Chromosomes 2n Research Articles

Chromosome-scale genome assembly of three-spotted seahorse (Hippocampus trimaculatus) with a unique karyotype

Three-spotted seahorse (Hippocampi trimaculata) is a unique fish with important economic and medicinal values, and its total chromosome number is potentially quite different from other seahorse species. Herein, we constructed a chromosome-level genome assembly for this special seahorse by integration of MGI short-read, PacBio HiFi long-read and Hi-C sequencing techniques. A 416.57-Mb haplotypic genome assembly was obtained. Subsequently, 99.38% of its scaffold sequences were anchored onto 18 chromosomes, with identification of 29.1% repeat sequences in the assembled genome. Additional karyotype analysis validated the diploid chromosomes of 2n = 36, which are remarkably different from other seahorses’ 2n = 42 or 44. The genome completeness (BUSCO score: 96.5%, CEGMA score: 97.87%) confirmed that this chromosome-scale assembly is indeed of high quality. Moreover, a total of 18,712 protein-coding genes were annotated, of which 96.36% could be predicted with functions. Based on construction of a phylogenetic tree, we estimated that Hippocampus and Syngnathoides diverged approximately 50.1 million years ago (Mya). Taken together, our genome data presented in this study provide a valuable genetic resource for numerical chromosome changes and in-depth evolutionary and functional investigations, as well as conservation and molecular breeding of this endangered teleost.

Rapid Sex Identification in Spotted Knifejaw (Oplegnathus punctatus) Using tmem88 Gene Structural Variation Markers.

Spotted knifejaw (Oplegnathus punctatus) is an economically important marine cultured species exhibiting a unique complex sex chromosome system (X1X1X2X2 in females and X1X2Y in males), with males possessing one fewer chromosome (2n = 47) than females (2n = 48) and an abnormally large Y chromosome. Additionally, males demonstrate significant growth advantages over females. Rapid and accurate sex identification is essential for effective culture management, selective breeding, and population control. In this study, we identified a homologous region of the tmem88 gene containing large DNA insertion markers on the X and Y chromosomes through whole-genome sequencing of O. punctatus. The X1 chromosome harbors a 278bp DNA fragment, whereas the Y chromosome contains a 1472bp fragment, resulting in a 1194bp size difference indicative of structural variation in the non-coding region of the tmem88 gene. We developed a rapid detection method based on this variation, utilizing a pair of primers that amplify two distinct bands (278bp and 1472bp) in male (X1X2Y) individuals and a single 278bp band in female (X1X1X2X2) individuals when analyzed by agarose gel electrophoresis. This method enables efficient and accurate sex differentiation in O. punctatus, significantly reducing the time required for identification and enhancing detection efficiency. This study provides a valuable tool for the rapid identification of sex in O. punctatus, facilitating improved breeding strategies and supporting the large-scale production of high-quality fry.

Chromosome-level genome assembly of the Australian rainforest tree Rhodamnia argentea (malletwood).

Myrtaceae are a large family of woody plants, including hundreds that are currently under threat from the global spread of a fungal pathogen, Austropuccinia psidii (G.Winter) Beenken, which causes myrtle rust. A reference genome for the Australian native rainforest tree Rhodamnia argentea Benth. (malletwood) was assembled from Oxford Nanopore Technologies (ONT) long-reads, 10x Genomics Chromium linked-reads, and Hi-C data (N50 = 32.3 Mbp and BUSCO completeness 98.0%) with 99.0% of the 347 Mbp assembly anchored to 11 chromosomes (2n = 22). The R. argentea genome will inform conservation efforts for Myrtaceae species threatened by myrtle rust, against which it shows variable resistance. We observed contamination in the sequencing data and further investigation revealed an arthropod source. This study emphasises the importance of checking sequencing data for contamination, especially when working with non-model organisms. It also enhances our understanding of a tree that faces conservation challenges, contributing to broader biodiversity initiatives.

Karyotype and molecular genetic differentiation of a 24-chromosomal form of the gray hamster <i>Nothocricetulus migratorius</i> from the Tien Shan

The widespread Palaearctic rodent species gray hamster Nothocricetulus migratorius has a karyotype with a stable number of chromosomes 2n = 22 throughout the entire range of its habitat. We found gray hamsters with diploid number of chromosomes 2n = 24 locally distributed in the Qurama Ridge of the Tyan Shan. A new karyotype and analysis of G- and NORs-bands of differentially stained chromosome sets were described for the first time. The described karyotype differs from the 22-chromosomal karyotype of gray hamsters by the Y-chromosome morphology and the presence of an additional pair of heteromorphic small chromosomes. Molecular genetic analysis revealed genetic divergence of 24- and 22-chromosomal forms of N. migratorius, and the differences between them in mitochondrial markers are comparable, and in nuclear markers exceed the differences between C. barabensis (2n = 20) and C. psevdogriseus (2n = 24). The data obtained give grounds to discuss the taxonomic status of the 24-chromosomal form of gray hamsters from the Qurama Ridge and consider the differentiation of N. migratorius karyomorphs as a stage of chromosomal speciation.

What is the True Karyotype of <i>Bufotes latastii</i> (Amphibia, Anura, Bufonidae)?

The karyotype is one of the most important characteristics of an animal species and can be very useful for identifying taxa. The chromosome sets of the West Himalayan endemic Ladakh toad, Bufotes latastii, were previously described in several papers, but differed greatly from each other. To deal with these contradictions, we re-examined the karyotype of B. latastii from India and compared it with the sets of chromosomes of the most morphologically similar toad species inhabiting East Asia. It turned out that the diploid set of B. latastii consists of 22 chromosomes (2n = 22; NF = 44), of which six pairs are large and five are small. As a rule, the 4th, 5th, and 7th pairs of chromosomes are submetacentric and all the others are metacentric. The chromosomal formula is 2n = 16 m + + 6 sm = 22. The nucleolar organizers (NOR) in B. latastii are located on the long arms of submetacentric chromosomes of the 5th pair, which greatly distinguishes this species from most diploid species of the genus Bufotes. Karyotypes of two other studied species (Duttaphrynus stomaticus and Strauchbufo raddei), which can be morphologically similar to B. latastii, also consist of 22 chromosomes (2n = 22; NF = 44) of which six pairs are large and five are small, but there is only a pair of submetacentric chromosomes (2n = 20 m + 2 sm = 22). The most notable differences between these three species were in the position of NORs. In B. latastii they were located in the telomeric region of the long arm of the 5th pair, in D. stomaticus in the submedial region of the short arm of the 7th pair, and in S. raddei in the telomeric region of the short arm of the 4th pair. Discriminant analyses of the relative length of chromosomes and centromeric indices also revealed significant differences between the karyotypes of these three species. Our study made it possible to clearly distinguish B. latastii from D. stomaticus and S. raddei by karyotype characteristics. This may be important if it is necessary to identify East Asian morphologically similar toad species.

Genus Zingiber: A Review on Botanical, Major Bioactivities and Genetic Diversity

Zingiberaceae is a perennial plant family that is found across the tropics, particularly in Southeast Asia from low land to hill forests. In Peninsular Malaysia, it is believed that 160 ginger species are widely distributed belonging to 18 genera. Most of the Zingiber species in Peninsular Malaysia are less investigated and less understood taxonomically, thus remaining as under-utilized crops. The description of their morphologies in parallel with phytochemicals and molecular information are crucial to provide valuable information for further discovery of potent compounds, identification of potential new sources of genetic variation, as well as to provide insight into the domestication and breeding of ginger. The majority of Zingiber species are perennial herbs with a fragrant scent, an upright stem, and a fibrous rhizome. The presence of volatile components such as monoterpenoids, sesquiterpenes, sesquiterpenoids and some non-volatile compounds like gingerols, shagaols, and zingerone have contributed to the strong scent of the ginger oils. Among the dominant components of Zingiber are α-zingiberene, geranial, neral, camphene, neral, neric acid, α-curcumene, and zerumbone. The crude extracts and essential oils of Zingiber have proven to show some biological activities such as antimicrobial, anti-bacterial, insecticidal, larvicidal, anti-cancer, anti-inflammatory, anti-ulceration, antioxidant, anti-fungal, immunomodulatory, and anti-nociceptive. Most Zingiber species are known to have 22 somatic chromosomes (2n=22) which is the lowest among genera in Zingiberaceae. This study underscores the crucial significance of breeding programs and germplasm conservation, specifically emphasizing the potential of common ginger as a prominent contributor.

Unfurling an improved method for visualizing mitotic chromosomes in ferns.

Cytotaxonomy employs chromosome visualization to study organismal relationships and evolution. Despite the critical value of cytogenetic data, cytotypes are lacking for many plant groups. Here, we present an improved approach for visualizing mitotic chromosomes in ferns, a key lineage of land plants, using the dividing cells of unfurling croziers (fiddleheads). Our modified mitotic chromosome preparation incorporates a brief pectinase-cellulase pretreatment, as well as colchicine fixation and the Feulgen reaction to improve the staining and separation of mitotic chromosomes. To demonstrate this easy and efficient assessment, we determined the sporophytic (2n) chromosome number for three fern species: Cheilanthes mollis (2n = 60), Cheilanthes hypoleuca (2n = 120), and Nephrolepis cordifolia (2n = 82). The new method presented here improves visualizations of mitotic chromosomes from the dividing nuclei of young fern croziers. Fiddleheads are widely accessible in nature and in living collections worldwide, and this modified approach increases their suitability for fern cytotaxonomic studies.

Chromosome Analysis of Dendrobium stockelbuschii and Dendrobium sylvanum Orchids

Abstract Dendrobium stockelbuschii and Dendrobium sylvanum orchids are in great demand in Indonesia because of their uniqueness. Plant breeders keep trying to breed this orchid to maintain its uniqueness. Cytological information of D. stockelbuschii and D. sylvanum helps plant breeders in the breeding process. This research aims to determine the cytological characteristics such as chromosome number, size, shape, and karyotype. This study was conducted at the Plant Breeding Laboratory, Faculty of Agriculture, Sebelas Maret University. Data analysis was carried out descriptively based on chromosome observations. The results show that both orchid species have several chromosomes 2n = 38. The average chromosome length in D. stockelbuschii was 1.84 ± 0.52 μm to 2.05 ± 0.54 μm and in D. sylvanum was 2.32 ± 0.64 μm to 2.60 ± 0.68 μm. D. stockelbuschii and D. sylvanum had an average karyotype pattern of 2n = 2x = 38 = 18m + 1sm. The intrachromosomal asymmetry index (A1) value in both species tends to be metacentric, while the interchromosomal asymmetry index (A2) value in all species shows relatively tiny deviations in chromosome size.

Major chromosome rearrangements in intergeneric wheat × rye hybrids in compatible and incompatible crosses detected by GBS read coverage analysis

The presence of incompatibility alleles in primary amphidiploids constitutes a reproductive barrier in newly synthesized wheat-rye hybrids. To overcome this barrier, the genome stabilization process includes large-scale chromosome rearrangements. In incompatible crosses resulting in fertile amphidiploids, the elimination of one of the incompatible alleles Eml-A1 or Eml-R1b can occur already in the somatic tissue of the wheat × rye hybrid embryo. We observed that the interaction of incompatible loci Eml-A1 of wheat and Eml-R1b of rye after overcoming embryo lethality leads to hybrid sterility in primary triticale. During subsequent seed reproductions (R1, R2 or R3) most of the chromosomes of A, B, D and R subgenomes undergo rearrangement or eliminations to increase the fertility of the amphidiploid by natural selection. Genotyping-by-sequencing (GBS) coverage analysis showed that improved fertility is associated with the elimination of entire and partial chromosomes carrying factors that either cause the disruption of plant development in hybrid plants or lead to the restoration of the euploid number of chromosomes (2n = 56) in the absence of one of the incompatible alleles. Highly fertile offspring obtained in compatible and incompatible crosses can be successfully adapted for the production of triticale pre-breeding stocks.

Comparison of haracteristics of the karyotype and meiosis of cryptic forms of the viviparous lizard Zootoca vivipara and species of the closely related genus Takydromus (Squamata: Lacertidae)

Characteristics of the karyotype and early meiosis of two males of the cryptic “western” form of the viviparous lizard (Zootoca vivipara Lichtenstein, 1823) (genus Zootoca Wagler, 1830) with multiple sex chromosomes (female Z1Z2W/Z1Z1Z2Z2 male) were examined. The data obtained were compared with 1) those of the males of the same cryptic form from other locality, with 2) those of the males of other cryptic form also possessing the multiple sex chromosomes and with 3) those of the species of closely related genus Takydromus Daudin, 1802 with simple sex chromosomes, ZW/ZZ. Multiple sex chromosomes may influence meiosis and play a role in isolation. The males of cryptic western form of Z. vivipara studied revealed the karyotype with 36 acrocentric chromosomes (2n=36A). In early meiosis the spreading of synaptonemal complexes (SC) of the bivalents of these males were obtained and analyzed. Eighteen SC were observed, including SC of the Z1Z1 (pair 6) sex chromosomes. Characteristics of SC are compared with the number and the shape of bivalents and chromosomes at the diakinesis and metaphase 11 stages of the meiosis of the males from other population and with those in the other cryptic Russian form of the species. Comparative analysis of two cryptic forms has demonstrated some differences in the morphology of SC Z1Z1 sex chromosomes at the early stages of prophase 1 of meiosis (the late zygotena – the middle pachytene stages). However both the SC of sex chromosomes and SC of all remained chromosomes were fully synapted. All 18 bivalents were regular segregated forming haploid spermatocyte II with18 chromosomes, including two sex chromosomes (n=8, Z1Z2) Thus characteristics of karyotype and early meiosis of the males of western form belonging to different localities are fully coincident with those of Russian cryptic forms of Z. vivipara with multiple sex chromosomes as well. However, these features were differed from those for the species of the closely related genus Takydromus with simple sex chromosome system (ZW) where some disturbances in the course of mitoses and meiosis were observed. The results are in agreement with those suggested previously about the genomic factor(s) stabilizing the meiosis and the maintenance of multiple sex chromosome in the different cryptic forms of complex Z. vivipara.

A haplotype-like, chromosome-level assembled and annotated genome of Biomphalaria glabrata, an important intermediate host of schistosomiasis and the best studied model of schistosomiasis vector snails.

Schistosomiasis is one of the world's most devastating parasitic diseases, afflicting 251 million people globally. The Neotropical snail Biomphalaria glabrata is an important intermediate host of the human blood fluke Schistosoma mansoni and a predominant model for schistosomiasis research. To fully exploit this model snail for biomedical research, here we report a haplotype-like, chromosome-level assembled and annotated genome of the homozygous iM line of B. glabrata that we developed at the University of New Mexico. Using multiple sequencing platforms, including Illumina, PacBio, and Omni-C sequencing, 18 sequence contact matrices representing 18 haploid chromosomes (2n = 36) were generated (337x genome coverage), and 96.5% of the scaffold sequences were anchored to the 18 chromosomes. Protein-coding genes (n = 34,559), non-coding RNAs (n = 2,406), and repetitive elements (42.52% of the genome) were predicted for the whole genome, and detailed annotations for individual chromosomes were also provided. Using this genomic resource, we have investigated the genomic structure and organization of the Toll-like receptor (TLR) and fibrinogen-domain containing protein (FReD) genes, the two important immune-related gene families. Notably, TLR-like genes are scattered on 13 chromosomes. In contrast, almost all (39 of 40) fibrinogen-related genes (FREPs) (immunoglobulin superfamily (IgSF) + fibrinogen (FBG)) are clustered within a 5-million nucleotide region on chromosome 13, yielding insight into mechanisms involved in the diversification of FREPs. This is the first genome of schistosomiasis vector snails that has been assembled at the chromosome level, annotated, and analyzed. It serves as a valuable resource for a deeper understanding of the biology of vector snails, especially Biomphalaria snails.

Chromosome-level genome assembly of Oncomelania hupensis: the intermediate snail host of Schistosoma japonicum

BackgroundSchistosoma japonicum is a parasitic flatworm that causes human schistosomiasis, which is a significant cause of morbidity in China, the Philippines and Indonesia. Oncomelania hupensis (Gastropoda: Pomatiopsidae) is the unique intermediate host of S. japonicum. A complete genome sequence of O. hupensis will enable the fundamental understanding of snail biology as well as its co-evolution with the S. japonicum parasite. Assembling a high-quality reference genome of O. hupehensis will provide data for further research on the snail biology and controlling the spread of S. japonicum.MethodsThe draft genome was de novo assembly using the long-read sequencing technology (PacBio Sequel II) and corrected with Illumina sequencing data. Then, using Hi-C sequencing data, the genome was assembled at the chromosomal level. CAFE was used to do analysis of contraction and expansion of the gene family and CodeML module in PAML was used for positive selection analysis in protein coding sequences.ResultsA total length of 1.46 Gb high-quality O. hupensis genome with 17 unique full-length chromosomes (2n = 34) of the individual including a contig N50 of 1.35 Mb and a scaffold N50 of 75.08 Mb. Additionally, 95.03% of these contig sequences were anchored in 17 chromosomes. After scanning the assembled genome, a total of 30,604 protein-coding genes were predicted. Among them, 86.67% were functionally annotated. Further phylogenetic analysis revealed that O. hupensis was separated from a common ancestor of Pomacea canaliculata and Bellamya purificata approximately 170 million years ago. Comparing the genome of O. hupensis with its most recent common ancestor, it showed 266 significantly expanded and 58 significantly contracted gene families (P < 0.05). Functional enrichment of the expanded gene families indicated that they were mainly involved with intracellular, DNA-mediated transposition, DNA integration and transposase activity.ConclusionsIntegrated use of multiple sequencing technologies, we have successfully constructed the genome at the chromosomal-level of O. hupensis. These data will not only provide the compressive genomic information, but also benefit future work on population genetics of this snail as well as evolutional studies between S. japonicum and the snail host.Graphical

Estudos anatômicos, cariotípicos e de conteúdo de DNA nuclear em quatro morfotipos de alface silvestre

ABSTRACT Wild lettuce (Lactuca aff. canadensis L.), belonging to the Asteraceae family, occurs subspontaneously in Brazil and may originate from Africa, Asia, Europe and North America. Popularly known as Canada lettuce, it is an unconventional leafy vegetable. Studies on this species are scarce in Brazil, and its scientific name is debated among experts. It has high morphological variability and controversial botanical classification. This study characterized the stomata, organized the karyotype, and determined the nuclear DNA content of four morphotypes of wild lettuce to facilitate correct classification. The genetic material used was acquired from the non-conventional vegetable germplasm in UFLA. The leaves of wild lettuce morphotypes are hypoamphiestomatic with a greater number of stomata in the abaxial epidermis. There were similarities between the morphotypes (green and purple) and between the smooth purple types (narrow leaf and broad leaf) for the number and size of stomata. No variation was found in the number of chromosomes (2n = 18) or DNA content among the four morphotypes. The separation of the morphotypes of wild lettuce did not match the morphological classification or the karyological data. The four morphotypes evaluated were placed under the same species, and the results obtained when compared to other studies led us to infer that the four morphotypes of wild Lactuca belonged to the species L. indica and not L. canadensis as previously assumed. Further investigation may provide insights into the evolutionary history of this species.

Characteristics of the karyotype of Ukrainian buffalos

The article presents the results of studying the karyotype of the Ukrainian buffalo population. With the help of routine and GTG methods of analysis of metaphase plates of chromosomes, it was established that in the studied animals the diploid chromosome set was equal to fifty chromosomes (2n=50), which consisted of 5 pairs of meta- and submetacentric and 19 pairs of acrocentric autosomes and one pair (XX) or (XY) sex chromosomes. The total number of chromosome arms (FN) was 60, which correspond to animals of the water buffalo species (Bubalus bubalis), a subspecies of the river buffalo (B. b. Bubalis). Cytogenetic control revealed wide intraspecies limits of spontaneous somatic mutagenesis: absence of constitutive chromosomal disorders; the frequency of metaphases with aneuploidy, the average value (M±m) of which was equal to 10.5±0.13%, polyploidy (M±m=0.7±0.25%), asynchronous separation of the centromeric regions of chromosomes - (M±m=5.3±2.00), chromosomal breaks (M±m=0.7±0.24%), the proportion of cells with micronuclei (M±m=2.5±0.39‰), binucleated cells (M±m=2.6±0.32‰) and mitotic index (M±m=4.8±0.65‰). It has been established that Ukrainian river buffaloes are characterized by high karyotype stability.

Chromosomal dynamics in Senna: comparative PLOP-FISH analysis of tandem repeats and flow cytometric nuclear genome size estimations.

Tandem repeats (TRs) occur abundantly in plant genomes. They play essential roles that affect genome organization and evolution by inducing or generating chromosomal rearrangements such as duplications, deletions, inversions, and translocations. These impact gene expression and chromosome structure and even contribute to the emergence of new species. We investigated the effects of TRs on speciation in Senna genus by performing a comparative analysis using fluorescence in situ hybridization (FISH) with S. tora-specific TR probes. We examined the chromosomal distribution of these TRs and compared the genome sizes of seven Senna species (estimated using flow cytometry) to better understand their evolutionary relationships. Two (StoTR03_159 and StoTR04_55) of the nine studied TRs were not detected in any of the seven Senna species, whereas the remaining seven were found in all or some species with patterns that were similar to or contrasted with those of S. tora. Of these studies species, only S. angulata showed significant genome rearrangements and dysploid karyotypes resembling those of S. tora. The genome sizes varied among these species and did not positively correlate with chromosome number. Notably, S. angulata had the fewest chromosomes (2n = 22) but a relatively large genome size. These findings reveal the dynamics of TRs and provide a cytogenetic depiction of chromosomal rearrangements during speciation in Senna. To further elucidate the dynamics of repeat sequences in Senna, future studies must include related species and extensive repeatomic studies, including those on transposable elements.

Whole-genome sequencing and comparative genomics reveal the potential pathogenic mechanism of Neoscytalidium dimidiatum on pitaya

ABSTRACT Neoscytalidium dimidiatum (class Dothideomycetes ) is a fungus responsible for canker disease in pitaya stems and fruits, leading to significant economic losses. However, little is known about the pathogenesis, family evolution, and genetic variants of this species. In this study, we report a high-quality genome sequence of N. dimidiatum based on the Nanopore sequencing technology platform for sequencing and Hi-C assembly technology for genome assembly. The genome contains 12 chromosomes (2 n = 2× = 12; diploid), with a sequencing depth of 186.1×, encoding 12,349 proteins. Molecular phylogenetic analysis showed that N. dimidiatum is evolutionarily close to Botryosphaeria dothidea . Compared to other fungi, the N. dimidiatum genome contains many carbohydrate-active enzymes and secondary metabolites. Additionally, we predict that N. dimidiatum contains 121 candidate effectors that may play important roles in infection and colonization, promoting pathogenicity in pitaya. Nine of these effectors were confirmed to contain signal peptides and inhibit BAX/INF1-induced necrosis in Nicotiana benthamiana , demonstrating their importance during infection. Finally, we also confirm that N. dimidiatum does not form an appressorium or infection thread but instead infects pitaya via open stomata. In conclusion, the results provide a foundation for future research on N. dimidiatum and the control of pitaya canker. IMPORTANCE Pitaya canker is a significant disease in the pitaya industry in China, causing significant economic losses. Therefore, systematic research on Neoscytalidium dimidiatum , the fungus implicated in pitaya canker, is essential for comprehending the pathogenesis of this disease and developing effective control strategies. We applied comparative genomics to reveal the genetic evolution, metabolic diversity, environmental adaptation, and pathogenicity of N. dimidiatum , providing ideal targets for studies of pathogenesis and molecular targets for fungicide development. Moreover, the systematic study of the N. dimidiatum growth cycle, morphological characteristics, and molecular phylogenetic analysis can promote a comprehensive understanding of its genetic basis.

Chenopodium ucrainicum (Amaranthaceae), a new ‘BB’ genome diploid species: karyological, cytological, and molecular evidence

Abstract In 2020, S. Mosyakin and B. Mandák described a new species from the Chenopodium album aggregate, C. ucrainicum. The description of the species was based mainly on its distinct morphological characters. This study aims to improve our understanding of C. ucrainicum by combining karyological, cytological, molecular, and distribution information. All analyses demonstrated that C. ucrainicum is closely related to C. ficifolium and C. suecicum, the species with the ‘BB’ subgenome. It has the same diploid number of chromosomes (2n = 2x = 18), has very similar genome size (mean ± SD, 1.865 ± 0.026 pg), and is included in the same haplogroup together with polyploid species with the subgenome combination ‘BBDD’. Nevertheless, the haplotype of C. ucrainicum is unique and is not shared with any known closely related species, indicating that the species is very well delimited from other related taxa. A similar result was obtained by RAD-seq data. This finding is particularly significant because species with the ‘BB’ genome played an integral part in the evolution of several allopolyploid taxa, some of which are widespread weeds (C. album s.s., C. berlandieri) or economically important species (C. quinoa). Morphologically, the closest species remains C. suecicum, which is, however, very well genetically differentiated.

Induced Tetraploidy in the African Catfish, &lt;i&gt;Clarias anguillaris&lt;/i&gt;

Tetraploidy was successfully induced in Clarias anguillaris. Hatchability in tetraploids ranged between 50% and 70%, and above 95% in diploid control. About 80% and 100% of the tetraploid and diploid fry survived in the first seven days, respectively. Tetraploids showed better growth performance (12.61 g) but not significant compared to 11.2 g for the diploid. Metaphase chromosome complement of tetraploid was 108 and diploid was 54. About 20% of cells in tetraploid preparation showed 3n and 2n chromosome complements. About 1% phenotypic abnormalities were recorded after hatching in tetraploid but absent in the control.

Collectible Cell Lines of Larix sibirica Obtained by Somatic Embryogenesis and Their Ability to Regenerate

A protocol for the cultivation of Larix sibirica Ledeb. by somatic embryogenesis was developed (RF Patent No. 2456344, 2012). The L. sibirica collection consisted of 22 actively proliferating cell lines (CLs) obtained from immature zygotic embryos. The age of CLs ranged from 1 to 14 years. CLs differed in their growth intensity, embryonic productivity, hormonal balance, and genetic stability, as well as in their regenerative ability. In most proliferating CLs, the formation of globular somatic embryos continued for 2–4 years. Here, a number of CLs actively proliferated for 9–14 years or more. The formation of embryogenic cultures in L. sibirica is associated with the content of phytohormones and their localization in embryo cells. The cytogenetic studies revealed the genetic stability of young CLs (up to 1 year), in which the karyotype consisted of the diploid number of chromosomes (2n = 24). Genomic mutations were observed in the long-term proliferation of CLs. Individual CLs can maintain cytogenetic stability for many years; such CLs can successfully be used to preserve germplasm, obtain planting material, and for plantation reforestation.

Karyomorphology of two subspecies of Anthemis maritima (Asteraceae) from Algeria

The chromosome number and karyomorphology of two subspecies of the Anthemis maritima complex collected from two different coastal localities in the Skikda region (northeastern Algeria) are reported in this study: Anthemis maritima subsp. maritima, which is common throughout the Mediterranean, and A. maritima subsp. bolosii, a strict Algerian endemic recently rediscovered after 100 years of disappearance. The Feulgen staining method indicated that Anthemis maritima subsp. maritima is a tetraploid with 2n=4x=36 chromosomes (2n=11m+3sm+4st), and Anthemis maritima subsp. bolosii is a diploid with 2n=2x=18 chromosomes (2n=4m+3sm+2st). Both taxa have symmetrical karyotypes, 2A and 1A, respectively, according to Stebbins classification. These findings are novel for both the subspecies Anthemis maritima subsp. bolosii and the Algerian population of Anthemis maritima subsp. maritima.