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  • 1
    Electronic Resource
    Electronic Resource
    A major photoperiod-sensitivity gene tagged with RFLP and isozyme markers in rice (1993)
    Springer
    Theoretical and applied genetics 85 (1993), S. 536-540 
    Details
    ISSN: 1432-2242
    Keywords: Molecular markers ; Restriction fragment length polymorphism ; Oryza sativa L ; Isozymes ; Rainfed lowland
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Photoperiod-sensitive rice (Oryza sativa L.) cultivars are widely grown in rainfed lowland areas with unfavorable water regimes. A molecular marker for the trait would be useful in genetic and physiological studies and in developing improved photoperiod-sensitive cultivars. Previous genetic studies identified a major gene for photoperiod sensitivity on chromosome 6. We have tested an isozyme marker and several RFLP probes mapping to chromosome 6 in an attempt to identify marker(s) tightly linked to photoperiod sensitivity in tropical rice cultivars. We report here that the isozyme gene Pgi-2 is linked (23.2±4.7 cM) to the photoperiod-sensitivity gene in the cultivar GEB-24. Although association of duration with Pgi-2 alleles can be used to detect segregation of the photoperiod sensitivity gene in crosses, it will probably not be useful as a marker in selection because of its loose linkage. In contrast, a gene for photoperiod sensitivity in the cultivar Puang Rai 2 was found to be closely linked to the rice genomic clone RG64. Among 15 F3 lines homozygous for photoperiod insensitivity, no recombinants were detected with RG64. This clone is thus an excellent probe to follow segregation of the major photoperiod-sensitivity gene in rice crosses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00220910
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  • 2
    Electronic Resource
    Electronic Resource
    Asymmetric somatic hybridization between tall fescue (Festuca arundinacea Schreb.) and irradiated Italian ryegrass (Lolium multiflorum Lam.) protoplasts (1994)
    Springer
    Theoretical and applied genetics 88 (1994), S. 509-519 
    Details
    ISSN: 1432-2242
    Keywords: Asymmetric somatic hybrids ; forage grasses: fescues and ryegrasses ; Plastome-genome interaction ; Festuca arundinacea ; Lolium multiflorum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Intergeneric asymmetric somatic hybrids have been obtained by the fusion of metabolically inactivated protoplasts from embryogenic suspension cultures ofFestuca arundinacea (recipient) and protoplasts from a non-morphogenic cell suspension ofLolium multiflorum (donor) irradiated with 10, 25, 50, 100, 250 and 500 Gy of X-rays. Regenerating calli led to the recovery of genotypically and phenotypically different asymmetric somatic hybridFestulolium plants. The genome composition of the asymmetric somatic hybrid clones was characterized by quantitative dot-blot hybridizations using dispersed repetitive DNA sequences specific to tall fescue and Italian ryegrass. Data from dot-blot hybridizations using two cloned Italian ryegrass-specific sequences as probes showed that irradiation favoured a unidirectional elimination of most or part of the donor chromosomes in asymmetric somatic hybrid clones obtained from fusion experiments using donor protoplasts irradiated at doses ≤ 250 Gy. Irradiation of cells of the donor parent with 500 Gy prior to protoplast fusion produced highly asymmetric nuclear hybrids with over 80% elimination of the donor genome as well as clones showing a complete loss of donor chromosomes. Further information on the degree of asymmetry in regenerated hybrid plants was obtained from chromosomal analysis including in situ hybridizations withL. multiflorum-specific repetitive sequences. A Southern blot hybridization analysis using one chloroplast and six mitochondrial-specific probes revealed preferentially recipient-type organelles in asymmetric somatic hybrid clones obtained from fusion experiments with donor protoplasts irradiated with doses higher than 100 Gy. It is concluded that the irradiation of donor cells before fusion at different doses can be used for producing both nuclear hybrids with limited donor DNA elimination or highly asymmetric nuclear hybrid plants in an intergeneric graminaceous combination. For a wide range of radiation doses tested (25–250Gy), the degree of the species-specific genome elimination from the irradiated partner seems not to be dose dependent. A bias towards recipient-type organelles was apparent when extensive donor nuclear genome elimination occurred.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01240911
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  • 3
    Electronic Resource
    Electronic Resource
    Intergeneric symmetric and asymmetric somatic hybridization in Festuca and Lolium (1955)
    Springer
    Euphytica 85 (1955), S. 235-245 
    Details
    ISSN: 1573-5060
    Keywords: intergeneric somatic hybrids ; forage grasses ; fescue ; Festuca arundinacea ; F. rubra ; ryegrasses ; Lolium multiflorum ; L. perenne ; Alopecurus pratensis ; species-specific repetitive DNA sequences
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Intergeneric symmetric and asymmetric somatic hybrids have been obtained by fusion of metabolically inactivated protoplasts from embryogenic suspension cultures of tall fescue (Festuca arundinacea Schreb.) and unirradiated or 10–500 Gy-irradiated protoplasts from non-morphogenic cell suspensions of Italian ryegrass (Lolium multiflorum Lam.). Genotypically and phenotypically different somatic hybrid Festulolium mature flowering plants were regenerated. Species-specific sequences from F. arundinacea and L. multiflorum being dispersed and evenly-represented in the corresponding genomes were isolated and used for the molecular characterization of the nuclear make-up of the intergeneric, somatic Festulolium plants recovered. The irradiation of Italian ryegrass protoplasts with ≤250 Gy X-rays prior to fusogenic treatment favoured the unidirectional elimination of most or part of the donor chromosomes. Irradiation of L. multiflorum protoplasts with 500 Gy produced highly asymmetric (over 80% donor genome elimination) nuclear hybrids and clones showing a complete loss of donor chromosomes. The RFLP analysis of the organellar composition in symmetric and asymmetric tall fescue (+) Italian ryegrass regenerants confirmed their somatic hybrid character and revealed a bias towards recipient-type organelles when extensive donor nuclear genome elimination had occurred. Approaches aimed at improving persistence of ryegrasses based on asymmetric somatic hybridization with largely sexually-incompatible grass species (F. rubra and Alopecurus pratensis), and at transferring the cytoplasmic male sterility trait by intra- and inter-specific hybridization in L. multiflorum and L. perenne, have been undertaken.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00023952
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  • 4
    Electronic Resource
    Electronic Resource
    Molecular mapping of rice chromosomes (1988)
    Springer
    Theoretical and applied genetics 76 (1988), S. 815-829 
    Details
    ISSN: 1432-2242
    Keywords: Oryza sativa ; Molecular markers ; RFLP ; Genetic map ; Trisomies ; DNA methylalion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We report the construction of an RFLP genetic map of rice (Oryza sativa) chromosomes. The map is comprised of 135 loci corresponding to clones selected from a PstI genomic library. This molecular map covers 1,389 cM of the rice genome and exceeds the current classical maps by more than 20%. The map was generated from F2 segregation data (50 individuals) from a cross between an indica and javanica rice cultivar. Primary trisomics were used to assign linkage groups to each of the 12 rice chromosomes. Seventy-eight percent of the clones assayed revealed RFLPs between the two parental cultivars, indicating that rice contains a significant amount of RFLP variation. Strong correlations between size of hybridizing restriction fragments and level of polymorphism indicate that a significant proportion of the RFLPs in rice are generated by insertions/delections. This conclusion is supported by the occurrence of null alleles for some clones (presumably created by insertion or deletion events). One clone, RG229, hybridized to sequences in both the indica and javanica genomes, which have apparently transposed since the divergence of the two cultivars from their last common ancestor, providing evidence for sequence movement in rice. As a by product of this mapping project, we have discovered that rice DNA is less C-methylated than tomato or maize DNA. Our results also suggest the notion that a large fraction of the rice genome (approximately 50%) is single copy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00273666
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    Paper (German National Licenses)
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