestingly, all three cytotypes of Phoenicaulis proved to be apomictic, regardless of the presence or absence of a Het chromosome, and sexual populations have yet to be identified. [ABSTRACT FROM AUTHOR]

From noble beginnings as a prospective forage, polyploid Sorghum halepense ('Johnsongrass') is both an invasive species and one of the world's worst agricultural weeds. Formed by S. bicolor x S. propinquum hybridization, we show S. halepense to have S. bicolor -enriched allele composition and striking mutations in 5,957 genes that differentiate it from representatives of its progenitor species and an outgroup. The spread of S. halepense may have been facilitated by introgression from closely-related cultivated sorghum near genetic loci affecting rhizome development, seed size, and levels of lutein, a photochemical protectant and abscisic acid precursor. Rhizomes, subterranean stems that store carbohydrates and spawn clonal propagules, have growth correlated with reproductive rather than other vegetative tissues, and increase survival of both temperate cold seasons and tropical dry seasons. Rhizomes of S. halepense are more extensive than those of its rhizomatous progenitor S. propinquum , with gene expression including many alleles from its non-rhizomatous S. bicolor progenitor. The first surviving polyploid in its lineage in ∼96 million years, its post-Columbian spread across six continents carried rich genetic diversity that in the United States has facilitated transition from agricultural to non-agricultural niches. Projected to spread another 200–600 km northward in the coming century, despite its drawbacks S. halepense may offer novel alleles and traits of value to improvement of sorghum. [ABSTRACT FROM AUTHOR]

Polyploidy is conspicuous in the genus Phlox, and some species exhibit variation in ploidy levels, or cytotypic variation. Diploid, tetraploid and hexaploid populations of P. nana occur across parts of the species distribution in the southwestern United States and northern Mexico. A recent study highlighted two areas for which ploidy level inferences were challenging: a population on the Pecos Plains of New Mexico ("Caprock") and the Davis Mountains region of West Texas. Plants in these areas were sampled and chromosome counts and flow cytometry methods were used to assess ploidy levels and genome sizes. Homoploid variation in genome size was unambiguously documented: the genome size of tetraploid plants from the Davis Mountains was significantly larger than that of plants from Caprock. The general condition of larger genome sizes for plants in the Davis Mountains explains previous difficulty in determining ploidy levels within the region. Most plants at the Caprock population appeared to be tetraploid (2n=28), but chromosome counts revealed variants, including some putative pentaploids. Within the Davis Mountains region, both diploid (2n=14) and tetraploid (2n=28) cytotypes were documented, with a parapatric distribution. Overall, this study clarifies patterns of cytotypic diversity in P. nana, highlights an example of infraspecific, homoploid genome size variation, and contributes to a framework for ongoing evolutionary investigation in this study system. [ABSTRACT FROM AUTHOR]

Prunus laurocersaus L. (2n = 22.v =176), common cherrylaurel, is an evergreen shrub generally used as a hedge or screen. This species produces large drupes that are a nuisance when they drop on walkways or deposited by birds and also has escaped cultivation in parts of northwestern United States, which has raised concern about the invasive potential of common cherrylaurel. Therefore, a fruitless and sterile form of common cherrylaurel is desirable. As part of our efforts to develop sterile common cherrylaurel cultivars, we conducted two experiments to induce chromosome doubling using in vitro exposure of 'Otto Luyken' and 'Schipkaensis' cherrylaurel to oryzalin. For 'Otto Luyken' (Expt. 1), we tested the effects of treatment duration (1,2,14, or 28 days) and oryzalin concentration (0, 6.25, 12.5, 25, 50, 100, or 150 µM) applied in a liquid phase over explants. In Expt. 2, we treated 'Schipkaensis' cherrylaurel shoots with a single duration of 28 days and exposed explants to the same varying concentrations of oryzalin incorporated into the solidified medium. In Expt. 1, the 14-day treatment had reduced survival compared with 1- and 2-day treatments and there was still greater mortality in the 28-dav treatment. Duration of the treatment affected mortality more than oryzalin concentration. Sixteen treatment combinations resulted in 44.v plants. The percentage of 44x plants increased with concentration in the 1- and 2-dav treatments up to 30% of treated shoots at 150 µM. Overall, the longer duration treatments in Expt. 1 were less efficient for inducing 44.v plants. Expt. 2 was less effective for inducing homogenous 44.v plants. It is unclear if this is due to treatment or cultivar differences but the highest concentration was 8% in the 6.25 µM treatment. [ABSTRACT FROM AUTHOR]

* Premise of the study: Previous phylogenetic studies of moonworts (Botrychium sensustricto (s.s.)) included few taxa from outside of North America. This low geographical representation limited interpretations of relationships of this group rich in cryptic species. With 18 out of 30 species in the genus being polyploid, understanding their evolutionary history remains a major challenge. * Methods: A new molecular phylogeny was reconstructed using Maximum Likelihood (ML) and Bayesian Inference (BI) analyses based on multiple accessions of the most wide-ranging Arctic taxa of Botrychium in North America and Europe using three noncoding plastid DNA regions (psbA-tmHGUG, trnLUAA-trnFGAA intergenic spacer, and rpL16 intron). * Key results: The new phylogeny confirms the identity of several recently described species and proposed new taxa. Nine sub- clades are newly identified within the two major clades in Botrychium s.s.: Lanceolatum and Lunaria. Chloroplast DNA was variable enough to separate morphologically cryptic species in the Lunaria clade. On the contrary, much less variation is seen within the morphologically variable Lanceolatum clade despite sampling over the same broad geographic range. The chloroplast region psbA-tmHGUG is identified as an efficient DNA barcode for the identification of cryptic taxa in Botrychium s.s. * Conclusions: The combined increase in species representation, samples from throughout the geographic range of each species, and sequencing of multiple plastid DNA regions supports morphologically cryptic species in Botrychium s.s. [ABSTRACT FROM AUTHOR]

Abstract: Ethanolic extracts of diploid Artemisia dracunculus L. (wild tarragon) from populations in the U.S., and polyploid tarragon from a variety of sources, were screened for the anti-diabetic compounds davidigenin; sakuranetin; 2’,4’-dihydroxy-4-methoxydihydrochalcone; 4,5-di-O-caffeoylquinic acid; 5-O-caffeoylquinic acid and 6-demethoxycapillarisin using LC-MS. Only decaploid plants contained all six target compounds and were the only plants that contained davidigenin and 2,4-dihydroxy-4-methoxydihydrochalcone. These results exhibit the importance of germplasm selection and provenance when studying plants for medicinal activity. Relying only on the “right species” for consistent medicinal activities may not be sufficient, as intraspecific variation may be highly significant. [Copyright &y& Elsevier]

Previous accounts of polyploidy in the North American salt desert shrub Atriplex confertifolia (shadscale) have dealt with the distribution of polyploidy and the morphological and secondary chemical differences between races. The present study amplifies these studies and reveals additional ploidy-flavonoid races, with ploidy levels known to extend from 2x to 12x, and all except 2x and 12x represented by races with and without 6-methoxylation of flavonol compounds. Results of this study show that diploids across their range have about 113% as much DNA per genome as do polyploids and that parallel variation in monoploid genome size between diploids and accompanying polyploids can be shown in different parts of the species' range. Polyploidy, therefore, appears to have developed independently in several areas of the western United States. Hexaploids are generally not as common as octoploids in shadscale, which could be an indication of diploidization of older tetraploid races. [ABSTRACT FROM AUTHOR]

Abstract  Southern chinch bug, Blissus insularis Barber (Hemiptera: Blissidae), is a serious insect pest of St. Augustinegrass, Stenotaphrum secundatum (Walt.) Kuntze, a turfgrass commonly grown in the southeastern United States. Resistance to southern chinch bug has been identified in the polyploid St. Augustinegrass varieties ‘Floratam’ and ‘FX-10’, and the diploid ‘Captiva’. However, southern chinch bug in Florida and elsewhere has overcome Floratam’s resistance. This research investigated the potential role of selected plant oxidative enzymes in resistance/susceptibility to southern chinch bug in two polyploid varieties (FX-10 and Floratam) and two diploid varieties (Captiva and Palmetto). Oxidative enzyme activity was estimated spectrophotometrically from plant samples collected 1, 3, 5, and 8 days after southern chinch bug infestation and from uninfested control plants. Resistant FX-10 and Captiva had significantly higher peroxidase activity, while Captiva had significantly higher polyphenol oxidase activity 5 and 8 days after infestation compared to uninfested controls. FX-10 had higher lipoxygenase activity 3, 5, and 8 days after infestation compared to uninfested controls. Catalase activities did not differ between infested and control plants in any of the varieties tested. Native gels stained for peroxidase indicated that certain isozymes in FX-10 and Captiva were induced 5 and 8 days after infestation. Isozyme profiles of polyphenol oxidase and lipoxygenase did not differ between control and infested FX-10, Floratam, Captiva, and Palmetto. Potential mechanisms to explain the correlation of resistance to southern chinch bug in FX-10 and Captiva with higher activities of oxidative enzymes are discussed. [ABSTRACT FROM AUTHOR]

In plants, polyploidy has been a significant evolutionary force on both recent and ancient time scales. In 1950, Ownbey reported two newly formed Tragopogon allopolyploids in the northwestern United States. We have made the first synthetic lines ofT nhirus and T miscellus using T dubius, T porrifolius, and T pratensis as parents and colchicine treatment of F1 hybrids. We also produced allotetraploids between T porrifolius and T prarensis, which are not known from nature. We report on the crossability between the diploids, as well as the inflorescence morphology, pollen size, meiotic behavior, and fertility of the synthetic polyploids. Morphologically, the synthetics resemble the natural polyploids with shortand long-liguled forms of T miscellus resulting when T pratensis and T dubius are reciprocally crossed. Synthetic T mirus was also formed reciprocally, but without any obvious morphological differences resulting from the direction of the cross. Of the 27 original crosses that yielded 171 hybrid individuals, 18 of these lineages have persisted to produce 386 5 progeny; each of these lineages has produced S2 seed that are viable. The successful generation of these synthetic polyploids offers the opportunity for detailed comparative studies of natural and synthetic polyploids within a nonmodel system. [ABSTRACT FROM AUTHOR]

The role of polyploidy in facilitating invasiveness of introduced plants has not been well explored. Examination of traits of diploid and polyploid plants in both their native and introduced ranges can shed light on evolutionary processes occurring postintroduction in invasive plants. We determined the distribution and prevalence of cytotypes of So/ida go gigantea in both its native range (USA) and introduced range (Europe), and measured a suite of biochemical, physiological, and reproductive characters for plants from both continents. Tetraploids were the most frequent cytotype encountered on both continents, while hexaploids were found only in the USA. Hexaploids were the most distinctive cytotype, with fewer differences observed between diploids and tetraploids. Comparison of diploids and tetraploids in the USA and Europe showed that traits changed in concert for both cytotypes. Both diploids and tetraploids in Europe had reduced concentrations of three classes of secondary chemical and invested relatively more into rhizomes than into flowers. The same changes occurring in both cytotypes in the introduced range show that altered phenotypes of European plants are not due to shifts in the proportions of cytotypes but instead occur within them. There was no evidence that polyploids evolve more quickly in the introduced range. [ABSTRACT FROM AUTHOR]

We investigated genetic variation in asexual polyploid members of the water flea Daphnia pulex complex from a set of 12 Bolivian high-altitude lakes. We used nuclear microsatellite markers to study genetic relationships among all encountered multilocus genotypes, and combined this with a phylogenetic approach using DNA sequence data of three mitochondrial genes. Analyses of mitochondrial gene sequence divergence showed the presence of three very distinct clades that likely represent cryptic undescribed species. Our phylogenetic results suggest that the Daphnia pulicaria group, a complex of predominantly North American species that has diversified rapidly since the Pleistocene, has its origin in South America, as specific tests of topology indicated that all three South American lineages are ancestral to the North American members of this species group. A comparison between variation of nuclear and mitochondrial markers revealed that closely related polyploid nuclear genotypes sometimes belonged to very divergent mitochondrial lineages, while distantly related nuclear genotypes often belonged to the same mitochondrial lineage. This discrepancy suggests that these South American water fleas originated through reciprocal hybridization between different endemic, sexually reproducing parental lineages. It is also likely that polyploidy of the investigated lineages resulted from this hybridization. Nevertheless, no putative diploid parental lineages were found in the studied region. [ABSTRACT FROM AUTHOR]

Achillea millefolium agg. is an ecologically most diverse N Hemisphere polyploid complex. Because of ubiqui- tous hybridization and polyploidization, the aggregate is extremely polymorphic and notorious for its difficult taxonomy. AFLP analyses were applied to 61 populations representing most of the known taxa ofA. millefolium agg. Genetic distance methods ofpopulation pairwise FST and Neighbour Joining for tree constructions and the 2D^Euklid algorithm for scatter plots were used to evaluate the AFLP-matrix with 459, mostly polymorphic bands. The aggregate is monophyletic and sister to the subalpine relic A. latiloba-2x from NE Turkish and adjacent Georgian mountains. The seven 2x-species of A. millefolium agg. have differentiated vicariously in Europe/SW Asia and expanded into C and E Asia. Both, the NJ trees and the 2D^Euklid scatterplots demon- strate these 2x as genetically monophyletic and distinct; only A. roseoalba-2x, close to A. asplen~folia-2x, may be the product of hybrid introgression. The polyploids of the aggregate (about 20 taxa and cytotypes) exhibit various combinations of 2x AFLP bands, but in addition also 16.9% of exclusive bands, documenting new genetic variation. Whereas the ALFP trees suggest most of these polyploid taxa to be polyphyletic, the AFLP 2DEuklid scatterplots demonstrate their phyletic coherence. This conflicting evidence apparently is due to wide-spread secondary hybrid merging between sympatric populations ofdifferent polyploid taxa, resulting in geographic instead of phyletic clustering of their populations in the AFLP trees. Available data suggest several parallel reticulating and ascending polyploid lines and their eco-geographical radiations. This has resulted in the origin of eight taxa of 4x, four or five of 6x and three of 8x in Europe and the Caucasus. One of them, A. millefolium subsp. millefolium-6x, also occurs throughout Asia, where two more 4x taxa, one additional 6x and one 8x can be recognized. Finally, from ancestors close to A. asialica s.str.-4x, the A. borealis s.l. dade has originated in N America, where it has radiated with numerous 4x- and 6x-ecotypes into most diverse habitats. Thus, the polyploid complex A. millefolium agg., shaped by successive cycles of differentiation and hybridiza- tion + polyplodization, has expanded stepwise from Europe and SW Asia to E Asia, then to N America and finally world-wide with A. millefolium-6x as a weed. [ABSTRACT FROM AUTHOR]

There is growing realization that intraspecific polyploidy in plants has important implications for the evolution of plant diversity and for plant and plant-herbivore community dynamics. Nonetheless, the rate at which polyploid cytotypes arise and their fate in local mixed-cytotype populations are not well understood. Although within- and especially among-population cytotype variation has been documented in many plants, particularly at the largest (continental) spatial scales, local and regional distributions of cytotypes have been well characterized only for a handful of species. Furthermore, few if any studies have addressed both local and regional patterns in the same plant species with sufficient power to detect cytotype variation on both scales. We assessed the co- occurrence and frequency distributions of diploid, tetraploid, and hexaploid cytotypes of Solidago altissima (Asteraceae) at local and regional spatial scales, sampling across a zone of presumed ploidy-form overlap in the midwestern United States. Determining ploidy by flow cytometry, we found many local populations containing two or three cytotypes, with the relative frequencies of cytotypes varying dramatically even among neighboring populations. AFLP marker data suggest that polyploid cytotypes of S. altissima likely have multiple origins from different diploid lineages. Our results are consistent with recent perspectives on polyploidization as an evolutionarily dynamic phenomenon with frequent multiple origins of higher-ploidy cytotypes. [ABSTRACT FROM AUTHOR]

Species may often exhibit geographic variation in population genetic structure due to contemporary and historical variation in population size and gene flow. Here, we test the predictions that populations on the margins of a species’ distribution contain less genetic variation and are more differentiated than populations towards the core of the range by comparing patterns of genetic variation at five microsatellite loci between disjunct and core populations of the perennial, allohexaploid herb Geum triflorum. We sampled nine populations isolated on alvar habitat within the eastern Great Lakes region in North America, habitats that include disjunct populations of several plant species, and compared these to 16 populations sampled from prairie habitat throughout the core of the species’ distribution in midwestern Canada and the USA. Alvar populations exhibited much lower within-population diversity and contained only a subset of alleles found in prairie populations. We detected isolation by distance across the species’ range and within alvar and prairie regions separately. As predicted, genetic differentiation was higher among alvar populations than among prairie populations, even after controlling for the geographic distance between sampled populations. Low diversity and high differentiation can be accounted for by the greater contemporary spatial isolation of alvar populations. However, the genetic structure of alvar populations may also have been influenced by postglacial range expansion and contraction. Our results are consistent with alvar populations being founded during an expansion of prairie habitat during the warmer, hypsithermal period ∼5000bp and subsequently becoming stranded on isolated alvar habitat as the climate grew cooler and wetter. [ABSTRACT FROM AUTHOR]

Original chromosome determinations are presented for 20 American Lupinus taxa, including, for the first time, unifoliolate species, together with first data on meiotic behaviour and pollen fertility for some South American species. Most of the Brazilian multifoliolate L. lanatus, L. rubriflorus, L. multiflorus, L. paranensis, L. bracteolaris and L. reitzii and unifoliolate L. crotalarioides, L. guaraniticus and L. velutinus accessions analysed presented regular chromosome pairing. Meiotic indexes and estimations of pollen viability were higher than 90% for all species and accessions analysed, reflecting the generally regular meiotic behaviour of these plants. Chromosome numbers were determined for the first time for the eastern South-American species L. guaraniticus, L. crotalarioides, L. paranensis, L. paraguariensis and L. velutinus ( n = 18 or 2 n = 36) and for the Andean L. ballianus, L. eanophyllus, L. huaronensis, L. semperflorens, plus another eight taxa (2 n = 48) from Peru and Bolivia, and L. bandelierae (2 n = 36) from Bolivia. Chromosome numbers were confirmed for L. lanatus, L. rubriflorus (2 n = 36), L. bracteolaris (2 n = 34) and L. microphyllus (2 n = 48). In the three accessions of the North American unifoliolate species, L. cumulicola and L. villosus, a chromosome number (2 n = 52) previously unknown among American taxa was found. The results of the study, plus published data, support the suggestions that south-eastern South American species are a group cytologically differentiated from the Andean as well as from most other American ones, and that the Brazilian and the North American unifoliolate Lupinus had independent origins. © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society, 2006, 150, 229–240. [ABSTRACT FROM AUTHOR]

We examined the genetic composition, habitat use, and morphological variation of a Phoxinus eos- neogaeu unisexual hybrid complex and its sexually reproducing progenitor species inhabiting beaver- modified drainages of Voyageurs National Park, Minnesota. In addition to the single diploid P. eos- neogaeus gynogenetic clone, triploid and diploid-triploid mosaic biotypes were present at our study sites. Both P. eos and P. neogaeus, and all three hybrid biotypes were ubiquitous throughout one intensively surveyed drainage, but abundances and relative frequencies of the parental species and hybrids varied considerably within and among successional environments. Data from a large number of additional sites indicated that the proportion of polyploid hybrids within an environment was negatively related to hybrid relative frequency, implying that the genomic constitution of hybrids is an important determinant of clonal fitness among successional environments. Statistical comparisons of variation along size-free multivariate body shape axes indicated that despite its genetic uniformity, the P. eos-neogaeus clone is no less variable than its sexual progenitors, suggesting that a single genotype may actually respond to environmental variation with as much phenotypic variation as a genetically variable sexual population. The incorporation and expression of a third genome in triploid and diploid-triploid mosaic biotypes derived from the gynogenetic clone significantly expanded phenotypic variation of the clone. This additional variation results in greater similarities in habitat use and morphological overlap with the parental species, primarily P. eos, the predominant sperm donor for gynogenetic hybrid females in this complex. Polyploid augmentation of a diploid gynogenetic clone appears to be typical in the P. eos-neogaeus complex, and the additional genetic and phenotypic variation that it generates has potentially significant ecological and evolutionary... [ABSTRACT FROM AUTHOR]

Large-scale collections of Zygnemataceae in the continental United States of America were made between March and August in 1982, 1989, and 1984, Collections were made on a 31000-km transect through 35 states, Zygnernataceae were found at 318 sites, although more than three times that number of sites was inspected. Temperature averaged 19°C and pH averaged 6.1 over all sites. Algal strains in collections were identified to genus, characteriaed for filament width, chloroplast number, and end wall type, then photographed and isolated into unialgal culture. Spirogyra was the most common genus collected (632 strains), followed in nbundnnce by Zygnema (174 strains) and Mougeotia (135 strains). These three genera contained 95% of the strains collected and were equally widely distributed. Strains of the three genera frequently occurred together; no genus displayed evidence of habitat specialization among the three habitat types: flowing water permanent ponds or lakes, and temporary pools. In Spirogyra, strains with plane (flat) end walls were four times more abundant than those with replicate (interlocking) end walls. Spirogyra with plane end walls showed more variation in filament width than Zygnema. Mougeotia, or Spirogyra with replicate end walls. In Spirogyra with plane end walls, filament width was correlated with auclear DNA content and number of strains found per collection site was twice that of other genera or Spirogyra with replicate end walls. Spirosyra strains wider than 70 μm were more frequent on the northern part of the transect. It is proposed that polyploidy may be of widespread occurrence in Spirogyra with plane end walls and that associated morphological plasticity may account for the high apparent species diversity and survival of the genus in a wider variety of microhabitats than occupied by other Zynemataceae. [ABSTRACT FROM AUTHOR]

The conventional breeding of fruits and fruit trees has led to the improvement of consumer-driven traits such as fruit size, yield, nutritional properties, aroma and taste, as well as the introduction of agronomic properties such as disease resistance. However, even with the assistance of modern molecular approaches such as marker-assisted selection, the improvement of fruit varieties by conventional breeding takes considerable time and effort. The advent of genetic engineering led to the rapid development of new varieties by allowing the direct introduction of genes into elite lines. In this review article, we discuss three such case studies: the Arctic ® apple, the Pinkglow pineapple and the SunUp/Rainbow papaya. We consider these events in the light of global regulations for the commercialization of genetically modified organisms (GMOs), focusing on the differences between product-related systems (the USA/Canada comparative safety assessment) and process-related systems (the EU "precautionary principle" model). More recently, genome editing has provided an efficient way to introduce precise mutations in plants, including fruits and fruit trees, replicating conventional breeding outcomes without the extensive backcrossing and selection typically necessary to introgress new traits. Some jurisdictions have reacted by amending the regulations governing GMOs to provide exemptions for crops that would be indistinguishable from conventional varieties based on product comparison. This has revealed the deficiencies of current process-related regulatory frameworks, particularly in the EU, which now stands against the rest of the world as a unique example of inflexible and dogmatic governance based on political expediency and activism rather than rigorous scientific evidence.

Long-term climate change and periodic environmental extremes threaten food and fuel security 1 and global crop productivity 2-4 . Although molecular and adaptive breeding strategies can buffer the effects of climatic stress and improve crop resilience 5 , these approaches require sufficient knowledge of the genes that underlie productivity and adaptation 6 -knowledge that has been limited to a small number of well-studied model systems. Here we present the assembly and annotation of the large and complex genome of the polyploid bioenergy crop switchgrass (Panicum virgatum). Analysis of biomass and survival among 732 resequenced genotypes, which were grown across 10 common gardens that span 1,800 km of latitude, jointly revealed extensive genomic evidence of climate adaptation. Climate-gene-biomass associations were abundant but varied considerably among deeply diverged gene pools. Furthermore, we found that gene flow accelerated climate adaptation during the postglacial colonization of northern habitats through introgression of alleles from a pre-adapted northern gene pool. The polyploid nature of switchgrass also enhanced adaptive potential through the fractionation of gene function, as there was an increased level of heritable genetic diversity on the nondominant subgenome. In addition to investigating patterns of climate adaptation, the genome resources and gene-trait associations developed here provide breeders with the necessary tools to increase switchgrass yield for the sustainable production of bioenergy.

Unlabelled: •, Premise of the Study: Information about geographic distribution of cytotypes can provide insight into the origin and maintenance of autopolyploid complexes and builds a foundation for understanding cytotype differentiation and the dynamics of mixed-ploidy populations. Here, we investigate environmental correlates of the geographic distributions of 6x and 9x individuals in the ecologically dominant grass Andropogon gerardii to examine the role of climate in shaping patterns of cytotype distribution in this species.•, Methods: Flow cytometry was used to estimate ploidy level in 352 individuals from 32 populations across North America. Ecological differentiation of cytotypes was tested by relating BIOCLIM variables to cytotype distribution using principal components analysis and partial linear regression.•, Key Results: Broad geographic sampling confirmed two primary cytotypes-6x (hexaploid) and 9x (enneaploid)-and revealed that 9x plants are more common than previously thought. Enneaploids occur frequently in the southern portions of the range, with hexaploids dominating in northern regions. Mixed-ploidy populations were common (46.9%). Principal components analysis and partial linear regression indicated that reduced summer precipitation and increased variation in diurnal and seasonal temperature range were significant predictors of the frequency of 9x plants in a population.•, Conclusions: Results indicate that (1) geographic distribution of 6x and 9x individuals is nonrandom; (2) environmental variables are associated with cytotype distribution in A. gerardii; and (3) nearly half of populations surveyed include both 6x and 9x individuals. The persistence of mixed-ploidy populations may reflect a combination of recurrent polyploid formation and the prevalence of clonal reproduction., (© 2015 Botanical Society of America, Inc.)

Genome duplication has played an important role in plant evolution. Variation in genome size within species is common, particularly in grasses, but rarely considered when planning restorations. We surveyed ploidy variation within one habitat (tall grass prairie) in one region (northeast Iowa, U.S.A.) to assess the risk of ploidy mismatch in restoration plantings. Genome sizes were estimated using flow cytometry for samples from 19 remnant prairies, 5 restoration plantings, and 2 seed sources. Intraspecific ploidy variation in remnant prairie populations was found for two species of grasses, Andropogon gerardii (big bluestem) and Panicum virgatum (switchgrass). Restoration seeds differed from remnants in ploidy for three species of grass, P. virgatum, Sorghastrum nutans (Indian grass), and Spartina pectinata (prairie cordgrass), and for one species of forb, Amorpha canescens (lead plant). In the case of S. pectinata, local ecotype seeds were found to consist of two different ploidy levels. Restorations in grasslands in the United States and elsewhere are likely to create mixed ploidy populations, probably resulting in lower reproductive success for the remnant population. Prevention of mixed ploidy populations will require the screening of restoration seed sources and regional surveys for ploidy variation. [ABSTRACT FROM AUTHOR]

Premise of the Study: Polyploidization is a key factor involved in the diversification of plants. Although polyploids are commonly found, there remains controversy on the mechanisms that lead to their successful establishment. One major problem that has been identified is that newly formed polyploids lack mates of the appropriate ploidy level and may experience severely reduced fertility due to nonproductive intercytotype crosses. Niche differentiation has been proposed as a primary mechanism that can alleviate this reproductive disadvantage and facilitate polyploid establishment. Here we test whether the establishment of tetraploid cytotypes of Heuchera cylindrica (Saxifragaceae) is consistent with climatic niche differentiation. •, Methods: We use a combination of field surveys, flow cytometry and species distribution models to: (1) examine the distribution of diploid and tetraploid cytotypes; and (2) determine whether tetraploid Heuchera cylindrica occupy climates that differ from those of its diploid progenitors. •, Key Results: The geographic distributions of diploid and tetraploid cytotypes are largely allopatric as an extensive survey of 636 plants from 43 locations failed to detect any populations with both cytotypes. Although diploids and tetraploids occur in different geographic areas, polyploid Heuchera cylindrica occur almost exclusively in environments that are predicted to be suitable to diploid populations. •, Conclusions: Climatic niche differentiation does not explain the geographic distribution of tetraploid Heuchera cylindrica. We propose instead that tetraploid lineages were able to establish by taking advantage of glacial retreat and expanding into previously unoccupied sites.

Premise of the Study: Molecular studies have shown that multiple origins of polyploid taxa are the rule rather than the exception. To understand the distribution and ecology of polyploid species and the evolutionary significance of polyploidy in general, it is important to delineate these independently derived lineages as accurately as possible. Although gene flow among polyploid lineages and backcrossing to their diploid parents often confound this process, such post origin gene flow is very infrequent in asexual polyploids. In this study, we estimate the number of independent origins of the apomictic allopolyploid fern Astrolepis integerrima, a morphologically heterogeneous species most common in the southwestern United States and Mexico, with outlying populations in the southeastern United States and the Caribbean., Methods: Plastid DNA sequence and AFLP data were obtained from 33 A. integerrima individuals. Phylogenetic analysis of the sequence data and multidimensional clustering of the AFLP data were used to identify independently derived lineages., Key Results: Analysis of the two datasets identified 10 genetic groups within the 33 analyzed samples. These groups suggest a minimum of 10 origins of A. integerrima in the northern portion of its range, with both putative parents functioning as maternal donors, both supplying unreduced gametes, and both contributing a significant portion of their genetic diversity to the hybrids., Conclusions: Our results highlight the extreme cryptic genetic diversity and systematic complexity that can underlie a single polyploid taxon.

Premise of the Study: Exotic diseases are threatening many North American tree species, and management of diseases requires understanding the biology of the host as well as the pathogen. Ulmus americana is a widespread dominant tree of eastern North America that has been widely planted as an ornamental and shade tree. Populations of the species have suffered heavy mortality from Dutch elm disease, caused by an introduced fungus. Ulmus americana is generally reported to be tetraploid, but the discovery of triploid trees in cultivation suggested that lower ploidy levels may exist in the wild, so the species was surveyed for nuclear DNA content., Methods: Ploidy level was estimated by flow cytometry for 81 individuals from wild populations of U. americana from throughout the range of the species and for four cultivated trees of interest., Key Results: Most specimens were tetraploid, as previously reported for the species, but 21% of the wild trees sampled were diploid, a ploidy level not previously confirmed for the species. Tetraploids are found throughout the range of the species. Diploids are most common on the Atlantic coastal plain, Cumberland Plateau, and in southern Ohio, but isolated diploids were also found in central Texas, Oklahoma, and eastern Missouri. Diploids and tetraploids grew in proximity in several areas, but no wild triploids were found in the course of this survey., Conclusions: The species is genetically heterogeneous, but further research is needed to understand the origin and relations of the different ploidy levels. Understanding the ploidy situation in U. americana will be important in the search for further genotypes that are resistant to Dutch elm disease.

Polyploidy plays a prominent role in the speciation process in plants. Many species are known to be part of agamic complexes comprising sexual diploids and more or less exclusively asexual polyploids. However, polyploid formation has been studied in very few cases, primarily because of the challenges in examining these cases phylogenetically. In this study, we demonstrate the use of a variety of phylogenetic approaches to unravel origins and infer reticulation history in a diploid-polyploid complex of black-fruited Crataegus. The tree approaches are shown to be useful in testing alternative hypotheses and in revealing genealogies of nuclear genes, particularly in polyploid organisms that may contain multiple copies. Compared to trees, network approaches provide a better indication of reticulate relationships among recently diverged taxa. Taken together, our data point to both the autopolyploid and allopolyploid origins of triploids in natural populations of Crataegus suksdorfii, whereas tetraploids are formed via a triploid bridge, involving the backcross of allotriploid offspring with their diploid C. suksdorfii parent, followed by gene introgression from sympatric C. douglasii. Our findings provide empirical evidence for different pathways of polyploid formation that are all likely to occur within natural populations and the allopatric establishment of neopolyploids subsequent to their formation., (© 2010 The Author(s). Evolution© 2010 The Society for the Study of Evolution.)

Polyploidy is often assumed to increase the spread and thus the success of alien plant species, but few empirical studies exist. We tested this hypothesis with Centaurea maculosa Lam., a species native to Europe and introduced into North America approximately 120 years ago where it became highly invasive. We analyzed the ploidy level of more than 2000 plants from 93 native and 48 invasive C. maculosa populations and found a pronounced shift in the relative frequency of diploid and tetraploid cytotypes. In Europe diploid populations occur in higher frequencies than tetraploids and only four populations had both cytotypes, while in North America diploid plants were found in only one mixed population and thus tetraploids clearly dominated. Our results showed a pronounced shift in the climatic niche between tetraploid populations in the native and introduced range toward drier climate in North America and a similar albeit smaller shift between diploids and tetraploids in the native range. The field data indicate that diploids have a predominately monocarpic life cycle, while tetraploids are often polycarpic. Additionally, the polycarpic life-form seems to be more prevalent among tetraploids in the introduced range than among tetraploids in the native range. Our study suggests that both ploidy types of C. maculosa were introduced into North America, but tetraploids became the dominant cytotype with invasion. We suggest that the invasive success of C. maculosa is partly due to preadaptation of the tetraploid cytotype in Europe to drier climate and possibly further adaptation to these conditions in the introduced range. The potential for earlier and longer seed production associated with the polycarpic life cycle constitutes an additional factor that may have led to the dominance of tetraploids over diploids in the introduced range.

Multiple origins of the same polyploid species pose the question: Does evolution repeat itself in these independently formed lineages? Tragopogon is a unique evolutionary model for the study of recent and recurrent allopolyploidy. The allotetraploids T. mirus (T. dubius x T. porrifolius) and T. miscellus (T. dubius x T. pratensis) formed repeatedly following the introduction of three diploids to the United States. Concerted evolution has consistently occurred in the same direction (resulting in loss of T. dubius rDNA copies). Both allotetraploids exhibit homeolog loss, with the same genes consistently showing loss, and homeologs of T. dubius preferentially lost in both allotetraploids. We have also documented repeated patterns of tissue-specific silencing in multiple populations of T. miscellus. Hence, some aspects of genome evolution may be "hardwired," although the general pattern of loss is stochastic within any given population. On the basis of the study of F(1) hybrids and synthetics, duplicate gene loss and silencing do not occur immediately following hybridization or polyploidization, but gradually and haphazardly. Genomic approaches permit analysis of hundreds of loci to assess the frequency of homeolog loss and changes in gene expression. This methodology is particularly promising for groups such as Tragopogon for which limited genetic and genomic resources are available.

Objective: To test the hypothesis that intracytoplasmic sperm injection (ICSI) overcomes a high incidence of tripronucleate zygotes resulting from standard insemination in a previous cycle., Design: A retrospective analysis of matched-pair cycles., Setting: Assisted reproductive technologies (ART) program of Brigham and Women's Hospital., Patient(s): Ninety-five patients with a > or = 20% incidence of tripronucleate zygotes in an IVF cycle with use of ICSI in a subsequent attempt., Intervention(s): Cycles with either standard insemination or ICSI., Main Outcome Measure(s): Incidence of diploid (2pn) and triploid (3pn) zygotes and number and quality of embryos obtained., Result(s): Patient age, ampules of gonadotropin used, peak E2, number of follicles at hCG trigger, and total number of oocytes were all significantly higher in the ICSI cycles, but the number of mature oocytes did not differ. After ICSI, the percentage of 2pn was higher (65.0% vs. 34.1%) and the percentage of 3pn was lower (5.0% vs. 33.9%) than after IVF, and more diploid embryos were obtained with ICSI (5.5 +/- 3.7 vs. 3.4 +/- 2.2 [mean +/- SD]). There was no difference in embryo quality between the two groups., Conclusion(s): ICSI appears beneficial in women with a high 3pn occurrence from IVF because it increases the number of diploid zygotes without affecting embryo quality.

Hexaploid triticale has many advantages over both parental species for both grain and forage production in certain environments. Additional information on environmental stability and heritability would be desirable to develop appropriate selection strategies in the production of superior widely-adapted cultivars. The grain yield of 22 diverse genotypes grown at four ecologically-distinct geographical locations [Quincy, FL, USA (approximate geographical coordinates (AGC) = 30 degreesN 84 degreesW, approximate elevation (AE) = 58 m), Plains, GA, USA (AGC = 32 degreesN 84 degreesW, AE = 76 m), Bozeman, MT USA (AGC = 45 degreesN 111 degreesW, AE = 1458 m), and Aberdeen, ID, USA (AGC = 42 degreesN 112 degreesW, AE = 1360 m)] was measured in two years with winter and spring planting dates only at Bozeman and Aberdeen. Test weight (grain weight in a given volume) was determined for two years at Bozeman and Aberdeen at both planting dates and one year at Quincy. Stability analyses indicated that significant (P < 0.01) variation in means, regression coefficients, and deviation mean squares of the genotypes were present for both characters. Realized heritability (h2) estimates were as follows: grain yield ranged from -0.02 to 0.80 with a mean of 0.57; test weight ranged from 0.63 to 1.05 with a mean of 0.93. The results indicated that substantial genetic variation is present and selection for widely-adapted cultivars would be effective for both characters especially test weight.

Recent molecular phylogenetic studies of polyploid plants have successfully clarified complex patterns of reticulate evolution. In this study of Elymus repens, an allohexaploid member of the wheat tribe Triticeae, chloroplast and nuclear DNA data reveal an extreme reticulate pattern, revealing at least five distinct gene lineages coexisting within the species, acquired through a possible combination of allohexaploidy and introgression from both within and beyond the Triticeae. Earlier cytogenetic studies of E. repens suggested that Hordeum (genome H) and Pseudoroegneria (St) were genome donors to E. repens. Chloroplast DNA data presented here (from the rpoA gene and from the region between trnT and trnF) identify three potential maternal genome donors (Pseudoroegneria, Thinopyrum, and Dasypyrum), and information from previous molecular work suggests that, of these, Pseudoroegneria is the most likely maternal donor. Nuclear starch synthase gene data indicate that both Hordeum and Pseudoroegneria have contributed to the nuclear genome of E. repens, in agreement with cytogenetic data. However, these data also show unexpected contributions from Taeniatherum, and from two additional donors of unknown identity. One of the sequences of unknown origin falls within the Triticeae, but is not closely associated with any of the sampled diploid genera. The second falls outside of the clade containing Triticeae and its outgroup Bromus, suggesting the acquisition of genetic material from a surprisingly divergent source. Bias toward the amplification of certain starch synthase variants has complicated attempts to thoroughly sample from within individuals, but the data clearly indicate a complex pattern of reticulate evolution, consistent not only with allohexaploidy, but also with introgression from unexpectedly divergent sources.

Plant breeding in black chokeberry (Aronia melanocarpa) is based mainly on seedlings derived from domesticated Russian plants. Previous studies have, however, demonstrated very low levels of phenotypic variation within this gene pool. The present investigation was undertaken in order to study the genetic structure in native populations growing in North America. Random amplified polymorphic DNA (RAPD) marker variation was analysed in eight populations (three or five mother plants/population and five seedlings/mother plant) and compared with the variation in four cultivars and 15 seedlings derived from a Russian plantation. The four cultivars and all the Russian seedlings turned out to have identical RAPD profiles. In the native plant material, there were two types of mother plants: diploid plants that produced very heterogeneous offspring and tetraploid plants that produced homogeneous offspring. Partitioning of variability based on Shannon's diversity index attributed approx. 22% of the variation to the among-population level in diploids, compared to approx. 55% in the tetraploids. However, the diploid populations and the tetraploid populations did not differ significantly in within-population variation. These results prompted a second set of RAPD analyses, which were carried out on offspring obtained through open pollination of the initially examined material when growing in an experimental field. The analyses showed that tetraploid plants produced tetraploid offspring that, with few exceptions, were identical, indicating apomixis, whereas offspring of diploid plants were diploid or triploid, and highly heterogeneous, indicating outcrossing. Presumably, the tetraploid form of Aronia is an allopolyploid, with A. melanocarpa as one of the parents.

Studies on the biogeographical patterning of reproductive systems promise to extend understanding of the factors which modulate breeding system transitions. Two closely allied cladoceran crustaceans, Daphnia pulex and D. pulicaria, show varied modes of reproduction, with populations reproducing by either cyclic or obligate parthenogenesis. Prior studies have provided a detailed understanding of their breeding system diversity in the polar and cold temperate regions of North America. The present investigation extends this analysis, characterizing breeding systems and clonal diversity at sites throughout the United States and Mexico. Genotypic diversity in these southern areas was high, but only diploids were detected, indicating that polyploids are restricted to the north. F(1) hybrids and their two parental species were present in most areas, although their frequencies varied geographically. Hybrids invariably reproduced by obligate asexuality, but both parental taxa showed regional shifts in their breeding system. The complexity of these latter patterns suggests that they reflect the interplay of historical factors and selection.