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  • Articles  (34)
  • Articles: DFG German National Licenses  (34)
  • Atomic, Molecular and Optical Physics  (24)
  • Solanum  (10)
  • 1
    Electronic Resource
    Electronic Resource
    Active-site α-helix in papain and the stability of the ion pair RS- ··· ImH+. Ab initio molecular orbital study (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 651-671 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ab initio MO calculations, using both minimal (STO-3G) and extended (Roos-Siegbahn) basis sets are reported for the systems methanethiol-imidazole, methanethiol-imidazole-formaldehyde, and methanethiol-imidazole-formamide, which, together with a point-change representation of a long α-helix, form models for the active site of papain. It is shown that the large electric field exerted by the helix in the active-site region is responsible for the presence of the essential residues Cys 25 and His 159 in the form of an ion pair RS- ··· ImH+, which is crucial for a recently proposed mechanism for the catalytic action of the enzyme. Also, an explanation is given for the anomalies in measured pK values for these residues. Detailed studies on the (sub)systems show that minimal basis sets lack the flexibility necessary for describing the type of proton transfer involved. We conclude that α-helices are essential parts of enzymes and that they play a significant role in the catalytic process.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560170407
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  • 2
    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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  • 3
    Electronic Resource
    Electronic Resource
    Production of potato monohaploids (2n=x=12) through prickle pollination (1987)
    Springer
    Theoretical and applied genetics 73 (1987), S. 751-758 
    Details
    ISSN: 1432-2242
    Keywords: Monohaploids ; Prickle pollination ; Gynogenesis ; Solanum ; Potato
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Data are presented on the potential of gynogenesis for the production of monohaploids and on factors affecting their frequency and relative vigour. Diploid Solanum tuberosum L. and S. tuberosumxS. phureja Juz et Buk hybrids were used as maternal parents and selected S. phureja clones as prickle pollinators with embryo-spot and nodal band as dominant seed and plant marker. About 2 million seeds were screened for absence of embryo-spot. After raising plants from phenotypically spotless seeds, further screening for absence of nodal bands and for ploidy level was carried out. Finally more than 500 monohaploid plants from three genetically different groups of maternal parents were obtained. Frequency and vigour of the monohaploids were clearly dependent on their maternal genotypes. The data also indicated an effect of the pollinator genotype, the physiological stage of the maternal plant and the environment on monohaploid frequency. On the basis of these results the possibility of breeding for a higher monohaploid production rate and for more stable and vigorous monohaploids is discussed. Furthermore, gynogenesis and androgenesis are compared. It is suggested that both should be used in order to obtain monohaploids from sufficiently various diploid breeding material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00260786
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  • 4
    Electronic Resource
    Electronic Resource
    Relative performance of monohaploid potato clones and their diploid parents at plant level and after protoplast isolation and subsequent fusion (1987)
    Springer
    Theoretical and applied genetics 74 (1987), S. 451-458 
    Details
    ISSN: 1432-2242
    Keywords: Monohaploids ; Solanum ; Potato ; In vitro-performance ; Protoplast fusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Plant growth performance was studied in 118 potato monohaploids and in their diploid parents. Of these monohaploids 76 were also investigated at the protoplast level and eight of these were used in protoplast fusion experiments as well. No correlation was found between relative performance of greenhouse grown and in vitro grown plants. No or only weak correlations were found between different in vitro characteristics such as plant growth, protoplast yield per gram plant material, plating efficiency and callus growth. This indicates the unpredictability of these characters. The protoplast fusion experiments indicated that only in some genotype combinations increased callus growth rates may be found. However, it is not clear whether such calli were hybrids or not. In protoplast monocultures only diploid and tetraploid regenerants were obtained. After fusion, tetraploids but also some triploids could be regenerated. The finding of triploids indicates that monoploid protoplasts were involved in fusion. Isozyme analysis and morphological assessment of the plants pointed out that the majority of the fusion regenerants were hybrids. The implications of these results are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00289820
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  • 5
    Electronic Resource
    Electronic Resource
    Investigation of a self-compatible mutation in Solanum tuberosum clones inhibiting S-allele activity in pollen differentially (1991)
    Springer
    Molecular genetics and genomics 226 (1991), S. 283-288 
    Details
    ISSN: 1617-4623
    Keywords: Self-incompatibility ; SLG ; S-locus ; Solanum ; Pollen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A self-compatible (SC) mutation, identified in dihaploid lines of Solanum tuberosum, was investigated. It has previously been proposed that this mutation arose by translocation of an S-allele (S1) to a new chromosomal location. When present in pollen grains of genotype Sx, it overcomes the incompatibility reaction normally seen on styles carrying the Sx allele. However, when present in S1-bearing pollen grains, the normal incompatibility reaction on styles carrying S1 is still observed. using probes for the potato (S. tuberosum L.) S-linked glycoprotein (SLG) genes, it is shown that no sequence derived from SLG allele S1 can be linked to the presence of the SC mutation. The polypeptide product of the SLG allele S1 is also not detectable in SC mutant lines unless the S1 allele is also present. It is concluded that the SC mutation arose in a sequence other than that encoding the SLG S1 polypeptide, either in a part of the S-locus that is distinct from the S-gene, or at a different locus, giving rise to an inhibitor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00273614
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  • 6
    Electronic Resource
    Electronic Resource
    Barriers to hybridization of Solanum bulbocastanum Dun. and S. Verrucosum Schlechtd. and structural hybridity in their F1 plants (1976)
    Springer
    Euphytica 25 (1976), S. 1-10 
    Details
    ISSN: 1573-5060
    Keywords: Solanum ; interspecific hybridization ; structural hybridity ; unilateral inhibition ; sterility ; pollen tube growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Results of reciprocal crosses between Solanum verrucosum (2n=2x=24) and S. bulbocastanum (2n=2x=24) are described in terms of pollen tube behaviour in styles, of berry and seed set, of fertility and of meiotic behaviour of the F1 hybrids. Pollen tube growth of S. verrucosum is strongly inhibited in styles of S. bulbocastanum, whereas no inhibition is observed in the reciprocal cross. Therefore S. bulbocastanum x S. verrucosum fails to set berries or seeds, whereas the reciprocal cross produces both berries (54.4% berry set) and seeds (0.3 per berry). Only 14.6% of the seeds germinate. Both the diploid and corresponding tetraploid hybrid plants are vigorous, flower abundantly, have a rather regular meiosis (mainly rod bivalents), but show a high degree of cytoplasmic-genic male sterility. Crossability of the diploid hybrid plants is nil when used as pollen parents and near to zero when used as pistillate parents. The barriers to hybridization of the parent species (unilateral inhibition of pollen tube growth, somatoplastic sterility, cytoplasmic-genic male sterility and structural differences of the parental chromosomes) are discussed and methods are suggested to overcome these barriers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00041523
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  • 7
    Electronic Resource
    Electronic Resource
    Gene transfer from non-tuberous to tuberous Solanum species: Evidence from meiosis in hybrids (1982)
    Springer
    Euphytica 31 (1982), S. 565-572 
    Details
    ISSN: 1573-5060
    Keywords: Solanum ; potato ; gene transfer ; interspecific hybridization ; meiosis ; chromosome doubling ; non-tuberous
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The distant hybrids between non-tuberous Solanum species and tuberous S. pinnatisectum display little or no pairing in F1 and predominantly bivalent formation (preferential pairing) after chromosome doubling. In such a situation the question about the potential and extent of gene transfer from the non-tuberous parent to the tuberous one is relevant to potato breeding. This question was investigated by studying meiosis in triploid and hexaploid hybrids from crosses between diploid TV5 x tetraploid (S. etuberosum x S. pinnatisectum). TV5 is similar to S. verrucosum with cytoplasm of S. tuberosum. The following evidence was found for the desirable transfer of S. etuberosum genes to the tuberous species. The triploid F1 hybrids did not display the configurations 12 II+12 I expected if no gene exchange would take place between S. etuberosum and the tuberous species; however, a considerable number of multivalents per cell was observed in all plants studied. In the hexaploid F1 hybrids, obtained from the triploids through somatic doubling in vitro, 36 bivalents could reasonably be expected. Although bivalents were predominant (an overall average of 24.2 per cell) quite a few chromosomes were associated as multivalents in all plants investigated. It is concluded that in the hybrids studied a considerable amount of pairing and chiasma formation occurs between chromosomes of non-tuberous and those of tuberous Solanum species. This pairing affinity is larger than that found in 2x and 4x hybrids from S. etuberosum x S. pinnatisectum. Some hypotheses are put forward to explain this increased pairing affinity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00039194
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  • 8
    Electronic Resource
    Electronic Resource
    Analysis of parental effects on mean vine maturity and chip colour of 4x.2x potato progenies (1996)
    Springer
    Euphytica 88 (1996), S. 175-179 
    Details
    ISSN: 1573-5060
    Keywords: chip colour ; diploids ; sexual polyploidization ; Solanum ; vine maturity ; potato
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The parental effects on progenies from potato 4x.2x(FDR) crosses were analyzed to determine anether and to what extent selection criteria used for selecting tetraploid breeding lines have to be adjusted when selecting diploid breeding lines. For vine maturity and chip colour multiple regression analysis of progeny means on means of diploid and tetraploid parents revealed high coefficients of determination (R2) for both characters, indicating good predicting power of the performance of both diploid and tetraploid parents on the performance of their 4x.2x progenies. For vine maturity the multiple regression slope for the tetraploid perents was significantly larger than for the diploid parents, and progeny means were towards the tetraploid parents. This indicates that selection criteria for vine maturity may be less stringent at the diploid level. However, diploids may be earlier maturing than tetraploids and therefore selection criteria can better be similar at both ploidy levels. For chip colour, multiple regression slopes for diploid and tetraploid parents were similar and progeny means were towards the darkest coloured parent irrespective of its ploidy level. This indicates that selection of breeding lines for chip colour can be conducted similarly at both ploidy levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00023888
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  • 9
    Electronic Resource
    Electronic Resource
    Unique meiotic behaviourin F1 plants from a cross between a non-tuberous and a tuberous Solanum species in section Petota (1979)
    Springer
    Euphytica 28 (1979), S. 9-15 
    Details
    ISSN: 1573-5060
    Keywords: Meiosis ; interspecific hybridization ; chromosomal differentiation ; parallel spindles ; Solanum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Uniformly abnormal meiotic behaviour was observed in 12 F1-plants from a cross between Solanum etuberosum (non-tuberous) and S. pinnatisectum (tuberous). Per pollen mother cell at MI an average was found of 3.64 bivalents (all rodshaped, 1–2 per cell, heteromorphic), 16.64 univalents (scattered haphazardly on a continuous bipolar spindle) and 0.03 trivalents (all Y-shaped). Lagging chromosomes and precocious division of univalents very frequently occurs, leading to unequal distribution of chromosomes, aneuploid gametes and male sterility. Heteromorphic bivalents at MI, loops in bivalents at pachytene and non-disjunction in one hybrid plant, point to a highly abnormal meiotic behaviour. The occurrence of few trivalents is discussed. Considering that according to the literature nearly normal pairing was observed in the intergeneric F1-hybrids Lycopersicon esculentum × Solanum lycopersicoides and L. esculentum x S. pennellii, the lack of chromosome pairing in an interspecific F1-hybrid, of which both Solanum parents belong to the same section, is paradoxical to a plant breeder and might even be conspicuous to a taxonomist.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00029167
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  • 10
    Electronic Resource
    Electronic Resource
    Chromosome doubling through adventitious shoot formation on in vitro cultivated leaf explants from diploid interspecific potato hybrids (1981)
    Springer
    Euphytica 30 (1981), S. 239-246 
    Details
    ISSN: 1573-5060
    Keywords: Solanum ; potato ; explant culture ; interspecific hybrid ; adventitious shoots ; in vitro ; chromosome doubling ; solid mutants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Nearly 450 plantlets were produced from 51 diploid Solanum etuberosum x S. pinnatisectum F1 hybrids through adventitious shoot formation on in vitro cultivated rachis and petiole explants. On the basis of phenotypical assessment of the ploidy level of 425 plants, 84.7% of the plants were scored as doubled or doubled twice. A cytological analysis of ploidy in the three layers L1.L2 and L3 of 112 plants revealed 83.9% complete doubling: periclinal ploidy chimeras were not found and only two sectorial ploidy chimeras were detected. Doubled plants were obtained from all 51 clones. Various flower colours and epinastic leaves (in 1 clone) may be indications of mutagenesis through the treatment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00033983
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