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  • 1
    Electronic Resource
    Electronic Resource
    Modification of Relative Mutagenic Efficiency in Barley of Mesyloxy Esters by Different Treatments (1966)
    [s.l.] : Nature Publishing Group
    Nature 211 (1966), S. 1099-1100 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Table 1. FREQUENCY OF SOMATIC CHROMOSOME BREAKAGE INDUCED BY EMS, MMS AND MYLERAN IN VARIOUS TREATMENT CONDITIONS OF TEMPERATURE AND pU (BREAKS/CELL) EMS MMS Myleran level. :EMS for 9-2 7-0 3-5 9-2 7-0 3-5 9-2 7-0 3-5 ,nd ! A B C X2 0C 18 C 32 C for A and C 0-42 0-42 0-50 0-694 ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/2111099b0
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  • 2
    Electronic Resource
    Electronic Resource
    The extent and position of homoeologous recombination in a distant hybrid of Alstroemeria: a molecular cytogenetic assessment of first generation backcross progenies (1999)
    Springer
    Chromosoma 108 (1999), S. 52-63 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract.  To estimate the extent and position of homoeologous recombination during meiosis in an interspecific hybrid between two distantly related Alstroemeria species, the chromosome constitution of six first generation backcross (BC1) plants was analysed using sequential fluorescent in situ hybridization (FISH) and genomic in situ hybridization (GISH) analysis. Four different probes were used for the FISH analysis: two species-specific and two rDNA probes. The six BC1 plants were obtained from crosses between the hybrid A. aurea×A. inodora with its parent A. inodora. GISH clearly identified all chromosomes of both parental genomes as well as recombinant chromosomes. The sequential GISH and FISH analysis enabled the accurate identification of all individual chromosomes in the BC1 plants, resulting in the construction of detailed karyotypes of the plants. The identification of the recombinant chromosomes provided evidence which chromosomes of the two species are homoeologous. Two of the BC1 plants were aneuploid (2n=2x+1=17) and four triploid (2n=3x=24), indicating that both n and 2n gametes were functional in the F1 hybrid. Using GISH, it was possible to estimate homeologous recombination in two different types of gametes in the F1 hyrid. The positions of the crossover points ranged from highly proximal to distal and the maximum number of crossover points per chromosome arm was three. Compared with the aneuploid plants, the triploid plants (which received 2n gametes) clearly possessed fewer crossovers per chromosome, indicating reduced chromosome pairing/recombination prior to the formation of the 2n gametes. Besides homeologous recombination, evidence was found for the presence of structural rearrangements (inversion and translocation) between the chromosomes of the parental species. The presence of the ancient translocation was confirmed through FISH analysis of mitotic and meiotic chromosomes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004120050351
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  • 3
    Electronic Resource
    Electronic Resource
    Chromosome breakage induced by alkyl-alkane-sulfonates under different physical treatment conditions (1966)
    Springer
    Chromosoma 18 (1966), S. 44-59 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract A detailed study of chromosome breakage induced by three alkane sulfonates, which differ in chemical structure, functionality and reaction mechanism has been made in barley under different treatment conditions of temperature and hydrogen ion concentration. This study has indicated that, (i) the frequency and the types of chromosome breakage, at mitosis and meiosis, indicate certain qualitative and quantitative differences between the biological action of these three chemicals, (ii) the temperature of the treatment solution profoundly influences the frequency of chromosome breakage — a high frequency of breakage is observed at higher temperature, (iii) the effect of pH, though not very significant, is evident from the production of appreciably low frequency of breakage at alkaline pH for a given dose of chemical, (iv) by appropriate manipulation of treatment conditions, increase or decrease in the frequency of chromosome breakage can be accomplished to a considerable extent, (v) the qualitative and quantitative differences observed with respect to chromosoma breakage reflect the differences in the mode of biological action of these agents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00326442
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  • 4
    Electronic Resource
    Electronic Resource
    Formation of first division restitution (FDR) 2n-megaspores through pseudohomotypic division in ds-1 (desynapsis) mutants of diploid potato: routine production of tetraploid progeny from 2xFDR × 2xFDR crosses (1991)
    Springer
    Theoretical and applied genetics 82 (1991), S. 645-656 
    Details
    ISSN: 1432-2242
    Keywords: 2n Megaspores ; Desynapsis ; Pseudohomotypic division ; Sexual polyploidization ; apomixis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The level and mode of 2n megaspore formation was studied in full-sib diploid potato clones with either normal or desynaptic (ds-1ds-1) meiosis. Cytological analysis revealed that functional 2n megaspores produced by normal and desynaptic clones originate exclusively from ‘second division restitution (SDR)’ and ‘first division restitution (FDR)’, respectively. SDR 2n megaspores resulted from the omission of the second meiotic division following chromosome doubling after anaphase I, whereas FDR 2n megaspores resulted from a direct equational division of univalent chromosomes at anaphase I (pseudohomotypic division). Comparative data strongly indicated that the observed mechanisms of SDR and FDR 2n megaspore formation are extremes of a continuum that is being brought about by common genes for precocious chromosome division. Depending on the relative timing of cell cycle and chromosome division, this precocious chromosome division may impose postreductional (SDR) or prereductional (FDR) ‘restitution’ of the sporophytic chromosome number under normal synaptic and desynaptic conditions, respectively. The observed frequencies of 2n megaspores closely correlated with seed set, following pollination by tetraploid varieties and by desynaptic diploid clones with exclusive FDR 2n pollen formation. Up to 54.0 and 21.5 seeds/ fruit were obtained from normal synaptic (SDR) and desynaptic (FDR) progeny, respectively. The high frequency of segregants with either SDR or FDR 2n megaspore formation (78.0 and 45.2%, respectively) supports the hypothesis that sexual polyploidization is the driving force behind the origin and evolution of polyploid Solanum species. The present identification of diploid potato clones with consistent FDR 2n megaspore formation extends the opportunities for direct transfer of enhanced diploid germ plasm to tetraploids, and particularly advocates the feasibility of 2x(ds-1; FDR)×2x(ds-1; FDR) breeding schemes in cultivar development and the production of relatively vigorous and uniform true potato seed (TPS) varieties. Its potential value and limitations for breeding and the experimental induction of diplosporic apomixis are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00226804
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  • 5
    Electronic Resource
    Electronic Resource
    Isolation of a new paramutagenic allele of thesulfurea locus in the tomato cultivar Moneymaker following in vitro culture (1993)
    Springer
    Theoretical and applied genetics 87 (1993), S. 289-294 
    Details
    ISSN: 1432-2242
    Keywords: Sulfurea ; Tomato ; Paramutation ; Dominant position effect variegation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A new allele, SC148, of thesulfurea locus inLycopersicon esculentum was detected in a line derived after repeated selfing of plants that had been regenerated from tissue culture. Like the originalsulf mutant, SC148 displayed two mutant phenotypes: green-yellow speckled plants in which thesulf vag allele is present and pure yellow plants homozygous for thesulf tpura allele. Although the mutant alleles are recessive to wild-type, an unpredictable number of variegated and pura plants appeared in F1 progenies that had been derived from crosses between SC148 and wild-type tomato plants. The presence of the wild-typesulf + allele in these variegated heterozygotes was demonstrated using a cytological marker that is linked tosulf. It is concluded that the mutantsulf allele of SC148, imposes its variegated expression state on the wild-typesulf + allele present insulf +/sulfvag heterozygotes. This behaviour, known as paramutation, has also been described for the originalsulf allele. The SC148 allele, however, seems to induce changes at an earlier stage in development. The analogy of this paramutagenic system to dominant position effect variegation inDrosophila is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01184914
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  • 6
    Electronic Resource
    Electronic Resource
    Transmission of alien tomato chromosomes from BC1 to BC2 progenies derived from backcrossing potato (+) tomato fusion hybrids to potato: the selection of single additions for seven different tomato chromosomes (1998)
    Springer
    Theoretical and applied genetics 96 (1998), S. 155-163 
    Details
    ISSN: 1432-2242
    Keywords: Key words Solanum tuberosum ; Lycopersicon esculentum ; Protoplast fusion ; Monosomic additions ; GISH ; FISH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  By backcrossing three BC1 genotypes of potato (+) tomato fusion hybrids to different tetraploid potato pollinators, BC2 populations were produced. A combined total of 97 BC2 plants from three BC2 populations were analysed with chromosome-specific probes through restriction fragment length polymorphism (RFLP) for the presence of alien tomato chromosomes. The number of different alien tomato chromosomes transmitted through the female BC1 parent ranged from 0 to 6, and the average number of different alien chromosomes transmitted per BC2 plant varied between 1.7 and 3.4 in the different populations. This variation corresponded to the chromosome constitution of the individual BC1 parents: parent 6739, which possessed 11 different alien chromosomes in a single condition, gave rise to progeny with a lower average number of alien chromosomes per plant than the BC1 parent 2003 that possessed 2 of the 12 alien chromosomes in a disomic condition. In the latter case, the higher transmission rate was attributed to the more regular distribution of the two alien chromosomes in the disomic condition because of regular bivalent formation during meiosis as revealed by genomic in situ hybridisation (GISH) and fluorescent in situ hybridisation (FISH). The transmission frequencies of individual alien chromosomes were subjected to statistical analysis to test whether the maternal genotypes had an effect on alien-chromosome transmission. Among the BC2 plants, a total of 27 single additions were detected for as many as seven different chromosomes (1, 2, 4, 6, 8, 10 and 12) out of the 12 possible types.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001220050722
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  • 7
    Electronic Resource
    Electronic Resource
    Chiasma formation in the short arm of the nucleolar chromosome of the tomato (1971)
    Springer
    Theoretical and applied genetics 41 (1971), S. 371-374 
    Details
    ISSN: 1432-2242
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A translocation heterozygote in tomato (Lycopersicon esculentum) is shown to have a cyclical type of interchange between the long arms of chromosomes 1, 2 (nucleolar) and 3. A study of chromosome association in this plant at metaphase I has indicated that in 21% of the cells a ring of six chromosomes is present. Since an open ring hexavalent can occur only if there is chiasma formation in all the translocated segments and in all the short arms of the three chromosomes, it is concluded that there is considerable frequency of chiasma formation in the short arm of the nucleolar chromosome. This conclusion contradicts the previous observations that chiasma formation is either absent or very rare in the entirely dark staining chromatic, sometimes referred to as heterochromatic, short arm of the nucleolar chromosome.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00277338
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  • 8
    Electronic Resource
    Electronic Resource
    Chromosome breakage-fusion-bridge-cycle and phenotypic instability in isochromosome lines of tomato (1985)
    Springer
    Theoretical and applied genetics 71 (1985), S. 145-152 
    Details
    ISSN: 1432-2242
    Keywords: Tomato ; Isochromosomes ; Breakage-fusion-bridge-cycle ; Phenotypic instability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Cultivated tomato lines with 7–9 copies of extra chromosomes, which were fully heterochromatic, were found to have normal growth and reproduction. Cytological evidence suggested that all extra chromosomes in the 24 plants investigated were derived from a single isochromosome of the short arm of chromosome 2. In spite of their common origin, the individual extra chromosomes within and between plants varied considerably with respect to size and morphology. The morphological variation of these extra chromosomes was found to result from chromosome-or chromatid breakage-fusion-bridge-cycle (BFBC). In order to verify whether BFBC could induce “genomic shock” and instability, the phenotypes of more than 10,000 seedlings from some of the progeny were examined. There was a 3-to 4-fold increase in the occurrence of the number of chlorophyll variegated sectors in the progeny of plants with BFBC when compared to the control variety.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00252048
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  • 9
    Electronic Resource
    Electronic Resource
    Comparative performance of FDR and SDR progenies from reciprocal 4x-2x crosses in potato (1994)
    Springer
    Theoretical and applied genetics 89 (1994), S. 545-550 
    Details
    ISSN: 1432-2242
    Keywords: First division restitution ; Second division restitution ; Reciprocal 4x-2x crosses ; Solanum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Numerically unreduced (2n) gametes from first division restitution (FDR) are considered to be superior to 2n-gametes from second division restitution (SDR) because they transfer a larger proportion of the total parental heterozygosity and epistasis intact to the tetraploid progeny. This supposed superiority was investigated by comparing 12 sets of reciprocal 4x-2x crosses. Each diploid parent used in a reciprocal set produced 2n-pollen by FDR and 2n-eggs by SDR. Six agronomic characters were investigated. FDR progenies (from 4x.2x) were found to have higher mean yields due to more and bigger tubers. With respect to underwater weight, the overall progeny mean of FDR progenies was significantly higher than that of SDR progenies (from 2x.4x). However, the absolute difference found between both overall progeny means was too small to be of practical significance. No differences between FDR and SDR progeny means were found for vine maturity and chip colour. In addition to the progeny mean, within-progeny variation is important in potato breeding. For vine maturity a higher within-progeny variation was detected in SDR progenies, whereas within-progeny variations for yield, underwater weight and chip colour were not different in FDR and SDR progenies. With regard to vine maturity, we conclude that SDR 2n-gametes are superior to FDR 2n-gametes because, with the same progeny means of FDR and SDR progenies, the within-progeny variation was higher in SDR progenies. Therefore the assumed superiority of FDR 2n-gametes was confirmed for yield but was not observed for vine maturity, underwater weight and chip colour.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00222446
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  • 10
    Electronic Resource
    Electronic Resource
    Pollen markers for gene-centromere mapping in diploid potato (1996)
    Springer
    Theoretical and applied genetics 93 (1996), S. 1040-1047 
    Details
    ISSN: 1432-2242
    Keywords: Key words 2n gametes ; Crossing-over ; Desynapsis ; Amylose-free starch ; Alcohol dehydrogenase ; Solanum tuberosum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The utility of two pollen genetic markers for estimating the extent of meiotic recombination between the centromere and a marker gene was tested in 2n pollen of diploid potato clones. One of these markers was the distal locus amylose-free (amf) on chromosome 8 and the other was the isozyme locus alcohol dehydrogenase (Adh-1) on chromosome 4. In the case of the amf locus, the gene-centromere distance was estimated in a normal synaptic and a desynaptic genotype. In both cases the genetic analysis was confined to: (1) a direct estimation of the phenotypic (blue vs red) segregation ratios in FDR (first-division restitution) 2n pollen and (2) a classification of the 4x progeny from 4x (nulliplex amf) × 2x (Amf/amf) crosses into duplex, simplex and nulliplex classes. The recombination frequency between the centromere and the amf locus in the normal synaptic genotype B92-7015-4 corresponded to a gene-centromere distance of 48.8 cM, whereas this distance amounted to 13.3 cM in the desynaptic genotype RS93-8025–1. Hence desynapsis reduced crossing-over by 73%. The observed genetic distance of 48.8 cM in the normal synaptic clone, B92-7015–4, is the highest gene-centromere distance reported so far in potato and this could be explained on the assumption of absolute chiasma interference. For the Adh-1 locus, it was found that heterozygous 2n pollen grains could be detected in pollen samples of the diploid clones, because of the occurrence of a heterodimeric band of the isozyme. Unlike the amf locus, the gene-centromere distance for the Adh-1 locus was estimated only on the basis of the duplex, simplex and nulliplex classes in the progenies from 4x (nulliplex Adh-1 2 ) × B92-7015–4 (Adh-1 1 /Adh-1 2 ) crosses and was found to be 19.4 cM. Because the accurate positions of centromeres in relation to other loci are not available in the existing genetic maps of potato, which are saturated with molecular markers, half-tetrad analysis is a promising additional approach to the basic genetics of this crop.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001220050332
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