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  • Oryza sativa  (5)
  • Springer  (5)
  • 1995-1999  (4)
  • 1990-1994  (1)
  • 1970-1974
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  • 1930-1934
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  • Springer  (5)
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  • 1
    ISSN: 1432-2242
    Keywords: Heterozygosity ; Oryza sativa ; Heterosis ; RFLP ; Recombinant inbred lines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Forty-seven recombinant inbred (RI) lines derived from a cross between two indica rices, cv ‘Phalguna’ and the Assam land race ARC 6650, were subjected to restriction fragment length polymorphism (RFLP) analysis using cloned probes defining 150 single-copy loci uniformly dispersed on the 12 chromosomes of rice. Of the probes tested, 47 detected polymorphism between the parents. Heterozygosity was calculated for each line and for each of the polymorphic loci. Average heterozygosity per line was 9.6% but was excessive (〉20%) in the 5 lines that seemed to have undergone outcrossing immediately prior to harvest. Average heterozygosity detected by each probe across the 47 RI lines was 9.7%. The majority of probes revealed the low level of heterozygosity (〈8%) expected for F5-F6 lines in a species showing about 5% outbreeding. On the other hand, 7 probes exhibited heterozygosity in excess of 15%, while with a eighth probe (RG2 from chromosome 11) heterozygosity varied according to the restriction enzyme employed, ranging from 2% with SaII to 72% with EcoRV. The presence of 34 recombination sites in a segment of the genome as short as 24 kb indicates a strong selection for recombination between two neighbouring loci, one required as homozygous for the ‘Phalguna’ allele, and the other heterozygous. Since selection was principally for yield advantage over that of the high-yielding parent, ‘Phalguna’, one or both of these loci may be important for heterosis in this cross. The results also indicate that heterozygosity as measured by RFLP can depend on the particular restriction endonuclease employed.
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  • 2
    ISSN: 1432-2242
    Keywords: PCR ; RAPDs ; Oryza sativa ; Insect resistance ; Marker-aided selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have developed a polymerase chain reaction (PCR)-based assay that could effectively reduce the time period required to screen and select for Gall Midgeresistant rice lines under field conditions. The primers for the assay were designed on the basis of sequence information of two phenotype specific random amplified polymorphic DNA fragments which were found to be tightly linked to Gall Midge biotype-1 resistance gene (Gm2). The two RAPD fragments, F81700 in the susceptible parent ‘ARC6650’ and F10600 in the resistant parent ‘Phalguna’, were identified after screening 5450 loci using 520 random primers on genomic DNAs of ‘ARC6650’ and ‘Phalguna’. These primers, when used in a multiplexed PCR, amplified specifically a 1.7-kb and 0.6-kb fragment in the susceptible and resistant parents, respectively. When this assay was performed on genomic DNAs of 44 recombinant inbred lines derived from ‘ARC6650’ x ‘Phalguna’ and 5 lines derived from other crosses where one of the parents was ‘Phalguna’, ‘ARC6650’ or their derivatives, the primers amplified a 1.7-kb fragment in all of the susceptible lines or a 0.6-kb fragment in all of the resistant ones. These markers can be of potential use in the marker-aided selection of Gall Midge biotype-1 resistant phenotypes. As screening for resistance can now be conducted independent of the availability of insects, the breeding of resistant varieties can be hastened.
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  • 3
    ISSN: 1432-2242
    Keywords: Oryza sativa ; Orseolia oryzae ; Gallmidge ; Diptera ; Bulked segregant analysis ; Recombinant inbred lines ; Insect resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Gm2 is dominant gene conferring resistance to biotype 1 of gall midge (Orseolia oryzae Wood-Mason), the major dipteran pest of rice. The gene was mapped by restriction fragment length polymorphism (RFLP) analysis of a set of 40 recombinant inbred lines derived from a cross between the resistant variety ‘Phalguna’ and the susceptible landrace ‘ARC 6650’. The gene is located on chromosome 4 at a position 1.3 cM from marker RG329 and 3.4 cM from RG476. Since the low (28%) polymorphism of this indica x indica cross hindered full coverage of the genome with RFLP markers, the mapping was checked by random amplified polymorphic DNA (RAPD)/bulked segregant analysis. Through the use of 160 RAPD primers, the number of polymorphic markers was increased from 43 to 231. Two RAPD primers amplified loci that co-segregated with resistance/susceptibility. RFLP mapping of these loci showed that they are located 0.7 cM and 2.0 cM from RG476, confirming the location of Gm2 in this region of chromosome 4. Use of these DNA markers will accelerate breeding for gall midge resistance by permitting selection of the Gm2 gene independently of the availability of the insect.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Euphytica 95 (1997), S. 45-48 
    ISSN: 1573-5060
    Keywords: Oryza sativa ; non-allelic ; segregation ; semidwarfism ; sd1 gene ; dwarf ; mutations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The mode of inheritance of five semidwarf (SD) mutants and allelic relationship with DGWG (sd1) locus was studied. The five SD mutants viz., Basmati 370 (SD1), Basmati 370 (SD2), Basmati 370 (SD3), TCA 2 (SD) and TCA P2-5 (SD) when crossed with their tall parents exhibited monogenic inheritance of 3 tall: 1 semidwarf in the F2 progenies. The SD mutants were also crossed with semidwarf varieties (DGWG and Bala) possessing sd1 gene. Crosses between Basmati 370 (SD1) × Bala, Basmati 370 (SD3) × Bala and TCA 2 (SD) × DGWG produced tall F1 hybrids and in F2 generation, modified dihybrid ratios (9 : 6 : 1 and 9 : 7) were observed indicating that the mutants Basmati 370 (SD1), Basmati 370 (SD3) and TCA 2 (SD) are non-allelic to sd1 gene. Whereas, the mutants Basmati 370 (SD2) and TCA P2-5 (SD) when crossed with Bala produced semidwarf F1 hybrids and in F2 generation, segregation for plant height was not observed indicating that these mutants are allelic to sd1 gene. The three non-allelic SD mutants identified in the present study can be used in rice breeding as alternative gene sources for semidwarfism.
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  • 5
    ISSN: 1573-9368
    Keywords: protoplast ; β-glucuronidase ; electroporation ; PEG ; transformation ; DNA integration pattern ; Oryza sativa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Transformation of cereal protoplasts has been reported using several methods; however, the efficiencies of transformations are still very low. We have evaluated a number of parameters that influence electroporation-mediated DNA uptake and have also compared the efficiency of transient GUS activity and stable transformation obtained using an optimized electroporation method with that of the PEG method. The electroporation conditions tested were ionic composition of buffer, ionic strength, resistivity of buffer, type of anions, voltage, and capacitance. Protoplasts isolated from suspension cultures derived from immature embryos of rice (cvs Radon and IR-54) were used for this study. Stable transformation or transient GUS expression experiments were carried out using a plasmid construct containing the CaMV 35S promoter driving thebar gene and a rice actin promoter driving thegus A (uid A) gene (pAG35bar). Electroporation under optimized conditions resulted in about 13-fold higher GUS activities compared to the PEG method. Protoplast survival following optimized electroporation conditions was 55–60%, compared to 35–40% with the PEG treatment. Protoplasts isolated from a suspension culture at different ages gave substantially different levels of transient GUS expression following electroporation-mediated DNA uptake. In contrast, the age of the suspension culture did not influence PEG-mediated DNA uptake and transient GUS activities, which remained low throughout the culture period examined (21 months). Putatively transformed calluses were selected after three to four weeks on medium containing phosphinothricin as the selection agent. The transformation frequencies ranged from 6.2×10−5 to 5.4×10−4 with the electroporation method compared to 1.3×10−5 to 5.3×10−5 with the PEG method. Southern blot analysis of PPT-resistant calluses obtained by the electroporation-mediated transformation showed simple intergration patterns of integrated DNA in most of the transformants.
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