The present study reports the first finding of the NOR (nucleolar organizer region) polymorphism and chromosome analysis in the John's snapper (Lutjanus johnii) from Thailand. Kidney cell samples were taken from four male and four female fish. Mitotic chromosome preparations were conducted using the standard squash technique, as well as directly from kidney cells. Metaphase spreads were performed on microscopic slides and then air-dried. Conventional and Ag-NOR banding techniques were applied to stain the chromosome. The results showed that the diploid chromosome number of L. johnii was 2n=48, and the fundamental number (NF) was 48 in both male and female. Karyotpes were present as 28 large telocentric, 16 medium telocentric, and 4 small telocentric chromosomes. No strange-sized chromosomes related to sex were observed. The results indicated that the long arm subcentromeric of the telocentric chromosome pair 1 showed clearly observable NORs (satellite chromosomes). In addition, a heteromorphism of one female had different-sized NORs in chromosome pair 1 (1a1b), while three females and four males had equal-sized NORs in chromosome pair 1 with a homomorphism (1a1a). The karyotype formula for L. johnii is as follows: 2n (diploid) 48=Lt28+Mt16+St4
The standardized karyotype and idiogram of the titan triggerfish, Balistoides viridescens (Bloch & Schneider 1801) from Phuket Province, Thailand, were obtained from the present study. Kidney cell samples were taken from five male and five female fish. The mitotic chromosome preparations were conducted directly from the kidney cells. Conventional staining and Ag-NOR banding techniques were applied to stain the chromosomes. The results indicated that the diploid chromosome number of B. viridescens was 2n=44, and the fundamental number (NF) was 60 in both sexes. The chromosome types consist of 2 large metacentric, 4 large acrocentric, 2 large telocentric, 8 medium acrocentric, 10 medium telocentric, 2 small acrocentric, and 16 small telocentric chromosomes. No strange-sized chromosomes related to sex was observed. The region adjacent to the subtelomeric of short arm of chromosome pair 3 showed clearly observable secondary constriction/NORs. The karyotype formula for B. viridescens is as follows: 2n (diploid) 44=Lm2+La4+Lt2+Ma8+Mt10+Sa2+St16
This is the first karyological analysis of the hoary bamboo rat (Rhizomys pruinosus) from the Nongbualamphu, Nongkhai, and Loei Provinces in northeast Thailand. Conventional staining, GTG-, CBG-, and Ag-NOR banding, and high-resolution analysis were carried out on standard whole blood T-lymphocyte cultures from six specimens of R. pruinosus from three localities. The results showed that 2n=50 and the fundamental number is 100 in both sexes. The autosomes consisted of 12 large acrocentric, 4 medium submetacentric, 6 medium acrocentric, 6 small metacentric, and 20 small acrocentric chromosomes. The X chromosome is the largest metacentric chromosome, while the Y chromosome is a small acrocentric chromosome. A multiple sex chromosome system of the X1Y,X2Y/X1X2 type was found in R. pruinosus, which is the first description in the subfamily Rhizomyinae. From GTG-banding and high-resolution techniques, the numbers of bands and locations in R. pruinosus are determined to be 234 and 280, respectively, and each chromosome pair could be clearly differentiated. CBG-banding shows C-positive (dark band) on the centromere of all autosomes. However, C-negative (light band) was observed on the Y chromosome. The results demonstrated that chromosome pair 3 had an interstitial large band on the long arm near the telomere. In addition, the short arms near the telomere of chromosome pairs 4, 7, and 10 had clear nucleolar organizer regions (NORs). This is the first report on the natural polymorphism of NORs in bamboo rats, and it indicates the presence of heteromorphism of chromosome pair 10 (10a10b) in all males and females. There are NORs in 10b, but not in 10a.
We evaluated the genome structure and salt stress response of BC1F6 lines derived from a cross between an Iranian salt tolerant bread wheat cultivar ‘Roushan’ (2n=6x=42, AABBDD) and a synthetic allohexaploid Tritipyrum (2n=6x=42, AABBEbEb). Sixteen lines (L1 to L16) and their parents were studied for their chromosome composition, K+ : Na+ ratio, and relative dry mass (RDM) by growing them in nutrient solution containing 0 (control) or 100 mM NaCl (treatment). Among the studied lines, eight wheat—Thinopyrum bessarabicum (Eb genome) disomic substitution lines were identified using PCR-based Landmark Unique Gene (PLUG) markers and cytogenetic analysis. Ten (37%) of 27 PLUG markers used were informative for Eb chromosomes 1, 2, 3, 4, and 6 in a wheat background. PLUG markers also revealed that one line, L9, was a disomic substitution line DS2Eb(2B), and that seven lines, L3, L4, L7, L8, L14, L15, and L16, were DS6Eb(6D). There were large differences in morphological traits and salinity tolerance even among DS6Eb(6D) substitutions or untranslocated lines, due perhaps to unidentified rearrangements or small introgressions.
Nigella damascena has 2n=12 chromosomes composed of five long metacentric chromosome pairs and a short telocentric chromosome pair. FISH using rDNA probes was applied on the chromosomes of this species. 45S rDNA were located at the terminal region of three pairs of long metacentric chromosomes and a pair of short chromosomes. 5S rDNA appeared at the interstitial regions of the short arm of two long metacentric chromosomes.
The present paper deals with meiotic studies on 31 populations covering nine species belonging to three genera of the family Caesalpiniaceae from different geographical areas of the Western Himalayas. Variable chromosome number reports for Cassia demidiata (2n=32) and C. mimosoides var. wallichiana (2n=32) world-wide and Caesalpinia decapetala (2n=22) in India have been added to the previous reports of these species. The course of meiosis varies from normal to abnormal in different populations of three species: Caesalpinia decapetala, Cassia fistula, and C. occidentalis. Meiotic abnormalities are in the form of cytomixis, chromosomal stickiness, and formation of laggards and bridges, all resulting in abnormal microsporogenesis. Heterogenously sized fertile pollen grains and reduced reproductive potentialities have invariably been observed in all the meiotically abnormal populations.
Four released varieties of Lablab purpureus L. from Bangladesh Agriculture Research Institute (BARI), viz. BARI Sheem-1, BARI Sheem-2, BARI Sheem-5, and BARI Sheem-6, were characterized by differential karyotype and RAPD analysis. 2n=22 metacentric chromosomes were found for all except BARI Sheem-1 (20m+2sm). The four varieties were found to possess symmetric karyotypes. Each variety had a different fluorescent banding pattern. BARI Sheem-2 showed a maximum of 10 CMA bands. All terminal CMA bands supported the equilocal distribution of heterochromatin. The four varieties showed different DAPI banding patterns. DAPI bands in different locations suggested the random distribution of AT-rich repeats. Few chromosomes of these varieties could be used as markers. Every variety had its own RAPD fingerprinting pattern with different primer combinations. In spite of similar conventional karyotype features, the four varieties could be differentiated by their CMA, DAPI, and RAPD banding patterns. This information may be helpful for the correct breeding of BARI.
The karyotype of Bellevalia romana L., which is composed of two long metacentric chromosomes (chromosome 1), two short subtelocentric chromosomes (chromosome 2), and four short submetacentric chromosomes (chromosomes 3 and 4), were analyzed by several techniques. C-bands, CMA3 bands, Ag-staining bands, and FISH signals of 18S rDNA appeared at the same sites on the end of an arm of chromosomes 1 and 3. A large FISH signal with 5S rDNA was localized at the end of the long arm of chromosome 2, and a small signal appeared at the interstitial region of the long arm of chromosome 1. When compared with a previous report, there were differences in the CMA3 band on chromosome 2 and a small 5S rDNA signal on chromosome 1.
Karyotype and RAPD analysis of four varieties of Capsicum frutescens L. (Chilli), namely BARI Chilli-1, Bogra Chilli, Binti Chilli, and Coarse Chilli, were conducted. These four varieties were found to possess 2n=24 chromosomes. The total length of 2n chromosome complement was highest (86.35 μm) in the Coarse Chilli and lowest (38.57 μm) in the Bogra Chilli. The centromeric formulae of these four varieties were different; they were 20m+2sm+2ac for BARI Chilli-1, 21m+3sm for Bogra Chilli, 19m+2sm+3ac for Binti Chilli, and 10m+14sm for Coarse Chilli. The range of individual chromosome length was largest (1.92–4.84 μm) in the Coarse Chilli and smallest (0.84–2.22 μm) in the Bogra Chilli. Heteromorphicity in respect of centromeric position in a member of pair XI of Bogra Chilli and Binti Chilli suggested the occurrence of deletion. Four CMA-bands were found in BARI Chilli-1 and Bogra Chilli, whereas two chromosomes of the Coarse Chilli entirely fluoresced with CMA. No CMA band was found in the Binti Chilli. Each variety had a definite RAPD fingerprinting pattern. The Coarse Chilli had several unique DNA fragments. Therefore, the four variety of Capsicum frutescens L. could be characterized with the help of karyotype and RAPD analysis.
The diploid chromosome number and male meiosis in Ectomocoris atrox, E. tibialis, E. melanopterus, and Peirates bicolor (Heteroptera: Reduviidae: Peiratinae) have been described. Three species of Ectomocoris have 2n=23=20A+X1X2Y, while Peirates bicolor has 2n=23=20A+X1X2Y. One pair of autosomes is distinctly large in all the species of Ectomocoris, while Peirates bicolor possesses three pairs of large bivalents suggesting autosomal fusion. In Peirates bicolor with XY mechanism, X is larger than the X components of E. atrox, E. tibialis, and E. melanopterus with X1X2Y mechanism, indicating fragmentation of X to be the mode of origin of X multiplicity. In the presently studied four species, the general course of meiosis is typical of Reduviidae. Sex chromosomes remain condensed and distantly placed during the diffuse stage. Single terminal chiasma per bivalent is seen in all except Ectomocoris atrox. At metaphase I, chromosomes arrange in a regular pattern in all the species, which is strikingly different from the typical random arrangement pattern previously reported in Reduviidae.
Diploid human embryonic cells were exposed to demecolcine for 3 d and then released from this exposure. At that time, the cell population was a mixture of diploid and tetraploid cells. Tetraploid cells were obtained through the cloning of this mixture of cells. The doubling time of the tetraploid cells was 16 h, identical to that of the diploid cells. The tetraploid cells had 92 chromosomes and double the DNA content of the parent diploid cells. The cell volume of the tetraploid cells was about twice that of the diploid cells. The duration of the G1, S, and G2/M phases was almost the same as for diploid cells. It was concluded that the established tetraploid human embryonic cells have cellular characteristics similar to those of diploid human embryonic cells.
The present investigation was carried out on six economically important species of Asparagus using chromosomal characteristics, 4C nuclear DNA contents, SDS PAGE of total leaf proteins, isozyme polymorphism, and molecular markers to assess their relationship both at inter- and intraspecific levels. Karyotype analysis revealed diploid (2n=2x=20) status in most of the species except tetraploidy (2n=4x=40) in A. cooperi and hexaploidy (2n=6x=60) in A. densiflorus. Karyotype asymmetry existed among the species as well as in same ploidy level of different species. The inter-chromosomal and intra-chromosomal asymmetry ranged from values of 0.902–0.977 and 0.197–0.486, respectively. Again, considering chromosome number, length, volume, and median chromosome number, the primitive nature has been observed in A. densiflorus. The difference in chromosome parameters in all the species suggested the occurrence of structural changes at the chromosomal level. However, a higher degree of correlations has been found between chromosome volume and 4C nuclear DNA content in the six species studied so far. The dendogram obtained from SDS-PAGE and isozyme analysis clearly revealed a close relationship between A. racemosus and A. pyramidalis, but the dendogram obtained from RAPD and ISSR revealed a close relationship among A. pyramidalis, A. densiflorus, and A. racemosus. Asparagus plumosus and A. cooperi also showed a close relationship in all aspects except in ISSR study. All these data clearly indicated that a better phylogenetic relationship can be drawn from the combination of cytological and molecular marker-based analysis, which may assist the breeding pattern or germplasm conservation of the gene pool of specified crops.
Detailed cytological studies are conducted on seven ornamental species of Chrysanthemum, namely, C. carinatum (2n=18), C. cinerarifolium (2n=18), C. coronarium (2n=18), C. leucanthemum (2n=36), C. morifolium (2n=36), C. paludosum (2n=18), and C. segetum (2n=36). The chromosome report for C. paludosum is the first report for the species. Diploid species are mostly heterozygous for chromosomal alternation involving variable number of chromosomes in reciprocal translocations. Large-sized, ring-shaped bivalents accommodate two chiasmata each, and multiple associations are also mostly ring-shaped with distal localization of chiasmata. The presence of multivalents leads to unbalanced chromosomal distribution with formation of laggards and abnormal microsporogenesis, resulting in low pollen fertility.
In this study, we clarified the origin of Iris setosa var. nasuensis (2n=54) and I. setosa var. hondoensis (2n=53), which are endemic to Japan. Four interspecific hybrids were obtained from the cross I. setosa var. setosa (2n=2x=38) × I. laevigata (2n=2x=32). Two of these, DSL1 and DSL2, survived, and were shown to be allotriploid hybrids (2n=54) between I. setosa var. setosa (n=38) and I. laevigata (n=16) by mitotic and meiotic observations and random amplified polymorphic DNA (RAPD) analyses. In addition, it was shown that I. setosa var. nasuensis and I. setosa var. hondoensis were derived from allotriploid hybrids (2n=54) of I. setosa var. setosa and I. laevigata and their aneuploids (2n=53) from meiotic observations and RAPD analyses of I. setosa var. nasuensis, I. setosa var. hondoensis, DSL1, DSL2, I. setosa var. setosa (2x), and I. laevigata. These conclusions were supported by the characterization of these species (lines) and SL4 (2n=53) obtained from the cross I. setosa var. setosa (4x) × I. laevigata. Finally, the mechanisms of 2n (n=38) and 2n−1 (n=37) gamete production of I. setosa var. setosa (2x) are discussed.