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Annex 2 CONCLUSION (English version) In my thesis, ecological and evolutionary consequences of gene flow and introgression from transgenic oilseed rape (Brassica napus) and its wild relatives (B. juncea and Raphanus raphanistrum) were detected, considering the effects of morphological traits, interactive competition, fitness components in individual plants and population. The three effects that are discussed above in every chapter will be concluded integrally as follows. 1. Morphological traits Generally, the hybrids show intermediate morphologic characteristics compared to their parents (Lefol et al. 1996; Choudhary et al. 2000), because the cytoplasm of crops or wilds introgress into hybrids would affect the morphology of the progeny (e.g. Lefol et al. 1996; Zhang et al. 2002; Guéritaine et al. 2002; Chang et al. 2007). The morphological traits the successive generations might be altered and even further diverge from others by the long- term introgression, which depends on the transgenes, growth conditions and how many generations passed. Small seeds were produced by hybridization between crops and wild relatives because the effects of interaction between different genome and heterozygote in embryo limit their development (Eber et al. 1994; Chadoeuf et al. 1998; Wei and Darmency 2008), and small seeds are disadvantaged in their early establishment to plants in nature (Aparicio et al. 2002; Westoby et al. 2002). Indeed, in our study, seed size significantly affected plant growth and reproduction. However, its influence on plant fitness varied among genetic backgrounds and was affected by plant density and competing neighbors. The significant differences depend also on survive strategy for developing, and the same species could produce small or large seeds. Small-seeded transgenic oilseed rape plants produced less seeds, lower biomass and delayed flowering than large-seeded plants. For mustard and ntrF1, small-seeded plants delayed flowering but had similar biomass and seed set compared to large-seeded ones. Small-seeded trF1 plants had the same fitness as the large- seeded trF1. These results imply that further gene flow could not be reduced by the production of small-sized seeds in transgenic hybrids in field. Moreover, small seeds are 199
more easily sieved out by harvesters and fall onto the soil, and further buried in the seed bank of soil. In addition, the small seed dispersed more easily through wind and animals, such that the survival of small-sized seeds of weeds could be higher in conventional tillage systems and arable habitats. These seeds could be volunteers in the subsequent years, and they might represent the main risk of transgene escape in the field. Hence, the small size in hybrids might not be a counterbalancing force exposing them to higher competition from the neighborhood but be possible resources for further gene flow (Chapter 2.2). We did not study the successive generations of these plants with different seed size in fields. Backcross progeny with pollens of oilseed rape (Brassica napus) is more easily formed and produces more seeds than that with pollens of mustard (B. juncea). Hence, the progeny that has traits of oilseed rape will be produced in or outside of arable fields. Most of plants backcrossed with oilseed rape pollen had crop-like traits, for example larger flower that permit pollinators more easily to access and produced more seeds. Their seeds were larger and germinated better than the seeds produced with B. juncea pollen, suggesting they show a similar survive dynamic and emergence with oilseed rape. In our experiment with herbicide resistance, their chromosome number followed a Normal distribution, and the herbicide-resistance gene was consistent with Mendelian ratio. However, this is not automatic, and it depends on the insertion loci of transgene on A or C genome and on the backcrossing with A or B genome in mustard (Frello et al. 1996). This transgene could also be resistant to insects or others that permit them continue survive in fields. Pollen flow to susceptible plants within the mixed stand was occurred. These results suggest that the resistant BC1 produced with B. napus pollen could frequently occur and easily establish as a false feral crop population within cultivated fields and along roadsides. The establishment of crop-like progeny is much more rapid and hosts a large genetic variability compared to crops, which could be the source of further rapid adaptation and evolution (Chapter 2.3). Does the hybridization effects on morphology will exist after long term introgression of crop gene in wild relatives, even without transgene conferring new traits? We first propose the hypothesis that gene flow increases with the increasing coexistence between two species, oilseed rape and wild radish (Raphanus raphanistrum). The putative ancient introgressed populations showed polymorphism and intermediate characteristics in silique 200
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UNIVERSITE DE BOURGOGNE THÈSE Pour
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REMERCIEMENTS My heartfelt thanks g
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forming many of the ideas I present
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Abstract In the framework of commer
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2.3 A rticle 2: Les r étrocroiseme
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Table 3.2. Parameters of linear reg
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experiment. BC1NS is separated into
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Fig. 4.7. Mean and standard error (
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INTRODUCTION GENERALE Dans le cadre
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chapitre 1 dressant l’état des c
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CHAPTER 1 LITERATURE REVIEW ON THE
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oilseed rape and B. oleracea is ver
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populations is reduced as the dista
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into hybrids would affect the morph
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Snow e t a l. ( 1999) f ound no f i
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1.5 Consequences of introgression I
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more flowers and larger plant size
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Moreover, beside the introgression
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their parental plants. Moon et al.
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2.1 Introduction CHAPTER 2 CONDITIO
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ARTICLE 1 The effect of seed size o
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plant growth was evaluated without
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These two experiments were kept wee
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interactions were found among the t
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2006) or m ore f it t han their pa
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they b ear b eneficial t ransgenes
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Diggle PK, Abrahamson NJ, Baker RL
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Ramachandran S , B untin G D, A ll
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Table 2.2. F -values f rom a f ive-
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Days to flowering Biomass Per. of s
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2.3 Article 2: Les rétrocroisement
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Photo.2.3. S praying chlorsulfuron
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Introduction In t he f ramework o f
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eceived p ollens f rom wild B. j un
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Statistical analysis Mean values ar
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Characteristics of the backcrosses
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Table 2.7. Mean (±95% CL) of plant
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plants w ith B. napus morphology t
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Productivity of the resistant proge
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References [1] A .A. Snow, D .A. A
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insight into adaptive life-history
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CHAPTER 3 EFFETS DE LA RESISTANCE A
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3.2 A rticle 3 : S imulation d e l
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compétition et le devenir des popu
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difficult to predict. Similarly, it
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Table 3.1: ANOVA results of the eff
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Table 3.2: Parameters of linear reg
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herbivores than when exposed to Bt
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esistant hybrid populations might i
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Letourneau D .K., H agen J .A., 200
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Germination rate 0.6 0.5 0.4 0.3 0.
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3.3 Article 4: Compétition entre p
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Introduction The invasion of transg
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Whether a popul ation w ill e volve
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while ensuring that the same ratio
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silique number, seed number, seed w
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Our ga rden e xperiments s howed t
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experiment, harsh growth conditions
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References Agrawal AA. 2004. R esis
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density- dependent c osts of vi ral
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Table 3.5. F values of the analysis
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Table 3.7. Results of Helmert contr
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Fig. 3.4. Examples of experimental
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Flowering date Seed weight Biomass
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No. viable seeds Biomass 50000 4000
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Photo 3.3. Cotton bollworm (Helicov
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Introduction Spontaneous introgress
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screening as transgenic BC2 (trBC2)
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2002), but certain studies showed n
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Acknowledgements We t hank Z hixi T
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92, 368-374. Rieseberg, LH, and Bur
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Table 3.10. F-values of three-way A
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Seed number Biomass 140 120 100 80
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CHAPTER 4 RECHERCHE DES CONSEQUENCE
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Photo 4.1. Wild radish in a herbici
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Introduction Plant divergence is ge
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Page 157 and 158: Field experiment Number of siliques
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Page 163 and 164: Conner, J. K., Rice A. M., Stewart
Page 165 and 166: Rattenbury J A. 1962. C yclic h ybr
Page 167 and 168: Fig. 4.1. Four r egions where w ild
Page 169 and 170: Fig. 4.3. Flower phot os showing pe
Page 171 and 172: Fig. 4.5. Plot of the first two axe
Page 173 and 174: Plant weight No. of seeds per plant
Page 175 and 176: Emergence rate Plant weight No.of a
Page 177 and 178: CONCLUSION 172
Page 179 and 180: véritable s uccès ad aptatif d an
Page 181 and 182: Dans l e cas d es p remières gén
Page 183 and 184: REFERENCES Abbott RJ, Comes HP.2007
Page 185 and 186: Bing D J, D owney R K and R akow G
Page 187 and 188: carinata and Brassica rapa. Plant B
Page 189 and 190: Hybridisation within Brassica and a
Page 191 and 192: etween weedy Brassica rapa and oils
Page 193 and 194: Hybridization between oilseed rape
Page 195 and 196: Nosil P. 2008. Speciation with gene
Page 197 and 198: 32:305-32 Schadler, M., R. Brandl,
Page 199 and 200: Thalmann C, Guadagnuolo R, Felber F
Page 201 and 202: Zheng XM and Ge S. 2010. Ecological
Page 203: Therefore, after a review of the st
Page 207 and 208: Transgenic F1 produced higher bioma
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