The objective of this study in Rhoeo spathacea was the cytological identification of a trisomic plant which includes an acrocentric chromosome. The homology of the extra chromosome was not identified with certainty by karyotype analysis because of its lack of similarity with any other chromosome. Somatic metaphase analysis indicates that interchanges take place in terminal regions of Rhoeo chromosomes. The presence of the acrocentric also supports this idea. On the basis of behavior at MI, this extra chromosome seems to be homologous with one of the largest chromosome. MI was as expected for ring forming Rhoeo (Chains of 13, 45.7%; 12+1I, 15.7%; or 11+2I, 15%) and not as expected for a desynaptic. The extra chromosome was either associated by its long arm with its supposed homologue or free; when associated, its short arm was free. At AI the segregation was mostly 6:7, with microspores with n=5 to n=26, n=7, 34.4% and also producing SDR with n=13 (22.4%). When all the progeny is included in the observations, a possible apomictic mechanism of origin was postulated.
Karyological characteristics of six Argentinian Astragalus species are reported: A. crucksh-anksii (2n=28), A. illinii (2n=28), A. neuquenensis (2n=28), A. moyanoi (2n=28), A. pehuenches (2n=22) and A. palenae var. grandiflora (2n=26). The x=13 and 14 species have bimodal complements but differ in chromosome morphology and asymmetry indices. All species have a single pair of chromosomes with satellites located on the long arms. A. pehuenches (2n=22, x=11) has a more symmetrical karyotype and a pair of SAT chromosomes with a satellite located on the short arms. Among the species with 2n=28, A. moyanoi has significantly greater DNA content than the rest. The species with the lowest chromosome number, A. pehuenches, has the highest DNA content. The members of species with 2n=28 studied in the present work are similar in both vegetative and reproductive morphology.
Original chromosome observations for eleven taxa (21 populations) of the genus Centaurea in Iran are presented. One of them report for first time, although the all determinations are new for the geographic distribution areas, where the plants collected. Meiotic behaviors (position, situation and average of chiasma, etc.) are noted for all investigated taxa. Significance differences for chromosomal behaviors were not observed between the populations belonging to the same taxa.
The cytology, meiotic behaviour and breeding system were investigated in this work for Panicum repens trying to find out its genetic situation with other Egyptian species and to study the reasons cause reduction in seed set and induce sterility. Mitotic counts of chromosomes shows 36 as tetraploid species based on 9 as basic number. Based on length and centromere position the karyotype formula shows 14 pairs of metacentric, 3 pairs of submetacentric and one pair of telocentric chromosomes. The mean chromosome length measure 0.97μm and arm ratio of 1.25. The heterogenity in chromosome set suggests the alloploid origin of the species. Meiotic behaviour of chromosomes was found somehow irregular with high frequency of univalents and low multivalents. The latter insures that the species is not autotetraploid in origin. Also the high level of univalents suggests the structural hybridity of the species. Irregular meiosis lead to form abnormal pollen and non functional gamets which directly decrease fertility and probably affect seed set either at open or self pollination. Cytological results indicate that the species is cytologically complex with alloploid origin and more self incompatible in breeding system.
In this paper, chromosome numbers and karyotypes of three species, Vicia amurensis, V. pseudo-orbus and V. japonica, were investigated. V. amurensis and V. pseudo-orbus were diploid taxa, and V. japonica was a tetraploid taxon. The karyotype formulae were as follows: V. amurensis 2n=12=4m(2SAT)+6sm(2SAT)+2st; V. pseudo-orbus 2n=12=2m(2SAT)+ 8sm(2SAT)+2st; V. japonica 2n=24=8m(4SAT)+10sm+6st. The karyotypes of the three species belonged to ‘2A’. According to karyotypic features, the authors consisdered that karyotypes of the above taxa were similar. Finally, it was discussed that variation and evolution of karyotypes in Vicia sect. Vicilla.
Sexually competent cells of a cellular slime mold Dictyostelium discoideum strain NC4, were mixed with fusion-competent cells of either HM1, or WS2162, and mixed cell suspensions were incubated with rotation in the dark. Cells 30min after mixing NC4 and SW2162 contained giant cells and smaller cells. Mitochondria of giant cells were charastenstically distributed to the cell periphery. This trend was more evident in giant cells as nucleus number increased in a cell. At 24hr after mixing, blue fluorescences from cell wall, and dark brown fluorescence in the center of and around squashed structures were eminent, while both fluorescences were not detected in 30min cell. Western blot analysis using rabbit polyclonal antibody against bacterial maltose-binding protein detected a major 40 kD and a minor 43 kD peptides in total protein from cells at 24 and 66 hr after mixing NC4 and HN1 cells, while these bands were not detected in two types of gametes before mixing and cells 30min after mixing.
The value of 2n=46, which has been considered ancestral for Balistidae, Ostraciidae, Tetraodontidae and Diodontidae, and not detected previously in any representative of the family Tetraodontidae, is the diploid number presented by S. greeleyi and S. spengleri, tetraodontids that occur in sympatry along the Brazilian coast.
Leporinus is a fish group rich in species which occurs from Central America to the River Plate basin in South America. From a cytologic viewpoint, this group is characterized by the occurrence of both homogametic and heterogametic species, a fact that renders it highly interesting for the study of sex chromosome evolution. In the present paper we report new occurrences of ZW sex chromosomes in L. trifasciatus from the Amazon region and L. conirostris from the basin of Eastern Brazil. Considerations about the origin and distribution of these sex chromosomes within the genus are also presented. The material was analyzed by standard Giemsa staining, by silver nitrate staining for the localization of nucleolar organizer regions, and by C banding for heterochromatin identification. The two species presented 2n=54 for both sexes as well as a large subtelocentric chromosome, the largest in the complement, exclusively detected in females, characterizing a W chromosome in both species. The heterochromatin data obtained permit us to assume that this system involves the same chromosomes not only in the species reported here but also in four others reported in previous studies. Thus the ZW system seems to have arisen only once in Leporinus and currently represent a unit of species more related to one another and cytologically distinct from the remaining species in the genus.
Variation in the NORs in nine eu-diploid and two aneuploid cultivars and two wild forms of Iris ensata was examined by a silver-staining method. Although the number of NOR-bearing chromosomes at somatic metaphase ranged from 3 to 6 among the cultivars and wild forms, 4 NOR-bearing chromosomes which were recognized in the wild form “Normal type” accounted for eight cultivars. Therefore, this number is regarded as the basic one for I. ensata. The numerical variations of NOR-bearing chromosomes might be caused by the structural changes of chromosomes such as translocations or deletions. In addition, the conclusive evidence for a translocation came from a NOR-bearing chromosome with two NOR-bands observed in the cultivar “Shakyo”.
The 5S rRNA gene (5S rDNA) was physically mapped on the somatic chromosomes (2n=22) in Cycas revoluta Thunb. by in situ hybridization using biotin-labeled probes amplified from total genomic DNA. The 5S rDNA was localized at approximate terminal region of the longest pair of telocentric chromosomes. The site of 5S rDNA were the same as C- or chromomycin A3-band.
The oocytes of Euscelidius variegatus Kirschbaum could be arbitrarily divided into 8 sequential sizes. The nucleus (including nucleolus), mitochondria, dense bodies, and vacuoles were clearly seen. All oocytes contained microvilli suggesting ‘active’ solute transport from the surrounding areas. Vitellogenesis began at oocyte 4. Yolk reserves in the form of protein and lipid spheres appeared to be accumulated, and were particularly abundant at oocytes 6 and 7. At oocyte 8 a chorion enclosed the fully mature egg. The follicular epithelium might be active in nutrient syntheses and transport to the oocytes. The presence of abundant rough en-doplasmic reticula, mitochondria, and dense bodies suggested these functions. Nutrients might be derived both from the germarium through the trophic cord and the follicular epithelium.
The chromosome number and karyotype of Aquilaria agallocha Roxb. was investigated. The species had the chromosome counts of n=8 and 2n=16. The karyotype is symmetric with 5 metacentric pairs and 3 sub-metacentric pairs one of which had secondary constriction. No meiotic irregularities were recorded.
In this study, several fundamental questions concerning the ability of abamectin (Avermectin B1) and its degradates to induce chromosomal aberrations in bone marrow cells and spermhead abnormalities in male Swiss albino mice were addressed. Male mice were injected intraperitoneally with two doses of abamectin (i.e. 1/10 and 1/30 LD50, 1.0 and 3.0μg/g body weight, respectively). One, two, five, and eight days after treatment, males were sacrified and bone marrow cells slides were prepared for chromosomal studies. Also, after one, three, five, and eight weeks of treatment; other males were sacrificed and sperm suspension slides were prepared for spermhead abnormalities' counting. Abamectin induced clastogenic type of chromosomal aberrations which significantly decreased by the days following treatment until reached the least after 8 days of treatment. Also, abamectin was found to induce physiological type of aberrations. At the same time, abamectin treatment resulted in high frequency of spermhead abnormalities after one week of injection, which represents the epididymal sperm stage of the animal spermatogenesis. It was found that abamectin which had been degradated for 1-3 days induced significant increase in the percentage of clastogenic metaphases; whereas insignificant effect was observed after 4-6 days.