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  • Electronic Resource  (7)
  • somatic embryogenesis  (4)
  • Phytophthora infestans  (3)
  • 1
    ISSN: 1432-203X
    Keywords: leek ; Allium ampeloprasum L. ; somatic embryogenesis ; genotypic effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In leek (Allium ampeloprasum L.) a cyclic system of somatic embryogenesis was developed. Somatic embryos used for cyclic embryogenesis were able to develop the same type of embryogenic callus as zygotic embryos in the primary cycle. For the first time a comparison of the efficiencies of both expiants was made. Ten families were investigated for somatic embryogenesis. There was a genetic relationship with respect to somatic embryo production between the reciprocal crosses. From each family one genotype was selected for investigating cyclic somatic embryogenesis. Different levels of somatic embryo production were found between the expiants of zygotic and somatic embryos. The two best genotypes, 92.001-03 and 92.002-33 produced twice as many somatic embryos as the overall average. On average, 56% of the somatic embryos finally developed into greenhouse plantlets.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2242
    Keywords: Key words Ac/Ds transposon tagging ; Somatic selection ; Hygromycin ; Phytophthora infestans ; R1 resistance gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Potato is an autotetraploid crop plant that is not very amenable to the deployment of transposon tagging for gene cloning and gene identification. After diploidisation it is possible to get potato genotypes that grow well, but they are self-incompatible. This prevents the production of selfed progeny that are normally used in gene tagging approaches to select for parental lines with the target gene to be tagged in a homozygous stage. We describe here an alternative selection method for directed transposon tagging for a gene of interest in a heterozygous background. Diploid potato plants with a Ds transposon linked to the desired gene of interest (the Phytophthora infestans R1 resistance locus) in a heterozygous stage were used for the development of this directed transposon tagging strategy. After crossing to a diploid Ac transposon-containing genotype, 22 ’interesting’ seedlings (R1Ds/r–; Ac/–) were selected that showed active Ds transposition as displayed by DNA blot hybridisation, empty donor site PCR and sequencing. Protoplast isolation and the use of the hygromycin gene as a cell-specific selection marker of Ds excision enabled the direct selection of Ds excision sectors in these highly chimaeric seedlings. This somatic selection of Ds transpositions and the regeneration through protoplasts resulted in the development of a large population of almost 2000 hygromycin-resistant plants. Southern blot analysis confirmed the insertion of Ds at independent positions in the genome. Every selected plant displayed independent Ds excisions and re-insertions due to the expression of the Ac transposase throughout development. This population, which is developed from seedlings with the desired R1 gene in a heterozygous stage, is directly useful for searching for transposon-tagged R1 mutants. In general, this approach for selecting for somatic transpositions is particularly suitable for the molecular isolation of genes in a heterozygous crop like potato.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 91 (1995), S. 557-562 
    ISSN: 1432-2242
    Keywords: Solanum tuberosum ; Phytophthora infestans ; Transposable element ; Transformation competence ; Linkage analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the course of improving diploid potato genotypes for transformation ability, selection for specific components affecting regeneration and transformation was carried out. From a segregating population between two good regenerating clones a selection was made to yield an optimal well-transforming and fertile genotype J92-6400-A16. This plant yielded predominantly diploid transformants and was heterozygous for the gene R1, conferring resistance to Phytophthora infestans. The speed of, and competence for, regeneration and transformation on both sides of the stem explant were improved. A competence factor for tranformation was found to be linked with the R1 locus and a molecular marker on chromosome 5. The male fertility of transformants was frequently decreased to a great extent, whereas female fertility was not so markedly affected.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1617-4623
    Keywords: Potato ; Solanum tuberosum ; Phytophthora infestans ; RFLP ; R genes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phytophthora infestans (Mont.) de Bary is the most important fungal pathogen of the potato (Solanum tuberosum). The introduction of major genes for resistance from the wild species S. demissum into potato cultivars is the earliest example of breeding for resistance using wild germplasm in this crop. Eleven resistance alleles (R genes) are known, differing in the recognition of corresponding avirulence alleles of the fungus. The number of R loci, their positions on the genetic map and the allelic relationships between different R variants are not known, except that the R1 locus has been mapped to potato chromosome V The objective of this work was the further genetic analysis of different R alleles in potato. Tetraploid potato cultivars carrying R alleles were reduced to the diploid level by inducing haploid parthenogenetic development of 2n female gametes. Of the 157 isolated primary dihaploids, 7 set seeds and carried the resistance alleles R1, R3 and R10 either individually or in combinations. Independent segregation of the dominant R1 and R3 alleles was demonstrated in two F1 populations of crosses among a dihaploid clone carrying R1 plus R3 and susceptible pollinators. Distorted segregation in favour of susceptibility was found for the R3 allele in 15 of 18 F1 populations analysed, whereas the RI allele segregated with a 1:1 ratio as expected in five F1 populations. The mode of inheritance of the R10 allele could not be deduced as only very few F1 hybrids bearing R10 were obtained. Linkage analysis in two F1 populations between R1, R3 and RFLP markers of known position on the potato RFLP maps confirmed the position of the R1 locus on chromosome V and localized the second locus, R3, to a distal position on chromdsome XI.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Plant cell, tissue and organ culture 33 (1993), S. 151-156 
    ISSN: 1573-5044
    Keywords: cassava ; plant regeneration ; somatic embryogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Four Indonesian and two Latin-American cassava genotypes (Manihot esculenta Crantz), were evaluated for their ability to develop somatic embryos from young leaf lobes. All genotypes formed somatic embryos but they differed in the frequency of embryos induced. The best genotypes, M. Col 22 and Tjurug, produced germinating embryos (GE) on 81% (22.1 GE/initial leaf lobe) and 46% (4.3 GE/initial leaf lobe) of the cultured leaf lobes, respectively. Up to 57% of the germinating embryos of M. Col 22 and 12% of Tjurug produced either normal or malformed shoots. Most malformed shoots developed into shoots with normal morphology after prolonged culture. All shoots formed roots after transfer to medium without BAP. Roots of all normal and most malformed regenerants had the original ploidy level (2n=36). Regardless of whether the plants were multipliedin vitro (150 plants) or in the greenhouse (30 plants) there were no morphological differences compared to parent plants.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-5060
    Keywords: Allium ampeloprasum ; 2,4-dichlorophenoxy acetic acid ; Murashige and Skoog medium ; organogenesis ; somatic embryogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A high frequency plant regeneration system via organogenesis and somatic embryogenesis was established with callus cultures derived from mature zygotic embryos of different leek genotypes (Allium ampeloprasum L.). Four different callus types with varying morphogenetic potential were obtained. Relatively high concentrations of the auxin 2,4-dichlorophenoxy-acetic acid reduced callus weight and subsequent shoot regeneration and primordia formation of the callus. Shoot regeneration and primordia formation of the callus decreased after prolonged subculture on media containing 2,4-dichlorophenoxy acetic acid. A callus growth period of six weeks on Murashige and Skoog medium with 0.25–0.5 mg l-1 2,4-dichlorophenoxy acetic acid showed the highest rate of shoot regeneration after transfer of callus to regeneration medium with 1 mg l-1 kinetin. Differences between leek genotypes in callus type, callus weight, shoot regeneration and primordia formation were observed. Histological observations showed that plant regeneration took place, both via the pathway of somatic embryogenesis and organogenesis.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Euphytica 96 (1997), S. 153-161 
    ISSN: 1573-5060
    Keywords: cassava ; transformation ; review ; somatic embryogenesis ; adventitious shoot formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A prerequisite for the development of a successful transformation system is the availability of efficient regeneration systems. Up to 1995 the only available regeneration system in cassava was an organized type of somatic embryogenesis. Transformation of these organized somatic embryogenic cultures with particle bombardment or Agrobacterium tumefaciens resulted in chimeric transformed embryos. However, the transformed sector was lost after repeated cycles of secondary somatic embryogenesis. After 1995 a less organized system of somatic embryogenesis was developed, so called friable embryogenic callus (FEC) and a system of adventitious shoot regeneration. The FEC regeneration system was combined successfully with particle bombardment. Selection of transgenic plants was based on either luciferase activity, or resistance to the aminoglycoside paromomycin or the herbicide phosphinothricin. Furthermore, protoplasts of FEC are able to regenerate into plants and can be transformed by electroporation. The adventitious shoot regeneration system was combined successfully with Agrobacterium tumefaciens. For this mature somatic embryos were cocultivated with Agrobacterium and cultured for adventitious shoot development. After selection based on the aminoglycoside geneticin or on hygromycin transgenic plants were formed.
    Type of Medium: Electronic Resource
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