Location of the Ph1 locus in the metaphase chromosome map and the linkage map of the 5Bq arm of wheat

1986 ◽  
Vol 28 (4) ◽  
pp. 511-519 ◽  
Author(s):  
R. Jampates ◽  
J. Dvořák
Keyword(s):  
Linkage Map ◽  
Chromosome Pairing ◽  
Chinese Spring ◽  
Chromosome Rearrangement ◽  
Distal Region ◽  
Crossing Over ◽  
Chromosome 5B ◽  
Ph1 Locus ◽  
The Difference ◽  
Two Populations

Heterogenetic chromosome pairing in wheat is prevented by the Ph1 locus on the q (=L) arm of chromosome 5B. Two durum wheat cv. Cappelli structural mutants with rearranged 5Bq chromosome arms were investigated to determine the location of the Ph1 locus in the metaphase map and the linkage map of the arm. One of the mutants, Cap5Bq−, has a deletion of subregion 5Bq12.3 between C-bands 5Bq12.2 and 5Bq21 and the other one, Cap5Bq+, has the same subregion duplicated. Each mutant and standard cv. Cappelli were crossed with Aegilops kotschyi, Ae. ovata, Ae. cylindrica, Ae. ventricosa, Ae. juvenalis, and "Ae. crassa 6x." Hybrids involving Cap5Bq− had higher levels of chromosome pairing than those involving cv. Cappelli, whereas those involving Cap5Bq+ had lower levels of pairing than those involving cv. Cappelli. Cap5Bq− was crossed with cv. Cappelli and the F1 was hybridized with Ae. kotschyi and Ae. ventricosa. All hybrids with the 5Bq− chromosome had a higher level of chromosome pairing than those with the standard chromosome. Cap5Bq+ was crossed with cv. Cappelli and the F1 was hybridized with Ae. kotschyi. Most hybrids with the 5Bq+ chromosome had a lower level of chromosome pairing than those with the standard chromosome. Because the difference between the means of the two populations was small (0.43 chiasmata per cell) and the distributions overlapped, the strength of the linkage between the duplication and reduced pairing could not be determined; the data, nevertheless, showed that the reduced pairing must be strongly, if not completely, linked to the duplication. It is therefore concluded that the Ph1 locus is in the euchromatic subregion 5Bq12.3, 5Bq− is a null for Ph1, and 5Bq+ has two Ph1 loci. The 5Bq+ chromosome was substituted into Triticum aestivum cv. Chinese Spring, the substitution was crossed with cv. Chinese Spring ditelosomic 5Bq, and the F1 was crossed with cv. Chinese Spring monosomic 5B. Recombination of C-bands relative to each other and the centromere was determined with the objective of determining the distribution of crossing-over along the 5Bq arm and the linkage of the subregion 5Bq12.3 with the centromere. The distibution of crossing-over was greatly distorted, most occurred in the distal region of the arm. The subregion 5Bq12.3 showed a tight linkage with the centromere, even though it is in the middle of the 5Bq arm. It is proposed to designate the cv. Cappelli Ph1− mutation as ph1c.Key words: Triticum, map distortion, homoeologous pairing, chromosome pairing, chromosome rearrangement.

GENETIC REGULATION OF HETEROGENETIC CHROMOSOME PAIRING IN POLYPLOID SPECIES OF THE GENUS TRITICUM sensu lato

1982 ◽  
Vol 24 (1) ◽  
pp. 57-82 ◽  
Author(s):  
Patrick E. McGuire ◽  
Jan Dvořák
Keyword(s):  
Triticum Aestivum ◽  
Chromosome Pairing ◽  
Chinese Spring ◽  
Genetic Regulation ◽  
Triticum Aestivum L ◽  
Polyploid Species ◽  
D Genome ◽  
Chromosome 5B ◽  
A Genome

Polyploid species of Triticum sensu lato were crossed with Triticum aestivum L. em. Thell. cv. Chinese Spring monotelodisomics or ditelosomics that were monosomic for chromosome 5B. Progeny from these crosses were either euploid, nullisomic for 5B, monotelosomic for a given Chinese Spring chromosome, or nullisomic for 5B and monotelosomic simultaneously. The Chinese Spring telosome in the hybrids permitted the evaluation of autosyndesis of chromosomes of the tested species. In addition, several Chinese Spring eu- and aneuhaploids were produced. Genotypes of T. cylindricum Ces., T. juvenale Thell., T. triunciale (L.) Raspail, T. ovatum (L.) Raspail, T. columnare (Zhuk.) Morris et Sears, T. triaristatum (Willd.) Godr. et Gren., and T. rectum (Zhuk.) comb. nov. were all shown to have suppressive effects on heterogenetic pairing in hybrids lacking 5B or 3AS, whereas T. kotschyi (Boiss.) Bowden had no effect. It was concluded that diploid-like meiosis in these species is due to genetic regulation. A number of these genotypes promoted heterogenetic pairing in the presence of 5B. A model is presented to explain this dichotomous behavior of the tested genotypes. Monotelosomic-3AL haploids had a greater amount of pairing than did euhaploid Chinese Spring, which substantiated the presence of a pairing suppressor(s) on the 3AS arm. Evidence is presented that shows that T. juvenale does not have a genome homologous with the D genome of T. aestivum.

Mapping of a chromosome pairing gene and 5S rRNA genes in Triticum aestivum L. by a spontaneous deletion in chromosome arm 5Bp

1986 ◽  
Vol 28 (2) ◽  
pp. 266-271 ◽  
Author(s):  
Rama S. Kota ◽  
Jan Dvořák
Keyword(s):  
Triticum Aestivum ◽  
Chromosome Pairing ◽  
Chinese Spring ◽  
Triticum Aestivum L ◽  
5S Rrna ◽  
Rrna Genes ◽  
C Banding ◽  
Aegilops Longissima ◽  
Chromosome 5B ◽  
5S Rrna Genes

A deletion in the p arm of chromosome 5B of Triticum aestivum L. cv. Chinese Spring was identified by C-banding during the production of disomic substitutions of 6B of Aegilops longissima Schweinf. et Muschl. for chromosome 5B of cv. Chinese Spring. The deletion was terminal with a breakpoint just proximal to the interstitial C-band. The degree of metaphase I chromosome pairing in plants homozygous for the deletion indicated that the chromosome pairing promoting gene known to be in the p arm of chromosome 5B is located in the deleted portion of that arm. Additionally, all of the 5S ribosomal RNA genes known to exist on arm 5Bp were mapped to this deleted portion.Key words: C-banding, 5S rRNA genes, Triticum, Aegilops chromosome aberration.

scholarly journals DISTRIBUTION OF NONSTRUCTURAL VARIATION BETWEEN WHEAT CULTIVARS ALONG CHROMOSOME ARM 6Bp: EVIDENCE FROM THE LINKAGE MAP AND PHYSICAL MAP OF THE ARM

Genetics ◽  
1984 ◽  
Vol 106 (2) ◽  
pp. 325-333
Author(s):  
Jan Dvořák ◽  
Kuey-Chu Chen
Keyword(s):  
Linkage Map ◽  
Chinese Spring ◽  
Physical Map ◽  
Rrna Genes ◽  
Gene Region ◽  
Rrna Gene ◽  
Crossing Over ◽  
Wheat Cultivars ◽  
Chromosome Arm ◽  
26S Rrna

ABSTRACT Metaphase I (MI) pairing of homologous chromosomes in wheat intercultivar hybrids (heterohomologous chromosomes) is usually reduced relative to that within the inbred parental cultivars (euhomologous chromosomes). It was proposed elsewhere that this phenomenon is caused by polymorphism in nucleotide sequences (nonstructural chromosome variation) among wheat cultivars. The distribution of this polymorphism along chromosome arm 6Bp (=6BS) of cultivars Chinese Spring and Cheyenne was investigated. A population of potentially recombinant chromosomes derived from crossing over between telosome 6Bp of Chinese Spring and Cheyenne chromosome 6B was developed in the isogenic background of Chinese Spring. The approximate length of the Chinese Spring segment present in each of these chromosomes was assessed by determining for each chromosome the interval in which crossing over occurred (utilizing the rRNA gene region, a distal C-band and the gliadin gene region as markers). The MI pairing frequencies of these chromosomes (only the complete chromosomes were used) with the normal Chinese Spring telosome 6Bp were determined. These were directly proportional to the length of the euhomologous segment. The longer the incorporated euhomologous segment the better was the MI pairing. This provided evidence that the heterohomologous chromosomes are differentiated from each other in numerous sites distributed throughout the arm.—The comparison of the physical map of arm 6Bp with the linkage map showed a remarkable distortion of the linkage map; no crossing over was detected in the proximal 68% of the arm. A population of 49 recombinant chromosomes was assayed for recombination within the rRNA gene region, but none was detected. No new length variants of the nontranscribed spacer separating the 18S and 26S rRNA genes were detected either.

Meiotic duration in wheat genotypes with or without homoeologous meiotic chromosome pairing

1974 ◽  
Vol 187 (1087) ◽  
pp. 191-207 ◽  
Keyword(s):  
Chromosome Pairing ◽  
Chinese Spring ◽  
Meiotic Chromosome ◽  
Meiotic Pairing ◽  
Homoeologous Pairing ◽  
Meiotic Chromosome Pairing ◽  
Chromosome 5B ◽  
Homoeologous Chromosome Pairing ◽  
The Cross ◽  
Pairing Behaviour

In order to investigate the possible relation between meiotic time and meiotic chromosome pairing behaviour, meiosis was timed in various forms of wheat and wheat hybrids. First, meiosis was timed in ten Triticum aestivum (var. Chinese Spring) genotypes with different chromosome constitutions which differed widely in the meiotic pairing behaviour. Secondly, in order to escape from the disadvantage of aneuploid material, meiosis was also timed in plants which differed in the extent of homoeologous pairing because of the activities of different alleles at one or two loci. For this experiment use was made of F 1 -hybrids from the cross T. aestivum x Aegilops mutica which, although they all have 28 chromosomes, differ widely in the amount of homoeologous pairing. Thirdly, meiosis was also timed in 28-chromosome and 29-chromosome plants derived from the cross between rye (Secale cereale) x 43-chromosome T. aestivum containing a single Ae. mutica addition chromosome known to carry genes which greatly affect the level of homoeologous pairing in wheat. Although the 28-chromosome plants display very little pairing (chiasma frequency per cell (c. f.) = 0.5) while 29-chromosome plants display a much higher amount of pairing (c. f. = 7.8) no difference in meiotic time was detected between them. Similarly, the duration of meiosis was not significantly different between the three types of F 1 -hybrids between T. aestivum x Ae. mutica which had chiasma frequencies of 14.3, 7.4 and 0.9. Thus, these results agree in showing that there was no correlation between the duration of meiosis and the amount of homoeologous chromosome pairing. The results obtained for genotypes of Chinese Spring also provided no evidence to support the notion that there is a relation between the level of chromosome pairing and the duration of the pairing process. Consequently some doubt must be cast upon the idea that the time available for pairing is limiting to the pairing process. It was shown that individual wheat chromosomes in Chinese Spring differed in their effects on meiotic duration. For instance, the absence of chromosome 7B has no detectable effect on meiotic duration. The absence of chromosome 5B in two genotypes resulted in an increase in meiotic time from that found in euploid plants (24 h) to that found in tetraploid wheat species (about 30 h). By using plants ditelosomic for chromosome 5B L it was shown that most, if not all, of the genetic effects of chromosome 5B on meiotic time are determined by the short arm.

The effect of the Ph1 gene in diploid rye, Secale cereale L.

Genome ◽  
1991 ◽  
Vol 34 (6) ◽  
pp. 913-917 ◽  
Author(s):  
R. Schlegel ◽  
A. Boerner ◽  
V. Thiele ◽  
G. Melz
Keyword(s):  
Chromosome Pairing ◽  
Chiasma Frequency ◽  
Addition Line ◽  
Homologous Pairing ◽  
Chromosome 5B ◽  
Secale Cereale L ◽  
Ph1 Locus ◽  
Ph1 Gene ◽  
Bivalent Formation ◽  
Octoploid Triticale

Experimental results demonstrated clearly that the dominant Ph1 allele of chromosome 5B of wheat affects the homologous pairing of rye chromosomes. A rye-wheat monotelosomic 5BL addition line was produced and used for meiotic studies. Compared with 14-chromosome control plants, the 5BL addition to rye causes an increase in univalents and rod bivalent formation, i.e., a significant reduction of chiasma frequency (11.21 chiasmata per pollen mother cell). The 5BL telosome itself does not associate with any of the rye chromosomes. Thus, the double dosage of 5BL, present in hexaploid or octoploid triticale, could be one of the main causes of pairing failure of the rye genome.Key words: chromosome pairing, Ph1 locus, wheat, rye, rye-wheat addition.

Synthesis and cytological characterization of trigeneric hybrids of durum wheat with and without Ph1

Genome ◽  
2004 ◽  
Vol 47 (6) ◽  
pp. 1173-1181 ◽  
Author(s):  
Prem P Jauhar ◽  
M Doğramaci ◽  
T S Peterson
Keyword(s):  
In Situ Hybridization ◽  
Chromosome Pairing ◽  
Genetic Recombination ◽  
Genomic In Situ Hybridization ◽  
Homoeologous Pairing ◽  
Alien Gene Transfer ◽  
Chromosome 5B ◽  
Alien Gene ◽  
Trigeneric Hybrids

Wild grasses in the tribe Triticeae, some in the primary or secondary gene pool of wheat, are excellent reservoirs of genes for superior agronomic traits, including resistance to various diseases. Thus, the diploid wheatgrasses Thinopyrum bessarabicum (Savul. and Rayss) Á. Löve (2n = 2x = 14; JJ genome) and Lophopyrum elongatum (Host) Á. Löve (2n = 2x = 14; EE genome) are important sources of genes for disease resistance, e.g., Fusarium head blight resistance that may be transferred to wheat. By crossing fertile amphidiploids (2n = 4x = 28; JJEE) developed from F1 hybrids of the 2 diploid species with appropriate genetic stocks of durum wheat, we synthesized trigeneric hybrids (2n = 4x = 28; ABJE) incorporating both the J and E genomes of the grass species with the durum genomes A and B. Trigeneric hybrids with and without the homoeologous-pairing suppressor gene, Ph1, were produced. In the absence of Ph1, the chances of genetic recombination between chromosomes of the 2 useful grass genomes (JE) and those of the durum genomes (AB) would be enhanced. Meiotic chromosome pairing was studied using both conventional staining and fluorescent genomic in situ hybridization (fl-GISH). As expected, the Ph1-intergeneric hybrids showed low chromosome pairing (23.86% of the complement), whereas the trigenerics with ph1b (49.49%) and those with their chromosome 5B replaced by 5D (49.09%) showed much higher pairing. The absence of Ph1 allowed pairing and, hence, genetic recombination between homoeologous chromosomes. Fl-GISH analysis afforded an excellent tool for studying the specificity of chromosome pairing: wheat with grass, wheat with wheat, or grass with grass. In the trigeneric hybrids that lacked chromosome 5B, and hence lacked the Ph1 gene, the wheat–grass pairing was elevated, i.e., 2.6 chiasmata per cell, a welcome feature from the breeding standpoint. Using Langdon 5D(5B) disomic substitution for making trigeneric hybrids should promote homoeologous pairing between durum and grass chromosomes and hence accelerate alien gene transfer into the durum genomes.Key words: alien gene transfer, chiasma (xma) frequency, chromosome pairing, fluorescent genomic in situ hybridization (fl-GISH), homoeologous-pairing regulator, specificity of chromosome pairing, wheatgrass.

PrBn, a Major Gene Controlling Homeologous Pairing in Oilseed Rape (Brassica napus) Haploids

Genetics ◽  
2003 ◽  
Vol 164 (2) ◽  
pp. 645-653 ◽  
Author(s):  
Eric Jenczewski ◽  
Frédérique Eber ◽  
Agnès Grimaud ◽  
Sylvie Huet ◽  
Marie Odile Lucas ◽  
...  
Keyword(s):  
Brassica Napus ◽  
Oilseed Rape ◽  
Chromosome Pairing ◽  
Major Gene ◽  
Major Effect ◽  
F1 Hybrids ◽  
Precise Control ◽  
Ph1 Locus ◽  
Likelihood Approach ◽  
Likelihood Ratio Statistics

Abstract Precise control of chromosome pairing is vital for conferring meiotic, and hence reproductive, stability in sexually reproducing polyploids. Apart from the Ph1 locus of wheat that suppresses homeologous pairing, little is known about the activity of genes that contribute to the cytological diploidization of allopolyploids. In oilseed rape (Brassica napus) haploids, the amount of chromosome pairing at metaphase I (MI) of meiosis varies depending on the varieties the haploids originate from. In this study, we combined a segregation analysis with a maximum-likelihood approach to demonstrate that this variation is genetically based and controlled mainly by a gene with a major effect. A total of 244 haploids were produced from F1 hybrids between a high- and a low-pairing variety (at the haploid stage) and their meiotic behavior at MI was characterized. Likelihood-ratio statistics were used to demonstrate that the distribution of the number of univalents among these haploids was consistent with the segregation of a diallelic major gene, presumably in a background of polygenic variation. Our observations suggest that this gene, named PrBn, is different from Ph1 and could thus provide complementary information on the meiotic stabilization of chromosome pairing in allopolyploid species.

scholarly journals A genetic linkage map for the domesticated silkworm, Bombyx mori, based on restriction fragment length polymorphisms

1995 ◽  
Vol 66 (2) ◽  
pp. 109-126 ◽  
Author(s):  
Jinrui Shi ◽  
David G. Heckel ◽  
Marian R. Goldsmith
Keyword(s):  
Linkage Map ◽  
Bombyx Mori ◽  
Restriction Fragment ◽  
Fragment Length ◽  
Restriction Fragment Length Polymorphisms ◽  
Genetic Maps ◽  
Crossing Over ◽  
Linkage Groups ◽  
Length Polymorphisms ◽  
Restriction Fragment Length

SummaryWe present data for the initial construction of a molecular linkage map for the domesticated silkworm, Bombyx mori, based on 52 progeny from an F2 cross from a pair mating of inbred strains p50 and C108, using restriction fragment length polymorphisms (RFLPs). The map contains 15 characterized single copy sequences, 36 anonymous sequences derived from a follicular cDNA library, and 10 loci corresponding to a low copy number retrotransposon, mag. The 15 linkage groups and 8 ungrouped loci account for 23 of the 28 chromosomes and span a total recombination length of 413 cM; 10 linkage groups were correlated with established classic genetic maps. Scoring data from Southern blots were analysed using two Pascal programs written specifically to analyse linkage data in Lepidoptera, where females are the heterogametic sex and have achiasmatic meiosis (no crossing-over). These first examine evidence for linkage by calculating the maximum lod score under the hypothesis that the two loci are linked over the likelihood under the hypothesis that the two loci assort independently, and then determine multilocus linkage maps for groups of putatively syntenic loci by calculating the maximum likelihood estimate of the recombination fractions and the log likelihood using the EM algorithm for a specified order of loci along the chromosome. In addition, the possibility of spurious linkage was exhaustively tested by searching for genotypes forbidden by the absence of crossing-over in one sex.

A Critique and Improvement of the CL Common Language Effect Size Statistics of McGraw and Wong

2000 ◽  
Vol 25 (2) ◽  
pp. 101-132 ◽  
Author(s):  
András Vargha ◽  
Harold D. Delaney
Keyword(s):  
Effect Size ◽  
Continuous Distribution ◽  
Interval Estimation ◽  
Continuous Variable ◽  
Common Language ◽  
Exact Methods ◽  
Normal Distributions ◽  
The Difference ◽  
Discrete Values ◽  
Two Populations

McGraw and Wong (1992) described an appealing index of effect size, called CL, which measures the difference between two populations in terms of the probability that a score sampled at random from the first population will be greater than a score sampled at random from the second. McGraw and Wong introduced this "common language effect size statistic" for normal distributions and then proposed an approximate estimation for any continuous distribution. In addition, they generalized CL to the n-group case, the correlated samples case, and the discrete values case. In the current paper a different generalization of CL, called the A measure of stochastic superiority, is proposed, which may be directly applied for any discrete or continuous variable that is at least ordinally scaled. Exact methods for point and interval estimation as well as the significance tests of the A = .5 hypothesis are provided. New generalizations ofCL are provided for the multi-group and correlated samples cases.

Testing for Asymmetrical Gene Flow in aDrosophila melanogasterBody-Size Cline

Genetics ◽  
2003 ◽  
Vol 165 (2) ◽  
pp. 667-673 ◽  
Author(s):  
W Jason Kennington ◽  
Julia Gockel ◽  
Linda Partridge
Keyword(s):  
Drosophila Melanogaster ◽  
Gene Flow ◽  
Body Size ◽  
Genetic Parameter ◽  
Good Evidence ◽  
Microsatellite Data ◽  
Eastern Australia ◽  
The Difference ◽  
Two Populations ◽  
Private Alleles

AbstractAsymmetrical gene flow is an important, but rarely examined genetic parameter. Here, we develop a new method for detecting departures from symmetrical migration between two populations using microsatellite data that are based on the difference in the proportion of private alleles. Application of this approach to data collected from wild-caught Drosophila melanogaster along a latitudinal body-size cline in eastern Australia revealed that asymmetrical gene flow could be detected, but was uncommon, nonlocalized, and occurred in both directions. We also show that, in contrast to the findings of a previous study, there is good evidence to suggest that the cline experiences significant levels of gene flow between populations.

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