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  • 1
    Electronic Resource
    Electronic Resource
    Fish farming and aquaculture (1988)
    [s.l.] : Nature Publishing Group
    Nature 333 (1988), S. 505-506 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SIR-The article "Fish farming and influ-enza pandemics" by Christoph Scholtissek and Ernest Naylor (Nature 331,215; 1988) has been widely reported in Asian and Western newspapers. We feel that it deserves clarification because of adverse effects it might have on the promotion of aquaculture in ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/333505b0
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  • 2
    Electronic Resource
    Electronic Resource
    Genetic variation in tissue cultures of red clover (1980)
    Springer
    Theoretical and applied genetics 58 (1980), S. 265-271 
    Details
    ISSN: 1432-2242
    Keywords: Tissue culture ; Somatic embryogenesis ; Genetic variance ; Plant breeding ; Trifolium pratense L
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Design II matings were made among randomly selected clones of ‘Arlington’ red clover (Trifolium pratense L.). Progeny were evaluated in vitro on two regeneration media for callus growth and differentiation. Additive genetic variance was a significant source of variability for nearly all traits evaluated, including somatic embryogenesis. In vitro traits, such as rapid callus growth, colony vascularization, root initiation, chlorophyll production and embryogenesis were highly heritable and should respond to breeding and selection. Dominance genetic variance was significant for only a few in vitro characters. Maternal and cytoplasmic factors were significant primarily in the early subcultures. Highly significant additive genetic correlation of performance on two regeneration media was found. A population selected on one of the regeneration media for such characteristics as improved plantlet regeneration, rapid callus growth, long term colony viability or the frequency of root initiation should show correlated improvement on the other medium. No significant differences for embryogenesis were attributable to differences in the regeneration media used. Furthermore, no interaction of additive genetic effects with regeneration media were observed. These data indicate that improvement in the frequency of plantlet regeneration from callus of red clover could effectively be achieved by breeding and selection for embryogenic types.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00265178
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  • 3
    Electronic Resource
    Electronic Resource
    Interspecific hybridization of red clover (Trifolium pratense L.) with T. sarosiense Hazsl. Using in vitro embryo rescue (1982)
    Springer
    Theoretical and applied genetics 62 (1982), S. 17-24 
    Details
    ISSN: 1432-2242
    Keywords: Interspecific hybridization ; Trifolium pratense L. (red clover) ; Forage legume ; in vitro ; Embryo culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Interspecific hybrid clover plants from the cross Trifolium sarosiense Hazsl. X T. pratense L. were obtained in the present investigation. Immature hybrid embryos were excised aseptically from the pistillate parent, T. sarosiense (2 n = 48), and cultured in vitro prior to in situ abortion. Agar-solidified nutrient media modified from that developed previously for tissue and cell cultures of red clover (2 n = 14) were used for embryo rescue. The heart shaped embryos obtained were cultured for 8 to 14 days on a medium containing a high level of sucrose, a moderate level of auxin, and low cytokinin activity. Viable embryos were then transferred to a standard medium with low auxin and moderate cytokinin levels for the direct germination of shoots. Some embryos produced only callus. Plants were regenerated from callus using an alternate culture scheme. Hybrid shoot numbers were increased on a low auxin, high cytokinin medium and subsequently rooted before transfer to soil in the greenhouse. About 10% of the hybrid embryos were rescued using the optimal culture sequence. Five full-sib families of the F1 hybrid were successfully grown to maturity. Root-tip cells of hybrid plants possessed the expected somatic chromosome number of 31. The genetically determined leaf-mark trait carried by the staminate parent and the rhizomatous root habit of the pistillate parent were expressed in hybrid plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00276274
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  • 4
    Electronic Resource
    Electronic Resource
    Hybridization of some Trifolium species through stylar temperature treatments (1970)
    Springer
    Theoretical and applied genetics 40 (1970), S. 59-62 
    Details
    ISSN: 1432-2242
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung In der Gattung Trifolium ist sowohl nach Selbstung als auch nach Artkreuzungen häufig Inkompatibilität zu beobachten. Es wird über Untersuchungen berichtet, durch Wärmebehandlung während der Blüte die Inkompatibilität zu überwinden. Zu diesen Zweck wurden die Blüten der mütterlichen Eltern einer Temperatur von 40 °C ausgesetzt und danach mit Pollen von unbehandelten Pflanzen bestäubt, die auf dem Feld oder im Gewächshaus aufblühten: Trifolium pratense wurde mit T. ambiguum, T. hirtum, T. ochroleucum, T. rubens, T. sarosiense und T. medium bestäubt, T. medium mit T. pratense. Aus allen Bestäubungen wurden Samen erhalten. 86% der Nachkommen entsprachen jedoch morphologisch und cytologisch ihrem mütterlichen Elter und waren vermutlich das Ergebnis einer Selbstbefruchtung. Viele Samen, die möglicherweise aus Kreuzungen stammten, waren klein und/oder keimten nicht. Aus einigen Samen erwuchsen schwache oder albino-Sämlinge, die bald abstarben. Griffel von T. medium, die aus Blüten herausgelöst wurden, die sich bei 40 °C geöffnet hatten, waren für Pollen von T. pratense verträglicher als Griffel, die sich auf dem Felde entwickelten. Dieser Befund läßt den Schluß zu, daß die höhere Temperatur einen besseren Hybridsamenansatz bewirkt hat, als er in unseren früheren Untersuchungen beobachtet wurde. Eine Temperaturbehandlung kann sich demnach bei Trifolium für eine Erzeugung von Hybriden als günstig erweisen.
    Notes: Summary Plants of seven perennial Trifolium species were interspecifically pollinated. The female flowers opened at 40 °C, and the male flowers opened in the greenhouse or field without a temperature treatment. T. pratense was pollinated with T. ambiguum, T. hirtum, T. ochroleucum, T. rubens, T. sarosiense, and T. medium. T. medium was pollinated with T. pratense. Seeds were obtained from all pollinations ; however, 86 of the progeny were morphologically and cytologically similar to their female parent, and probably resulted from self-fertilization. Many seeds of possible hybrid origin were small and/or did not germinate. Some seeds produced weak or albino seedlings which died at an early age. Excised pistils of T. medium from flowers that opened at 40 °C were more compatible with pollen of T. pratense than pistils of T. medium that developed in the field, indicating that the elevated temperature caused greater hybrid seed production than was observed in our earlier studies. The high temperature technique may prove useful in obtaining hybrids in Trifolium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00277271
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  • 5
    Electronic Resource
    Electronic Resource
    Growth of Trifolium pratense L. Pollen tubes in compatible and incompatible styles of excised pistils (1971)
    Springer
    Theoretical and applied genetics 41 (1971), S. 275-278 
    Details
    ISSN: 1432-2242
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The excised pistil technique was used to study effects of pollen treatments on self-incompatibility in red clover. Pollen was treated directly with infrared or ultraviolet radiation, and indirectly with chemicals that were applied to the stigmas before pollination. The chemicals (boric acid, calcium nitrate, colchicine, cyclohexamide, gibberellic acid, glycine, and indole butyric acid) were each used at five concentrations. High dosage rates of most treatments inhibited pollen growth in styles that were genetically compatible, but none of the treatments had a specific effect on the self-incompatibility mechanism. The effects of growth of compatible or incompatible pollen tubes in a style on subsequent growth of both types of pollen tubes in the same style were studied in an experiment with 6 hr between pollinations. The passage of some compatible pollen tubes through the style did not influence either self- or cross-compatibility in the style after the second pollination. The passage of some self-incompatible tubes into the styles caused a slightly higher number of incompatible tubes to penetrate the style after the second pollination. Each pollen tube appeared to traverse the style independently of other tubes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00277797
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of temperature on intra- and interspecific crosses of diploid and tetraploid red clover, Trifolium pratense L. (1974)
    Springer
    Theoretical and applied genetics 44 (1974), S. 73-76 
    Details
    ISSN: 1432-2242
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Reciprocal intraspecific crosses of diploid and tetraploid Trifolium pratense L. and reciprocal interspecific crosses of 4N T. pratense and T. medium were attempted in conjunction with a 40 °C temperature treatment on the female parent. The temperature treatment was found to be of little benefit in interspecific and intraspecific hybridization attempts. No cytologically verified interspecific hybrids were found from either heat-treated or non-heat-treated crosses. Intraspecific crosses produced no viable triploid offspring. One seedling was found to possess 17 chromosomes but died before positive verifications could be made. However, several seedlings from male-sterile diploid × tetraploid crosses were found to possess 28 chromosomes. These resulting tetraploids were cross compatible with other tetraploids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00277956
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  • 7
    Electronic Resource
    Electronic Resource
    Effect of temperature on pseudo-self-compatibility in Trifolium pratense L. (1969)
    Springer
    Theoretical and applied genetics 39 (1969), S. 123-126 
    Details
    ISSN: 1432-2242
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung Durch eine Behandlung normalerweise selbstunverträglichen Rotklees (Trifolium pratense L.) mit verhältnismäßig hohen Temperaturen während der Anthesis ergab sich eine Erhöhung des Samenertrages durch Pseudo-Selbstverträglichkeit. Die Samen aus der Selbstbefruchtung wurden an Kulturen abgeschnittener Stengel erzielt, die in 2.5% Sucrose gehalten wurden. Die Stengel waren zu dem Zeitpunkt, an dem die Petalenfarbe in den Knospen sichtbar wurde, abgeschnitten worden. In einem Brutraum wurden die Blütenköpfe während der Anthesis bei 40 °C und die Stengel durch Eintauchen der Kulturgläser in ein Wasserbad bei 25 °C gehalten. Sobald sich die Mehrzahl der Blütchen geöffnet hatte, wurden die Kulturen in 20 °C übergeführt und in dieser Temperatur während des Pollenwachstums durch die Griffel und auch während der Samenentwicklung belassen. Eine Beigabe von Kalziumnitrat und Borsäure zum Kulturmedium steigerte weder die Anthesis noch das Samengewicht und die Anzahl der erzeugten Samen. Der Genotyp der Pflanze und die Umwelt vor der Anthesis waren die Primärfaktoren, die die Anzahl der Samen aus Selbstbefruchtung beeinflußten. Obwohl nicht alle Versuche, Samen aus Selbstbefruchtung zu erzielen, erfolgreich waren, erzeugten in wiederholten Versuchen doch alle untersuchten Klone etwas Samen.
    Notes: Summary A relatively high temperature treatment, applied during anthesis, was shown to enhance self-seed production through pseudo-self-compatibility in normally self-incompatible red clover (Trifolium pratense L.). The self-seeds were produced in cultures of excised stems held in 2.5 percent sucrose. The stems were excised when petal color was beginning to appear in the buds. During anthesis the cultures were incubated with the flower heads at 40 ° and the stems at 25 °C. When most of the florets per head had opened the cultures were transferred to 20 °C and held at that temperature during the period of pollen growth through the styles and also during seed development. The addition of calcium nitrate and boric acid to the culture medium did not enhance anthesis, seed weight, or the number of seeds produced. Plant genotype and the environment provided before anthesis were the primary factors influencing the number of self-seed produced. Although not all attempts to produce self-seed have been successful, with repeated trials all clones we tested produced some seed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00366488
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  • 8
    Electronic Resource
    Electronic Resource
    Genotype-dependent whole plant regeneration from protoplasts of red clover (Trifolium pratense L.) (1989)
    Springer
    Plant cell, tissue and organ culture 19 (1989), S. 113-127 
    Details
    ISSN: 1573-5044
    Keywords: somatic embryogenesis ; plant regeneration ; protoplasts ; Trifolium pratense ; red clover ; protoclonal variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Protoplasts are useful for subcellular studies, in vitro selection, somatic hybridization and transformation. Whole plant regeneration from protoplasts is a prerequisite to producing altered crop plants using these methods. Whole plant regeneration was achieved from leaf- and suspension culture-derived protoplasts of T. pratense. Regeneration was most dependent upon identifying genotypes with genetic capacity to regenerate. Additional factors that were used to select genotypes, but which proved to be less important, were a high rate of cell growth in culture and a high plating efficiency of protoplasts. One genotype was identified which had a regeneration response equivalent to that of T. rubens and which regenerated from both leaf- and suspension culture-derived protoplasts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00035811
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  • 9
    Electronic Resource
    Electronic Resource
    Effect of inbreeding on pseudo-self-compatibility in red clover (Trifolium pratense L.) (1973)
    Springer
    Euphytica 22 (1973), S. 535-542 
    Details
    ISSN: 1573-5060
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effect of inbreeding on pseudo-self-compatibility (PSC) was investigated in I0, I1, and I2 clones of red clover, Trifolium pratense L., at 40°C. PSC was found to decrease with inbreeding. Significant differences were found among I0 clones, among I1 clones, and among I2 clones for PSC. Significant differences in PSC within generations were found in two of eight I1 clones and one of five I2 clones. A new method of inbred line maintenance is proposed which combines the desirable features of vegetative and seed maintenance of inbred lines. Superior I1 clones with different but homozygous S genotypes and PSC values of 8 to 10% would be vegetatively increased. Clones would be isolated under high temperature field conditions and selfed seed (PSC) would produce the I2. Selfed seed from two different I1 clonal lines would then be mixed and sown to produce single-cross seed. Singlecross seed obtained from different clonal sources would be mixed and sown for the production of double-cross hybrid red clover.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00036653
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  • 10
    Electronic Resource
    Electronic Resource
    Self-incompatibility genotype identification and stability as influenced by inbreeding in red clover (Trifolium pratense L.) (1974)
    Springer
    Euphytica 23 (1974), S. 140-148 
    Details
    ISSN: 1573-5060
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary S allele genotypes of I1 progenies from eight I0 red clover (Trifolium pratense L.) clones were determined under isolated field conditions. Each I1 progeny was vegetatively increased and isolated under a cage for pollination by honey bees. Clones within each I1 progeny producing relatively large and small amounts of seed were classified homozygous and heterozygous, respectively, for S allele genotype. S allele genotypes were verified by extensive sib crosses in the greenhouse, and almost complete agreement was found with the field classification. I2 progenies were reciprocally test-crossed with their parental I0 clones to detect any changes in S specificity and also to confirm the previous S genotype classifications in the I1 generation. It was concluded that the reliability of field and greenhouse sib classification of S genotypes is based on the strength of the incompatibility reaction in each particular clone. Most I1's showed a strong incompatibility reaction as evidenced by low seed set for heterozygous S genotypes, but one progeny showed a weak incompatibility reaction which resulted in S genotype misclassifications. An S specificity was changed in one I2 progeny.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00032753
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