Progenies of Thinopyrum elongatum × Agropyron mongolicum

Genome ◽  
1987 ◽  
Vol 29 (5) ◽  
pp. 738-743 ◽  
Author(s):  
Richard R-C. Wang
Keyword(s):  
Embryo Rescue ◽  
Chromosome Elimination ◽  
Root Tip ◽  
Hybrid Necrosis ◽  
Genome Chromosome ◽  
Pollen Mother Cells ◽  
Close Phylogenetic Relationship ◽  
Mother Cells ◽  
Thinopyrum Elongatum ◽  
High Degree

With the aid of embryo rescue, both a monoploid and several hybrids were obtained from the cross Thinopyrum elongatum × Agropyron mongolicum. The monoploid was a result of gradual and eventually complete elimination of A. mongolicum chromosomes in the hybrid. About 95% of the root-tip cells, and nearly all of the pollen mother cells, had only the seven chromosomes of the Je genome of the maternal parent. Very little autosyndesis occurred between chromosomes within the Je genome. Extensive chromosome pairings were observed in one headed hybrid, averaging 6.42 I + 2.53 rod II + 0.85 ring II + 0.25 III + 0.02 IV at metaphase I in pollen mother cells, which revealed a high degree of chromosome homology between the two genomes and thus justifying the close phylogenetic relationship between the two species. All plants died from hybrid necrosis, some as seedlings and some after heading. The Je and P genomes in the accessions used in this study carry complementary genes for hybrid necrosis. Key words: hybrid (intergeneric), haploid, genome, chromosome elimination, meiosis.

Coenocytism, ameiosis, and chromosome diminution in intergeneric hybrids in the perennial Triticeae

Genome ◽  
1988 ◽  
Vol 30 (5) ◽  
pp. 766-775 ◽  
Author(s):  
Richard R.-C. Wang
Keyword(s):  
Intergeneric Hybrid ◽  
Chromosome Elimination ◽  
Intergeneric Hybrids ◽  
Pollen Grain ◽  
Unreduced Gamete ◽  
Pollen Mother Cells ◽  
Psathyrostachys Juncea ◽  
Hybrid Plants ◽  
Mother Cells ◽  
Pollen Grain Wall

Three different pathways of ameiotic microsporogenesis were observed in some intergeneric hybrids of the perennial Triticeae grasses. In one of the hybrids between Pseudoroegneria spicata ssp. inermis and Psathyrostachys juncea, pollen mother cells remained as premeiotic interphase cells when the pollen grain wall started to form. The microspores in such an ameiotic plant are presumably unreduced. Coenocyte formation coupled with ameiosis occurred in two hybrid plants of Psathyrostachys huashanica × Secale montanum. Less than 10% of the pollen mother cells had one nucleus. An average of 4.44 nuclei, ranging from 1 to 25 per pollen mother cell, was observed. The nuclei in coenocytes remained unfused when the pollen grain wall was formed. Nucleus splitting followed by cytoplasmic budding or cleavage, possibly a process of chromosome diminution or elimination, replaced meiotic divisions in most of the pollen mother cells in one plant of Leymus angustus × Hordeum bulbosum and two plants of Thinopyrum elongatum × Psathyrostachys juncea. It is evident that these meiotic abnormalities are under genetic control. Probable locations for these genes controlling these phenomena are suggested.Key words: coenocyte, ameiosis, chromosome diminution, chromosome elimination, microsporogenesis, unreduced gamete, polyploidy, intergeneric hybrid.

Diploid perennial intergeneric hybrids in the tribe Triticeae. IV. Hybrids among Thinopyrum bessarabicum, Pseudoroegneria spicata, and Secale montanum

Genome ◽  
1988 ◽  
Vol 30 (3) ◽  
pp. 356-360 ◽  
Author(s):  
Richard R.-C. Wang
Keyword(s):  
Meiotic Chromosome ◽  
Embryo Rescue ◽  
Intergeneric Hybrids ◽  
Root Tip ◽  
Pseudoroegneria Spicata ◽  
Genome Phylogeny ◽  
Karyotype Analyses ◽  
Thinopyrum Bessarabicum ◽  
Mother Cells ◽  
Secale Montanum

Diploid intergeneric hybrids among Thinopyrum bessarabicum, Pseudoroegneria spicata, and Secale montanum were synthesized with the aid of embryo rescue. Karyotype analyses of mitotic root-tip cells revealed that all satellited chromosomes in the J, S, and R genomes were present in their hybrid combinations, making it possible to identify these hybrids at the seedling stage. Spikes of these hybrids were intermediate to, but distinctly different from, those of the parental species. Meiotic chromosome associations at metaphase I in the pollen mother cells averaged 4.34 I + 2.77 rod II + 1.42 ring II + 0.24 III + 0.14 IV for P. spicata × T. bessarabicum; 11.05 I + 1.22 rod II + 0.04 ring II + 0.13 III + 0.01 IV for T. bessarabicum × S. montanum; and 12.98 I + 0.52 rod II + 0.01 III for P. spicata × S. montanum. These meiotic data suggest that the S genome of Pseudoroegneria and the J genome of Thinopyrum are more closely related to each other than they are with the R genome of Secale. The R genome is slightly closer to the J genome than to the S genome. Since these synthetic hybrids represent genomic combinations that may not exist in nature, their induced amphiploids should be created and evaluated.Key words: intergeneric hybrids, genome, phylogeny, Thinopyrum, Pseudoroegneria, Secale.

scholarly journals Cytogenetic characterization of a triploid mulberry (Morus spp.) cultivar Suvarna-2

2018 ◽  
Vol 7 (4) ◽  
pp. 2156
Author(s):  
Daryoush Shafiei ◽  
Basavaiah Prof.
Keyword(s):  
South India ◽  
Pollen Sterility ◽  
Meiotic Behavior ◽  
Pollen Mother Cells ◽  
Cytogenetic Characterization ◽  
Morus Spp ◽  
Mother Cells ◽  
High Degree

Mulberry exehibits a high degree of polyploidy ranging from haploidy to docosaploidy and its various species are being cultivated for foliage to practice sericulture and edible fruits. Triploid mulberries for sericulture porpuse and higher polyploids are proved to be superior.  The cultivar Suvarna-2 is an improved high leaf yielding triploid in south India. The meiotic behavior of this cultivar has been presented here. Meiosis was highly irregular. Various anomalies such as univalent, bivalents, trivalent, hexavalent, loose association, unequal separation and precocious movement of chromosomes and laggards have been observed in pollen mother cells. These irregularities prevented the formation of viable gamete that leads to pollen sterility.

Genome doubling and chromosome elimination with fragment recombination leading to the formation of Brassica rapa–type plants with genomic alterations in crosses with Orychophragmus violaceus

Genome ◽  
2007 ◽  
Vol 50 (11) ◽  
pp. 985-993 ◽  
Author(s):  
Min Liu ◽  
Zai-Yun Li
Keyword(s):  
Brassica Rapa ◽  
Embryo Rescue ◽  
Chromosome Elimination ◽  
Intergeneric Hybrids ◽  
Aflp Analysis ◽  
Genetic Introgression ◽  
Orychophragmus Violaceus ◽  
Distant Hybridization ◽  
Genome Doubling ◽  
Mother Cells

In distant hybridization of plants, nonclassical hybrids with unexpected chromosome complements, chromosome elimination, and genetic introgression have been well documented. We obtained intergeneric hybrids between Brassica rapa , B. rapa var. chinensis, and another cruciferous species, Orychophragmus violaceus , following embryo rescue. Hybrids mainly displayed phenotypes of B. rapa, although certain O. violaceus or novel characteristics also appeared. Variable numbers of chromosomes were observed in somatic cells in the roots of plantlets on medium and in ovaries and pollen mother cells (PMCs). However, higher numbers were recorded in the roots. GISH revealed that the majority of ovary cells and PMCs contained 20 chromosomes of B. rapa with or without individual O. violaceus chromosomes or fragments added or introgressed. AFLP analysis showed that fragments deleted from the B. rapa genome were much more frequent than novel and O. violaceus fragments. The mechanisms involved genome doubling and successive elimination of O. violaceus chromosomes accompanied by fragment recombination and introgression, producing B. rapa–type plants with modified genetic constitutions and phenotypes.

An advanced generation of Aranda orchids

Genome ◽  
1988 ◽  
Vol 30 (4) ◽  
pp. 608-611 ◽  
Author(s):  
Y. H. Lee ◽  
F. Y. Tham
Keyword(s):  
Somatic Chromosome ◽  
Intergeneric Hybrids ◽  
Root Tip ◽  
Chromosome Counts ◽  
Pollen Mother Cells ◽  
Mother Cells ◽  
Tip Cells ◽  
Somatic Chromosome Numbers ◽  
Root Tip Cells ◽  
Advanced Generation

Aranda orchids are a group of artificially bred intergeneric hybrids between member species (2n = 38) of two natural genera, Vanda and Arachnis, of Orchidaceae. Nine second generation Aranda cultivars were selected for analysis of somatic chromosome numbers, meiotic behaviour, and sporad formation. Eight of the cultivars were derived from Aranda × Vanda crosses and one from an Aranda × Aranda cross. Chromosome counts of their root tip cells showed that eight of them contained 2n = 3x = 57 chromosomes each, presumably resulting from unreduced eggs of the Aranda parent fertilized by haploid Vanda pollen. The ninth revealed 2n = 2x = 38 chromosomes. Pollen mother cells of eight of the cultivars (2n = 3x = 57) commonly formed more than 10 bivalents, presumably between homologous Vanda chromosomes, as well as many univalents, mainly of Arachnis chromosomes. Only 8–10 bivalents were observed in pollen mother cells of the ninth cultivar (2n = 2x = 38). All the cultivars formed a range of dyads containing unreduced microspores. Two mechanisms are proposed for the origin of these dyad sporads.Key words: Aranda orchids, intergeneric hybrids, cytology.

scholarly journals Cytogenetics of Mimosa bimucronata (DC.) O. Kuntze (Mimosoideae, Leguminosae): chromosome number, polysomaty and meiosis

2011 ◽  
Vol 11 (1) ◽  
pp. 27-36 ◽  
Author(s):  
Denise Olkoski ◽  
Maria Teresa Schifino Wittmann
Keyword(s):  
Seed Set ◽  
Pollen Grains ◽  
Root Tip ◽  
Rio Grande Do Sul ◽  
Root Tips ◽  
Pollen Mother Cells ◽  
Species Area ◽  
Mother Cells ◽  
Tip Cells ◽  
Root Tip Cells

Chromosome numbers (somatic and/or gametic) were determined in 50 populations of M. bimucronata (DC.) O. Kuntze collected in the species area of distribution in Rio Grande do Sul, south Brazil. All populations were diploid (2n = 2x = 26, n = 13). Polysomatic (mostly tetraploid) cells were detected in the seedlings root-tip cells in 39 out of the 41 populations examined, ranging from 3.0 to 28.2 % among populations, but were absent in the root-tips of grown plants. Polysomaty was as well absent in pollen-mother cells. In M. bimucronata pollen-mother cells are joined two-by-two before the onset of meiosis, remaining attached during all the meiotic division until the formation of pollen grain polyads, composed of two sets of four pollen grains each, that are dispersed in this way, which, according to previous suggestions would be an adaptation to ensure high seed set after a single pollination event.

Chromosome localization of genes that control synchronous development of pollen mother cells in wheat

Caryologia ◽  
2003 ◽  
Vol 56 (3) ◽  
pp. 275-279 ◽  
Author(s):  
Wei Li ◽  
Jun Yang ◽  
You-Fu Pan ◽  
Guang-Qin Guo ◽  
Guo-Chang Zheng
Keyword(s):  
Chromosome Localization ◽  
Pollen Mother Cells ◽  
Synchronous Development ◽  
Mother Cells

An ultrastructural study of cytomixis in tobacco pollen mother cells

PROTOPLASMA ◽  
2011 ◽  
Vol 248 (4) ◽  
pp. 717-724 ◽  
Author(s):  
Sergey R. Mursalimov ◽  
Elena V. Deineko
Keyword(s):  
Ultrastructural Study ◽  
Pollen Mother Cells ◽  
Tobacco Pollen ◽  
Mother Cells

Persisting demibivalents: a unique meiotic behaviour in Cuscuta babylonica Choisy

Genome ◽  
1987 ◽  
Vol 29 (1) ◽  
pp. 63-66 ◽  
Author(s):  
Batia Pazy ◽  
Uzi Plitmann
Keyword(s):  
Key Words ◽  
Chromosome Segregation ◽  
Meiotic Behaviour ◽  
Chromosome Behaviour ◽  
Chromosome Movement ◽  
Pollen Mother Cells ◽  
Key Words Meiosis ◽  
Mother Cells ◽  
Telomeric Association

Idiosyncratic chromosome behaviour during meiosis was found in pollen mother cells of Cuscuta babylonica Choisy, a thread-like holoparasitic herb. Its main features are among the following: (i) telomeric association between homologues through most stages of the process, which leads to persisting chromatid bivalents (= "demibivalents"); (ii) uncommon chromosome segregation in first and second anaphase; and (iii) prolonged intensified heterochromatinization. Although "regular" in its own way, this process leads to the formation of unviable products. Its further investigation might contribute to our understanding of the role of the spindle and chromosome movement in the ordinary process of meiosis. Key words: meiosis (abnormal), persisting demibivalents, Cuscuta babylonica.

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