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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Chromosoma 67 (1978), S. 123-143 
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The meiotic process in PMCs of Hypochoeris maculata is progressively disrupted in the presence of two or more B-chromosomes. Bivalent formation and chiasma conditions are unaffected by up to 3Bs although some univalence occurs with higher numbers. Spindle behaviour, however, is inefficient at both first and second division in the presence of two or more Bs. At metaphase I, regular equatorial alignment breaks down and A-bivalents sometimes show amphitelic or monosyntelic orientation. Anaphase I is characterised by irregular segregation, equatorial laggards and centric division products. The proportion of normal anaphase segregations declines by 20% for every B more than one. A-chromosome laggards, but not Bs, can induce nuclear restitution at telophase I. Following centric division at anaphase II poleward movement can fail leading to further nuclear restitution. Telophase II nuclei thus can be approximately haploid, diploid or tetraploid with aneuploid variation around the haploid and diploid levels. The frequency of numerical mutants in the offspring indicates that EMC meiosis is much less susceptible to the presence of Bs than PMC meiosis: only 4- and 5Bt plants have an enhanced frequency of numerically-aberrant offspring. The deleterious effects of Bs on meiotic efficiency will contribute to setting an upper limit on B-numbers in natural populations of this species.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Chromosoma 85 (1982), S. 299-310 
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The stable telocentric B-chromosomes of Hypochoeris maculata show an overall accumulation through the egg but a loss through the pollen. When crosses involve a single Bt the joint transmission gives an accumulation of 8%. The individual crosses, however, show great heterogeneity. Transmission through the megaspore ranged from 0.287 to 1.037 per B while pollen transmission was much less variable (0.360 to 0.560 per B) and close to the expected value. There is no intraplant correlation between pollen and egg transmission. Crosses repeated in different years show a clear positive correlation through the egg but no correlation through the pollen indicating that some B-transmission variation is of environmental origin. Despite this discrepancy, the outcome of crosses between plants of known transmission rate can be predicted. Stability of the A-chromosome complement is clearly reduced by the presence of B-chromosomes.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 67 (1984), S. 469-473 
    ISSN: 1432-2242
    Keywords: Maize ; Pollen anther ; Esterase ; Male ; sterility ; Restorer genes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary During anther development, characterized in maize plants with N cytoplasm, certain esterase isozymes in non-microspore cells decrease in amount with anther age and new isozymes appear in the developing microspores. In anthers from male sterile plants with cms T or cms C cytoplasm, neither of these changes in esterase patterns occurred. In anthers from plants with cms S cytoplasm, the decrease in the esterases of non-microsporogenous cells was observed but not the appearance of microspore esterases. In lines carrying cms S cytoplasm and nuclear restorer genes, esterase changes during anther development were as in normal fertile anthers. These results are discussed with respect to the phenomenon of cytoplasmic male sterility in the different maize genotypes.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 68 (1984), S. 219-226 
    ISSN: 1432-2242
    Keywords: Hexaploid genotypes ; Allelic variation ; Esterase ; Isozymes ; Isoelectric focusing ; Wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Analysis of grain esterase isozymes in Chinese Spring aneuploid genotypes by IEF confirmed that genes on the long arms of chromosomes 3A, 3B and 3D (Est-5) control the production of 19 isozymes. Allelic variants have been found for the isozyme pattern controlled by each chromosome. Segregational data involving null alleles and complex phenotypic differences indicate that the wheat grain esterases are encoded by three compound and probably homoeoallelic loci, each capable of producing at least six different isozymes. In a sample of 138 hexaploid genotypes, seven alleles were distinguished.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 66 (1983), S. 39-49 
    ISSN: 1432-2242
    Keywords: Hexaploid wheat ; β-amylase ; Isozymes ; Isoelectric focusing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Thirty-three β-amylase isozymes were separated in ‘Chinese Spring’ by IEF and the structural genes encoding seventeen of these were located by nullisomic analysis. The locations of the previously reported β-Amy-1 loci on chromosome arms 4Aβ (β-Amy-A1) and 4DL (β-Amy-D1) were confirmed and another set, β-Amy-2, was found on the group 5 chromosomes. A locus on 5AL (β-Amy-A1) was identified by nullisomic analysis and another on chromosome 5B (β-Amy-B2) was identified by analysis of inter-varietal chromosome substitution lines. The loci are complex, each coding for several isozymes, and allelic variation occurs at all four. Two alleles were identified at β-Amy-A1, five at β-Amy-D1, five at β-Amy-A2 and two at β-Amy-B2. Eleven different β-AMY phenotypes were distinguished amongst the 46 wheat varieties screened. The β-Amy-A2 locus was mapped by employing chromosome 5A recombinant lines and found to be closely linked and proximal to the awn inhibitor, B1, on the long arm. An attempt to map the β-Amy-D1 locus on chromosome 4D showed the gene to be located in the distal region of the long arm.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 72 (1986), S. 219-225 
    ISSN: 1432-2242
    Keywords: Esterase isozymes ; Isoelectric focusing ; Wheat ; Rye ; Barley ; Aegilops ; Agropyron
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A comparison of EST-5 grain esterase phenotypes from wheat-alien amphiploid, addition and substitution genotypes, resolved by flat-bed isoelectric focusing identified homoeologous Est-5 loci on chromosome 3H of Hordeum vulgare, 3Hch of H. chilense, 3Sb of Aegilops bicornis, 3S1 of Ae. sharonensis and Ae. longissima and 6R of Secale cereale and 6Rm of S. montanum. The Est-5 genes in alien species provide evidence for chromosome homoeology with wheat.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 69 (1984), S. 205-210 
    ISSN: 1432-2242
    Keywords: Hexaploid wheat ; Rye ; Barley ; Leaf peroxidase ; Isozymes ; Isoelectric focusing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Eight leaf peroxidase isozymes were distinguished by IEF in ‘Chinese Spring’. Two genes which control the production of three of these isozymes were located on chromosome arms 1BS and 1DS by nullisomic analysis. These loci probably form part of a homoeoallelic series and have been designated Per-B1 and Per-D1 respectively. Analysis of chromosome 1B short arm terminal deletion stocks indicated that the Per-B1 locus is located between the nucleolar organiser region and another isozyme marker, Hk-B1. Two variant leaf peroxidase phenotypes were distinguished in a small sample of hexaploid wheat varieties. Analysis of wheat-alien addition and substitution lines identified homoeologous loci in rye (Per-R1) and barley (Per-H1).
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 70 (1985), S. 400-406 
    ISSN: 1432-2242
    Keywords: Hexaploid wheat ; Endosperm ; Allelic variation ; α-Amylase ; Isozymes ; Isoelectric focusing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A study of α-amylase isozyme patterns from gibberellin-induced endosperms from more than 200 wheat genotypes has revealed allelic variation at five of the six α-Amy-1 and α-Amy-2 structural loci. These differences will find application as genetic markers and in varietal identification. The α-Amy-B1 locus on chromosome 6B was most variable and displayed eight distinct allelic forms. The nature of the allelic phenotypes, observations of segregating populations and the number of in vivo translation products of mRNAs from the α-Amy-1 and α-Amy-2 loci indicated that the individual loci are multigenic, each consisting of tightly linked subunits which produce several different isoforms.
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  • 9
    ISSN: 1432-2242
    Keywords: Pollen irradiation ; Wheat ; Differential gene transfer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The use of irradiated pollen to bring about limited gene transfer in wheat has been investigated. Doses of X-rays of 2Kr, 3Kr and 5Kr were used to generate M1 progeny between maternal and paternal genotypes differing in quantitative and major gene characters. Cytological studies of M1 plants revealed hybrids with widespread aneuploidy and structural rearrangements in the paternal genome. These effects resulted in phenotypic variation between M1 progeny and complex multivalent formation at meiosis. All M1 plants at the 5Kr and 3Kr doses were sterile and all but 2 plants at the 2Kr dose. Studies of the two M2 families from these plants revealed disturbances in genotype frequencies for some of the marker loci with an excess of maternal homozygotes and a deficit of paternal homozygotes. This was also reflected in a more maternal appearance for quantitative characters. These results are interpreted as showing that irradiation damage to the paternal genome in M1 plants results in the differential transmission of maternal alleles.
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  • 10
    ISSN: 1573-5044
    Keywords: Dioscoreaceae ; DNA uptake ; microcallus induction ; monocot tuber crop ; PEG-mediated
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Leaf mesophyll protoplasts from immature leaves of in vitro shoot cultures of a range of cultivars of three species of food yam (Dioscorea alata, D. bulbifera and D. cayenensis-rotundata) were isolated and their responses to culture in agarose-solidified media compared. Leaves at early stages of development (〈 1.0 cm in length) proved most suitable for production of active yam protoplasts capable of cell division. Formation of cell colonies to the 50-cell stage was observed in protoplast cultures in five of ten cultivars of D. alata and to the 30-cell stage in two cultivars of D. cayenensis-rotundata but not in cultures of D. bulbifera. Embryogenic cell suspension protoplasts of D. alata cv. Oriental Lisbon were successfully transformed with plasmids pBI 221.2, pBI 221.54, pBSGUS1 and pJT137 using a standard polyethylene glycol-mediated uptake method. Levels of transient expression of the uidA gene varied according to the plasmid used and the cell lines from which yam protoplasts were derived. This is the first report of yam protoplast culture leading to cell regeneration and direct gene transfer into protoplasts of this monocotyledonous genus.
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