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  • 1
    ISSN: 1573-5060
    Keywords: biosafety ; gene inactivation ; phosphinothricin tolerance gene ; transgenic Brassica napus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The commercial and economic value of genetically modified crops is determined by a predictable, consistent and stable transmission and expression of the transgenes in successive generations. No gene inactivation is expected after selfings or crosses with non-transformed plants of homozygous transgenic oilseed rape plants if the expression of the transgene in homozygous or hemizygous nature in such plants is stable. The segregation ratios of phosphinothricin (PPT) tolerance in successive generations of selfings and mutual crosses of a few independent transgenic PPT-tolerant oilseed rape plants indicated a dominant, monogenic inheritance. In within-variety and between-variety crosses no transgene inactivation was observed. However, after selfings and backcrosses with non-transgenic oilseed rape infrequent loss of the expression of the PPT tolerance transgene was observed independent from its homozygous or hemizygous nature. Molecular analysis of PPT-susceptible plants showed that the loss of expression was due to gene inactivation and not to the absence of the transgene. Methylation and co-suppression are mechanisms that might cause reduced or even loss of expression of the transgene in later generations. The implications of this observation for seed multiplication of varieties and breeding activities with transgenic oilseed rape are discussed.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1572-9788
    Keywords: ecology ; genetic modification ; herbicides ; risk assessment ; toxicology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The microbial bar and pat genes confer tolerance to the non-selective herbicide phosphinothricin (PPT; sold as Basta or Finale). This tolerance in plants could provide an environmental gain compared to current-day herbicide cocktails, but the safety of such a transgene approach is questioned by many. The biosafety of the presence of these herbicide tolerance genes in plants is evaluated in a ‘transgene-centered approach’. Potentially, the introduction of transgenic PPT-tolerant crops could result in acquired PPT tolerance in weedy relatives of these crops. Assuming responsible use of this trait in agronomy, the ecological consequences with respect to weediness or spread of the transgenic PPT tolerance are concluded to be negligible. The key issue for the toxicological evaluation is whether or not the plant has actually been sprayed with PPT. Consumption of the gene and/or gene product from unsprayed transgenic plant material will not have adverse effects. In case of PPT-sprayed material, PPT or its derivatives could be present in food and feed and crop-specific metabolites might be formed. To date, the toxicological impact of such a putative exposure is not sufficiently clear, and further premarket testing is recommended.
    Type of Medium: Electronic Resource
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