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X Reboud

Publications and source records attributed to X Reboud.

4 recordsLinked to original sources
PubMed2003

Low frequency transmission of a plastid-encoded trait in Setaria italica.

It has been claimed that engineering traits into the chloroplast will prevent transgene transmission by pollen, precluding transgene flow from crops. A Setaria italica (foxtail or birdseed millet) with chloroplast-inherited atrazine resistance (bearing a nuclear dominant red-leaf base marker) was crossed with five male-sterile yellow- or green-leafed herbicide susceptible lines. Chloroplast-inherited resistance was consistently pollen transmitted at a 3x10(-4 )frequency in >780,000 hybrid offspring. The nuclear marker segregated in the F(2), but resistance did not segregate, as expected. Pollen transmission of plastome traits can only be detected using both large samples and selectable genetic markers. The risk of pollen transmission at this frequency would be several orders of magnitude greater than spontaneous nuclear-genome mutation-rates. Chloroplast transformation may be an unacceptable means of preventing transgene outflow, unless stacked with additional mechanisms such as mitigating genes and/or male sterility.

Cell Nucleus↗
PubMed2002

Effect of a gap on gene flow between otherwise adjacent transgenic Brassica napus crops.

Gene flow resulting from cross pollination becomes an issue when transgenic crops are involved and the genetic modification carries a trait of ecological importance. As crop fields are often separated by a barren gap, such as an intervening roadway or unplanted area, I measured cross contamination between two herbicide-resistant transgenic fields (canola, Brassica napus) across a gap of up to 12 m. I focused on pollen exchange from the field border up to 7 m inside each field over two seasons. In the absence of a gap, I found that gene dispersal diminished rapidly with distance, with more than 40% of transgenic progeny found within the first meter from the edge of the adjacent crop. Cross contamination between fields declined more rapidly when there were intervening plants, however. Plants separated from the transgenic source by a gap of 3-4 m, yielded the same level of transgenic progeny as those separated by 1 m of crop. Both insects and wind pollinate canola, and so the explanation for my observations could involve the influence of gaps on wind patterns or on the behaviour of pollinators. The gap effect does not seem to depend only upon the variation in the density of neighbours that surrounds those plants at the crop edge versus those in the crop matrix. On the basis of this study, it is recommended that economic profit would be maximised by removing field borders after flowering rather than by leaving a surrounding gap, which would need to occupy up to threefold as much field surface to achieve the same level of containment.

Analysis of Variance↗
PubMed1997

The evolutionary dynamics of selfish replicators: a two-level selection model.

The aim of the present paper is to study the evolutionary dynamics of selfish replicators in a constant genetic background. Selfish replicators are viewed as alleles at a single locus, having a pleiotropic effect. Infinitely many alleles are possible; they act on individual fitness and have various levels of ability to distort segregation. This results in a two-level process of selection, including inter-individual selection (effect on individual fitness) and intra-individual selection (ability to distort segregation). The model takes other parameters into account, such as dominance, inbreeding and inbreeding depression. The system can have two different behaviours. (1) In some cases, evolutionary cycles are possible. The cycles correspond to an alternation of phases with predominant inter-individual selection, corresponding to major-effect mutations, and phases with predominant intra-individual selection, corresponding to small-effect mutations. (2) For other values of the parameters, a synthetic fitness can be defined: this absolute allelic fitness is estimated as a function of one's fitness due to both inter-individual and intra-individual selection. During the course of evolution, the synthetic fitness increases. The optimisation of a synthetic fitness is the most general process. The optimised value is essentially homologous to the value optimised for resource allocation to male and female function in hermaphrodites (female function being homologous to the effect on individual fitness, and male function being homologous to distortion ability). The relative importance of both behaviours is discussed. It is argued that repeated sequences causing some human degenerative hereditary diseases may follow a two-step evolutionary process: a progressive increase in number of sequences accompanied by a decrease of the individual fitness would be followed by massive elimination of such sequences. But in general the optimisation of the synthetic fitness seems to be more likely.

Animals↗