Haploid Set Of Chromosomes Research Articles

Membrane and organelle rearrangement during ascospore formation in budding yeast.

SUMMARYIn ascomycete fungi, sexual spores, termed ascospores, are formed after meiosis. Ascospore formation is an unusual cell division in which daughter cells are created within the cytoplasm of the mother cell by de novo generation of membranes that encapsulate each of the haploid chromosome sets created by meiosis. This review describes the molecular events underlying the creation, expansion, and closure of these membranes in the budding yeast, Saccharomyces cerevisiae. Recent advances in our understanding of the regulation of gene expression and the dynamic behavior of different membrane-bound organelles during this process are detailed. While less is known about ascospore formation in other systems, comparison to the distantly related fission yeast suggests that the molecular events will be broadly similar throughout the ascomycetes.

Naturally occurring horse model of miscarriage reveals temporal relationship between chromosomal aberration type and point of lethality

Chromosomal abnormalities are a common cause of human miscarriage but rarely reported in any other species. As a result, there are currently inadequate animal models available to study this condition. Horses present one potential model since mares receive intense gynecological care. This allowed us to investigate the prevalence of chromosomal copy number aberrations in 256 products of conception (POC) in a naturally occurring model of pregnancy loss (PL). Triploidy (three haploid sets of chromosomes) was the most common aberration, found in 42% of POCs following PL over the embryonic period. Over the same period, trisomies and monosomies were identified in 11.6% of POCs and subchromosomal aberrations in 4.2%. Whole and subchromosomal aberrations involved 17 autosomes, with chromosomes 3, 4, and 20 having the highest number of aberrations. Triploid fetuses had clear gross developmental anomalies of the brain. Collectively, data demonstrate that alterations in chromosome number contribute to PL similarly in women and mares, with triploidy the dominant ploidy type over the key period of organogenesis. These findings, along with highly conserved synteny between human and horse chromosomes, similar gestation lengths, and the shared single greatest risk for PL being advancing maternal age, provide strong evidence for the first animal model to truly recapitulate many key features of human miscarriage arising due to chromosomal aberrations, with shared benefits for humans and equids.

Exploring the maternal inheritance transmitted by the oocyte to its progeny.

Fertility is declining worldwide and many couples are turning towards assisted reproductive technologies (ART) to conceive babies. Organisms that propagate via sexual reproduction often come from the fusion between two gametes, an oocyte and a sperm, whose qualities seem to be decreasing in the human species. Interestingly, while the sperm mostly transmits its haploid genome, the oocyte transmits not only its haploid set of chromosomes but also its huge cytoplasm to its progeny. This is what can be defined as the maternal inheritance composed of chromosomes, organelles, lipids, metabolites, proteins and RNAs. To decipher the decline in oocyte quality, it is essential to explore the nature of the maternal inheritance, and therefore study the last stages of murine oogenesis, namely the end of oocyte growth followed by the two meiotic divisions. These divisions are extremely asymmetric in terms of the size of the daughter cells, allowing to preserve the maternal inheritance accumulated during oocyte growth within these huge cells to support early embryo development. Studies performed in Marie-Hélène Verlhac's lab have allowed to discover the unprecedented impact of original acto-myosin based mechanisms in the constitution as well as the preservation of this maternal inheritance and the consequences when these processes go awry.

High-quality haploid genomes corroborate 29 chromosomes and highly conserved synteny of genes in Hyles hawkmoths (Lepidoptera: Sphingidae)

BackgroundMorphological and traditional genetic studies of the young Pliocene genus Hyles have led to the understanding that despite its importance for taxonomy, phenotypic similarity of wing patterns does not correlate with phylogenetic relationship. To gain insights into various aspects of speciation in the Spurge Hawkmoth (Hyles euphorbiae), we assembled a chromosome-level genome and investigated some of its characteristics.ResultsThe genome of a male H. euphorbiae was sequenced using PacBio and Hi-C data, yielding a 504 Mb assembly (scaffold N50 of 18.2 Mb) with 99.9% of data represented by the 29 largest scaffolds forming the haploid chromosome set. Consistent with this, FISH analysis of the karyotype revealed n = 29 chromosomes and a WZ/ZZ (female/male) sex chromosome system. Estimates of chromosome length based on the karyotype image provided an additional quality metric of assembled chromosome size. Rescaffolding the published male H. vespertilio genome resulted in a high-quality assembly (651 Mb, scaffold N50 of 22 Mb) with 98% of sequence data in the 29 chromosomes. The larger genome size of H. vespertilio (average 1C DNA value of 562 Mb) was accompanied by a proportional increase in repeats from 45% in H. euphorbiae (measured as 472 Mb) to almost 55% in H. vespertilio. Several wing pattern genes were found on the same chromosomes in the two species, with varying amounts and positions of repetitive elements and inversions possibly corrupting their function.ConclusionsOur two-fold comparative genomics approach revealed high gene synteny of the Hyles genomes to other Sphingidae and high correspondence to intact Merian elements, the ancestral linkage groups of Lepidoptera, with the exception of three simple fusion events. We propose a standardized approach for genome taxonomy using nucleotide homology via scaffold chaining as the primary tool combined with Oxford plots based on Merian elements to infer and visualize directionality of chromosomal rearrangements. The identification of wing pattern genes promises future understanding of the evolution of forewing patterns in the genus Hyles, although further sequencing data from more individuals are needed. The genomic data obtained provide additional reliable references for further comparative studies in hawkmoths (Sphingidae).

Chromosome-level genome assembly of a triploid poplar Populus alba 'Berolinensis'.

Many recent studies have provided significant insights into polyploid breeding, but limited research has been carried out on trees. The genomic information needed to understand growth and response to abiotic stress in polyploidy trees is largely unknown, but has become critical due to the threats to forests imposed by climate change. Populus alba 'Berolinensis,' also known "Yinzhong poplar," is a triploid poplar from northeast China. This hybrid triploid poplar is widely used as a landscape ornamental and in urban forestry owing to its adaptation to adverse environments and faster growth than its parental diploid. It is an artificially synthesized male allotriploid hybrid, with three haploid genomes of P.alba 'Berolinensis' originating from different poplar species, so it is attractive for studying polyploidy genomic mechanisms in heterosis. In this study, we focused on the allelic genomic interactions in P.alba 'Berolinensis,' and generated a high-quality chromosome-level genome assembly consisting of 19 allelic chromosomes. Its three haploid chromosome sets are polymorphic with an average of 25.73 nucleotide polymorphism sites per kilobase. We found that some stress-related genes such as RD22 and LEA7 exhibited sequence differences between different haploid genomes. The genome assembly has been deposited in our polyploid genome online analysis website TreeGenomes (https://www.treegenomes.com). These polyploid genome-related resources will provide a critical foundation for the molecular breeding of P.alba 'Berolinensis' and help us uncover the allopolyploidization effects of heterosis and abiotic stress resistance and traits of polyploidy species in the future.

PROGRESS IN SEQUENCING OF THE COMPLETE HAPLOTYPE-RESOLVED DIPLOID GENOMES OF PLANTS

Now most of the genomes of higher organisms are assembled for haploid set of chromosomes, in which DNA fragments from paired chromosomes from different parents alternate in the mosaic order. In this regard, such assemblies are more logical to consider as quasi-genomes, since they do not provide accurate information about the relationship between genotype and phenotype. A new level of genome assembly is haplotype-resolved diploid genomes of higher organisms, including plants and their polyploid forms that have undergone cytological and functional diploidization. Given the importance of such genome assemblies, a large number of corresponding computer programs have been developed that allow phased genome assembly and analysis. To date, haplotype-resolved diploid genomes have been assembled for more than 60 species of plants. Among them are various agricultural plants, ornamental plants, fruit trees and shrubs, forest trees, medicinal plants and others. For the most part, they are represented by diploid plants, but there are also triploids, auto- and allo-tetraploids, hexaploids and even octaploids. The sizes of the assembled genomes also vary greatly - from 135 million bp to 21.6 billion bp. In many articles it is note that phased genome assembly helped to more accurately determine individual important characteristics of the studied plants, including origin, evolution, domestication, yield, resistance to diseases and pests, as well as better understanding of metabolic pathways and mechanisms of heterosis.

The Production of Helianthus Haploids: A Review of Its Current Status and Future Prospects.

The genus Helianthus comprises 52 species and 19 subspecies, with the cultivated sunflower (Helianthus annuus L.) representing one of the most important oilseed crops in the world, which is also of value for fodder and technical purposes. Currently, the leading direction in sunflower breeding is to produce highly effective heterosis F1 hybrids with increased resistance to biotic and abiotic stresses. The production of inbred parental lines via repeated self-pollination takes 4-8 years, and the creation of a commercial hybrid can take as long as 10 years. However, the use of doubled haploid technology allows for the obtainment of inbred lines in one generation, shortening the time needed for hybrid production. Moreover, it allows for the introgression of the valuable genes present in the wild Helianthus species into cultivated sunflowers. Additionally, this technology makes it possible to manipulate the ploidy level, thereby restoring fertility in interspecific hybridization. This review systematizes and analyzes the knowledge available thus far about the production of haploid and dihaploid Helianthus plants using male (isolated anther and microspore cultures) and female (unpollinated ovaries and ovules culture) gametophytes, as well as by induced parthenogenesis using γ-irradiated pollen and interspecific hybridization. The genetic, physiological, and physical factors influencing the efficiency of haploid plant production are considered. A special section focuses on the approaches used to double a haploid chromosome set and the direct and indirect methods for determining the ploidy level. The current analyzed data on the successful application of haploid sunflower plants in breeding are summarized.

New Chromosome Numbers and Karyotype Analysis of Tordylium (Apiaceae) Species with Emphasis on Their Systematics and Evolutionary Significance

In Turkey, there are eighteen Tordylium (Apiaceae) species out of twenty in the worldwide and seven of them are endemic. In this research, karyotypes of T. apulum, T. pestalozzae, T. syriacum, T. trachycarpum and karyotypes and chromosome numbers of T. cappadocicum, T. aegaeum, T. hasselquistiae, T. ketenoglui (endemic), T. macropetalum (endemic), T. pustulosum (endemic) are provided for the first time. Tordylium species were separated into five cytotypes according to chromosome numbers as 2n=8, 16, 18, 20 and 22. Besides, idiograms of haploid chromosome set, length of the chromosome arms, arm ratios, centromeric index, relative length and haploid karyotype formulas are given. T. ketenoglui has longest chromosome lengths (3,39–1,66 µm) while T. aegaeum has shortest (1,10–0,59 µm). Additionally, principal component analysis (PCA) was performed by quantitified karyological characters. PCA results showed that the median type and haploid chromosome length have significant variants among karyological characters. Also, it is discussed correlation among karyological data, current infrageneric classification and the phylogenetic hypothesis based morphological dataset of Tordylium. Karyological characters are incompatible with current infrageneric classification, similarly with conflict between the phylogenetic hypothesis and infrageneric classification. In the light of the phylogeny, it can be said that the ancestral number is 2n=16.

Polyploidy and its Importance in Modern Plant Breeding Improvement

Polyploidy is defined as having more than two sets of chromosomes, and it has long been recognized as a major driver of plant evolution and speciation. A creature with more than two haploid sets of chromosomes is known as a polyploid. Polyploidization has considerably aided plant breeding and agriculture improvement. Polyploidy is likely one of the most important mechanisms of plant adaptation, having been researched extensively over the previous century. It occurs frequently in both plants and mammals. One evolutionary mechanism aids speciation, diversification, and adaptation to changing environmental conditions. Polyploidy is currently an interesting research topic for understanding agricultural plant evolution and utilizing its diversity in crop breeding. The most common use of polyploidy is to overcome or remove sterility in hybrids created via interspecific or inter-generic hybridization or remote cross. Significant economic and societal benefits have resulted from the invention and application of polyploidy breeding. Polyploidy is induced in numerous agricultural plants using diverse ways. The purpose of this paper is to assess polyploidy, classification, and its application in plant breeding.

Разнообразие количественных оценок содержания ДНК в ядрах растений, их разброс, некоторые термины и понятия (геном, C-value, пангеном)

As confirmation of the huge diversity of DNA content in the nuclei of plant cells, the boundary values of minimum and maximum parameters such as the number of chromosomes, varying in plants per haploid genome from two chromosomes to 480 (or even up to 720) chromosomes, as well as the "weight" sizes of genomes in picograms in the form of 1C-value with a range from 0.065 to 152.23 pg per haploid set of chromosomes. The importance of knowledge of the amount of DNA and the number of chromosomes for the implementation of projects for sequencing complete yet unknown plant genomes was noted. Examples of sequenced complete genomes of plants with very different sizes (less than 100 million bp and more than 30 billion bp) are also given. Attention is paid to the need to give the century-old term "genome" a new meaning, according to which it should already mean the entire amount of DNA in all chromosomes, regardless of ploidy, but not a haploid set, as before, since only the totality of all DNA (all alleles, both homologous and homeologous chromosomes) determines the vital status of a plant, and of any other eukaryotic organism. Attention is drawn to the fact that the concept of a "complete genome" includes various levels of their completeness from contigs and other draft quasi-haploid genomes to the so-called T2T genomes, which represent established nucleotide sequences chromosomally from "telomere to telomere". The most complete information about the organism can be given by the diploid genome, which is determined by the so-called phased assembly by haplotypes. At the same time, for plants and especially for cultivars of agricultural plants, as the reference genome should serve a pangenome that carries maximum information about the differences in nucleotide sequences characteristic of the sample under study. The use of plant pangenomic data in breeding will mark the transition to a new level of such work. Perhaps in the future, when the mass sequencing of truly complete diploid genomes in the T2T format begins, a new term will be needed for them, which could become "digenome" or briefly “dinome”.

Mitotic Antipairing of Homologous Chromosomes.

Chromosome organization is highly dynamic and plays an essential role during cell function. It was recently found that pairs of the homologous chromosomes are continuously separated at mitosis and display a haploid (1n) chromosome set, or "antipairing," organization in human cells. Here, we provide an introduction to the current knowledge of homologous antipairing in humans and its implications in human disease.

The duration of the life cycle is associated with C-value and affects reproductive features in the Fabeae, the tribe with largest genomes in Fabaceae

The amount of DNA per nucleus, usually expressed in terms of the amount within a haploid chromosome set (C-value), is known to have significant impacts on morphological and physiological features in plants. Among these features, C-value influences replication time and hence duration of the whole cell cycle, as well as sizes of cells. The Fabeae tribe of the family Leguminosae (Fabaceae) is remarkable in having both annual and perennial species and the largest C-values in the family. Polyploidy is rare in this tribe. This work aims to study the correlation between annuality/perenniality, C-value and some morphological characteristics of reproductive organs, such as the number of pollen grains, ovules, flowers per inflorescence as well as pollen and flower size, in annual and perennial species within the tribe Fabeae (Vicieae). The average C-value of perennials is statistically significantly higher than of annuals. Compared with perennials, annuals are mostly characterized by single- or few-flowered inflorescences and fewer ovules per carpel independently of flower size. All floral characteristics exhibit a range of intraspecific variation thus complicating the estimation of precise impact of C-value on phenotype. Features of the reproductive system in the Fabeae are therefore partly correlated with C-value, most probably mediated through the interaction between ecological adaptation of species with their life cycle duration.

Production of Doubled Haploid Embryos from Cork Oak Anther Cultures by Antimitotic Agents and Temperature Stress.

Cork oak (Quercus suber L.) is a forest tree species of the family Fagaceae. It is characterized by long life cycles which hamper doubled haploid plant production to obtain homozygotes and pure lines. The time-consuming method of repeated backcrossings by conventional breeding techniques to produce pure lines is impractical in woody species. Nevertheless, biotechnology has offered new tools to make it possible. A doubled haploid plant or embryo is one that is developed by the doubling of a haploid set of chromosomes. A protocol to produce doubled haploids of cork oak has been developed through microspore embryogenesis. By a heat stress treatment, the microspores inside the anther leave the gametophytic pathway and react shifting their development to the sporophytic pathway by means of which haploid embryos are obtained. Chromosome duplication of haploids from cork oak anther cultures occurs either spontaneously or may be induced by the application of antimitotic agents (e.g., colchicine, oryzalin, amiprophos-methyl). Furthermore, a genetic test is designed through microsatellite markers to elucidate whether the diploid embryos obtained are originally haploids which spontaneously duplicated their genome, or alternatively those embryos are generated from the diploid tissue of the anther wall. Here we describe a detailed protocol to produce doubled haploid individuals from cork oak anther cultures by using temperature stress and antimitotic agents.

Dictyostelium discoideum as a non-mammalian biomedical model.

Dictyostelium discoideum is one of eight non-mammalian model organisms recognized by the National Institute of Health for the study of human pathology. The use of this slime mould is possible owing to similarities in cell structure, behaviour and intracellular signalling with mammalian cells. Its haploid set of chromosomes completely sequenced amenable to genetic manipulation, its unique and short life cycle with unicellular and multicellular stages, and phenotypic richness encoding many human orthologues, make Dictyostelium a representative and simple model organism to unveil cellular processes in human disease. Dictyostelium studies within the biomedical field have provided fundamental knowledge in the areas of bacterial infection, immune cell chemotaxis, autophagy/phagocytosis and mitochondrial and neurological disorders. Consequently, Dictyostelium has been used to the development of related pharmacological treatments. Herein, we review the utilization of Dictyostelium as a model organism in biomedicine.

Regions enriched for DNA repeats in chromosomes of Macrostomum mirumnovem, a species with a recent Whole Genome Duplication.

The free-living flatworm Macrostomum mirumnovem is a neopolyploid species whose genome underwent a recent Whole Genome Duplication (WGD). In the result of chromosome fusions of the ancient haploid chromosome set, large metacentric chromosomes were formed. In addition to three pairs of small metacentrics, the current karyotype of M. mirumnovem contains two pairs of large metacentric chromosomes, MMI1 and MMI2. The generation of microdissected DNA libraries enriched for DNA repeats followed by DNA probe preparation and fluorescent in situ hybridization (FISH) were performed. The DNA probes obtained marked chromosome regions enriched for different DNA repeats in the M. mirumnovem chromosomes. The size and localization of these regions varied in different copies of large chromosomes. They varied even in homologous chromosomes, suggesting their divergence due to genome re-diploidization after a WGD. Besides the newly formed chromosome regions enriched for DNA repeats, B chromosomes were found in the karyotypes of the studied specimens of M. mirumnovem. These B chromosomes varied in size and morphology. FISH with microdissected DNA probes revealed that some Bs had a distinct DNA content. FISH could paint differently B chromosomes in different worms and even in the same sample. B chromosomes could carry a bright specific fluorescent signal or could show no fluorescent signal at all. In latter cases, the specific FISH signal could be absent even in the pericentromeric region of the B chromosome. Possible mechanisms of B chromosome formation and their further evolution are discussed. The results obtained indicate an important role that repetitive DNAs play in genome re-diploidization initiating a rapid differentiation of large chromosome copies. Taking together, karyotype peculiarities (a high level of intraspecific karyotypic diversity associated with chromosome number variation, structural chromosomal rearrangements, and the formation of new regions enriched for DNA repeats) and some phenotypic features of M. mirumnovem (small body size, short lifecycle, easy maintenance in the laboratory) make this species a perspective model in the studies of genomic and karyotypic evolution in species passed through a recent WGD event.

Hybrid larval lethality of Drosophila is caused by parent-of-origin expression: an insight from imaginal discs morphogenesis of Lhr pausing rescue hybrids of D. melanogaster and D. simulans

Hybrid males that inherit haploid set of chromosomes along with Hybrid male rescue, (Hmr+) gene from D. melanogaster mother and an autosomal set with Lethal hybrid rescue, (Lhr+) gene from D. simulans father, die at the larval/pupal transition phase due to insufficient growth of imaginal disc tissues. Comparable pattern reminiscent of hybrid F1female lethality was noted when D. melanogaster compound females were crossed with D. simulans males. The lethality is suppressed when the hybrids inherit one mutant allele of hybrid incompatibility gene (either Lhr−, or Hmr−) from either of the parent. In order to better understand the cause of lethality of F1 hybrids at larval stage, the imaginal discs development of lethal hybrids were examined and compared with those of ‘rescued’ hybrids with Lhr− and parental species. The study revealed the following major findings: (a) when hybrid male and female larvae carry only D. melanogaster X chromosome(s) in presence of both Lhr+ and Hmr+ genes, broad-ranging cell death reaction was induced in the disc tissues and eventually death of the hybrid larvae, (b) when hybrid females carry the X chromosome of both species in the background of maternal cytoplasm of D. melanogaster, the frequency of cell death in the discs was reduced significantly and discs were able to metamorphose, (c) when hybrid males and females inherit one set of autosome from Lhr null strain of D. simulans, the frequency of non-apoptotic cell death in the discs was suppressed significantly and discs development were restored, although the discs displayed fluctuating asymmetric of development. To understand the defects in the chromosomal organization associated with abnormal development of the ‘rescued’ hybrids, the functional organization of the polytene chromosomes of the ‘rescued’ hybrids were examined. It was noted that incomplete pairing of the autosomes of two species along with abnormal X chromosomal telomeric structure may have some bearing on developmental defects of the ‘rescued’ hybrids. From the results it is suggested that (1) cell death reaction in the imaginal discs of the larval lethal hybrids may be the result of divergent lineage of maternal and paternal sets of chromosomes in zygote in presences of two species specific mediator genes, Lhr+, and Hmr+, (2) suppression of larval lethality, in absence of Lhr function, indicated that the non-apoptotic type of cell death factor in the disc cells was controlled genetically by the two mediator genes in the disc cells, (3) re-specification of compartmental organization of paternal segment polarity genes in ‘rescued’ hybrid discs might cause non-random tissue damages and eventually the apoptotic type of cell death resulting into asymmetric development of the appendages in hybrids. In sum, our data revealed that cell death reaction in imaginal discs, associated with larval lethality in hybrids was a developmentally controlled program, through incompatible interactions between species specific mediator genes, Lhr+, Hmr+ and D. melanogaster X chromosome and the pattern of cell death reaction in the discs was different from apoptosis.

Somatic hybrids of Sinapis alba + Brassica juncea: study of backcross progenies for morphological variations, chromosome constitution and reaction to Alternaria brassicae

The wild relatives of crops represent a rich reservoir of genes for introducing resilience to climate change into cultivated crops. To introgress genes from Sinapis alba, a wild relative of Brassicaceae, into Brassica juncea, a cultivated member of this family, we initially produced somatic hybrids between the two species and then produced a large number of backcross populations involving the two somatic hybrids (H1 and H2) with Brassica juncea. BC1 progeny were morphologically very similar. However, when they were challenge inoculated with a highly virulent Alternaria brassicae (ITCC No. 2542) culture under in vivo and in vitro conditions in two growing seasons, they showed wide variations in their disease reaction. Of the 40 BC1 lines tested in one season, 36 showed a resistant reaction. BC1F2 progenies derived from these resistant BC1 plants also showed resistance to Alternaria brassicae, indicating stable inheritance of the resistant phenotype. However, BC1F2 progenies showed a wide variation in morphological traits, including plant height, basal branching, leaf thickness, trichome density on leaves and stem. BC1 plants were examined by genomic in-situ hybridization (GISH) to determine their chromosome constitution. All five plants were found to possess 12 strong hybridization signals upon hybridization with a FITC-labeled S. alba-specific probe. GISH studies on BC1F2 plants indicated localized signals in addition to 12 full chromosome hybridization signals, suggesting alien introgressions into B. juncea that requires further validation. The BC2 generation was found to possess half of the haploid set of alien chromosomes. The BC1F2 and BC2 generations were further screened against A. Brassiceae and found to be resistant/tolerant.

Factors affecting DH plants in vitro production from microspores of European radish.

Over the recent years the market demand for scaling up the production of European radish (Raphanus sativus L.) varieties and hybrids for open and protected production, varying in ripeness group, root shape and color, has drastically increased. Therefore, the expansion of genetic diversity and acceleration of the selection process are important. Doubled haploid technology considerably curtails the time required for creation of homozygous constant parental cell lines when in vitro microspore culture is used as the most promising method. For the first time, we were able to realize the full production cycle of DH plants of European radish by in vitro microspore culture up to inclusion of the produced material into the selection process. We have selected: preferable flower bud size, heat shock parameters, induction and regeneration media. It was revealed that linear length on the flower buds with the best possible stage of microspore development is genotype-specific: the flower bud length 2.8–3.3 mm is optimal for accessions of Rhodes and 3.7–4.2 mm is optimal for accessions of Teplichny Gribovsky. Heat shock at 32 °C for 48 hours is the most suitable for most genotypes. For the first time Murashige and Skoog based culture medium has been used for embryogenesis induction, and a major dependence of embryogenesis induction on the genotype × medium interaction was found. At regeneration and tiller stage it is advisable to add 1 mg/mL of benzylaminopurine and 0.1 mg/L of gibberellic acid to the medium, and rotting of micro-sprouts is performed with the use of hormone-free medium. Analysis of the produced regenerant plants by chromosome count and cell nucleus flow cytometry showed that 69 % of plants have a diploid chromosome set, 9 % have a haploid chromosome set, and 22 % have mixoploids and aneuploids chromosome sets. The seed progeny from doubled haploids and mixoploids were obtained by self-pollination, where all R1 plants had a doubled set of chromosomes. This study launches the development of an efficient method of radish doubled haploid production to be used in the selection process.

Chromosome evolution in the cosmopolitan genus Lycium (Solanaceae)

AbstractLycium is the only member of tribe Lycieae (Solanoideae, Solanaceae), and it has a cosmopolitan distribution with its greatest diversity in southern South America, southern Africa, and southwestern North America. To date, there has been no attempt to synthesize and evaluate the significance of the available cytogenetical data from a phylogenetic perspective, which is the objective of this study. Firstly, new data on 27 taxa from all its range of distribution (FISH in all of them, banding in 23, Feulgen technique in 14) were provided to fill gaps in the information. The chromosome numbers of L. australe, L. humile, and L. repens were recorded for the first time. Species showed x = 12 with different ploidy levels (mostly diploid or tetraploid), small chromosomes, and symmetrical karyotypes. Lycium fremontii and L. repens were outstanding for having the highest numbers reported for the genus: 10x and 11x, respectively. North American species showed comparatively longer chromosomes. Secondly, cytogenetical traits were mapped on a phylogenetic tree, using character mapping and ancestral states reconstruction, to understand the dynamics of the evolutionary changes. The main cytotaxonomical features were included: chromosome number, presence of polyploidy, total length of the haploid chromosome set, mean chromosome length, karyotype formula, A1 and A2 asymmetry indices, percentage of heterochromatin, number of CMA+/DAPI− NORs bands, and number and position of 5S and 18S‐5.8S‐26S sites. The mean chromosome length, total haploid chromosome length, number of 18S‐5.8S‐26S loci, number of CMA+/DAPI− NORs bands underwent comparatively few transitions compared with the ploidy level and number of 5S loci. The mapping of the characters on the phylogenetic tree showed that the most probable ancestral chromosome number was 2n = 24 with several independent polyploidization events and one pair of each rDNA locus. The most likely ancestral condition for the genus would be: diploid, with small chromosomes, scarce heterochromatin, asynteny of rDNA loci, and one pair of both 18S‐5.8S‐26S and 5S loci.

Characteristics of Mitotic Chromosomes of Rapana venosa (Valenciennes, 1846) (Gastropoda, Muricidae)

Predatory gastropod mollusk Rapana venosa (Valenciennes, 1846) was brought from the Sea of Japan to the Black Sea; it has spread in lots of areas of the World Ocean. The article presents a description of the karyotype in embryonic cells. There are 70 chromosomes in rapa whelk karyotype belonging to the following three morphological groups: metacentric (32), submetacentric (36), and subtelocentric (2) chromosomes, which are from 1.499 ± 0.019 to 5.575 ± 0.125 μm in length. The length of the haploid chromosome set is 100.783 μm. Multiple type of crossing provides high genetic diversity of R. venosa that explains the adaptive capabilities of the species reproductive strategy and its eurybioticity.