Karyotype and genome size variation in white-flowered Eranthis sect. Shibateranthis (Ranunculaceae)

Comparative karyomorphological analyses of six out of the eight white-flowered species of Eranthis sect. Shibateranthis have been carried out. All studied specimens of E. byunsanensis, E. lobulata, E. pinnatifida, and E. stellata had a somatic chromosome number 2n = 16 with basic chromosome number x = 8. On the contrary, E. tanhoensis and E. sibirica had a basic chromosome number x = 7. The specimens of E. tanhoensis were diploid with 2n = 14, while the specimens of E. sibirica were polyploid with 2n = 42. Monoploid chromosome sets of the investigated diploid species had 4–5 metacentric chromosomes and 2–4 submetacentric/subtelocentric/acrocentric chromosomes. The highest level of interchromosomal asymmetry, estimated via CVCL, was found in E. byunsanensis and E. pinnatifida. The highest levels of intrachromosomal asymmetry (MCA) and heterogeneity in centromere position (CVCI) were found in E. lobulata and E. byunsanensis, while E. sibirica had the most symmetric karyotype. A multivariate PCoA analysis of basic karyotype parameters (2n, x, THL, CVCL, MCA, and CVCI) highlighted no overlap among species accessions, which was also confirmed by LDA. The average absolute monoploid DNA content (1Cx) of the 23 investigated samples of six Eranthis species varied from 9.26 ± 0.25 pg in E. sibirica to 15.93 ± 0.32 pg in E. stellata. Overall karyological affinity was highlighted between E. lobulata and E. stellata, on one side, and between E. byunsanensis and E. pinnatifida, on the other side. Interestingly, there was no significant correlation between total haploid (monoploid) chromosome length (THL) and 1Cx values in these species.

Cytogenetical analysis of Clitoria ternatea

Clitoria ternatea L. of the family Fabaceae is an economical, ornamental as well as medicinal important species. Chromosome characterization of C. ternatea, encompassing karyomorphological as well as fluorochrome binding was carried out in the present investigation. Karyomorphological studies showed the presence of 2n = 16 somatic chromosome number with three pairs of metacentric chromosomes and five pairs of submedian chromosomes. The analysis also revealed the present of one pair of nucleolar organizing region or satellite. Fluorochrome binding using chromomycin A3 (CMA) and 4-6-diamidino-2-phenylindole (DAPI) showed the presence of GC- and AT- rich heterochromatic region. Further analysis revealed the percentage of GC-rich was comparatively higher than AT-rich heterochromatic region. This is the first report on heterochromatin characterization in C. ternatea.

Somatic chromosome number and ploidy level in three Curcuma spp. from Bangladesh

Three Curcuma L. species were investigated cytogenetically which represent diversed staining pattern of heterochromatins in interphase nuclei and prophase chromosomes with orcein staining. Curcuma longa and C. caesia were found to possess 2n = 3x = 63 somatic chromosomes whereas 2n = 2x = 42 chromosome number in C. zedoaria is reported for the first time from Bangladesh. Total chromosome length recorded in C. longa, C. caesia and C. zedoaria were 145.08 ± 2.85 μm, 164.93 ± 4.29 μm and 97.78 ± 2.41 μm, respectively. This was the first attempt to measure the length of the chromosomes for these species. The experiment confirmed the basic chromosome number x = 21 with triploid (C. longa, C. caesia) and diploid (C. zedoaria) Curcuma plants. Polyploidy could be employed in the evolution and diversification of the genus Curcuma, which is an essential factor to characterize the species of this genus. Dhaka Univ. J. Biol. Sci. 30(2): 133-140, 2021 (July)

Cytogenetic studies of three cultivated hill cotton (Gossypium arboreum L.) varieties from Bangladesh

Three hill cotton (Gossypium arboreum L.) varieties viz., HC-1, HC-2 and HC-3, released by Bangladesh Cotton Development Board were investigated through orcein, CMAand DAPI-banding for cytogenetical characterization and to elucidate the karyotypic diversity among these varieties. All these three varieties were found to possess 2n = 26 metacentric chromosomes with ‘1A’ karyotype. Based on TF%, AsK% and Syi index, HC-3 was little advanced over HC-1 and HC-2. These three varieties showed differential Chromomycin A3 (CMA)- and 4Ê-6 Diamidino-2-Phenyl Indole (DAPI)-banding patterns and a tendency of acumulation of repetitive sequences at the terminal regions was observed. Despite possessing same somatic chromosome number these three hill cotton varieties could be characterized by diversified karyotypic parameters through differential staining.

Karyomorphology of Two Species of the Genus Spilanthes (Heliantheae-Asteraceae)

In present investigation karyotype of mitotic chromosomes were determined, two species of the genus Spilanthes, namely Spilanthes acmella (L.) Murray and Spilanthes calva DC. from plants transplanted in earthen pots collected from different localities from Central Nepal in my home garden. The somatic chromosome number determined in present study were 2n=36 for both species, Spilanthes acmella (L.) Murray and Spilanthes calva DC. The chromosomes total length ranged from 0.6 to 1.6 µm in Spilanthes acmella (L.) Murray and 0.4 to 2.1µm in Spilanthes calva DC. The relative length ranged from 2.3 to 12.1 µm in the species Spilanthes calva and 2.0 to 8.5 µm in the species Spilanthes acmella. The Karyotype formula were M16+m2+sm16+st2 in Spilanthes calva DC. and M22 +sm14 in Spilanthes acmella (L.) Murray cytologically obtained by using 2% aceto-orcein. The karyotype of the two species shows considerable variation exists in morphology of chromosome and structure. The variation in karyomorphology shows evolved nature of this species which play a great role in evolution. Int. J. Appl. Sci. Biotechnol. Vol 8(4): 422-426

FIRST KARYOTYPE REPORT ON Colocasia oresbia: A COMPARATIVE CYTOGENETIC STUDY BETWEEN TWO VARIETIES

Karyotypes of two Colocasia oresbia botanical varieties from Bangladesh were analyzed and compared with orcein, chromomycin A3 (CMA) and 4´-6 diamidino-2-phenylindole (DAPI). Both varieties had 2n=2x=26 chromosomes (karyotypic formula: 20m+6sm) and a pair of satellites each. Total chromosome length was 144.18±2.45 μm in C. oresbia var. oresbia and 133.02±2.75 μm in C. oresbia var. stolonifera. The karyotype of Colocasia oresbia var. oresbia is 2A whereas that of C. oresbia var. stolonifera is 1A. Six CMA and four DAPI bands were observed in C. oresbia var. oresbia and eight CMA and six DAPI bands in C. oresbia var. stolonifera. However, in these two morphologically distinct C. oresbia varieties of two different ecological zones, the same somatic chromosome number, diversification in various karyotypic parameters and CMA/DAPI-banding patterns were observed. In addition to taxonomic characters, the studied karyotype features will contribute to the characterization of these two C. oresbia varieties and to establish a base for future research. Key words: chromosome banding; CMA; DAPI; Karyotype.

Interphase nuclear phenotype and chromosomal variation in Cynodon dactylon (L.) pers

Interphase nuclear phenotype in different accessions (Acc.) of Cynodon dactylon studied in the present experiment showed chromocentric nuclear organization and the chromocenters were found to be visible clearly. The chromocenter numbers were not same and sometimes it was found to be significantly less and never more than total number of chromosomes. Percentages of heterochromatin values were expressed per nuclear area and the values range from 19.759% (Acc. 16) to 66.022% (Acc.18). Nuclear volume as well as interphase chromosome volume was found to vary 0.674 μm3 (Acc.6) to 41.921 μm3 (Acc.10) and from 0.028 μm3 (Acc. 6) to 1.905 μm3 (Acc. 10), respectively. The somatic chromosome number found to vary from 12 to 40. 2n = 18 chromosomes were found in eight accessions of C. dactylon. Only one accession was found to be tetraploid and rest of them aneuploid whose chromosome numbers were 12, 14, 16, 22, 24, 26, 32, 40 etc. The availability of aneuploid shows great aspects of forage breeding programme. J. bio-sci. 27: 133-141, 2019

A report on new chromosome number of three Dioscorea species

Chromosomal study conducted in nine species of Dioscorea from different forest belts of Tripura revealed that their somatic chromosome number ranged from 2n=40 to 2n=60. The record of 2n=40 chromosome in the sexual phenotypes of Dioscorea hamiltonii, Dioscorea glabra and Dioscorea pubera are the first time report from Tripura, North East India. Moreover the somatic chromosome counts of 2n=60 in Dioscorea pentaphylla would be attributed as a new cytotype. However at the respective ploidy level no difference in somatic chromosome count was observed between their sexes.

Primulina anisocymosa(Gesneriaceae), a new species with a unique inflorescence structure from Guangdong, China

A newPrimulinaspecies from Guangdong, China with an unusual inflorescence is described here.Primulina anisocymosais vegetatively most similar toP. bobaiensis. It can be distinguished from all species withinPrimulinamorphologically by its unique zigzag monochasial cyme and infructescence. To confirm the phylogenetic relationships and generic placement of this species, not only morphological anatomical features but also chromosome and DNA sequence data were examined and analysed here. Two samples from different populations identified asPrimulina anisocymosaare monophyletic and were nested in a monophyletic clade withinPrimulinawith high branch support. The somatic chromosome number of the new species is also reported (2n = 36), supporting its placement in the genus.

Karyotype analysis of Solanum torvum Sw. - an ethnobotanical Solanaceous species of Tripura, North East India

Solanum torvum Sw. is a wild Solanaceous plant species, commonly used by the indigenous people of Tripura. Cytological study of the species was carried out to determine the somatic chromosome number and to construct the karyotype formula. The detailed karyomorphological analysis revealed 2n=24 somatic chromosomes having haploid number n=12. The size of chromosomal complement was found to range from 2.14±0.21 to 4.02±0.26 µm with a pair of chromosomes bearing secondary constrictions. Strictly median primary constriction was recorded in two pairs of chromosomes. In general, karyotype formula was found to be A2B4C18. The detailed karyotype analysis revealed that chromosomes are generally small in size and fall under the Stebbins category of “2A” indicating symmetrical nature of the karyotype. The present study could be utilised in understanding the cytogenetic nature of the species and for future crop improvement programme.