Variations in heterochromatin content reveal important polymorphisms for studies of genetic improvement in garlic (Allium sativum L.)

Allium sativum L. is an herb of the Alliaceae family with a specific taste and aroma and medicinal and nutraceutical properties that are widely marketed in several countries. Brazil is one of the largest importers of garlic in the world, despite of its production is restricted and limited to internal consumption. Thus, explore the genetic diversity of commercial garlic conserved at germplasm banks is essential to generate additional genetic information about its economically important crop. A suitable tool for this purpose is the cytogenetic characterisation of these accessions. This study aimed to characterise the cytogenetic diversity among seven accessions of garlic from a Germplasm Bank in Brazil. The karyotypes were obtained by conventional staining and with chromomycin A3 (CMA) and 4,6-diamidino-2-phenylindole (DAPI) fluorochromes. All accessions analysed showed chromosome number 2n = 16, karyotype formula 6M+2SM, symmetrical karyotypes, reticulate interphase nuclei, and chromosomes with uniform chromatin condensation from prophase to metaphase. The fluorochromes staining showed differences in the amount and distribution of heterochromatin along the chromosomes and between accessions studied. Based on the distribution pattern of these small polymorphisms, it was possible to separate the seven accessions into three groups. It was also possible to differentiate some of the accessions individually. One of the results obtained showed a heteromorphic distension of the nucleolar organiser region observed on the chromosome pairs 6 or 7 with peculiar characteristics. It was suggested for example, that the heteromorphic block of heterochromatin (CMA+++/DAPI-) on chromosome 6 of the “Branco Mineiro Piauí” accession can be used as a marker to identify this genotype or may be associated with some character of economic interest.

Check-list of chromosome numbers of the family Hygromiidae (Gastropoda: Stylommatophora) with new data on Circassina frutis

Chromosome number data on the Hygromiidae (Gastropoda: Stylommatophora) are summarized and reviewed briefly in the context of the phylogeny of the family. In hygromiids, the haploid chromosome numbers range from 21 to 26. It is supposed that n = 21 is the ancestral chromosome number in the family. The modal haploid number for Hygromiidae is 23. Description of karyotype in terms of chromosome number and morphology of hygromiid land snail Circassina frutis is provided for the first time. The diploid chromosome number of this species is 2n = 46. The karyotype is symmetric and consists of 21 pairs of metacentric and 2 pairs of submetacentric chromosomes. The karyotype formula is as follows: 2n = 42m + 4sm (n = 21m + 2sm). The fundamental number (FN) is 92. Chromosomes range in length from 2.53 μm for the smallest pair to 6.00 μm for the largest pair. The total length of chromosomes in diploid complement (TCL) is 170.40 ± 3.22 μm.

Comparative Cytogenetics Analysis Among Peckoltia Species (Siluriformes, Loricariidae): Insights on Karyotype Evolution and Biogeography in the Amazon Region

Peckoltia is widely distributed genus in the Amazon and Orinoco basins and the Guiana Shield, containing 18 valid species, and distinct morphotypes still needing description in the scientific literature due to its great taxonomic complexity. This study performed a comparative chromosomal analysis of two undescribed Peckoltia species (Peckoltia sp. 3 Jarumã and Peckoltia sp. 4 Caripetuba) from the Brazilian Amazon using conventional chromosome bands methods and in situ localization of the repetitive DNA (5S and 18S rRNA and U1 snRNA genes and telomeric sequences). Both species presented 2n = 52 but differed in their karyotype formula, probably due to inversions or translocations. The nucleolus organizer regions (NORs) showed distal location on a probably homeologous submetacentric pair in both species, besides an extra signal in a subtelocentric chromosome in Peckoltia sp. 4 Caripetuba. Heterochromatin occurred in large blocks, with different distributions in the species. The mapping of the 18S and 5S rDNA, and U1 snDNA showed differences in locations and number of sites. No interstitial telomeric sites were detected using the (TTAGGG)n probes. Despite 2n conservationism in Peckoltia species, the results showed variation in karyotype formulas, chromosomal bands, and locations of repetitive sites, demonstrating great chromosomal diversity. A proposal for Peckoltia karyotype evolution was inferred in this study based on the diversity of location and number of chromosomal markers analyzed. A comparative analysis with other Peckoltia karyotypes described in the literature, their biogeography patterns, and molecular phylogeny led to the hypothesis that the derived karyotype was raised in the left bank of the Amazon River.

A karyotype study in two fish species belonging to Genus Neolissochilus found in Meghalaya, India

The karyomorphological study of two species of Mahseer belonging to the genus Neolissochilus, namely Neolissochilus hexagonolepis and N. hexastichus were carried out. The study revealed the basic chromosome number in both the Masheer species was observed to be 100. However, the karyotype formula number varied among the species. N. hexagonolepis had a diploid chromosome number of 42 metacentric (m), 20 submetacentric (sm), 8 subtelocentric (st) and 30 telocentric (t) and N. hexastichus had a karyotypic formula of 32 metacentric (m), 22 submetacentric (sm), 4 subtelocentric (st) and 42 telocentric (t). This finding removed taxonomic confusion due to the differences in the chromosome number, the morphology of the chromosomes and chromosome formula between the two fish species of the genus and helped in distinctive and unblemished identification of the two species belonging to the genus Neolissochilus from Meghalaya, though they have a morphological similarity.

Measurement of Chromosomal Arms and FISH Reveal Complex Genome Architecture and Standardized Karyotype of Model Fish, Genus Carassius

The widely distributed ray-finned fish genus Carassius is very well known due to its unique biological characteristics such as polyploidy, clonality, and/or interspecies hybridization. These biological characteristics have enabled Carassius species to be successfully widespread over relatively short period of evolutionary time. Therefore, this fish model deserves to be the center of attention in the research field. Some studies have already described the Carassius karyotype, but results are inconsistent in the number of morphological categories for individual chromosomes. We investigated three focal species: Carassius auratus, C. carassius and C. gibelio with the aim to describe their standardized diploid karyotypes, and to study their evolutionary relationships using cytogenetic tools. We measured length (q+plength) of each chromosome and calculated centromeric index (i value). We found: (i) The relationship between q+plength and i value showed higher similarity of C. auratus and C. carassius. (ii) The variability of i value within each chromosome expressed by means of the first quartile (Q1) up to the third quartile (Q3) showed higher similarity of C. carassius and C. gibelio. (iii) The fluorescent in situ hybridization (FISH) analysis revealed higher similarity of C. auratus and C. gibelio. (iv) Standardized karyotype formula described using median value (Q2) showed differentiation among all investigated species: C. auratus had 24 metacentric (m), 40 submetacentric (sm), 2 subtelocentric (st), 2 acrocentric (a) and 32 telocentric (T) chromosomes (24m+40sm+2st+2a+32T) ; C. carassius: 16m+34sm+8st+42T; and C. gibelio: 16m+22sm+10st+2a+50T. (v) We developed R scripts applicable for the description of standardized karyotype for any other species. The diverse results indicated unprecedented complex genomic and chromosomal architecture in the genus Carassius probably influenced by its unique biological characteristics which make the study of evolutionary relationships more difficult than it has been originally postulated.

First Report on Nucleolar Organizer Regions (NORs) Polymorphism and Constitutive Heterochromatin of Moonlight Gourami, Trichopodus microlepis (Perciformes, Osphronemidae)

Nucleolar organizer regions (NORs) polymorphism, constitutive heterochromatin and chromosomal analysis of Moonlight gourami, Trichopodus microlepis in Thailand were firstly reported. Specimens were collected from the Chao Phraya and Mekong Basins, Thailand. The mitotic chromosomes were directly prepared from kidney tissues of ten males and ten females. Conventional staining, Ag-NOR banding and C- banding techniques were applied to stain the chromosomes. The results shown that the diploid chromosome number of T. microlepis was 2n=46 and the fundamental number (NF) was 46 in both males and females. The karyotype consisted of 46 telocentric chromosomes classifying as 14 large and 32 medium. No heteromorphic sex chromosome was observed in T. microlepis. The results also exhibited that the interstitial nucleolar organizer regions (NORs) were clearly observed at the long arm of the chromosome pair 7. This is the first report on NORs polymorphism in T. microlepis that a heteromorphic NOR type in one female had a single NOR-bearing chromosome of the chromosome pair 7, whereas 10 males and nine females had two NOR-bearing chromosomes of the chromosome pair 7 with a homomorphic NOR type. Constitutive heterochromatins located at all centromeres of all chromosome pairs. The karyotype formula of T. microlepis is 2n (46) = Lt14 + Mt32.

MORPHOLOGICAL AND CHROMOSOMAL CHARACTERIZATION OF ORCHID Peristylus goodyeroides Lindl. FROM CURUG SETAWING, KULONPROGO

Peristylus goodyeroides is a terestrial orchid that scattered around Southeast Asia. Morphological characters of P. goodyeroides can vary, depending on the ecological factors and habitat. Cytological characters in the form of chromosome configurations can be used as a taxonomic tool for the process of identifying and understanding variations in taxa. The purpose of this study was to determine the morphological characters and chromosome configuration of the P. goodyeroides from Curug Setawing, Kulonprogo. The method used was morphological characterization and plant chromosome preparation by squash method with the main steps of fixation, maceration, staining and observation. Data were analyzed with the help of Image raster 3, Corel Draw X7, and Microsoft Excel 2013. P. goodyeroides from Curug Setawing has the morphological characters of root tubers, cylindrical stems, ovate leaf shape, convolutive leaf arrangement and creamy white flowers. The orchid has a number of chromosomes 2n = 10 with a karyotype formula of 2n = 2x = 8m + 2t. Metacentric chromosomes are found on chromosomes 1-8 and telocentric chromosomes 9-10. The absolute arm length of the chromosomes has a range of 2.03-3.44 μm, the relative arm length of the chromosomes is 2.21-3.32 μm, the length of the p arm is 1.13-1.58 μm and the q arm is 1.23-2.12 μm.

Chromosome counts of eight Iranian endemic species of Nepeta L. (Lamiaceae)

In this survey, the chromosome counts of eight Nepeta L. species were investigated and the karyotypic diversity among these species was studied. The examined species belong to N. cephalotes Boiss. species group, namely N. eremokosmos Rech.f., N. gloeocephala Rech. f., cephalotes Boiss., N. pungens (Bunge) Benth., N. ispahanica Boiss., N. mahanensis Jamzad & Simonds, N. hormozganica Jamzad and N. denudata Benth. collected from different habitats in Iran. The ploidy levels, karyotype formula, chromosome length range, total karyotype length, several karyotype asymmetries values and Stebbins classification were determined in this study. Results showed the same chromosome number, 2n = 2x= 18 for all studied species. The basic chromosome number for the above mentioned species are x = 9. Also, the smallest chromosome length is 1.02 μm in N. mahanensis. The largest chromosome length is 2.3 μm in N. ispahanica. The chromosomes of species were metacentric or submetacentric. According to the Stebbins classification, these species were located into three classes 1A, 2A and 3A. The chromosome numbers for six of studied species are reported here for the first time.

First report of karyological analysis and heteromorphic nucleolar organizer region of Black Surgeonfish (Acanthurus gahhm, Acanthuridae) in Thailand

This research was the first report on karyological analysis and heteromorphic nucleolar organizer region of black surgeonfish (Acanthurus gahhm, Acanthuridae) in Thailand. The 10 male and 10 female specimens were collected from Phuket Marine Biological Center, and Phang Nga Coastal Research and Development Center, Andaman Sea, Thailand. Mitotic chromosomes were directly prepared from gill and kidney tissues. The chromosomes were stained by conventional Giemsa staining and Ag-NOR banding techniques. Results showed that the diploid chromosomes number of A. gahhm was 2n=48, the fundamental numbers (NF) was 54 in both male and female. The karyotype consist of 6 large acrocentric, 20 large telocentric, 18 medium telocentric and 4 small telocentric chromosomes. None of strange size chromosomes related to sex was found. The heteromorphic nucleolar organizer regions (NORs) were observed on telomeric short arm of first acrocentric which can defined as 1a1b. There is NOR in 1a and not in 1b. The karyotype formula of black surgeon fish was as follows: 2n (48) = La6+Lt20+Mt18+St4

Taxonomic diversity and karyology of Anthemis rigida (Anthemideae, Asteraceae) in the Aegean, Greece

This study investigates and taxonomically interprets the morphological variation of Anthemis rigida in the Aegean region (Greece). The eligulate plants are widespread and morphologically homogeneous whereas the ligulate forms are local and more variable. Based on a morphometric evaluation of 20 characters, four different ligulate subspecies are recognized; A. rigida subsp. antri-neptuni is described here as new. All taxa share the same chromosome number of 2n = 18 and are karyologically similar. The new subspecies slightly deviates in the karyotype formula, even though asymmetry indices do not discriminate among taxa in the group. Notes on the taxonomy, geographical distribution and habitat of all ligulate subspecies are provided, together with photographs and a distribution map.