Incomplete bivalent pairing in dihaploids of Brassica napus L

Genome ◽  
1988 ◽  
Vol 30 (3) ◽  
pp. 450-457 ◽  
Author(s):  
William Tai ◽  
H. Ikonen
Keyword(s):  
Brassica Napus ◽  
Chromosome Number ◽  
Anther Culture ◽  
Chromosome Numbers ◽  
Meiotic Behaviour ◽  
Homoeologous Pairing ◽  
Brassica Napus L ◽  
Normal Behaviour ◽  
Mother Cells ◽  
Homoeologous Chromosomes

Twenty five polyhaploid plants (2n = 2x = 19, genome formula AC) of Brassica napus (2n = 4x = 38, AACC) were cytogenetically studied. Seven of these were found among field populations and the rest were derived through anther culture of B. napus cv. Regent. Meiotic behaviour at diakinesis and metaphase I revealed nine bivalents and one univalent in more than 40% of the more than 400 pollen mother cells analyzed. However, when the chromosome number of the polyhaploids was doubled using colchicine, 19 bivalents were observed. These doubled plants (2n = 4x = 38, AACC) also had normal behaviour identical to a regular B. napus at other meiotic stages. Quadrivalent associations were observed when the chromosome numbers were doubled to the octaploid level (2n = 8x = 72, AAAACCCC). It is suggested that A and C are homoeologous genomes. If homologous partners are present, chromosomes would pair within the same genome to form bivalents as occurred in the allotetraploids and to form quadrivalents as occurred in the allooctaploids. However, when a homologous partner is not available, the homoeologous chromosomes would then pair to form bivalents in those polyhaploids.Key words: Brassica napus, polyhaploids, genome relationship, meiotic behaviour, homoeologous pairing.

Para-Fluorophenylalanine-induced chromosome number changes in higher plants. II. Tomato and rape

Genome ◽  
1991 ◽  
Vol 34 (6) ◽  
pp. 929-934 ◽  
Author(s):  
P. Banks ◽  
E. J. Britten ◽  
G. H. Gordon
Keyword(s):  
Brassica Napus ◽  
Chromosome Number ◽  
Lycopersicon Esculentum ◽  
Chromosome Numbers ◽  
Higher Plants ◽  
Morphological Changes ◽  
Brassica Napus L ◽  
Tomato Seedlings ◽  
Lycopersicon Esculentum Mill ◽  
Germinating Seeds

Germinating seeds of rape (Brassica napus L.) and of tomato (Lycopersicon esculentum Mill.), and 1-month-old tomato seedlings, were treated with para-fluorophenylalanine to change chromosome numbers. A number of morphological aberrations were found in treated plants of both species, some of which were also observed in progeny of treated tomatoes. Aneuploids and polyploids were confirmed cytologically in treated plants of both species. The investigations confirm the suggestion previously made for maize, that para-fluorophenylalanine is capable of changing chromosome numbers and the resulting morphology of plants of widely different phylogenetic categories.Key words: Para-fluorophenylalanine, chromosome number changes, plants, tomato, rape, aneuploids, polyploids, morphological changes.

Meiotic pairing in haploids and amphidiploids of spontaneous versus synthetic origin in rape, Brassica napus L.

1986 ◽  
Vol 28 (3) ◽  
pp. 330-334 ◽  
Author(s):  
T. Attia ◽  
G. Röbbelen
Keyword(s):  
Brassica Napus ◽  
Chromosome Number ◽  
Chromosome Pairing ◽  
Structural Modification ◽  
Meiotic Pairing ◽  
Chromosome Behaviour ◽  
Preferential Pairing ◽  
Brassica Napus L ◽  
Bivalent Formation ◽  
Homoeologous Chromosomes

Newly resynthesized AC amphihaploids, which were characterized by high meiotic pairing and multivalent formulation, after doubling of their chromosome number showed preferential pairing and bivalent formation in the resynthesized amphidiploid Brassica napus (AACC). However, univalents as well as multivalents were also formed indicating that their chromosome behaviour was not fully diploidized. Stabilization of chromosome pairing in newly resynthesized amphidiploids can be achieved through genetic control or structural modification of the homoeologous chromosomes. A comparison of the meiotic behaviour of spontaneous haploids of natural rapeseed with that of the newly synthesized AC amphihaploids provides some evidence that both processes may be involved in the regulation of chromosome pairing in Brassica.Key words: Brassica, amphihaploid, amphidiploid, meiosis, univalents, multivalents.

Cytogenetic analysis of plants regenerated from tissue explants and mesophyll protoplasts of winter rape, Brassica napus L.

1984 ◽  
Vol 26 (6) ◽  
pp. 752-761 ◽  
Author(s):  
C. A. Newell ◽  
M. L. Rhoads ◽  
D. L. Bidney
Keyword(s):  
Brassica Napus ◽  
Chromosome Number ◽  
Germ Line ◽  
Male Sterile ◽  
Male Sterile Line ◽  
Winter Rape ◽  
Brassica Napus L ◽  
Mesophyll Protoplasts ◽  
Regenerated Plants ◽  
Chromosome Associations

Plants were regenerated from seedling tissue explants of four lines of winter rape (Brassica napus L.) including a cytoplasmic male sterile line carrying Raphanus sativus L. cytoplasm, and from leaf mesophyll protoplasts of the cytoplasmic male sterile line. Chromosome number variability was investigated in 102 regenerated plants. Mitotic root-tip cells were scored initially; those plants exhibiting mixoploidy or an altered chromosome number were reexamined at meiosis to confirm the presence of alterations in germ line cells. Plants regenerated from seedling explants included 2n = 38 diploids (87.0%) similar to the parental line, monosomics (7.8%), trisomics (2.6%), and 2n = 76 tetraploids (1.3%). The germ line number was not resolved in one mixoploid (1.3%). Protoplast-derived regenerated plants were diploid (44%), hypodiploid (20%), and tetraploid or hypotetraploid (36%). Meiotic analysis of regenerated plants showed a range of multiple chromosome associations with no plants consistently exhibiting bivalent formation only. Chromosomal alterations other than number may have been induced by culture, but could not be substantiated since multiple chromosome associations were also frequent in control plants grown from seed.Key words: plant regeneration, protoplast regeneration, Brassica napus, cytogenetics.

A cytogenetic study of monosomics in Brassica napus L.

1985 ◽  
Vol 27 (6) ◽  
pp. 683-688 ◽  
Author(s):  
Zhegong Fan ◽  
William Tap
Keyword(s):  
Brassica Napus ◽  
Brassica Juncea ◽  
Centromeric Region ◽  
Cytogenetic Study ◽  
Pollen Grains ◽  
Meiotic Behavior ◽  
Cytological Examination ◽  
Brassica Napus L ◽  
Small Pollen ◽  
Mother Cells

Two types of monosomic plants of Brassica napus L. were discovered among the backcross progenies of crosses between Diplotaxis muralis L. and B. napus and between Brassica juncea L. and B. napus. These monosomics were designated mono-1 and mono-2, respectively. Morphologically the monosomic plants were virtually indistinguishable from their sib disomic plants. Seed production on both mono-1 and mono-2 plants was normal. Cytological examination revealed that most pollen mother cells (85%) of mono-1 plants formed 18 bivalents plus one univalent at diakinesis, while the remainder (15%) formed 17 bivalents plus a trivalent. The univaltn in mono-1 was submetacentric and its two arms were always stained more lightly than the centromeric region. Later meiotic stages in mono-1 plants appeared normal. The plants of mono-1 produced two types of pollen grains which were different in size. Both the large and small pollen grains of mono-1 were deeply stained with an I2–KI solution. Meiotic behavior of mono-2 plants was similar to that of mono-1 plants, but the frequency of trivalent formation was higher (62%). The univalent in mono-2 was longer than the two chromosomes it paired with to form a trivalent. Pollen produced on mono-2 plants was uniform in size and comparable to that of the normal disomics.Key words: Brassica napus, Brassica juncea, Diplotaxis muralis, aneuploidy, monosomics.

THE CYTOLOGY OF EUDESME VIRESCENS (CARM.) J. AG.: I. MEIOSIS AND CHROMOSOME NUMBER

1967 ◽  
Vol 45 (5) ◽  
pp. 665-673 ◽  
Author(s):  
Kathleen Cole
Keyword(s):  
Chromosome Number ◽  
Chromosome Numbers ◽  
Reduction Division ◽  
Maximum Diameter ◽  
Cytological Investigation ◽  
Normal Pattern ◽  
Stages Of Development ◽  
Unilocular Sporangium ◽  
Mother Cells ◽  
Complete Process

A cytological investigation of meiosis and chromosome number in Eudesme virescens was conducted on sporophytic field material and cultured gametophytes, using a modified iron acetocarmine squash technique. Meiosis was readily observed in the unilocular sporangium mother cells of the adult sporophyte, sporangia in all stages of development occurring on one thallus at one time. Although the nuclei reach a maximum diameter of only 7 μ, the chromosomes absorb the stain readily and can be distinguished throughout the complete process of reduction division. After meiosis, synchronous mitotic divisions ultimately produce 512 nuclei within the sporangium. At maturity the cone-like depression in the apex of the sporangium everts, and biflagellate zoospores are released. Mitosis in the gametophytes appears to follow a normal pattern. Chromosome numbers of 2n = 20 and n = 10 were recorded.

scholarly journals Cytological investigation of anther development in DGMS line Shaan-GMS in Brassica napus L.

2013 ◽  
Vol 49 (No. 1) ◽  
pp. 16-23 ◽  
Author(s):  
Z.D. Xiao ◽  
X.Y. Xin ◽  
H.Y. Chen ◽  
S.W. Hu
Keyword(s):  
Brassica Napus ◽  
Spindle Assembly Checkpoint ◽  
Anther Development ◽  
Male Sterile ◽  
Brassica Napus L ◽  
Cells With Micronuclei ◽  
New Type ◽  
Mother Cells ◽  
Cytological Mechanism ◽  
Dominant Genic Male Sterile

The cytological mechanism of male sterility of Shaan-GMS, a natural mutant dominant genic male sterile (DGMS) line in Brassica napus L., is not well studied. Cytological observation was made on different-size buds of DGMS line 0A30A derived from Shaan-GMS line. The pollen mother cells (PMCs) of DGMS line 0A30A were degenerating at the beginning of meiosis and could not pass the anaphase I stage, with no dyads or tetrads formed, suggesting that the DNA damage checkpoint and spindle assembly checkpoint were activated in sterile anthers. During the meiosis process of sterile anthers in the sterile plants, several kinds of abnormal meiotic cells could be observed: nuclei condensed PMCs, cells with micronuclei, collapsed cells, plasmolysis cells, cells connected with nucleoplasmic bridge, and microspore analogue developed from PMCs without meiosis but enclosed by the exine wall. The results suggested Shaan-GMS to be a new type of DGMS line in B. napus.

Male sterility in Brassica napus L. associated with an extra chromosome

1985 ◽  
Vol 27 (4) ◽  
pp. 467-471 ◽  
Author(s):  
Z. Fan ◽  
W. Tai ◽  
B. R. Stefansson
Keyword(s):  
Brassica Napus ◽  
Male Sterility ◽  
Extra Chromosome ◽  
Female Parent ◽  
Male Sterile ◽  
Cytological Examination ◽  
Brassica Napus L ◽  
Low Frequencies ◽  
Backcross Populations ◽  
Mother Cells

Male sterility was investigated in backcross populations from hybrids between Diplotaxis muralis and Brassica napus using the former as the female parent. The F1 was male sterile and low frequencies (less than 20%) of male sterile plants were obtained from subsequent backcross generations. The data did not fit any Mendelian genetic ratios. Cytological examination of pollen mother cells from 52 plants of these backcross populations indicated the presence of an extra chromosome in all 22 male sterile plants and the normal chromosome number (2n = 38) in the remaining 30 fertile plants. Thus an extra chromosome which is derived from Diplotaxis muralis appears to be the sole cause of male sterility in these backcross populations.Key words: male sterility, Brassica napus, Diplotaxis muralis.

Cytogenetic studies of aneuploids in rapeseed. II. Morphology, fertility, and cytology of self-pollinated progenies of monosomic plants of Brassica napus L.

Genome ◽  
1987 ◽  
Vol 29 (1) ◽  
pp. 174-179 ◽  
Author(s):  
Ru-ying Chang ◽  
William Tai ◽  
Z. Fan
Keyword(s):  
Brassica Napus ◽  
Key Words ◽  
Average Frequency ◽  
Dosage Effect ◽  
Brassica Napus L ◽  
Pollen Mother Cells ◽  
Cytogenetic Studies ◽  
Mode Of Transmission ◽  
Mother Cells ◽  
Multivalent Association

Cytogenic studies were conducted on self-pollinated progenies from two monosomic lines of Brassica napus to ascertain the mode of transmission of the monosomic chromosome. An approximately 1:1 ratio of disomic to monosomic plants was obtained. Only one nullisomic plant was found among a total of 71 plants analyzed. The 1:1 ratio and the anaphase I disjunction (19–18) suggest that the gametes (n) were twice as competitive or functional as their counterpart (n − 1). Since quadrivalents were observed in the disomic plants and only trivalents in the monosomics, the monosomic chromosomes were believed to be the ones that were involved in the formation of multivalents. The percentage of multivalent association in monosomic plants was almost double that in disomic plants. In the disomic plants, an average of 11.96% of pollen mother cells had one to two quadri-valents. The average frequency of trivalents in the monosomics was 23.63%. It was suggested that pairing of these homologs was genetically controlled with a dosage effect. The absence of one chromosome increased the frequency of multivalents. Key words: monosomic, Brassica, rapeseed, aneuploid.

Extraction of disomic addition lines of Brassica napus – B. nigra

Genome ◽  
1989 ◽  
Vol 32 (3) ◽  
pp. 408-413 ◽  
Author(s):  
J. Jahier ◽  
A. M. Chèvre ◽  
A. M. Tanguy ◽  
F. Eber
Keyword(s):  
Brassica Napus ◽  
Chromosome Number ◽  
Anther Culture ◽  
Genome Structure ◽  
Basic Chromosome Number ◽  
Meiotic Pairing ◽  
Addition Lines ◽  
Basic Chromosome ◽  
Disomic Addition Lines ◽  
First Time

The hybrid Brassica napus × B. nigra was produced and backcrossed three times to rapeseed. BC3 genotypes with one or two additional chromosomes were either selfed or haplodiploidized by using anther culture followed by colchicine doubling. Thirty-four fertile disomic addition lines have so far been obtained. Meiotic pairing in most of them was close to 20 II at metaphase I of meiosis. Their characterization is in progress. This material obtained for the first time in B. napus should be of great interest in the study of genome structure and basic chromosome number in Brassica species.Key words: Brassica, genome, disomic addition lines, meiotic behaviour.

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