UNIVERSITE DE BOURGOGNE THÈSE Yongbo LIU - Université de ...

population reproduction had a maximum when healthy plants occupied 75% of total
individuals. The outcome was the same no matter how the two plant types were distributed
within the plots, although both population production and individual fitness were
significantly higher in plot borders than in centers (Chapter 3.3). Insects decreased
population vegetative production but did not affect reproduction, and population
production, including vegetation and reproduction, increased with percentage of insect-
resistant transgenic BC2 in susceptible non-transgenic BC2 populations (Chapter 3.4).
Although these results showed the insect-resistant plants had advantage of competition and
fitness in the presence of insects, insects are not a regular selection pressure in natural fields,
and thus we could not conclude that Bt-transgene conferring insect-resistance could
colonize rapidly susceptible wild populations. Moreover, the compensatory growth of
susceptible plants and halo effect observed decreased the differences between resistant and
susceptible plants. Finally, competition caused differences among populations in the wild
radish experiments (Chapter 4).
In summary, my thesis present new evidences for the possible effects of gene flow
and introgression between transgenic crops and their wild relatives on morphology and
population dynamics in wild relatives by detecting the relative competition and fitness of
individual and population, and exploring the factors enhanced the introgression from crops
to wild relatives. These evidences showed that it is not easy to alter morphological traits and
population composition through the insertion of transgene in wild relatives, and the
consequences of gene flow between transgenic crops and wild relatives should be evaluated.
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