Diploid Species Research Articles

Combined foliar application of Zn and Fe increases grain micronutrient concentrations and alleviates water stress across diverse wheat species and ploidal levels

This study aimed to examine the reaction of several wheat species with different ploidy levels to foliar application of zinc (Zn) and iron (Fe) under different water regimes. Thirty-five wheat genotypes, including nineteen tetraploids from ten different species, ten hexaploids from five species, and six diploids from three species, were evaluated in the field over two moisture regimes with the following four treatments: control, foliar Zn application, foliar Fe application, and foliar Zn + Fe application. The experiments were conducted according to a split-plot scheme in a randomized complete block design with two replications in each moisture regime. Water stress negatively affected all measured traits, except grain Zn and Fe content. Combined foliar application of Zn + Fe significantly increased yield and alleviated yield reduction caused by water stress. Applying Zn and Fe significantly increased both micronutrient content in grains under both moisture conditions. Tetra and hexaploid species yielded nearly four times as much grain as unimproved diploid species and were less affected by water stress. All ploidy levels responded almost similarly to Zn and Fe treatments, with the combined application being as effective as each element separately. The highest yield increase in response to combined application of Zn + Fe under the two moisture conditions and the highest grain Zn content in response to Zn application under water stress was observed in hexaploid wheat. Combined foliar application of Zn and Fe increases grain Zn and Fe and alleviates water stress's adverse effects on all wheat ploidy levels, making biofortification cost-effective.

Detecting clonemate pairs in multicellular diploid clonal species based on a shared heterozygosity index.

Clonal reproduction, the formation of nearly identical individuals via mitosis in the absence of genetic recombination, is a very common reproductive mode across plants, fungi and animals. To detect clonal genetic structure, genetic similarity indices based on shared alleles are widely used, such as the Jaccard index, or identity by state. Here we propose a new pairwise genetic similarity index, the SH index, based on segregating genetic marker loci (typically single nucleotide polymorphisms) that are identically heterozygous for pairs of samples (NSH ). To test our method, we analyse two old seagrass clones (Posidonia australis, estimated to be around 8500 years old; Zostera marina, >750 years old) along with two young Z. marina clones of known age (17 years old). We show that focusing on shared heterozygosity amplifies the power to distinguish sample pairs belonging to different clones compared to methods focusing on all shared alleles. Our proposed workflow can successfully detect clonemates at a location dominated by a single clone. When the collected samples involve two or more clones, the SH index shows a clear gap between clonemate pairs and interclone sample pairs. Ideally NSH should be on the order of approximately ≥3000, a number easily achievable via restriction-site associated DNA (RAD) sequencing or whole-genome resequencing. Another potential application of the SH index is to detect possible parent-descendant pairs under selfing. Our proposed workflow takes advantage of the availability of the larger number of genetic markers in the genomic era, and improves the ability to distinguish clonemates from nonclonemates in multicellular diploid clonal species.

CRISPR-Cas9 Editing Induces Loss of Heterozygosity in the Pathogenic Yeast Candida parapsilosis.

Genetic manipulation is often used to study gene function. However, unplanned genome changes (including single nucleotide polymorphisms [SNPs], aneuploidy, and loss of heterozygosity [LOH]) can affect the phenotypic traits of the engineered strains. Here, we compared the effect of classical deletion methods (replacing target alleles with selectable markers by homologous recombination) with CRISPR-Cas9 editing in the diploid human-pathogenic yeast Candida parapsilosis. We sequenced the genomes of 9 isolates that were modified using classic recombination methods and 12 that were edited using CRISPR-Cas9. As a control, the genomes of eight isolates that were transformed with a Cas9-expressing plasmid in the absence of a guide RNA were also sequenced. Following gene manipulation using classic homologous recombination, only one strain exhibited extensive LOH near the targeted gene (8.9 kb), whereas another contained multiple LOH events not associated with the intended modification. In contrast, large regions of LOH (up to >1,100 kb) were observed in most CRISPR-Cas9-edited strains. LOH most commonly occurred adjacent to the Cas9 cut site and extended to the telomere in four isolates. In two isolates, we observed LOH on chromosomes that were not targeted by CRISPR-Cas9. Among the CRISPR-edited isolates, two exhibited cysteine and methionine auxotrophy caused by LOH at a heterozygous site in MET10, approximately 11 and 157 kb downstream from the Cas9 target site, respectively. C. parapsilosis isolates have relatively low levels of heterozygosity. However, our results show that mutation complementation to confirm observed phenotypes is required when using CRISPR-Cas9. IMPORTANCE CRISPR-Cas9 has greatly streamlined gene editing and is now the gold standard and first choice for genetic engineering. However, we show that in diploid species, extra care should be taken in confirming the cause of any phenotypic changes observed. We show that the Cas9-induced double-strand break is often associated with loss of heterozygosity in the asexual diploid human fungal pathogen Candida parapsilosis. This can result in deleterious heterozygous variants (e.g., stop gain in one allele) becoming homozygous, resulting in unplanned phenotypic changes. Our results stress the importance of mutation complementation even when using CRISPR-Cas9.

Study of phylogenetic relationships between wild and cultivated oat species (Avena L.)

We performed next generation sequencing (NGS) of wild and cultivated oat species (Avena L.) ITS1 sequence and the beginning of the gene 5.8S rRNA on the Illumina platform. For the first time, the NGS method was used to carry out a phylogenetic analysis of the domestication pathways of three cultivated oat species: tetraploid A. abyssinica (AB), hexaploid A. sativa and A. byzantina (ACD). We found that the A. abyssinica genome with the most massive number of reads is the A-genome, while in A. sativa, it is the D-genome. Also, we studied the putative ways of obtaining polyploid genomes from diploid species. According to NGS sequencing data, it was revealed that the most widespread A. sativa ribotype is inherited from A. ludoviciana, A. byzantina has two unique families of ribotypes, and A. abyssinica probably comes from the wild A. vaviloviana (A-genome was obtained by this species from the diploid A. atlantica (As-genome)). Putative ancestor of A. abyssinica, tetraploid A. agadiriana, forms unique families of ribotypes, to which the most widespread ribotype belongs. It most likely was not a direct ancestor of A. abyssinica. C-genome species A. clauda turned out to be related to the D-genome of A. sativa; it could also be involved in the formation of the hexaploid A. ludoviciana.

Comparative Genomics and Functional Studies of Putative m6A Methyltransferase (METTL) Genes in Cotton.

N6-methyladenosine (m6A) RNA modification plays important regulatory roles in plant development and adapting to the environment, which requires methyltransferases to achieve the methylation process. However, there has been no research regarding m6A RNA methyltransferases in cotton. Here, a systematic analysis of the m6A methyltransferase (METTL) gene family was performed on twelve cotton species, resulting in six METTLs identified in five allotetraploid cottons, respectively, and three to four METTLs in the seven diploid species. Phylogenetic analysis of protein-coding sequences revealed that METTL genes from cottons, Arabidopsis thaliana, and Homo sapiens could be classified into three clades (METTL3, METTL14, and METTL-like clades). Cis-element analysis predicated the possible functions of METTL genes in G. hirsutum. RNA-seq data revealed that GhMETTL14 (GH_A07G0817/GH_D07G0819) and GhMETTL3 (GH_A12G2586/GH_D12G2605) had high expressions in root, stem, leaf, torus, petal, stamen, pistil, and calycle tissues. GhMETTL14 also had the highest expression in 20 and 25 dpa fiber cells, implying a potential role at the cell wall thickening stage. Suppressing GhMETTL3 and GhMETTL14 by VIGS caused growth arrest and even death in G. hirsutum, along with decreased m6A abundance from the leaf tissues of VIGS plants. Overexpression of GhMETTL3 and GhMETTL14 produced distinct differentially expressed genes (DEGs) in A. thaliana, indicating their possible divergent functions after gene duplication. Overall, GhMETTLs play indispensable but divergent roles during the growth of cotton plants, which provides the basis for the systematic investigation of m6A in subsequent studies to improve the agronomic traits in cotton.

Gamete Binning to Achieve Haplotype-Resolved Genome Assembly.

Haplotype-resolved genome assemblies remain a challenge in practice. Here, we provide a step-by-step guide on gamete binning, a method to generate haplotype-resolved genome assemblies for diploid species. The protocol starts by phasing heterozygous variants to individual haplotypes of specific chromosomes using the genome information of individual haploid gametes of the focal individual. Using phased variants, the whole-genome sequencing reads from the diploid genome can be genotyped and assigned into groups, which represent the individual haplotypes of each of the chromosomes. Finally, haplotype-specific chromosomes can be assembled independently using standard assembly tools. First applications of gamete binning revealed a haplotyping accuracy over 99%, which outperformed sequence-only or Hi-C-based haplotype-resolved genome assemblies.Availability: github.com/schneebergerlab/GameteBinning_prac .

Insights and advances in integrating multi-omic approaches for potato crop improvement

In the forthcoming era of climate change and degradation of culturable land, there is an urgent need to secure global food supply in a sustainable manner. unraveling the genetic mysteries underlying interactions between functional genetic and metabolic networks through fostering the use of high-throughput -omic technologies can serve as a valuable tool towards characterizing plant phenotypic diversity and plasticity, to mitigate current threats of the climate change scenario on agriculture. Recently, a colossal number of -omic studies, including genomics, transcriptomics, proteomics, metabolomics, epigenomics and metagenomics, have enabled the identification of genes, proteins, and metabolites, that are related to desirable phenotypes, explaining the “holo-genetic” basis of agriculturally important traits, especially under resource-limiting environments. Undoubtedly, the integration of such big datasets with machine learning is highly demanding, mainly due to the lack of universal protocols to predict gene models or networks that govern various key traits. Among other important plant species contributing to food production, potato (Solanum tuberosum L.) represents one of top crop species worldwide, in terms of nutrition contribution, yielding capacity, and as a component of diverse cropping systems, especially for the developing counties. The potato genome is highly heterozygous as a result of self-incompatibility of the diploid potato species, suffering acute inbreeding depression. In this review, we discuss recent developments of high-throughput genomic technologies, as a useful tool for the selection of potato germplasm with improved nutritional value and quality traits.

Development and Degeneration of Retinal Ganglion Cell Axons in Xenopus tropicalis.

Neurons make long-distance connections via their axons, and the accuracy and stability of these connections are crucial for brain function. Research using various animal models showed that the molecular and cellular mechanisms underlying the assembly and maintenance of neuronal circuitry are highly conserved in vertebrates. Therefore, to gain a deeper understanding of brain development and maintenance, an efficient vertebrate model is required, where the axons of a defined neuronal cell type can be genetically manipulated and selectively visualized in vivo. Placental mammals pose an experimental challenge, as time-consuming breeding of genetically modified animals is required due to their in utero development. Xenopus laevis, the most commonly used amphibian model, offers comparative advantages, since their embryos ex utero during which embryological manipulations can be performed. However, the tetraploidy of the X. laevis genome makes them not ideal for genetic studies. Here, we use Xenopus tropicalis, a diploid amphibian species, to visualize axonal pathfinding and degeneration of a single central nervous system neuronal cell type, the retinal ganglion cell (RGC). First, we show that RGC axons follow the developmental trajectory previously described in X. laevis with a slightly different timeline. Second, we demonstrate that co-electroporation of DNA and/or oligonucleotides enables the visualization of gene function-altered RGC axons in an intact brain. Finally, using this method, we show that the axon-autonomous, Sarm1-dependent axon destruction program operates in X. tropicalis. Taken together, the present study demonstrates that the visual system of X. tropicalis is a highly efficient model to identify new molecular mechanisms underlying axon guidance and survival.

Variations in chlorophyll content, stomatal conductance, and photosynthesis in Setaria EMS mutants

Chlorophyll (Chl) content, especially Chl b content, and stomatal conductance (Gs) are the key factors affecting the net photosynthetic rate (Pn). Setaria italica, a diploid C4 panicoid species with a simple genome and high transformation efficiency, has been widely accepted as a model in photosynthesis and drought-tolerance research. The current study characterized Chl content, Gs, and Pn of 48 Setaria mutants induced by ethyl methanesulfonate. A total of 24, 34, and 35 mutants had significant variations in Chl content, Gs, and Pn, respectively. Correlation analysis showed a positive correlation between increased Gs and increased Pn, and a weak correlation between decreased Chl b content and decreased Pn was also found. Remarkably, two mutants behaved with significantly decreased Chl b content but increased Pn compared to Yugu 1. Seven mutants behaved with significantly decreased Gs but did not decrease Pn compared to Yugu 1. The current study thus identified various genetic lines, further exploration of which would be beneficial to elucidate the relationship between Chl content, Gs, and Pn and the mechanism underlying why C4 species are efficient at photosynthesis and water saving.

Estimation of Nuclear DNA Content in Some Aegilops Species: Best Analyzed Using Flow Cytometry.

The genera Triticum and Aegilops have been considered as the main gene pool of wheat due to their features, such as tolerance of all types of abiotic and biotic stresses. This study was conducted to evaluate the cytogenetic analyses in 115 native and wild populations from eleven Aegilops species using their nuclear DNA quantification. Mean 2C nuclear DNA contents of different ploidy levels in the wild wheat of Turkey and Iran were measured using the flow cytometry technique. The obtained results showed that the mean nuclear DNA content in diploid species varied from 10.09 pg/2C (Ae. umbellulata) to 10.95 pg/2C (Ae. speltoides var. ligustica) in Turkey. In Iranian diploids, the mean nuclear DNA content varied from 10.20 pg/2C (Ae. taushii) to 11.56 pg/2C (Ae. speltoides var. ligustica). This index in the tetraploid species of Turkey varied from 18.09 pg/2C (Ae. cylindrica) to 21.65 pg/2C (Ae. triaristata), and in Iranian species, it was from 18.61 pg/2C (Ae. cylindrica) to 21.75 pg/2C (Ae. columnaris). On the other hand, in the hexaploid species of Turkey, this index varied from 31.59 pg/2C (Ae. crassa) to 31.81 pg/2C (Ae. cylindrica); in the Iranian species, it varied from 32.58 pg/2C (Ae. cylindrica) to 33.97 pg/2C (Ae. crassa). There was a significant difference in the DNA content of Turkey and Iran diploid as well as tetraploid species; however, in hexaploid species, the difference was not significant. It was concluded that the variation in intraspecific genome size was very low in diploid and tetraploid populations; this means that the low variation is not dependent on geographic and climatic parameters. On the other hand, the interspecific variation is significant at the diploid and tetraploid populations. It is generally very difficult to distinguish Aegilops species from each other in natural conditions; meanwhile, in this study, all species could be, easily, quickly and unambiguously, distinguished and separated using the FCM technique.

De novo assembly and characterization of the draft genome of the cashew (Anacardium occidentale L.)

Cashew is the second most important tree nut crop in the global market. Cashew is a diploid and heterozygous species closely related to the mango and pistachio. Its improvement by conventional breeding is slow due to the long juvenile phase. Despite the economic importance, very little genomics/transcriptomics information is available for cashew. In this study, the Oxford nanopore reads and Illumina reads were used for de novo assembly of the cashew genome. The hybrid assembly yielded a 356.6 Mb genome corresponding to 85% of the estimated genome size (419 Mb). The BUSCO analysis showed 91.8% of genome completeness. Transcriptome mapping showed 92.75% transcripts aligned with the assembled genome. Gene predictions resulted in the identification of 31,263 genes coding for a total of 35,000 gene isoforms. About 46% (165 Mb) of the cashew genome comprised of repetitive sequences. Phylogenetic analyses of the cashew with nine species showed that it was closely related to Mangifera indica. Analysis of cashew genome revealed 3104 putative R-genes. The first draft assembly of the genome, transcriptome and R gene information generated in this study would be the foundation for understanding the molecular basis of economic traits and genomics-assisted breeding in cashew.

Perspective for genomic-enabled prediction against black sigatoka disease and drought stress in polyploid species.

Genomic selection (GS) in plant breeding is explored as a promising tool to solve the problems related to the biotic and abiotic threats. Polyploid plants like bananas (Musa spp.) face the problem of drought and black sigatoka disease (BSD) that restrict their production. The conventional plant breeding is experiencing difficulties, particularly phenotyping costs and long generation interval. To overcome these difficulties, GS in plant breeding is explored as an alternative with a great potential for reducing costs and time in selection process. So far, GS does not have the same success in polyploid plants as with diploid plants because of the complexity of their genome. In this review, we present the main constraints to the application of GS in polyploid plants and the prospects for overcoming these constraints. Particular emphasis is placed on breeding for BSD and drought-two major threats to banana production-used in this review as a model of polyploid plant. It emerges that the difficulty in obtaining markers of good quality in polyploids is the first challenge of GS on polyploid plants, because the main tools used were developed for diploid species. In addition to that, there is a big challenge of mastering genetic interactions such as dominance and epistasis effects as well as the genotype by environment interaction, which are very common in polyploid plants. To get around these challenges, we have presented bioinformatics tools, as well as artificial intelligence approaches, including machine learning. Furthermore, a scheme for applying GS to banana for BSD and drought has been proposed. This review is of paramount impact for breeding programs that seek to reduce the selection cycle of polyploids despite the complexity of their genome.

Divergent subgenome evolution in the allotetraploid frog Xenopus calcaratus

Allopolyploid genomes are divided into compartments called subgenomes that are derived from lower ploidy ancestors. In African clawed frogs of the subgenus Xenopus (genus Xenopus), allotetraploid species have two subgenomes (L and S) with morphologically distinct homoeologous chromosomes. In allotetraploid species of the sister subgenus Silurana, independently evolved subgenomes also exist, but their cytogenetics has not been investigated in detail. We used a diverse suite of cytogenetic and molecular FISH techniques on an allotetraploid species in Silurana—Xenopus calcaratus—to explore evolutionary dynamics of chromosome morphology and rearrangements. We find that the subgenomes of X. calcaratus have distinctive characteristics, with a more conserved a-subgenome resembling the closely related genome of the diploid species X. tropicalis, and a more rapidly evolving b-subgenome having more pronounced changes in chromosome structure, including diverged heterochromatic blocks, repetitive sequences, and deletion of a nucleolar secondary constriction. Based on these cytogenetic differences, we propose a chromosome nomenclature for X. calcaratus that may apply to other allotetraploids in subgenus Silurana, depending on as yet unresolved details of their evolutionary origins. These findings highlight the potential for large-scale asymmetry in subgenome evolution following allopolyploidization.

Fine mapping and marker development for the wheat leaf rust resistance gene Lr32.

Wheat leaf rust is caused by the fungal pathogen Puccinia triticina and is one of the wheat diseases of concern globally. Among the known leaf rust resistance genes (Lr) genes, Lr32 is a broadly effective gene derived from the diploid species Aegilops tauschii coss. accession RL5497-1 and has been genetically mapped to chromosome arm 3DS. However, Lr32 resistance has not been utilized in current cultivars in part due to the lack of modern, predictive DNA markers. The goals of this study were to fine map the Lr32 region and develop SNP-based kompetitive allele-specific polymerase chain reaction markers. The genomic analysis was conducted by using doubled haploid and F2-derived mapping populations. For marker development, a 90K wheat chip array, 35K and 820K Axiom R SNPs, A. tauschii pseudomolecules v4.0 and International Wheat Genome Sequencing Consortium ReqSeq v2.1 reference genomes were used. Total 28 kompetitive allele-specific polymerase chain reaction and 2 simple sequence repeat markers were developed. The Lr32 region was fine mapped between kompetitive allele-specific polymerase chain reaction markers Kwh142 and Kwh355 that flanked 34-35 Mb of the diploid and hexaploid reference genomes. Leaf rust resistance mapped as a Mendelian trait that cosegregated with 20 markers, recombination restriction limited the further resolution of the Lr32 region. A total of 10-11 candidate genes associated with disease resistance were identified between the flanking regions on both reference genomes, with the majority belonging to the nucleotide-binding domain and leucine-rich repeat gene family. The validation analysis selected 2 kompetitive allele-specific polymerase chain reaction markers, Kwh147 and Kwh722, for marker-assisted selection. The presence of Lr32 along with other Lr genes such as Lr67 and Lr34 would increase the resistance in future wheat breeding lines and have a high impact on controlling wheat leaf rust.

Chromosomes in the African frog genus Tomopterna (Pyxicephalidae) and probing the origin of tetraploid Tomopterna tandyi.

Speciation by polyploidization has been documented to have independently occurred in 12 families of anuran amphibians. Tomopterna tandyi was described as a South African allotetraploid species of sand frogs in the family Pyxicephalidae. Recent taxonomic revisions and new species descriptions in the genus present problems with respect to the evolution of this tetraploid species. Chromosomes, mitochondrial and nuclear gene sequences, isozymes, and male mating calls were examined for T. tandyi and for diploid species of Tomopterna. Mitochondrial sequences confirmed the diploid species, T. adiastola, to be the maternal ancestor that gave rise to the tetraploid about 5 mya. Nuclear sequences and isozymes reveal a complex reticulation of paternal ancestry that may be explained by occasional hybridization of T. tandyi with diploid species of Tompoterna at various times in sympatric populations. Interspecific diploid to tetraploid gene introgression is suspected to have also occurred in Australian and North American tetraploid species of frogs. Diploid to tetraploid introgression is facilitated through triploid hybrids that are more viable than diploid hybrids and produce unreduced triploid eggs.

Multiple origins, one evolutionary trajectory: gradual evolution characterizes distinct lineages of allotetraploid Brachypodium.

The "genomic shock" hypothesis posits that unusual challenges to genome integrity such as whole genome duplication may induce chaotic genome restructuring. Decades of research on polyploid genomes have revealed that this is often, but not always the case. While some polyploids show major chromosomal rearrangements and derepression of transposable elements in the immediate aftermath of whole genome duplication, others do not. Nonetheless, all polyploids show gradual diploidization over evolutionary time. To evaluate these hypotheses, we produced a chromosome-scale reference genome for the natural allotetraploid grass Brachypodium hybridum, accession "Bhyb26." We compared 2 independently derived accessions of B. hybridum and their deeply diverged diploid progenitor species Brachypodium stacei and Brachypodium distachyon. The 2 B. hybridum lineages provide a natural timecourse in genome evolution because one formed 1.4 million years ago, and the other formed 140 thousand years ago. The genome of the older lineage reveals signs of gradual post-whole genome duplication genome evolution including minor gene loss and genome rearrangement that are missing from the younger lineage. In neither B. hybridum lineage do we find signs of homeologous recombination or pronounced transposable element activation, though we find evidence supporting steady post-whole genome duplication transposable element activity in the older lineage. Gene loss in the older lineage was slightly biased toward 1 subgenome, but genome dominance was not observed at the transcriptomic level. We propose that relaxed selection, rather than an abrupt genomic shock, drives evolutionary novelty in B. hybridum, and that the progenitor species' similarity in transposable element load may account for the subtlety of the observed genome dominance.

Genome-wide characterization of the UDP-glycosyltransferase gene family reveals their potential roles in leaf senescence in cotton

Uridine diphosphate (UDP) glycosyltransferases (UGTs) involved in many metabolic processes and are essential for plant growth and development. Although UGTs proteins have been studied in many plants, the biological functions of UGT genes in cotton leaf senescence are still unknown. In the present study, we performed a genome-wide survey and identified 157 GrUGT, 152 GaUGT and 261 GHUGT genes in Gossypium raimondii, G. arboreum, and G. hirsutum, respectively, that were classified into 15 groups. Analysis of protein motif and gene structure demonstrated that structural and functional conservation occurred within same groups but diverged among the different groups. Gene duplication analysis indicated the different duplication ways happened between tetraploid G. hirsutum and the two diploid species. Whole genome or segmental duplications played a main role in the expansion of the GHUGT family in cotton, and experienced purifying selection during the long evolutionary process in cotton. Cis-acting regulatory elements analysis indicated that they were associated with complex hormone regulatory networks and the stress response. Additionally, to identify GHUGT candidate genes responsive to leaf senescence, we analyzed the expression patterns of GHUGT genes using our transcriptome data from two cultivars of upland cotton with contrasting tolerance to leaf senescence. Subsequently, gene expression profiling based on real-time quantitative PCR showed that selected GHUGT candidate genes might be involved in ABA and JA regulation. Through further functional verification, silencing GHUGT116 gene via VIGS (Virus-induced gene silencing) delayed dark-induced leaf senescence. Overall, the results provide useful and valuable information for understanding the evolution of cotton UGTs genes and the function in leaf senescence.

Chromosome-level genome of a leaf vegetable Glebionis coronaria provides insights into the biosynthesis of monoterpenoids contributing to its special aroma.

Glebionis coronaria is a popular vegetable with special aroma and a medical plant in East Asia and Mediterranean, but its biological studies and breeding have been hindered by the lack of reference genome. Here, we present a chromosome-level reference genome of G. coronaria, with assembled genome size of 6.8 Gb, which is the largest among all the published genomes of diploid Asteraceae species. The large genome size of G. coronaria is mainly caused by the recent widespread explosions of long-terminal-repeat retrotransposons. Analyses of macro-synteny and synonymous mutation rate distribution indicate that the G. coronaria genome experienced a whole-genome triplication at 40-45 million years ago, shared with all Asteraceae species. In subtribe Artemisiinae, Glebionis arose before the divergence of Chrysanthemum from Artemisia, and Glebionis species evolved much faster than Chrysanthemum and Artemisia species. In G. coronaria, the synthesis genes of monoterpenoids 8-oxocitronellyl enol and isopiperitenone were expanded, and the higher expressions of these expanded genes in leaves and stems may contribute to its special aroma. The G. coronaria genomic resources will promote the evolution studies of Asteraceae, the metabolism mechanism studies of bioactive compounds, and the breeding improvement of agronomic traits in G. coronaria.

Comparative Ecophysiology of Hybrid Wood Fern Species

Premise of research. Polyploidy and hybridization are prevalent and widespread phenomena in plants. The genetic consequences of genome duplication are numerous, but we understand very little about the comparative ecology of polyploids. In particular, the ways in which hybrid and polyploid offspring differ in ecology relative to their parents and relatives are poorly known. Among angiosperms, the triploid bridge is hypothesized to accrue some marginal fitness benefit to parent species from mostly sterile hybrid offspring. Because of the complexities of the fern life cycle, involving two free-living life stages, the ability to backcross via a triploid bridge should be more limited. If the triploid sporophyte offspring provide no fitness benefit to parents via subsequent generations, this raises the question about whether triploids further compete with parents by occupying similar ecological niches. We investigated comparative ecophysiology across light and wetness gradients of five members of the hybrid wood fern complex, Dryopteris. Methodology. We selected two related triads. Each triad consisted of a triploid and its diploid and tetraploid progenitor species: the D. × triploidea (3n) triad, with the parents D. carthusiana (4n) and D. intermedia (2n), and the D. × bootii (3n) triad, with the parents D. cristata (4n) and D. intermedia (2n). We sampled the temperature and relative humidity, population abundance and relative frequency, photosynthetic parameters, and hydraulic conductivity of populations to examine the extent of shared ecological niche space. Pivotal results. We found that triploids varied in habitat space relative to their parents. In the case of the triploid D. × bootii, this taxon occupied habitats similar to those of its parents at similar abundances and frequencies. In the case of D. × triploidea, the hybrid occurred across a more diverse range of habitats, which was more similar to its diploid parent. In both triads, the triploid’s photosynthetic rate was intermediate between those of its parents, and the majority of the photosynthetic parameters were similar to those of the parents. There were some differences in hydraulic conductivity: xylem-specific hydraulic conductivity of the triploid D. × bootii was significantly higher than that of its diploid parent. Conclusions. Our results show that related triploids, diploids, and tetraploids substantially overlap in morphological and physiological niche space. The high relative frequency of triploids in habitats and the lack of clear niche partitioning within triads suggest that in addition to not contributing to parental reproductive fitness, the triploids could also negatively impact their progenitors by potentially competing for space and light resources in similar ways.

Microsatellite marker based DNA fingerprinting of cotton (Gossypium spp.) hybrids and their parents

Cotton production in India by the vast majority comes from cotton hybrids whose genetic purity is of great significance in the seed production chain and trade. Therefore, there is a need to develop a rapid, reliable and reproducible technique to assess the genetic purity of cotton hybrids as the traditional, morphological traits-based ‘Grow-Out Test’ is resource intensive, time consuming, tedious and not an infallible procedure. In this regard, a study was planned to understand the genetic diversity among the hybrids and their parents and also to identify SSR markers for confirmation of genetic purity or hybridity. One intra-arboreum hybrid, CICR2 (DS 5 GMS × LD 327 Sel.), four intra-hirsutum hybrids viz., CSHH198 (CSH 19 × CSH 8), CSHH238 (SH 2379 9Y × PIL 8 Sel.), CSHH243 (CSH 2013 × CSH 43), CSHH1862 (GMS 16A × CB 33) and one hirsutum × barbadense hybrid, Phule 388 (RHC-006 × RHCb-001) along with their respective parental lines were selected for molecular characterization. Of the total 215 SSR markers surveyed, 60 markers conveyed polymorphism. The information conveyed by the polymorphic SSR markers was utilized to assess the molecular divergence among the study material. Maximum genetic dissimilarity of 0.66 was noted between Phule 388 and LD 327 (Sel.), and between RHC-006 and DS 5 (GMS). Minimum genetic dissimilarity of 0.07 was observed between CSHH1862 and CB 33, followed by 0.11 between CICR2 and DS 5 (GMS). SSR markers were highly efficient in capturing both intra-species and inter-species level diversity. The clustering and factorial analysis were  in congruence with the species of Gossypium. The diploid species genotypes were clustered separately and distinctly from the rest of the genotypes. All the hirsutum hybrids and their respective parents were found closely clustered. The inter-specific hybrid, Phule 388 along with its parents was found grouped closely. The genetic purity of the hybrids was confirmed using identified SSR markers [GH486, BNL1421, BNL3594, JESPR151 for G. hirsutum hybrids, CSHH198; GH486, BNL2449, JESPR151, TMB0436 for G. hirsutum hybrids, CSHH238; BNL2449, JESPR151, JESPR152 for G. hirsutum hybrid, CSHH243 and GH527, BNL3812, TMB1484, TMB1645, NAU1190, BNL3816 for inter-specific G. hirsutum × G. barbadense hybrid Phule 388]. The SSR markers were efficient in the analysis of hybrid seed purity. The information generated in the present study about genetic diversity and genetic purity testing will greatly facilitate quality seed production of these cotton hybrids and thus, better cotton production. Keywords: Cotton, DNA fingerprinting, Hybrids, Microsatellites, SSR markers, Diversity