scholarly journals Timing imbalance in the meiosis of the F1 hybrid Oryza sativa × O. australiensis

1961 ◽  
Vol 2 (3) ◽  
pp. 373-383 ◽  
Author(s):  
S. V. S. Shastry ◽  
D. R. Ranga Rao
Keyword(s):  
Oryza Sativa ◽  
Comparative Morphology ◽  
Meiotic Pairing ◽  
F1 Hybrid ◽  
Oryza Saliva ◽  
End To End ◽  
Primitive Member ◽  
Meiotic Cycle ◽  
Metaphase I

The meiosis in the F1 hybrid Oryza saliva × O. australiensis was studied. Contrary to the observations of Gopalakrishnan (1959), true allosyndetic bivalents were not found at metaphase I. The most frequent associations were non-chiasmatic, end-to-end pseudobivalents. Autosyndetic bivalents were recorded mostly in the complement belonging to O. sativa, which are distinguishable by their smallness and lighter staining. The meiotic cycle exhibits timing imbalance with earlier condensation, and possibly migration, of the univalents belonging to O. australiensis. The data on meiotic pairing in the F1 hybrid and the comparative morphology of O. sativa, O. officinalis and O. australiensis inicate that the last species is the most primitive member, having originated from the pre-Sativa and pre-Officinalis complex.

Evidence of nonchiasmate bonds at metaphase I in inbred rye

1984 ◽  
Vol 26 (4) ◽  
pp. 409-414 ◽  
Author(s):  
M. C. Cermeño ◽  
J. Orellana ◽  
J. R. Lacadena
Keyword(s):  
Secale Cereale ◽  
Chiasma Frequency ◽  
Meiotic Pairing ◽  
Secale Cereale L ◽  
Chromosome 1R ◽  
Metaphase I

The loss of bound chromosome arms through early, middle, and late metaphase I has been analyzed in a plant of inbred rye (Secale cereale L.) heterozygous for a terminal heterochromatic C-band of the long arm of chromosome 1R. From the increase in the number of univalent pairs due to bound arm loss, and from the comparison between the frequencies of bound arms at metaphase I and recombinant chromosomes at anaphase I, it is concluded that some of the chromosome bonds appearing at metaphase I are actually nonchiasmate associations that can be considered as remnants of prophase pairing. Conclusions concerning recombination obtained solely from the analysis of chiasma frequency measured as bound arms may be invalid.Key words: inbred rye, C-heterochromatin, meiotic pairing, nonchiasmate bonds.

Genome constitution of the Australian hexaploid grass Elymus scabrus (Poaceae: Triticeae)

Genome ◽  
1993 ◽  
Vol 36 (1) ◽  
pp. 147-151 ◽  
Author(s):  
J. Torabinejad ◽  
R. J. Mueller
Keyword(s):  
Chromosome Pairing ◽  
Interspecific Hybrids ◽  
Intergeneric Hybrid ◽  
Meiotic Pairing ◽  
Genome Constitution ◽  
Psathyrostachys Juncea ◽  
Hybrid Plants ◽  
Thinopyrum Bessarabicum ◽  
Mother Cells ◽  
Metaphase I

Eight intergeneric hybrid plants were obtained between Elymus scabrus (2n = 6x = 42, SSYY??) and Australopyrum pectinatum ssp. retrofractum (2n = 2x = 14, WW). The hybrids were vegetatively vigorous but reproductively sterile. Examination of pollen mother cells at metaphase I revealed an average of 16.63 I, 5.29 II, 0.19 III, and 0.05 IV per cell for the eight hybrids. The average chiasma frequency of 6.77 per cell in the above hybrids strongly supports the presence of a W genome from A. pectinatum ssp. retrofractum in E. scabrus. Meiotic pairing data of some other interspecific hybrids suggest the existence of the SY genomes in E. scabrus. Therefore, the genome constitution of E. scabrus should be written as SSYYWW. Two other hybrid plants resulted from Elymus yezoensis (2n = 4x = 28, SSYY) crosses with A. pectinatum ssp. pectinatum (2n = 2x = 14, WW). Both were weak and sterile. An average of 0.45 bivalents per cell were observed at metaphase I. This clearly indicates a lack of pairing between W genome of Australopyrum and S or Y genomes of E. yezoensis. In addition, six hybrid plants of E. scabrus with Psathyrostachys juncea (2n = 2x = 14, NN) and one with Thinopyrum bessarabicum (2n = 2x = 14, JJ) were also obtained. The average bivalents per cell formed in both combinations were 2.84 and 0.70, respectively. The results of the latter two combinations showed that there is no N or J genome in E. scabrus.Key words: wide hybridization, chromosome pairing, genome analysis, Australopyrum, Elymus.

scholarly journals Genetics of Hybrid Sterility and Hybrid Breakdown in an Intersubspecific Rice (Oryza sativa L.) Population

Genetics ◽  
1997 ◽  
Vol 145 (4) ◽  
pp. 1139-1148 ◽  
Author(s):  
Zhikang Li ◽  
Shannon R M Pinson ◽  
Andrew H Paterson ◽  
William D Park ◽  
James W Stansel
Keyword(s):  
Oryza Sativa ◽  
Oryza Sativa L ◽  
Hybrid Sterility ◽  
Rice Genome ◽  
F1 Hybrids ◽  
Progeny Testing ◽  
Hybrid Breakdown ◽  
F1 Hybrid ◽  
Genetic Mechanisms ◽  
Complicated Nature

F1 hybrid sterility and “hybrid breakdown” of F2 and later generations in rice (Oryza sativa L.) are common and genetically complicated. We used a restriction fragment length polymorphism linkage map and F4 progeny testing to investigate hybrid sterility and hybrid breakdown in a cross between “widely compatible” O. sativa ssp. japonica cultivar Lemont from the Southern U.S. and ssp. indica cultivar Teqing from China. Our results implicate different genetic mechanisms in hybrid sterility and hybrid breakdown, respectively. Hybrid sterility appeared to be due to recombination within a number of putative differentiated “supergenes” in the rice genome, which may reflect cryptic structural rearrangements. The cytoplasmic genome had a large effect on fertility of both male and female gametes in the F1 hybrids. There appeared to be a pair of complementary genes that behaved like “wide compatibility” genes. This pair of genes and the “gamete eliminator” (S1) or “egg killer” (S-5) may influence the phenotypic effects of presumed supergenes in hybrids. Hybrid breakdown appeared to be largely due to incompatibilities between indica and japonica alleles at many unlinked epistatic loci in the genome. These proposed mechanisms may partly account for the complicated nature of postreproductive barriers in rice.

scholarly journals MOST OF THE HOMOEOLOGOUS PAIRING AT METAPHASE I IN WHEAT-RYE HYBRIDS IS NOT CHIASMATIC

Genetics ◽  
1985 ◽  
Vol 111 (4) ◽  
pp. 917-931
Author(s):  
Juan Orellana
Keyword(s):  
Homoeologous Pairing ◽  
Homologous Pairing ◽  
End To End ◽  
Homoeologous Chromosomes ◽  
Metaphase I

ABSTRACT The use of telomeric C-bands in wheat-rye hybrids has made it possible to distinguish three types of wheat-wheat (1BL) and wheat-rye associations (a, end-to-end extremely distal; b, end-to-ed distal; and c, interstitial) between homoeologous chromosomes at different metaphase I stages (early, middle and late) and also to estimate the actual recombination frequencies for such associations at anaphase I. There was a decrease of the a and b association frequencies during the different metaphase I stages, whereas the c type remained without variation in all stages. A good fit between the frequencies of c associations at metaphase I and the number of recombinant chromosomes at anaphase I, assuming a maximum of one chiasma per bond, was found; however, there was no correspondence between metaphase I and anaphase I data when all associations (a + b + c) were considered. In addition, rye-rye homologous pairing was observed at metaphase I, but no evidence for rye-rye recombination was found at anaphase I. The results indicate that most of end-to-end (a and b) homoeologous and nonhomologous associations are actually nonchiasmatic and are a remnant of prophase pairing.

Amphidiploids of perennial Triticeae. I. Synthetic Thinopyrum species and their hybrids

Genome ◽  
1992 ◽  
Vol 35 (6) ◽  
pp. 951-956 ◽  
Author(s):  
Richard R.-C. Wang
Keyword(s):  
Gene Flow ◽  
Chromosome Pairing ◽  
Colchicine Treatment ◽  
Meiotic Pairing ◽  
Pseudoroegneria Spicata ◽  
Genomic Relationships ◽  
Thinopyrum Elongatum ◽  
Metaphase I

Amphiploids of the hybrid Thinopyrum elongatum (Host) D.R. Dewey (2n = 2x = 14; JeJe) × Pseudoroegneria spicata (Pursh) A. Löve (2n = 2x = 14; SS) were obtained by the colchicine treatment of regenerants from inflorescence culture. Meiotic pairings in the JJSS amphiploids averaged 2.90 I + 4.44 rod II + 7.50 ring II + 0.14 III + 0.20 IV at metaphase I but had 13.38 ring II + 0.30 IV at diakinesis. This amphidiploid was crossed with that of T. bessarabicum (Savul. &Rayss) A. Löve (2n = 2x = 14; JbJb) × T. elongatum and the latter was also crossed with T. scirpeum (K. Presl) D.R. Dewey (2n = 4x = 28; JeJeJeJe) to obtain JbJeJeS and JeJeJeJb hybrids, respectively. The former hybrid had a metaphase I pairing pattern of 7.82 I + 4.33 rod II + 2.76 ring II + 1.51 III + 0.35 IV. The latter hybrid had 3.04 I + 4.05 rod II + 4.31 ring II + 1.26 III + 1.08 IV. These meiotic pairing data are in agreement with the genomic relationships based on the diploid hybrids involving these genomes. Fertility of the hybrid between T. scirpeum and the amphiploid of T. bessarabicum × T. elongatum suggested that their genomes were similar and balanced and that gene flow could occur between the JJ diploids and the JJJJ tetraploid.Key words: hybrid, amphidiploid, genome, isozyme, chromosome pairing, Triticeae, Thinopyrum.

scholarly journals Instability of Alien Chromosome Introgressions in Wheat Associated with Improper Positioning in the Nucleus

2019 ◽  
Vol 20 (6) ◽  
pp. 1448 ◽  
Author(s):  
Kateřina Perničková ◽  
Veronika Koláčková ◽  
Adam Lukaszewski ◽  
Chaolan Fan ◽  
Jan Vrána ◽  
...  
Keyword(s):  
Plant Breeding ◽  
Nuclear Periphery ◽  
Host Genome ◽  
Meiotic Pairing ◽  
Alien Chromosome ◽  
3D Fish ◽  
Meiotic Event ◽  
Metaphase I

Alien introgressions introduce beneficial alleles into existing crops and hence, are widely used in plant breeding. Generally, introgressed alien chromosomes show reduced meiotic pairing relative to the host genome, and may be eliminated over generations. Reduced pairing appears to result from a failure of some telomeres of alien chromosomes to incorporate into the leptotene bouquet at the onset of meiosis, thereby preventing chiasmate pairing. In this study, we analysed somatic nuclei of rye introgressions in wheat using 3D-FISH and found that while introgressed rye chromosomes or chromosome arms occupied discrete positions in the Rabl’s orientation similar to chromosomes of the wheat host, their telomeres frequently occupied positions away from the nuclear periphery. The frequencies of such abnormal telomere positioning were similar to the frequencies of out-of-bouquet telomere positioning at leptotene, and of pairing failure at metaphase I. This study indicates that improper positioning of alien chromosomes that leads to reduced pairing is not a strictly meiotic event but rather a consequence of a more systemic problem. Improper positioning in the nuclei probably impacts the ability of introgressed chromosomes to migrate into the telomere bouquet at the onset of meiosis, preventing synapsis and chiasma establishment, and leading to their gradual elimination over generations.

Spreading synaptonemal complexes of B isochromosomes in the grasshopper Omocestus burri

Genome ◽  
1994 ◽  
Vol 37 (6) ◽  
pp. 1035-1040 ◽  
Author(s):  
A. L. del Cerro ◽  
A. Fernández ◽  
J. L. Santos
Keyword(s):  
Electron Microscopy ◽  
Meiotic Pairing ◽  
Synaptonemal Complexes ◽  
Peripheral Location ◽  
Hairpin Loops ◽  
Pairing Model ◽  
Similarities And Differences ◽  
Surface Spread ◽  
Pairing Behaviour ◽  
Metaphase I

Meiotic pairing behaviour of one and two B isochromosomes (iso-Bs) in the grasshopper Omocestus burri was analysed by electron microscopy in surface-spread prophase I nuclei and compared with light microscopic observations of metaphase I. Iso-Bs display a peripheral location in the surface-spread nuclei and early pairing relative to that of the long members of the A set. Single iso-Bs undergo foldback pairing to give symmetrical hairpin loops. Two iso-Bs may show interarm pairing, mterchromosome pairing, or combinations of the two. Pericentromeric interarm pairing can be delayed in one or both Bs and this delay is mostly observed in bivalents with pairing partner switches. The iso-B bivalent frequencies observed in the three males analysed were 64, 44, and 41%, respectively; the two latter values were significantly lower than the 66% predicted by the random-end-pairing model. There is a reduction in the frequencies of iso-ring univalents (in 1B males) and bivalents (in 2B males) from pachytene to metaphase I. Similarities and differences between the pairing behaviour of iso-Bs from different species are also discussed.Key words: B isochromosomes, meiosis, grasshopper, synaptonemal complexes, pairing partner switches.

Meiotic pairing in new hybrids of Hordeum procerum (6x) with H. parodii (6x) and Elymus virginicus (4x)

1986 ◽  
Vol 28 (3) ◽  
pp. 416-419 ◽  
Author(s):  
P. K. Gupta ◽  
George Fedak
Keyword(s):  
Chromosome Pairing ◽  
Interspecific Hybrid ◽  
Intergeneric Hybrids ◽  
Meiotic Pairing ◽  
Metaphase I

Hybrids of Hordeum procerum were readily produced with H. parodii (7.9%) and Elymus virginicus (14.3%). The average meiotic pairing per cell in the interspecific hybrid between H. procerum and H. parodii was 14.56 I + 12.19 II + 1.04 III, which indicated that the species have two genomes in common. In the hybrid between H. procerum and E. virginicus the average metaphase I configuration was 20.35 I + 6.86 II + 0.31 III indicating one common genome. Keywords: interspecific, intergeneric hybrids, chromosome pairing, Hordeum, Elymus.

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