Ploidy Level Research Articles

Ploidy affects phytochemistry and micromorphology of Thymus persicus (Ronniger ex Rech.f.) Jalas: An in vitro investigation

Thymus persicus (Ronniger ex Rech. f.) Jalas (Lamiaceae) is an endemic and valuable essential oil-bearing plant. Herein, the effect of ploidy level on both anatomical structure and essential oil composition was investigated. Leaves of in vitro-induced tetraploids had more glandular peltate, capitate, and elongated non-glandular trichomes compared to diploids. Gas chromatography-flame ionization detector (GC-FID), and GC–mass Spectrometry (GC-MS) techniques were employed to unravel chemicals in hydro-distilled essential oils from in vitro diploid, tetraploid, and mixoploid clones. Notably, 21, 27 and 17 compounds representing 97.0%, 96.9%, and 96.7% of the total essential oils were identified and quantified in diploids, tetraploids, and mixoploids plants, respectively. A wide chemical variability was observed so much so that thymol (32.8%), α-terpineol (26.4%), and carvacrol (6.2%) were the main constituent in diploids, while carvacrol (33.85%), δ-selinene (8.79%), ishwarone (8.23%), and octanoic acid (8.07%) were in tetraploids and mixoploids mostly accounted in δ-Selinene (21.26%), pogostol (13.92%), methyl thujate (10.94%), and (2E,6E)-farnesyl acetate (10.28%). To further underline the ploidy effects, it was observed a strong decrease in the contents of monoterpene hydrocarbons and oxygenated monoterpene hydrocarbons in tetraploids and myxoploids. The sesquiterpene hydrocarbons showed an inverse behaviour.

AGHmatrix: genetic relationship matrices in R.

The resemble between relatives computed from pedigree and genomic data is an important resource for geneticists and ecologists, who are interested in understanding how genes influence phenotypic variation, fitness adaptation, and population dynamics. The AGHmatrix software is an R-package focused on the construction of pedigree (A matrix) and/or molecular markers (G matrix), with the possibility of building a combined matrix of pedigree corrected by molecular markers (H matrix). Designed to estimate the relationships for any ploidy level, the software also includes auxiliary functions related to filtering molecular markers, compute linkage disequilibrium (LD) and check pedigree errors in large data sets. After computing the relationship matrices, results from the AGHmatrix can be used in different contexts, including on prediction of (genomic) estimated breeding values and genome-wide association studies (GWAS). AGHmatrix v2.1.0 is available under GPL-3 license in CRAN at https://cran.r-project.org/web/packages/AGHmatrix/index.html and also in GitHub at https://github.com/rramadeu/AGHmatrix. It has a comprehensive tutorial, and it follows with real data examples. Supplementary data are available at Bioinformatics online.

Investigation of genetic diversity of Iranian wild relatives of bread wheat using ISSR and SSR markers

BackgroundWild relatives of wheat are one of the most important genetic resources to use in wheat breeding programs. Therefore, identifying wild relatives of wheat and being aware of their diversity, is undeniably effective in expanding the richness of the gene pool and the genetic base of new cultivars and can be a useful tool for breeders in the future. The present study was performed to evaluate the molecular diversity among 49 accessions of the genera Aegilops and Triticum in the National Plant Gene Bank of Iran using two DNA-based markers, i.e., SSR and ISSR. Also, the present study aimed to examine the relationships among the accessions studied belonging to different genetic backgrounds. ResultsTen SSR and tan ISSR primers produced 2065 and 1524 polymorphism bands, respectively. The number of Polymorphic Bands (NPB), the Polymorphism Information Content (PIC), Marker Index (MI), and Resolving Power (Rp) in SSR marker was 162 to 317, 0.830 to 0.919, 1.326 to 3.167, and 3.169 to 5.692, respectively, and in the ISSR marker, it was from 103 to 185, 0.377 to 0.441, 0.660 to 1.151, and 3.169 to 5.693, respectively. This indicates the efficiency of both markers in detecting polymorphism among the accessions studied. The ISSR marker had a higher polymorphism rate, MI, and Rp than the SSR marker. Molecular analysis of variance for both DNA-based markers showed that the genetic variation within the species was more than the genetic diversity between them. The high level of genomic diversity discovered in the Aegilops and Triticum species proved to provide an ideal gene pool for discovering genes useful for wheat breeding. The accessions were classified into eight groups based on SSR and ISSR markers using the UPGMA method of cluster analysis. According to the cluster analysis results, despite similarities between the accessions of a given province, in most cases, the geographical pattern was not in accordance with that observed using the molecular clustering. Based on the coordinate analysis, neighboring groups showed the maximum similarities, and distant ones revealed the maximum genetic distance from each other. The genetic structure analysis successfully separated accessions for their ploidy levels. ConclusionsBoth markers provided a comprehensive model of genetic diversity between Iranian accessions of Aegilops and Triticum genera. Primers used in the present study were effective, informative, and genome-specific which could be used in genome explanatory experiments.

Phylogenetic Relationship among Grasses, Wheat and Pearl Millet using matK and rbcR Genes

Fourteen genotypes of tall fescue, Brachypodium, wheat and pearl millet were used to find out phylogenetic relationships at their different ploidy level. Isolated chloroplast DNA of the 14 genotypes was sequenced using some selected matK and rbcR genetic markers. The matK and rbcR chloroplast gene sequences length were 1539bp and 1431bp, respectively. The consensus sequence length of matK gene was 1265bp in Brachypodium and wheat, 1266bp in both tall fescue Continental and Mditerranean species, 1269bp in pearl millet and for rbcR gene was only 1156bp in all studied four species. Except in Brachypodium, the variations of SNP for both matK and rbcR genes were observed in different ploidy levels of pearl millet and between the tall fescue Continental and Mediterranean species. Wheat with their different ploidy level gave the SNP variations only for matK gene. In respect of all ploidy levels, pearl millet had the highest number of SNP for both matK (247) and rbcR (130) genes. The tall fescue Continental (129) and Mediterranean (123) were in second position to show their genetic variation for matK gene. The rbcR gene had higher SNP at 5¢ regions of all four species, but matK gene only in wheat and tall fescue and 3¢ in millet and Brachypodium species. There was no in-del for rbcR gene, but the insertion of nucleotide for the matK gene was found highest in diploid wheat (11) and the deletion was in pearl millet (6). The phylogenetic analysis stated that their relationships were tall fescue Continental and tall fescue Mediterranean was much more related to wheat than pearl millet and Brachypodium. Plant Tissue Cult. & Biotech. 33(1): 57-70, 2023 (June)

O-209 The incidence of different ploidy alterations in abnormally fertilized oocytes (AFO)-derived embryos

Abstract Study question Which is the incidence of de novo ploidy alterations in different abnormally fertilized embryos categories analysed with SNP-array? Summary answer Based on the number of pronuclei (PN) identified, 0PN embryos were mostly diploid, while 1PN and >2PN-derived embryos showed increased rates of ploidy abnormalities. What is known already Recent development of SNP-array and haplotyping by sequencing approaches are contributing to expanding preimplantation genetic testing (PGT) clinical utility including ploidy level evaluation. When applied to euploid embryos derived from AFO, the identification of abnormal ploidy constitution (i.e., haploidy, triploidy, or tetraploidy) could rescue viable diploid embryos otherwise considered non-transferable in IVF. However, no definitive genetic evidence has been obtained showing the incidence of different ploidy abnormalities in each AFO-derived blastocyst category. Here we present 4 years of experience in the clinical application of a validated SNP-array based protocol and custom-made algorithm to detect ploidy defects in AFO-derived embryos. Study design, size, duration Prospective observational study evaluating the incidence of altered ploidy configurations in AFO-derived blastocyst. After PN check, AFO samples were divided as follow: absence of observed pronuclei (0PN), monopronuclear (1PN), more than two pronuclei observed (2.1PN, with one smaller additional PN and 3PN). Genetic classification combining PGT-A and ploidy analysis was performed at Igenomix Italy laboratory between May 2019 and January 2023 on 133 AFO-derived embryos (44 0PN, 59 1PN, 30 >2PN). Participants/materials, setting, methods Multi-centre study involving 293 consenting patients of advance maternal age (mean=38.6±3.9) undergoing PGT-A on MDA-WGA using Ion ReproSeq kit and IonTorrent S5 (ThermoFisher). SNP-array-based ploidy test was performed using HumanKaryomap-12 kit and NextSeq550 (Illumina). Proprietary algorithm was based on genome-wide BAF obtained: expected BAFs were 1, 0.5 or 0 for diploids,1 or 0 for haploid and 1, 0.66, 0.33 or 0 for triploids, as determined by the frequency of each allele for 300000 SNPs loci. Main results and the role of chance Preclinical validation of SNP-array-based ploidy test included 26 samples with known ploidy status and karyotype: 7 triploid re-biopsies, 7 haploid left-overs and 12 cell lines. Moreover, inter-platform comparison of 72 diploids, 9 triploids, 8 haploids embryos analysed with an alternative targeted-NGS approach, validated by Igenomix, showed 100% (95% CI= 95.94%-100%) concordance. In this study, a total of 318 AFO-derived embryos were collected for PGT-A analysis for different indications. Of these, 58.2% (n = 185/318; 95%CI=52.54-63.66) resulted as aneuploid. The remaining 133 euploid AFO-derived blastocyst where subjected to SNP-array based ploidy assessment. 0PN-derived blastocysts (n = 44/133) were diploid in 93.2% (n = 41/44; 95%CI=81.34-98.57) of cases; only 4.5% (n = 2/44; 95%CI=0.56-15.47) were haploid and 2.3% (n = 1/44; 95%CI=0.06-12.02) were polyploid. 1PN-derived blastocysts showed all possible ploidy configurations in these proportions: 59.3% (n = 35/59; 95%CI=45.74-71.93) haploid, 35.6% (n = 21/59; 95%CI=23.55-49.13) diploid and 5.1% (n = 3/59; 95%CI=1.06-14.15) polyploid. Finally, in the group of AFO where more than 2PN were observed (2.1PN or 3PN), the additional PN resulted in 66.7% (n = 20/30; 95%CI=47.19-82.71) of polyploid configurations, the remaining 33.3% (n = 10/30; 95%CI=17.29-52.81) were diploid. No haploid results were obtained from this category. Chi-square test showed significant overall correlation between PN category and ploidy status configurations (p < 0.05). Collectively, ploidy evaluation of 133 AFO-derived embryos, allowed the clinical use of 72 additional euploid/diploid embryos otherwise not considered for transfer. Limitations, reasons for caution Ploidy assessment protocol was not tested to distinguish triploids from tetraploids. Parental origin of each chromosomal set could not be determined without analysing parental DNA. The way of performing PN check could have affected AFO classification. In future studies we will focus on evaluating clinical outcomes following euploid/diploid embryo transfer. Wider implications of the findings An altered number of pronuclei is predictive of the correspondent altered ploidy status, while 0PN category doesn’t represent a clear indication for ploidy evaluation. Nevertheless, a significant proportion of euploid/diploid embryos can be rescued from all types of AFO, potentially increasing the overall chance to achieve a live birth. Trial registration number n/a

Geometric morphometric analysis of Neolithic wheat grains: insights into the early development of free-threshing forms

Current knowledge of the origins and routes of introduction of both tetraploid and hexaploid free-threshing wheats (FTWs) from western Asia into Europe remains imprecise. Archaeobotanical distinction of ploidy level is often dependent on sparsely recovered rachis segments, while more specific identification of cultivars within ploidy groups using morphological characteristics of either grain or chaff is generally considered unreliable. This study offers a complementary approach by using geometric morphometric (GMM) analysis of grain shape to assess taxonomic and variety level distinctions in archaeobotanical FTW remains. Two substantial and well-preserved assemblages of Neolithic FTW grains from 7th millennium bce Çatalhöyük (central Anatolia, Turkey) and 6th millennium Kouphovouno (Peloponnese, Greece) were analysed with the aim of shedding light on the naked wheats cultivated by these early agricultural communities. While chaff remains from Çatalhöyük indicate a hexaploid FTW crop, no such diagnostic remains were recovered from Kouphovouno. GMM analysis of the archaeobotanical grains has corroborated early cultivation of hexaploid naked wheat at Çatalhöyük, whilst revealing that a tetraploid wheat, most closely resembling ‘unimproved’ durum wheat, was likely grown at Kouphovouno. The Kouphovouno findings are contextualised within existing theories of a Mediterranean route for introduction of tetraploid FTWs from western Asia to south-western Europe. At both sites, an assessment of the role of FTWs over time suggests changes in the cultural value attributed to these crops and/or the sustainability of the agricultural regimes they were associated with.

Предварительная оценка содержания ядерной ДНК в растениях Chondrilla (Asteraceae) Европейской России и Западного Казахстана с использованием проточной цитометрии

Preliminary data on the genome size of representatives of the genus Chondrilla (Asteraceae) of European Russia and Western Kazakhstan were obtained using flow cytometry. Among all studied specimens of the genus, for specimens of C. ambigua and C. pauciflora, a direct dependence of the genome size on the number of chromosomes was established. In our study, the DNA content of the diploid C. ambigua was 2С = 1.69 pg, and that of the triploid C. pauciflora was 2С = 2.65 pg. 2С values are within 2.29–2.69 pg in most specimens of the genus Chondrilla (typical for 13 out of 23 specimens) belonging to the following taxa: C. paucifora, C. laticoronata, C. brevirostris, C. canescens, C. graminea, C. latifolia, C. juncea. Most likely, they are triploids, and in many cases with a number of chromosomes deviating from a multiple of the main number of chromosomes. The C. latifolia sample from the population of the Kamyshinsky district of the Volgograd region showed two peaks on the histogram of the relative fluorescence intensity, corresponding to two values of the relative DNA content, 1.68 and 2.58 pg, i.e. it turned out to be a mixoploid with two levels of ploidy (2n = 2x = 10 and 2n = 3x = 15). The diversity of genome sizes within the genus can be explained by the previously established high variability in the number of chromosomes associated with aneu- and mixoploidy.

Endoreduplication in plant organogenesis: a mean to boost fruit growth.

Endoreduplication is the major source of somatic endopolyploidy in higher plants, leading to variation in cell ploidy levels due to iterative rounds of DNA synthesis in the absence of mitosis. Despite its ubiquitous occurrence in many plant organs, tissues and cells, the physiological meaning of endoreduplication is not fully understood, although several roles during plant development have been proposed, mostly related to cell growth, cell differentiation and specialization via transcriptional and metabolic reprogramming. Here we review the recent advances in the knowledge of the molecular mechanisms and cellular characteristics of endoreduplicated cells, and provide an overview of the multi-scale effects of endoreduplication on supporting growth in plant development. Finally, the effects of endoreduplication in fruit development are discussed, since during fruit organogenesis, endoreduplication is highly prominent where it acts as a morphogenetic factor supporting rapid fruit growth as illustrated with case of the fleshy fruit model tomato (Solanum lycopersicum).

Polyploidy as a strategy to increase taxane production in yew cell cultures: Obtaining and characterizing a Taxus baccata tetraploid cell line

Novel approaches to optimize the production of plant specialized metabolites are crucial to reach maximum productivity of plant biofactories. Plant polyploidization frequently enhances protein synthesis and thereby increases the biosynthesis of specialized metabolites. Paclitaxel is a valuable anticancer agent scarcely produced in nature. Therefore, plant biofactories represent a sustainable alternative source of this compound and related taxanes. With the aim of improving the productivity of Taxus spp. cell cultures, we induced polyploidy in vitro by treating immature embryos of Taxus baccata with colchicine. To obtain the polyploid cell lines, calli were induced from T. baccata plantlets previously treated with colchicine and ploidy levels were accurately identified using flow cytometry. In terms of cell morphology, tetraploid cells were about 3-fold bigger than the diploid cells. The expression of taxane pathway genes was higher in the tetraploid cell line compared to the diploid cells. Moreover, taxane production was 6.2-fold higher and the production peak was achieved 8 days earlier than in the diploid cell line, indicating a higher productivity. The obtained tetraploid cell line proved to be highly productive, constituting a step forward towards the development of a bio-sustainable production system for this chemotherapeutic drug.

Identifying successful combinations by fertility index in old garden roses and hybrid tea roses crosses.

The success of rose breeding programs is low due to poor seed sets and germination rates. Determining fertile parents and cross combinations that show high compatibility could increase the effectiveness of breeding programs. In this study, three rose varieties belonging to Rosa × hybrida (Jumilia, First Red and Magnum), and two old garden rose species (Black Rose and Cabbage Rose) with known ploidy levels were reciprocally crossbred under controlled conditions to determine the successful crosses by checking fertility. The pollen germination rate (PG), crossability rate (CR), seed number per fruit (SNpF), seed production efficiency (SPE), seed germination rate (SGR), fruit weight (FW), seed weight (SW) and stigma number (SiN), etc. were recorded. Comprehensive fertility index value was calculated. Principal component analysis (PCA), correlation matrix, and hierarchical heat map were used to evaluate the data. The findings showed that old garden roses had more viable pollen than hybrid tea roses. The crossing success improved as pollen fertility increased. Also, female parent fertility improved crossing success just as much as pollen fertility. Although the pollen fertility and stigma numbers were low, some combinations had higher CR and SPE. The maximum SPE (from 8.67% to 19.46%) was determined in combinations where Black Rose was the female parent despite the lower stigma number and low pollen fertility. The highest CR was recorded in Black Rose × First Red (94.36%). All combinations in which Black Rose was used as the female parent had a more stable CR. The SNpF of combinations where hybrid rose varieties were female parents and old garden roses were pollen parents was higher than other combinations where hybrid rose varieties were both female and pollen parents. The SPE in intraspecific crosses was lower than that obtained from interspecific crosses. Moreover, the SGR decreased in combinations that produced heavier seeds. The results suggested that SPE is a more accurate parameter than SNpF in demonstrating combination success in breeding programs. Black Rose × First Red, Black Rose × Jumilia, Black Rose × Magnum and Black Rose × Cabbage Rose combinations can be used successfully as the PCA and heat map showed. Black Rose showed better performance as both seed and pollen parents according to the comprehensive fertility index. From the correlation matrix, it is understood that the number of stigmas cannot be an important criterion in parent selection. Old garden roses can be used as parents to increase the success of breeding programs. However, it is necessary to reveal how successful they are in transferring desired characteristics such as scent, petal number, and color.

Back to Linnaeus: Proper Botanical Naming of the Tetraploid Indian Acorus (Acoraceae), an Important Medicinal Plant

The basal monocot genus Acorus comprises essential oil-producing plants widely used in traditional medicine in various countries, including India. Acorus calamus sensu lato is a polyploid complex where the essential oil composition, to some extent, depends on the ploidy level. The literature recognizes diploids (in temperate Asia and North America), triploids (Asian in origin, naturalized elsewhere) and tetraploids (temperate to tropical Asia) at the rank of varieties of A. calamus. We show that the current use of the name A. calamus var. angustatus for the tetraploids is not properly justified. The earliest name based on the Asian material is A. calamus var. verus published in 1753 by Linnaeus. We justify the use of the Linnaean variety for tetraploids by selecting an epitype based on the material cultivated in Peninsular India, for which direct chromosome counts are provided. The name A. verus is available if the tetraploid cytotype is recognized at the species rank. We support earlier data on the importance of leaf anatomy for cytotype diagnostics in Acorus, but also show the limitations of the use of this approach. The growth pattern of the tropical Indian tetraploid material is discussed, and the evergreen nature of the accession studied here is documented. The exact chromosome number of the tetraploid Acorus requires further clarification. All metaphase plates examined here showed at least 44 chromosomes, but plates apparently showing more than 44 chromosomes were found as well. They may be explained by technical difficulties in counting chromosomes in Acorus. Alternatively, our data may indicate the occurrence of aneuploid mixoploidy.

Differentiation of rhizosphere fungal assemblages by host ploidy level in mixed‐ploidy Larrea tridentata populations

Polyploidy – whole genome duplication – is common in plants. Studies over the last several decades have documented numerous mixed‐ploidy populations. Whether arising via recurrent whole genome duplication events within a population, or from secondary contact, the persistence of mixed populations is possible by niche differentiation. Specifically, one mechanism facilitating ploidy co‐occurrence is microbially‐mediated niche differentiation (MMND), wherein cytotypes occupy different niches via interactions with different sets of microbes. Inherently cryptic, MMND is underexplored in polyploid plant populations. Here, we search for evidence of MMND in creosotebush Larrea tridentata, a dominant desert shrub of the southwestern US and northern Mexico. We sequenced root‐associated fungal taxa in soils of diploid, autotetraploid, and autohexaploid plants growing in two naturally‐occurring mixed‐cytotype populations. Within populations, we found substantial fungal assemblage overlap across host plant cytotypes. However, using indicator species analysis, we identified some fungi that are differentiated by host plant cytotype, satisfying a necessarycondition for MMND. Future study is needed to determine the degree of niche differentiation conferred, if any, and whether the identified fungi play a role in the long‐term persistence of multiple cytotypes within populations.

Inference of Ploidy Level in 19th-Century Historical Herbarium Specimens Reveals the Identity of Five Acorus Species Described by Schott

Heinrich Wilhelm Schott (1794–1865) was one of the pioneering researchers in the taxonomy of the species-rich monocot family Araceae. He described numerous new plant species in various genera, including Acorus, which is currently segregated as a monogeneric family and order occupying a position sister to the rest of the monocots. While describing his new species of Acorus, Schott mostly used characters that are currently considered of low, if any, taxonomic value. His descriptions lack some key characters including, for obvious reasons, chromosome numbers. Therefore, Schott’s species concepts cannot be properly interpreted according to the current understanding of the taxonomic diversity of Acorus, even though his species names must be examined for implementation of the principle of nomenclatural priority. The only way of resolving the taxonomic identity of Schott’s species names is through the identification of type specimens among historical herbarium collections, by inferring taxonomically significant characters that are missing in Schott’s descriptions. On the basis of herbarium collections of the Komarov Botanical Institute, St. Petersburg (LE), we were able to infer ploidy levels of the materials used by Schott to describe Acorus triqueter (diploid, Siberia), A. tatarinowii (tetraploid, China), A. nilaghirensis (tetraploid, India), A. griffithii (tetraploid, Bhutan), and A. commutatus (tetraploid, Bhutan). Leaf anatomy and pollen stainability were used as cytotype markers. All five species belong to the polymorphic Acorus calamus complex that comprises important medicinal plants. Detailed historical and nomenclatural analyses of Schott’s species names and herbarium collections are provided.

The courtship choreography of homologous chromosomes: timing and mechanisms of DSB-independent pairing.

Meiosis involves deep changes in the spatial organisation and interactions of chromosomes enabling the two primary functions of this process: increasing genetic diversity and reducing ploidy level. These two functions are ensured by crucial events such as homologous chromosomal pairing, synapsis, recombination and segregation. In most sexually reproducing eukaryotes, homologous chromosome pairing depends on a set of mechanisms, some of them associated with the repair of DNA double-strand breaks (DSBs) induced at the onset of prophase I, and others that operate before DSBs formation. In this article, we will review various strategies utilised by model organisms for DSB-independent pairing. Specifically, we will focus on mechanisms such as chromosome clustering, nuclear and chromosome movements, as well as the involvement of specific proteins, non-coding RNA, and DNA sequences.

Molecular identification and population structure of emmer and einkorn wheat lines with different ploidy levels using SSR markers

Molecular identification and population structure of emmer and einkorn wheat lines with different ploidy levels using SSR markers

Clonal diploid and autopolyploid breeding strategies to harness heterosis: insights from stochastic simulation

Key messageReciprocal recurrent selection sometimes increases genetic gain per unit cost in clonal diploids with heterosis due to dominance, but it typically does not benefit autopolyploids.Breeding can change the dominance as well as additive genetic value of populations, thus utilizing heterosis. A common hybrid breeding strategy is reciprocal recurrent selection (RRS), in which parents of hybrids are typically recycled within pools based on general combining ability. However, the relative performances of RRS and other breeding strategies have not been thoroughly compared. RRS can have relatively increased costs and longer cycle lengths, but these are sometimes outweighed by its ability to harness heterosis due to dominance. Here, we used stochastic simulation to compare genetic gain per unit cost of RRS, terminal crossing, recurrent selection on breeding value, and recurrent selection on cross performance considering different amounts of population heterosis due to dominance, relative cycle lengths, time horizons, estimation methods, selection intensities, and ploidy levels. In diploids with phenotypic selection at high intensity, whether RRS was the optimal breeding strategy depended on the initial population heterosis. However, in diploids with rapid-cycling genomic selection at high intensity, RRS was the optimal breeding strategy after 50 years over almost all amounts of initial population heterosis under the study assumptions. Diploid RRS required more population heterosis to outperform other strategies as its relative cycle length increased and as selection intensity and time horizon decreased. The optimal strategy depended on selection intensity, a proxy for inbreeding rate. Use of diploid fully inbred parents vs. outbred parents with RRS typically did not affect genetic gain. In autopolyploids, RRS typically did not outperform one-pool strategies regardless of the initial population heterosis.

Creation and characteristics of tetraploid and mixoploid centipedegrass

AbstractPloidy manipulation has been used in many crop improvement programs to develop plant species with wider adaptability and desirable traits. The objectives of this study were to create stable tetraploid centipedegrass (Eremochloa ophiuroides [Munro] Hack.) lines and evaluate them for beneficial traits. To generate polyploid lines, “TifBlair” (2n = 2x = 18) seeds were exposed to gamma radiation and callus was generated using tissue culture, exposed to glyphosate and regenerated into plantlets. After 5 years of continuous propagation, two lines, Hongliang Wang (HW)16 and HW123, were found to be tetraploid, and one line, HW61, was found to be a mixoploid using flow cytometry and chromosome counts. Nuclear DNA contents for diploid and tetraploid lines ranged from 1.97 to 2.10 and 4.14 to 4.30 pg 2C−1, respectively. Ten centipedegrass lines were genotyped using seven simple sequence repeat markers and clustered by origin (derived from TifBlair or the University of Georgia breeding program). Six lines were evaluated for morphological and physiological traits under greenhouse conditions. Trait evaluation showed that tetraploid lines had larger stomata and leaf width and reduced stomatal density. For all other traits evaluated under greenhouse conditions, although significant differences were observed between lines, no consistent differences separated diploid and tetraploid lines. Between the tetraploid lines, HW16 had higher evapotranspiration, percentage green cover, and relative water content than HW123, whereas HW123 had a higher average clipping yield and root width than HW16. In conclusion, irradiation and tissue culture are valuable techniques for the generation of stable polyploid lines, and an increased ploidy level led to larger vegetative structures in centipedegrass.

Polyploidy affects responses to Nickel in Ni-hyperaccumulating plants: Evidence from the model species Odontarrhena bertolonii (Brassicaceae)

Compared with their diploid progenitors, polyploid plants often display enhanced vigor and adaptive ability to extreme conditions. Previous studies investigated polyploid fitness under various forms of environmental stress, but whether the whole-genome duplication can affect growth, accumulation ability and tolerance levels to trace metals in metal-accumulating species remains obscure. We investigated this topic using an experimental approach and Odontarrhena bertolonii as model system. This obligate serpentine endemic includes diploid and tetraploid accessions with allopatric distribution in Tuscany and Liguria. Three diploid (2 n = 2x = 16) and three natural autotetraploid (2 n = 4x = 32) accessions were compared for growth, leaf traits, photosynthetic parameters and metal accumulation after cultivation on natural serpentine soil and in Ni-containing hydroponic solutions. In soil cultivation, shoot Ni concentration was similar in diploid and tetraploid plants, but the metal content per plant was significantly higher in polyploids because of their higher biomass production. The latter was mainly due to the production of larger leaves, coupled to a lower specific leaf area, which pointed to a better adaptation of the tetraploids to serpentine soil. In hydroponics, all the accessions showed an hormetic-like Ni effect, with stimulation of growth and photosynthesis in the low-dose zone. The data fitting to the hormetic model displayed significant differences in some parameters, with the tetraploid plants showing higher maximal length of roots and shoots and higher requirement of both external and internal Ni concentrations for optimal growth, in respect to diploid plants. On the other hand, Ni tolerance to both external and internal metal concentrations was similar in the plants of the two ploidy levels. Our results suggest that whole-genome duplication can affect the potential for growth and Ni-hyperaccumulation in obligate Ni-accumulator plants like O. bertolonii. This points to the opportunity of selecting polyploid instead of diploid accessions for environmental restoration and metal cropping practices, when the candidate species includes both chromosome races.

New insights into polyploid evolution and dynamic nature of Ludwigia section Isnardia (Onagraceae)

BackgroundWhile polyploids are common in plants, the evolutionary history and natural dynamics of most polyploid groups are still unclear. Owing to plentiful earlier systematic studies, Ludwigia sect. Isnardia (comprising 22 wetland taxa) is an ideal allopolyploid complex to investigate polyploid evolution and natural dynamics within and among taxa. With a considerable sampling, we concentrated on revisiting earlier phylogenies of Isnardia, reevaluating the earlier estimated age of the most recent common ancestor (TMRCA), exploring the correlation between infraspecific genetic diversity and ploidy levels, and inspecting interspecific gene flows among taxa.ResultsPhylogenetic trees and network concurred with earlier phylogenies and hypothesized genomes by incorporating 192 atpB-rbcL and ITS sequences representing 91% of Isnardia taxa. Moreover, we detected three multi-origin taxa. Our findings on L. repens and L. sphaerocarpa were consistent with earlier studies; L. arcuata was reported as a multi-origin taxon here, and an additional evolutionary scenario of L. sphaerocarpa was uncovered, both for the first time. Furthermore, estimated Isnardia TMRCA ages based on our data (5.9 or 8.9 million years ago) are in accordance with earlier estimates, although younger than fossil dates (Middle Miocene). Surprisingly, infraspecific genetic variations of Isnardia taxa did not increase with ploidy levels as anticipated from many other polyploid groups. In addition, the exuberant, low, and asymmetrical gene flows among Isnardia taxa indicated that the reproductive barriers may be weakened owing to allopolyploidization, which has rarely been reported.ConclusionsThe present research gives new perceptions of the reticulate evolution and dynamic nature of Isnardia and points to gaps in current knowledge about allopolyploid evolution.

Ploidy effects on the relationship between floral phenotype, reproductive investment, and fitness in an autogamous species complex

AbstractPremiseThe relationships between reproductive investment, phenotype, and fitness have been broadly studied in cross‐pollinated plants in contrast to selfing species, which are considered less interesting in this area because they are supposed to be a dead end in any evolutionary pathway. Still, selfing plants are unique systems to study these questions since the position of reproductive structures and traits related to flower size play an important role in female and male pollination success.MethodsErysimum incanums.l. is a selfing species complex that has three levels of ploidy (diploids, tetraploids, and hexaploids) and traits that are typically associated with the selfing syndrome. Here, we used 1609 plants belonging to these three ploidies to characterize the floral phenotype and spatial configuration of reproductive structures, reproductive investment (pollen and ovule production), and plant fitness. Then, we used structural equation modelling to analyze the relationship between all these variables across ploidy levels.ResultsAn increase in ploidy level leads to bigger flowers with anthers exserted farther and more pollen and ovules. In addition, hexaploid plants had higher absolute values for herkogamy, which is positively correlated with fitness. Ovule production significantly mediated the natural selection acting on different phenotypic traits and pollen production, a pattern that is maintained across ploidies.ConclusionsThe changes in floral phenotypes, reproductive investment, and fitness with ploidy level suggest that genome duplication can be a driver for transitions in reproductive strategy by modifying the investment in pollen and ovules and linking them with plant phenotype and fitness.