Electronmicroscopic study has revealed a dicentric chromosome in the root tip cells of diploid Aloe vera, hitherto unreported in somatic cells of plants. The morphological aspects are described and the implications of such structural features of the dicentric are addressed in a functional perspective. It is also proposed that the presence of two functional kinetochores need not invariably lead to chromosome instability and loss.
A tetraploid callus line of Asparagus officinalis L. was identified from 4 regenerated callus lines. Plants were regenerated from these callus lines following somatic embryogenesis and the tetraploid clone of this species was established in the field with 80% survival rate. The embryogenic callus was induced in Murashige and Skoog's (MS) medium in presence of α-naphthaleneacetic acid (NAA) (0.2 mg/l) and kinetin (0.02 mg/l) and proliferated as well as maintained in 2,4-dichlorophenoxyacetic acid (2,4-D) (1.0 mg/l) containing MS medium. Somatic embryos were initiated in Gelrite-solidified MS medium with variable levels of NAA and 6-(γ-γ-dimethylallylamino) purine (2ip). A higher level of carbohydrate enhanced embryo conversion efficiency. The embryos induced in presence of 10% glucose for 2 weeks and subsequently transferred to 2% sucrose level showed higher conversion rate than those maintained in 3% sucrose concentration. Karyotype analysis of diploid and tetraploid clones revealed exact duplication of the diploid set in tetraploid plants.
Studies in pollen morphology and cytology were conducted using LM and SEM in control and gamma irradiated plants with 250, 500 and 1000 rad dosages in Narcissus tazetta cv. cicily white (Amaryllidaceae) to assess the effect of irradiation on these parameters. Pollens of control plants of Narcissus are boat shaped, monocolpate with reticulate exine where the lumina is circular and top of muri is flat. No change in apertural character was found in the pollen of irradiated plants while significant changes in exine ornamentation pattern comprising size and shape of lumina and type of muri was observed in all plants with all irradiated dosages. The changes in exine ornamentation involve structural elements of pollen exine and thus it is confered that the gene/s controlling pollen exine ornamentation are more radiosensitive than the gene/s controlling apertural character of pollen. The cytological analysis depicted a definite trend of increasing total chromosomal aberration percentages with respect to corresponding intensity of radiation.
A detailed investigation on the endosperm in Zephyranthes citrina Herb. was undertaken to understand its mode of development, cytological constitution and its failure in some fruits. The endosperm was found to be basically triploid (3x=72). Upon increasing maturity of the endosperm, cells showing higher ploidy levels, aneuploidy, abnormal mitosis and structural aberrations of chromosomes began to appear. Stickiness of chromosomes and mitotic arrest at various stages of the cell cycle were of common occurrence. Various types of spindle abnormalities such as tropokinesis, split spindle, somatic segregation of chromosomes, multipolar mitosis, atypical distribution of chromosomes at anaphase, lagging of chromosomes as well as nuclear polymorphism and the occurrence of micronuclei were the other salient features.
In this study, the cytogenetic effects of afugan were investigated in root tip cells of Allium cepa L. EC50 value of this fungicide was determined as 40 ppm using root growth inhibition test and then the roots of Allium cepa were treated with 10, 20, 40 and 60 ppm concentrations for 12, 24 and 48 h. Mitotic index, mitotic phase frequencies and mitotic abnormalities were determined for each concentration and treatment period. The most common types of abnormality are stickiness, c-mitosis, bridges, lagging chromosomes, fragments, multipolarity and micronucleated cells.
A plant having a double interchange was isolated from the population raised from gamma ray irradiated seeds in P. typhoides cv. Mainpuri. The plant was morphologically distinct in being weaker and much shorter than its normal counterparts. Diakinesis–Metaphase I configurations revealed the predominance of a hexavalent along with 4 bivalents. In a few PMCs univalents along with variable no. of bi and multivalents could also be observed. Anaphase I studies exhibited various anomalies as well, like unequal separation, bridges and lagging chromosomes. Perhaps, due to these overwhelming chromosomal aberrations pollen fertility was drastically reduced. The paper discusses the meiotic behaviour of this translocation heterozygote and analyses the probable causes for peculiar observations.
Chlorophyllin, a sodium-copper salt derivative of chlorophyll a and b was evaluated at concentrations of 6.25, 12.5 and 25 μg/ml with regard to its clastogenic and anticlastogenic potential in Chinese hamster ovary cells CHO-k1 (wild-type) and CHO-xrs5 (DNA repair-defective), using a chromosomal aberration test. Cells were subjected to continuous exposure for 12 h to chlorophyllin in the presence or absence of ethyl methane sulfonate (EMS, 310 μg/ml). The results demonstrate that under the experimental conditions utilized, chlorophyllin was not cytotoxic nor clastogenic in either of the cell systems employed. Moreover, anticlastogenic activity was also not observed.
Chromosome analyses by the cold-induced banding methods were applied to the Asian tetraploid species Trillium apetalon. From the data it has been found that intraspecific chromosome variation is fairly homogeneous. By means of chromosomal and morphological analyses, the species is considered to have originated as a hybrid between the Asian T. camschatcense and the American T. erectum.
The Astyanax aff. scabripinnis, of Apertados stream (PR), is characterized by a diploid number equal to 48 chromosomes (6M+22SM+4ST+16A). A female sample, however, showed 72 chromosomes being its karyotype constitute by 9M+33SM+6ST+24A, corresponding to a case of triploidy. In this triploid, the Ag-NORs showed more often in 4 chromosomes while the in situ hibridization (FISH) with 18Sr DNA probe showed 12 marked chromosomes, being that 3 chromosomes showed bitelomeric marks. The metaphases showed heterochromatin blocks in the telomeric regions in some acrocentric and subtelocentric chromosomes.
The basal apparatuses preserving the multilayered structure (MLS) were isolated from sperm of the an-1 strain of fern Lygodium japonicum by detergent extraction and DNase digestion, followed by Percoll discontinuous density centrifugation. Isolated basal apparatuses retained the spiral shape as that of the intact sperm and was consisted of the broad flagellar root (spline), MLS, crest, basal bodies and electron-dense material embedding the basal bodies (embedding material). In the isolated basal apparatus fine filaments were found between the basal bodies and the spline by electron microscopy. Three monoclonal antibodies (mAb h1c, 1C7 and 13D10) raised against the purified basal apparatuses were used to explore novel proteins in the MLS-type basal apparatus. A 42 kD protein recognized by mAb h1c was localized in the crest by immunogold electron microscopy. mAb 1C7 reacted with a 41 kD protein and 13D10 with a 43 kD in western blotting, though both antibodies uniformly decorated the embedding material by immunoelectron microscopy.
Chromosomal data of Hyphessobrycon anisitsi are presented for the first time, comprising 2 populations from adjacent hydrographical basins (Upper Paraná basin and Paraíba do Sul basin), separated by Mantiqueira Hills (water divisor). The same diploid number and karyotype formula were observed in both populations. However, after silver nitrate staining (Ag-NORs) and fluorescent in situ hybridization with 18S rDNA and 5S rDNA probes, it was possible to identify each population by the location of ribosomal sites. Some aspects related to geographical isolates and chromosomal differentiation are approached.
Cytogenetic analyses of 2 Astyanax scabripinnis populations from the Amores stream and from Índios river, Ivaí basin (state of Paraná, Brazil), were carried out. The 2 populations showed same diploid number (2n=48), although differed in the karyotype formulae (8M, 24SM, 4ST, 12A; 8M, 20SM, 6ST, 14A respectively) and in Ag-NOR chromosome number (4, 3 NOR pairs respectively). Constitutive heterochromatin pattern for both populations showed weak centromere markings and big highly stained blocks in the telomeric regions of chromosomes ST and A, coupled to intra- and inter-individual polymorphism with regard to the number of highly stained blocks and in the heterochromatin quantity in homologues of certain chromosomes. Karyotype diversity in different Astyanax scabripinnis populations from Ivaí river basin is discussed. The objective of the present study was to detect possible variations that would provide a better understanding of the group's evolution.
Since throughout history A. sativa has always been selected for grain production, thus requiring regular meiosis to ensure pollen fertility and since A. strigosa has been restricted to forage use, not requiring pollen fertility for its agronomic purposes, the present research compares the efficiency of the meiotic process in varieties of both species, to date under selection for animal fodder. Cytological analyses revealed several different kinds of meiotic abnormalities common to both species, including abnormal chromosome segregation, bridges, and cytomixis among microsporocytes. All varieties of A. sativa (2n=6x=42) were slightly more affected than those of A. strigosa (2n=2x=14). Results suggest that, despite its agronomic use that not requires pollen fertility, A. strigosa does not tolerate aneuploid gametes as a guaranty for species survival.
Triticale (Triticosecale Wittmack) is a material in evolution, consequently it carries typical reproductive problems of those individuals with two or more genomes in an unique cytoplasm and where the stabilization process is yet evolving. Grain yield, as final product, is attained through several biological steps where meiosis plays an essential role. To improve each reproductive step is nature and man common intention, however the plant breeder attention is focalized in fewer characters generally associated to the end of the reproductive process. The aim of the present research was to measure the associated changes for the meiotic index in an evolving triticale population selected disruptively for several agronomical traits. Significant differences between superior and inferior mean group values were observed for the grain yield per spike co-selected trait and the meiotic index co-responsive ones. The presence of significant mean differences for the meiotic index between superior and inferior groups, performed in accordance to a selection index constituted by several agronomical traits, suggests that is possible to obtain a positive effect on the meiotic index selecting for grain yield and its principal components. Consequently, the use of a selection index generated harmonious genotypes with respect to the cytological and grain yield triticale performance.
Genomic in situ hybridization (GISH) using S genomic DNA as a probe was applied to study inheritance of blue seed color and characterize the chromosome constitution of blue-grained lines selected from derivatives of Chinese Spring (CS)×Agrotana, a multiple disease resistant wheat-Th. ponticum partial amphiploid line. The results showed that the expression of blue seed color in the CS-Agrotana advanced hybrid lines was always linked with a pair of translocation chromosomes derived from J and Js genomes of Th. ponticum. The blue-grained lines had 43–44 chromosomes, which included 2 J-Js+2 (or 1) Js-J alien translocation chromosomes, while the red-grained lines had 41–42 chromosomes, only carried 2 J-Js translocation chromosomes. This suggested that the Js-J translocation chromosomes might carry the major gene(s) that controlled the blue grain color. Since the J-Js translocation chromosomes were always present with the Js-J translocation chromosomes in blue-grained lines, it is possible that the blue grain color resulted from an interaction between the 2 translocations. Meiotic analyses of chromosome pairing in the blue-grained lines indicated that the 2 pairs of the alien translocation chromosomes did not pair each other, nor did they pair with the wheat chromosomes. The occurrence of 2 bivalents and no alien quadrivalents in the blue-grained lines with Js-J and J-Js translocation chromosomes, demonstrated that the 2 alien chromosome translocations were not reciprocal translocations. The J-Js translocation chromosomes present in the blue-grained lines were more stable at meiosis than the Js-J translocation chromosomes. The Js-J chromosomes were easily lost, resulting in an instability in grain color that could change from light blue to red. Our results determined the molecular cytogenetic characteristics and inheritance of the alien translocation chromosomes present in the blue-grained lines carrying resistance genes to common root rot. This study further confirmed that the chromosome translocations among the Js and J genome were responsible for blue grain color.