This year marks the 90th anniversary of Cytologia. Modern wheat genetics began 16 years prior to the first issue of Cytologia in 1929. Flaksberger’s wheat stocks, which were sent to Minami in October 1913, were used by Sakamura to determine the number of chromosomes in wheat. Flaksberger’s death in prison in September 1942 was a tragedy for the research community. The Russian and Soviet contribution to modern wheat genetics is immeasurable, but its decline during and after the era of Lysenko was pitiful. This is made clear by the number of publications from each country since the first issue of Cytologia. The publication of Cytologia continued during World War II; after the war, the contribution of India, which became independent at that time, was considerable. Recently, India’s contribution has been relativized, and contributions from other Asian countries including Thailand and Japan, the Middle East and South America have increased, and Cytologia has been supported by increasingly diverse countries.
Basil, Ocimum L., is an economically important member of the family Lamiaceae. It has been widely used for many purposes, such as culinary herbs. The genus harbors large variation in chromosome number and size, which is believed to be a consequence of centuries of cultivation and selection for desirable traits. Meiosis was examined in five Ocimum species from Thailand, from five populations of each species. The results revealed that three of these species are cytogenetically related, forming a polyploid series with a base chromosome number of x=13: O. americanum L. (2n=2x=26, a new number for Thai plants), O. basilicum L. (2n=4x=52) and O. africanum Lour. (2n=6x=78, a new number for the genus). Two species with small chromosomes, O. tenuiflorum L. (2n=36) and O. gratissimum L. (2n=40), seem probably tetraploids with base numbers x=9 and 10, respectively. Meiotic irregularities in O. basilicum and O. africanum suggested that the species may be newly formed polyploids undergoing diploidization. Unlike recent polyploids, the meiotic chromosomes of O. tenuiflorum and O. gratissimum are entirely stable. Statistically significant intraspecific variation in chiasma frequencies was found in O. basilicum and O. africanum and the variation appeared to be geographically associated. The results presented here are useful both in the conservation of native basil species and in the breeding of elite accessions.
The present communication reports the meiotic analysis on three wild populations of Rorippa palustris collected from Ladakh division, Jammu & Kashmir and records the existence of first ever intraspecific euploid cytotypes, the diploid (2n=14) and hexaploid (2n=42). Beside chromosome number, the two cytotypes also differ in morphometric parameters such as flower color, plant height, size of leaf and number of leaves per plant. The 6x plants grow much taller and robust compared to those of 2x and size of stomata and pollen grains are also significantly larger in the 6x compared to the 2x. Both cytotypes exhibit normal meiotic behavior characterized by normal chromosome pairing, regular segregation of chromosomes and nearly perfect pollen fertility.
Seeds of Coriandrum sativum L. (Coriander) cultivar CO-2 were irradiated with different doses (100, 200, 300, 400 and 500 Gy) of gamma rays. During the meiotic analysis of pollen mother cells (PMCs), a plant having segmental exchanges between non-homologous chromosomes was isolated in populations raised from 100 Gy irradiated seeds. This paper documented with structural heterozygosity along with cytological behavior of translocation heterozygote induced and the probable cause of its occurrence in the coriander. Morphologically, the plant was weak with short height in contrary to control and irradiated populations. In the plant cytological manifestation of chromosome configurations at diakinesis and metaphase I revealed the predominance of ring octavalents with tetravalents and bivalents. In a few PMCs, the variable number of associations in the form of multivalents along with univalents and bivalents were also screened out. The induced translocation heterozygote showed unequal segregation of chromosomes, laggards, and bridges along with normal 11 : 11 separation at anaphase I. Furthermore, due to chromosomal anomalies, pollen fertility was declined to 37.36% as an overwhelming adjacent orientation (53.16%). Translocation heterozygotes may provide a source for creating aneuploids with novel gene combinations.
Dry seeds of Nigella sativa L. (2n=12) belongs to the family Ranunculaceae (rooted plant species possessing cytological novelty and economic importance) are exposed to 0.01 mg L−1 concentration (permissible dose laid down by WHO) of arsenic trioxide (As2O3; inorganic arsenic form available mostly in soil) for 12, 24, 48 and 96 h durations. The treatments are performed following the impregnation of filter papers with the test solution. Results suggest that in relation to control, As2O3 treatment at different durations can progressively reduce germination rate, seedling growth, and divisional cell frequency and enhance cytological aberrations in mitotic cells. Cytotoxicity induced by As2O3 in the studied plant species is clastogenic in nature (chromosome fragmentations, rings, bridges, and micronuclei) as well as it is found to affect spindle formation and function (polyploid cell formation and tripolar organization of chromosomes) and cellular metabolism (formation of giant cells of variable shapes). Polyploid (2n＞12) and giant cells are frequent aberration types recorded across the duration of treatments. The investigation is significant for the screening of arsenic-tolerant genotypes in relation to consumable dietary plant product(s).
Normal maturation of the pollen coat is important for pollination in higher plants. The pollen coat contains abundant lipids and proteins, which are derived from tapetum cell-specific organelles, i.e., the tapetosome and elaioplast. The wax-deficient mutant eceriferum1 (cer1) shows a conditional male sterile phenotype. It is considered that this phenotype is caused by dysfunction of the pollen coat, although cer1 mutant pollen coats appear normal at a particular stage. In the present study, abnormalities in the tapetum cells and pollen coat of cer1-1 mutants were observed by scanning electron microscope and light microscopic analysis. To investigate the effect of wax composition changes on the structure of the pollen coat, tapetosome, and elaioplast in cer1-1 mutants, we observed the ultrastructure of the cer1-1 male gametophyte at various developmental stages. We observed abnormal giant aggregation of the lipids, which might be due to a fusion of the tapetosome and elaioplast in the early bicellular pollen stage tapetum cell. On the contrary, in wild-type plants, the fusion of the tapetosome and elaioplast occurred at the late bicellular pollen stage. In cer1-1, abnormalities in the tapetum cell and the pollen coat might occur because of the unusual timing of fusion of the tapetosome and the elaioplast. This is the first report showing the role of tapetum wax in the maturation of the tapetosome and elaioplast, which may affect pollen coat function.
The intraspecific euploid (2x, 4x) cytotypes have been reported in Tragopogon pratensis from the cold deserts of Ladakh division in Jammu and Kashmir. Both the cytotypes showed perfect bivalent formation, regular meiotic course and normal microsporogenesis leading to high pollen fertility. The 4x plants are more vigorous and growing much taller than the 2x plants and show gigantism in various vegetative and floral characters besides the increase in the size of stomata and pollen grains. Analysis of meiotic chromosome pairing and chromosome size in the 4x cytotype suggests its allopolyploid nature.
The genus Pedicularis L. comprises many medicinal species in Sirmaur district of Himachal Pradesh, the Northwest Himalayan range. In the present study, male meiotic studies have been carried out in six species of the genus and revealed n=8 chromosome number in all taxa. The chromosome number (n=8) in P. heterodonta and P. punctata are new to the world, while P. oederi reveals the first chromosome report for Indian populations. Besides, a B chromosome and structural heterozygosity were reported for the first time in P. hoffmeisteri and P. pectinata, respectively. Further, meiotic anomalies, like chromatin bridges, interbivalent connections, laggards, un-even gamete formation and reduce pollen viability, were also observed in the studied populations.
Snake gourd is an agriculturally important cucurbit vegetable recognized presently as the cultivar ‘Anguina’ of Trichosanthes cucumerina ssp. cucumerina. The wild type plant occurs naturally that produces small fruits (TCSF) and thus can be distinguished from the cultivar with large elongated fruits (TCLF). Presently, chromosomal features were revealed by modern cytogenetic methods to characterize the two types of plants. Chromosome preparations were standardized by an enzymatic maceration and air-drying method (EMA). The cultivars had considerably different karyotypes than the TCSF plants in spite of the same chromosome numbers (2n=22). EMA-DAPI based meiotic cell preparations reconfirmed gametic chromosome number (n=11) and showed regular chromosome behavior in both plant types. Karyomorphometric study with 14 inter- and intra-chromosomal symmetry/asymmetry indices advocated higher asymmetry in the karyotype of TCLF. The fluorochrome banding pattern of somatic chromosomes revealed the differential distribution of CMA and DAPI bands in the types of plants. TCSF plants were characterized by the presence of CMA bands in two pairs of chromosomes with secondary constrictions while DAPI bands were found in all chromosomes of the complements. On the contrary, DAPI bands were completely absent in TCLF while distal CMA bands were scored in two pairs of chromosomes with secondary constrictions and one pair of other chromosomes. CMA-DAPI banding patterns and karyomorphometric parameters had a significant impact on the evaluation of karyotype relations. The plants of TCSF and TCLF formed distinct groups and clusters in PCA plot and UPGMA phenogram, respectively. The variation in karyoevolutionary status and fluorochrome banding pattern between TCSF and TCLF plants could be utilized for further cytotaxonomic and phylogenetic revisions.
Somatic chromosome numbers of seven Scorzonera L. species collected from different localities in Iran were counted. Except for S. mucida with 2n=28, the other species exhibited a somatic number of 2n=14. The chromosome numbers support the basic number (x=7) of Scorzonera. The chromosome numbers in S. tunicata, S. kandavanica, S. persepolitana, S. mucida, and S. raddeana are reported for the first time. Chromosome numbers in S. luristanica and S. songorica are different from those of the previous reports.
Meiotic studies have been carried out on three plants of Leontopodium jacotianum from Cold deserts of Ladakh. The chromosome number of n=24 counted in all the plants adds a new tetraploid cytotype for the species. The plants collected from Zoji-La showed a normal meiotic course leading to high pollen fertility. However, the plants collected from Sankoo region of cold deserts of Ladakh, Jammu, and Kashmir showed abnormal meiosis caused by structural heterozygosity for reciprocal translocations. The structural heterozygosity was observed for the first time in the species. Chiasma frequency was also calculated by using one-way analysis of variance (ANOVA) in the plants to see the effect of reciprocal translocations. Besides reciprocal translocation, the plant also showed various meiotic abnormalities in the form of early disjunction of bivalents, chromatin bridges, and laggards. Structural heterozygosity and other meiotic abnormalities in the plant seem to be responsible for a reduction in pollen fertility.
A male sterile (ms) plant was identified in each of the two turnip (Brassica rapa) cultivars ‘Kida-aokabu’ and ‘Tennhoji-kabu,’ which are two of the main domestic varieties in Japan. Morphological analysis of organs constituting the flowers in ‘Kida-aokabu’ and ‘Tennhoji-kabu’ showed differences in the features of ms plants between both cultivars, in addition to the differences in size between ms and male fertile (mf) plants in each cultivar. The results of a cross between an ms plant and two cultivars of B. rapa indicated that male sterility is controlled by a single genic recessive gene without any cytoplasmic effect in both cultivars. Light microscopic observations showed that at an early microspore stage, pollen and tapetum development of the ms plant was different from that of the mf plant in ‘Kida-aokabu’ and ‘Tennhoji-kabu,’ respectively. In ms anthers of both cultivars, microspores and tapetum have degenerated, and then completely disappeared before or during the developmental stage to pollen grains. Although the collapse of microsporogenesis in both cultivars occurred at a similar stage, the modes of collapse differed. This is because the collapse of microspores and the tapetum in the locule did not occur synchronously in the ms anther during early microspore development in ‘Tennhoji-kabu,’ which was different from that in ‘Kida-aokabu.’ Our results suggest that the ms plant of ‘Kida-aokabu’ and ‘Tennhoji-kabu’ may represent a new type of Brassica genic male sterility.
Allium cepa (2n=16) assay is used to determine cytotoxicity of environmental pollutants like heavy metal arsenic (in the form of arsenic trioxide—concentration used: 0.010, 0.050, 0.075 and 0.100 mg L−1 for 24 h duration) and azo-dye metanil yellow (concentration used: 100, 150, 200 and 400 mg L−1 for 24 h duration) with an objective to understand the toxic effects of the test materials on cells and chromosomes of a plant-based system. Assessment of cytotoxicity reveals that arsenic trioxide can induce chromosomal breakages, affects spindle organization and causes cellular metabolic defects; whereas, metanil yellow predominantly affects cellular metabolism. Cytological disturbances are mostly dose-dependent, and arsenic trioxide depicts pronounced effectivity in inducing mitotic aberrations in root tip cells of A. cepa than metanil yellow (in relation to employed doses). Furthermore, aqueous plant extracts (used due to its operational simplicity and cost-effectivity) of the leaf (Coriandrum sativum L., Ocimum tenuiflorum L., and Pteris vittata L.) and seed (Nigella sativa L.) samples are used to ascertain their amelioration potentiality against the environmental toxicants. The ameliorative study (decrement in their observed values) involves attributes like mitotic index, total abnormal dividing cell frequency and frequency of giant and anucleate cells in resting stages. Results suggest that all the employed extracts are ameliorative, and can be explored further for their role in bioremediation.
In order to produce an autotetraploid population of Lilium regale, different concentration of colchicine was used as chemical mutagen treatment to induce in vitro polyploidy. Bulb scales were soaked in various filter sterilized colchicine solutions (0.01, 0.05 and 0.1%) for 6, 12 and 24 h separately, then bulb scales were shifted to colchicine free MS medium for regeneration and normal growth. The ploidy level of the regenerated plantlets from treated bulb scales was estimated by chromosome counting in root tips. However, the length of stomatal guard cell, density and chloroplast number guard cell used as cytological parameters to compare between diploid and polyploid plantlets. The results of the experiment showed that high tetraploid plantlets (27.3%) were produced by 0.01%+ 24 h colchicine treatment. However, the highest survival rate (72%) was observed in 0.01%+ 6 h colchicine treatment. The stomatal number was reduced significantly (p≤0.01) in tetraploid compared to diploid. The result of the evaluation revealed that an increase in the length of stomatal and chloroplast number guard cell was found in polyploid plantlets as well as a reduction in stomatal number per unit area. It is found that colchicine at rate 0.01% for 24 h was the most effective treatment in inducing polyploidy in L. regale plantlets.
Nuclear movement and positioning are important for various plant growth and development events. In tobacco BY-2 cells, it has been reported that the pre-mitotic nuclear movement from the periphery to the central region of the cell requires both microfilaments and microtubules and that the movement of daughter cell nuclei away from the cell plate requires microfilaments. However, further molecular mechanisms of these nuclear migration events are not known. Here, we found that the kinesin-related protein TBK11 clearly localized to the nuclear envelope throughout the cell cycle in BY-2 cells by dual localization studies using fluorescent protein-fused TBK11 and inner nuclear membrane protein SUN. Our findings indicate that TBK11 is a viable candidate responsible for microtubule-dependent nuclear movement in BY-2 cells.
Kinesin-14-II is a plant-specific subclass of the kinesin-14 subfamily and includes kinesins with a calponin homology domain (KCHs). A tobacco member of kinesin-14-II, TBK11 is a viable candidate responsible for microtubule-dependent nuclear movement because of its apparent localization to the nuclear envelope. In tobacco BY-2 cells, it has been reported that the nuclear migration from the cell periphery to the central region in the pre-mitotic phase requires microtubules; however, the contribution of microtubules to the movement of daughter nuclei away from the cell plate in the post-cytokinetic phase has not been clarified. In the present study, we performed truncation analysis of TBK11 and found that TBK11 associates with the nuclear envelope via its central coiled-coil domain. We also found that the movement of daughter nuclei away from the cell plate is inhibited by treatment with microtubule inhibitors. These results suggest that TBK11 potentially plays a role in pre-mitotic and post-cytokinetic nuclear movement through interaction with the nuclear envelope via its central coiled-coil domain.