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apparent o nly with m ustard at l ow d ensity. S imilarly, s mall s eed s ize d ecreased t he s eed number of GT at high density but not at low density. Plant density could cause variation of the influences o f seed s ize on pl ant growth a nd r eproduction ( Gardner & V anderlip 1989) . Obviously, the strong competition at high density decreased plant fitness, although the effect varied through different plant types and seed categories. GT was the plant type more liable to be affected by plant density and seed category, less for ntrF1 and mustard, while trF1 was not affected. Influences of seed size on plant fitness varied with genetic background Seed size did not impact the growth and reproduction of trF1, and it also did not affect the biomass and seed output in ntrF1 and wild mustard, with the exception of flowering time. However, s eed s ize s ignificantly a ffected t he f itness of G T. T he s mall-seeded pl ants of transgenic F 1 did not show lower fitness compared to larger-seeded p lants o f t ransgenic F1. This i s pe rhaps due t o t he da te of t he m easurements, w hich w ere t aken a t m aturity. S ince hybrids p roduce f ew s eeds, t heir growth c an s urpass t hat of m ustard a nd O SR, w ith hi gh biomass and high per-seed weight, thus hindering any initial difference at the early stage of life. This is not the case for mustard and OSR that produced copious amounts of seed and thus ending the vegetative stage as compared with hybrids. There were no significant differences between trF1 and ntrF1 in seed set, which indicates costs associated with the transgene were probably negligible here. Fitness cost of transgene expression w as obs erved t o be a ssociated with he rbivore r esistance i n s ome reports (Bergelson & Purrington 1996; Strauss et al. 2002). Fitness costs depend on not only genetic background i n w hich r esistance t raits oc cur, b ut a lso on the e nvironment i n w hich t he comparisons between resistant and susceptible plants are made and on the ecological context in which costs are measured (Bergelson & Purrington 1996). In this study, transgenic F1- and non-transgenic F 1- plants w ere obt ained w ith t he s ame ge netic ba ckground. M ason et a l. (2003) found no fitness cost of Bt- transgene in transgenic B. napus under low and high insect pressure. Snow et al. (2003) also found that Bt transgene was n ot associated with a fitness cost in sunflower under insect pressure, and transgenic plants produced more seeds since they experienced r educed he rbivory. M oreover, s mall-seeded pl ants of t ransgenic F 1 plants ha d high ve getative pe rformance, w hich s uggests Bt resistance p lant mig ht e xhibit s tronger competitive cap acity and w ould co unterbalance t he d isadvantage o f s mall s eed s ize, since 45
they b ear b eneficial t ransgenes t hat m ight p rovide ad aptive ad vantages ( Darmency 1 994). Ramachandran et al. (2000) found that transgenic plants were more competitive under insect pressure. Vacher et al. (2004) showed higher fitness of Bt transgenic hybrids than wild plants under insect pressure. In addition, both F 1 hybrids produced the highest percentage of large seeds, although the difference was not drastic, which could make the second generation with more chance of establishment than the small-seeded F1 generation. Implications for gene flow between transgenic B. napus and wild B. juncea Seed size could affect the emergence and initial seedlings (Major 1977; Aparico et al. 2002), which further enhance plant fitness (Verdu & Traveset 2005). GT showed significantly seed size ef fects, an d s mall-seeded pl ants de monstrated l ower f itness t han l arge-seeded pl ants. However, s mall-seeded o f transgenic F 1 did not s how pl ant f itness di fference c ompared t o larger-seeded plants of transgenic F1. Small seeds are more easily sieved out by harvesters and fall onto the soil, and further buried in the seed bank of soil. The complex correlation between seed size and persistence in the soil is unclear. However, interspecific hybrid seeds survived as well as seeds of oilseed rape in the soil (Chadoeuf et al. 1998). In addition, the small seed dispersed more easily through wind and animals, such that the survival of small-sized seeds of weeds c ould be hi gher i n c onventional t illage s ystems a nd a rable h abitats ( Ghersa & Martinez-Ghersa, 2000). They might represent the main risk of transgene escape in the field, and their small size is not a counterbalancing force exposing them to higher competition from the neighborhood. Acknowledgements This work is supported by two projects of the Natural Science Foundation of China (grant no. 30970432 a nd 30670316 ) a nd enabled b y a U SDA Biotechnology R isk A ssessment G rant. This work was also supported by a PhD joint fellowship between China and France (CNOUS, No. 20072315). References Ahmed SU, Zuberi M I (1973) Effects of seed size on yield and some of its components in rape seed, Brassica campestris L. var. Toria. Crop Science, 13, 119-120. Allainguillaume J , Alexander M, Bullock J M, Saunders M, Allender CJ, King G, Ford CS, 46
Page 1 and 2: UNIVERSITE DE BOURGOGNE THÈSE Pour
Page 3 and 4: REMERCIEMENTS My heartfelt thanks g
Page 5 and 6: forming many of the ideas I present
Page 7 and 8: Abstract In the framework of commer
Page 9 and 10: 2.3 A rticle 2: Les r étrocroiseme
Page 11 and 12: Table 3.2. Parameters of linear reg
Page 13 and 14: experiment. BC1NS is separated into
Page 15 and 16: Fig. 4.7. Mean and standard error (
Page 17 and 18: INTRODUCTION GENERALE Dans le cadre
Page 19 and 20: chapitre 1 dressant l’état des c
Page 21 and 22: CHAPTER 1 LITERATURE REVIEW ON THE
Page 23 and 24: oilseed rape and B. oleracea is ver
Page 25 and 26: populations is reduced as the dista
Page 27 and 28: into hybrids would affect the morph
Page 29 and 30: Snow e t a l. ( 1999) f ound no f i
Page 31 and 32: 1.5 Consequences of introgression I
Page 33 and 34: more flowers and larger plant size
Page 35 and 36: Moreover, beside the introgression
Page 37 and 38: their parental plants. Moon et al.
Page 39 and 40: 2.1 Introduction CHAPTER 2 CONDITIO
Page 41 and 42: ARTICLE 1 The effect of seed size o
Page 43 and 44: plant growth was evaluated without
Page 45 and 46: These two experiments were kept wee
Page 47 and 48: interactions were found among the t
Page 49: 2006) or m ore f it t han their pa
Page 53 and 54: Diggle PK, Abrahamson NJ, Baker RL
Page 55 and 56: Ramachandran S , B untin G D, A ll
Page 57 and 58: Table 2.2. F -values f rom a f ive-
Page 59 and 60: Days to flowering Biomass Per. of s
Page 61 and 62: 2.3 Article 2: Les rétrocroisement
Page 63 and 64: Photo.2.3. S praying chlorsulfuron
Page 65 and 66: Introduction In t he f ramework o f
Page 67 and 68: eceived p ollens f rom wild B. j un
Page 69 and 70: Statistical analysis Mean values ar
Page 71 and 72: Characteristics of the backcrosses
Page 73 and 74: Table 2.7. Mean (±95% CL) of plant
Page 75 and 76: plants w ith B. napus morphology t
Page 77 and 78: Productivity of the resistant proge
Page 79 and 80: References [1] A .A. Snow, D .A. A
Page 81 and 82: insight into adaptive life-history
Page 83 and 84: CHAPTER 3 EFFETS DE LA RESISTANCE A
Page 85 and 86: 3.2 A rticle 3 : S imulation d e l
Page 87 and 88: compétition et le devenir des popu
Page 89 and 90: difficult to predict. Similarly, it
Page 91 and 92: Table 3.1: ANOVA results of the eff
Page 93 and 94: Table 3.2: Parameters of linear reg
Page 95 and 96: herbivores than when exposed to Bt
Page 97 and 98: esistant hybrid populations might i
Page 99 and 100: 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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or t he popul ation of wild r adish
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estimated. All the seeds of every h
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Field experiment Number of siliques
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aphanistrum from hybrids and R. sat
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competition diminished the differen
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Conner, J. K., Rice A. M., Stewart
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Rattenbury J A. 1962. C yclic h ybr
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Fig. 4.1. Four r egions where w ild
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Fig. 4.3. Flower phot os showing pe
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Fig. 4.5. Plot of the first two axe
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Plant weight No. of seeds per plant
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Emergence rate Plant weight No.of a
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CONCLUSION 172
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véritable s uccès ad aptatif d an
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Dans l e cas d es p remières gén
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REFERENCES Abbott RJ, Comes HP.2007
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Bing D J, D owney R K and R akow G
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carinata and Brassica rapa. Plant B
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Hybridisation within Brassica and a
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etween weedy Brassica rapa and oils
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Hybridization between oilseed rape
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Nosil P. 2008. Speciation with gene
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32:305-32 Schadler, M., R. Brandl,
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Thalmann C, Guadagnuolo R, Felber F
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Zheng XM and Ge S. 2010. Ecological
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Therefore, after a review of the st
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more easily sieved out by harvester
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Transgenic F1 produced higher bioma
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