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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 721 (1994), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 221 (1969), S. 865-866 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Tetraploid seed parents (Table 1) were descended from four different cytoplasmically male-sterile breeding stocks4. (Original stocks were obtained from Dr W. H. Davis, Teweles Seed Co., Milwaukee, Wisconsin.) Male-sterility ensured absolute control of pollination in hand crosses which were made in ...
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant breeding 117 (1998), S. 0 
    ISSN: 1439-0523
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Alfalfa (lucerne) plants can persist from one growing season to the next because of their perennial crowns. Plants with large crowns often are selected for breeding purposes. The objective of this study was to determine the forage yield potential of plants with a full range of crown sizes sampled from old stands. This was accomplished by field evaluation of clones and S1 progenies derived from plants of different crown sizes obtained from a 1 m2 of 5-year-old stands of cultivars ‘Agate’ and ‘Magnum III’. Significant differences (P 〈 0.05) in dry forage yield (DFY) were found among entries in both tests. However, there was no consistent trend in DEY with respect to the crown size of the parental plants. Although the crown of space-planted clones dug after 16 months showed a strong association (r 〉 0.7, P 〈 0.01) with DFY, the crown size of these clones was poorly correlated with the crown size of their parental plants. These results suggest that selections based on crown size from older stands may not lead to an improvement in either crown size or forage yield. Crown health will remain an important selection criterion when plants are sampled from old stands; crown size, however, may not be as important.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 67 (1984), S. 263-266 
    ISSN: 1432-2242
    Keywords: Medicago sativa L. ; 2n gametes ; Tissue culture ; Chromosome doubling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Tetraploid alfalfa (Medicago sativa L.) clones were derived from the same diploid genetic background by four different methods. A phenotypically superior clone was selected from each method and compared for herbage yield and fertility. The four methods and their best clones were: a) In vitro somatic chromosome doubling of one diploid hybrid (HG2-4x); b) selection within a two allele tetraploid synthetic population derived from HG2-4x (HAG); c) somaclonal variant selection from cell suspension culture of the diploid hybrid (NS1); and d) sexual polyploidization of a sibling hybrid (HXG). Clones HG2-4x, HAG, and NS1 were likely diallelic or monoallelic at all loci. Clone HXG was probably tetrallelic or triallelic at most loci. Experiments measured fertility, clonal herbage yield, and herbage yield of test cross progeny for each selected clone. Fertility rankings were HXG = HAG 〉 NS1 〉 HG2-4x. Clonal herbage yield rankings were HXG = HAG 〉 NS1 〉 HG2-4x. Test cross progeny herbage yield rankings varied depending on the tester, but, in general, HXG ≧ HAG ≧ NS1 HG2-4x. Overall the best clones from the sexual methods exceeded the best somaclonal variant which, in turn, was better than the chromosome doubled clone.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 59 (1981), S. 89-94 
    ISSN: 1432-2242
    Keywords: Methionine ; Mutagenesis ; Mutant selection ; Tissue culture ; Variants, Resistant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Diploid alfalfa (HG2), capable of plant regeneration from tissue culture, was used to select variant cell lines resistant to growth inhibition due to ethionine (an analog of methionine). Approximately 107 suspension-cultured cells were mutagenized with methane sulfonic acid ethylester and then plated in solid media containing ethionine. Callus colonies formed on media with 0.02 mM ethionine. Of the 124 cell lines recovered, 91 regenerated plants. After six months growth on media without ethionine, 15 of 110 cell lines of callus grew significantly better than HG2 on 1 mM ethionine. Several ethionine-resistant callus cultures were also resistant to growth inhibition due to the addition of lysine + threonine to the media. High concentrations, relative to unselected HG2 callus, of methionine, cysteine, cystathionine, and glutathione were found in some, but not all, ethionine-resistant callus cultures. Cell line R32, which had a ca. tenfold increase in soluble methionine, had a 43% increase in total free amino acids and a 40% increase in amino acids in protein as compared to unselected HG2 callus. Relative amounts of each amino acid in protein were the same in both.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Plant cell reports 5 (1986), S. 104-107 
    ISSN: 1432-203X
    Keywords: Plant tissue culture ; somaclonal variation ; mutable allele ; transposable element ; Medicago sativa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A white-flowered mutant (“WFM”) was regenerated from tissue culture of a purple-flowered plant of tetraploid alfalfa (Medicago sativa L.). When WFM was recultured, many regenerated plants (〉20%) were purple-flowered. Genetic analysis established that a functional allele, C2, of a locus required for anthocyanin pigmentation was in the simplex condition (C2c2c2c2) in the donor genotype when it mutated to an unstable recessive (“mutable”) allele, c2-m4, which is carried by WFM. Tissue culture experiments demonstrated that c2-m4 reverts to function at a high frequency in vitro. Results indicate that reversion occurs early in culture and may be the result of a genome shock associated with callus formation. Reversion also occurs in planta, but at a much lower frequency than in vitro. The c2-m4 allele is transmitted to progeny which revert in tissue culture. Revertant alleles, like the progenitor allele, are stable and are sexually transmitted. The action of a transposable element which is especially active in vitro is suggested.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Plant cell reports 5 (1986), S. 108-110 
    ISSN: 1432-203X
    Keywords: Plant tissue culture ; somaclonal variation ; mutable allele ; transposable element ; Medicago sativa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An unstable recessive (“mutable”) allele, c2-m4, of a locus required for anthocyanin pigmentation in alfalfa (Medicago sativa L.) reverts to a stable functional state at high frequency in vitro. It was previously established that a white-flowered mutant (“WFM”) and a white-flowered progeny of WFM (“WHGW3”) each carry the unstable allele. More than 20% of plants regenerated from tissue cultures of WFM and WHGW3 are revertant. It is here established that most nonrevertant plants regenerated from cultures of WFM and WHGW3 are stabilized in the recessive condition. Reculture of nonrevertants of WFM and WHGW3 indicated that there are three classes of nonrevertants: (i) Nonrevertants which revert in vitro at a high frequency typical of WFM; (ii) Nonrevertants which revert upon reculture but at significantly lower frequencies than WFM; and (iii) Nonrevertants which do not revert upon reculture. These observations are discussed in terms of transposable element action in vitro.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-2242
    Keywords: Heterozygosity ; Genetic diversity ; RFLPs ; Alfalfa ; Medicago sativa L
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Isogenic diploid and tetraploid alfalfa (Medicago sativa L.) was studied with molecular markers to help understand why diploid performance and breeding behavior does not always predict that of tetraploids. In a previous study of partially heterozygous alfalfa genotypes, we detected a low correlation between yields of isogenic diploid (2x) and tetraploid (4x) single-cross progenies, and genetic distances were more highly correlated with yields of tetraploids than diploids. These differences may be related to the level of RFLP heterozygosity expected among progenies derived from heterozygous parents at the two ploidy levels. The objectives of this study were to determine the relationships among genetic distance, forage yield and heterozygosity in isogenic 2 x and 4 x alfalfa populations. Four diploid genotypes were chromosome doubled to produce corresponding isogenic autotetraploids, and these genotypes were mated in 4 × 4 diallels to produce 6 single-cross families at each ploidy level for field evaluation. Allele compositions of parents were determined at 33 RFLP loci by monitoring segregation of homologous restriction fragments among individuals within progenies, and these were used to estimate RFLP heterozygosity levels for all single-cross progenies at both ploidy levels. RFLP heterozygosity rankings were identical between progenies of isogenic diploid and tetraploid parents; but significant associations (P 〈 0.05) between estimated heterozygosity levels and forage yield were detected only at the tetraploid level. Since tetraploid families were nearly 25% more heterozygous than the corresponding diploid families, inconsistencies in the association between molecular marker diversity and forage yields of isogenic 2 x and 4 x single crosses may be due to recessive alleles that are expressed in diploids but masked in tetraploids. The gene action involved in heterosis may be the same at both ploidy levels; however, tetraploids benefit from greater complementary gene interactions than are possible for equivalent diploids.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 97 (1998), S. 1289-1295 
    ISSN: 1432-2242
    Keywords: Key words Alfalfa ; Embryo sac ; Female sterility ; Callose ; Heritability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Ovule sterility was found to be associated with callose deposition in B17, a plant with low fertility from the alfalfa cv Blazer XL. The site of callose deposition, which began during embryo-sac development and affected 81% of the ovules in mature florets, at random positions in the ovary, appeared to be the embryo-sac wall or the integumentary tapetum. The fertile ovules of B17 transmitted the ovule-sterility trait to the progenies, thereby demonstrating a sporophytic genetic control. B17 was crossed with P13, a Peruvian plant with 5% callosized ovules, to generate reciprocal F1 populations, and an F1 plant (91% callosized ovules) was used to obtain the backcross populations. B17 was also crossed to unrelated, highly fertile, plants. S1 progenies from B17 and P13 were also studied. All the progeny populations displayed continuous variation for the percentage of sterile ovules, supporting a polygenic control. Narrow-sense heritability estimated by offspring-midparent regression was 0.85. Reduced transmission of the sterility trait through the pollen is hypothesized to explain the difference between reciprocal crosses. Six progeny plants showing 100% callosized ovules proved to be female-sterile. Ovule sterility could be an important component of the generally observed low realized seed potential in alfalfa.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 72 (1986), S. 37-41 
    ISSN: 1432-2242
    Keywords: Alfalfa ; Medicago genus ; Polysomic polyploids ; Sporogenesis ; Unreduced gametes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In the genus Medicago, it is known that 2n gametes have been important in the evolution and breeding of cultivated alfalfa, which is a natural polysomic polyploid (2n=4x=32), however little is known on the frequency of male and female 2n gametes in diploid relatives of alfalfa. To obtain data on the frequency of 2n gametes, more than 12,000 2x–4x and 4x–2x crosses were made in 1982 at Madison (USA). Diploid parents in crosses were from four populations of M. coerulea, two of M. falcata and one diploid population of cultivated M. sativa which was derived by haploidy. The tetraploid seed parent in the crosses was a male-sterile M. sativa clone and vigorous tetraploid M. sativa plants were used as pollen parents. Each of 274 diploid plants was utilized both as male and as female. Of the 548 cross combinations, 266 crosses produced variable quantities of seeds which were sown in 1983 in a greenhouse at Perugia (Italy); the plants were subsequently space transplanted in the field in 1984. The identification of ploidy level of these genotypes was made on the basis of morphological characters, plant fertility, pollen stainability and chromosome counts. Of the 515 plants analyzed, the majority behaved as normal tetraploids indicating that many diploid plants produced 2n gametes. Diplogynous and diplandrous gamete production was not correlated with each other, which indicated a different genetic control of 2n sporogenesis in the 2 sexes. Only 4 F1 triploid plants confirmed the presence of a very effective triploid block in alfalfa. In consequence, bilateral sexual polyploidization is a more likely alternative for the origin of tetraploid alfalfa than triploid bridges. The present study showed that it is possible to efficiently identify genotypes able to produce high frequencies of 2n gametes within natural populations of diploids Medicago that are useful in alfalfa breeding.
    Type of Medium: Electronic Resource
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