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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). For example, after seven backcrossing of B.
carinata to B. napus and B. juncea, plants with the cytoplasm of B. napus flowered later, had
shorter filaments and longer pistils, lower pollen amount, lower seed set, lower petal length
and w idth a nd di fferent petal c olor compared w ith pl ants w ith t he c ytoplasm of B. j uncea,
suggesting that the cytoplasm is involved in the development of flower organs (Chang et al.
2007).
In the case of B napus x R. raphanistrum crosses, F1 hybrids formed between oilseed
rape and wild radish a re mainly allotriploids and present low f ertility (3. 2 s eeds/ plant for
Darmency e t a l. 1998; 11 s eeds/ pl ant f or C hèvre e t a l.1998). T he F 1 h ybrids s howed
significantly r educed s eedling emergence, emergence d elay, l ower survival r ate, an d
decreased d ry m atter co mpared w ith t heir p arents ( Guéritaine et al. 2 003). H owever, t he
progeny of F1 (F2, BC1) grew well and produced viable seeds (Darmency et al. 1998), and
the fertility increased after repeated backcross to wild radish. In addition, the progeny having
wild radish cytoplasm were more likely to propagate in agronomic and natural sites and had a
fitness value 100 times more than that having oilseed rape cytoplasm (Guéritaine et al. 2002).
1.4 Consequences of the transgene
A transgene transferred from oilseed rape to wild relatives might be neutral, but it is likely to
increase o r d ecrease t he f itness o f r eceiving hybrid/ b ackcross p lants (Table 1.3) . T his
depends on t he transgenic character, its selection and costs, how and where the transgene is
introgressed in the genome, and the population composition (Felber et al. 2007). In response
to insect herbivory, the Bt-transgene for insect resistance was shown to confer high relative
fitness i n oi lseed r ape i n s everal s tudies ( Stewart e t a l. 1997; R amachandran e t a l. 2000;
Letourneau and Hagen 2009). In turn, no fitness cost in the absence of the selection pressure
was detected in the Brassiceae (Mason et al. 2003; Ramachandran et al. 2000; Di et al., 2009)
and in sunflower (Snow et al. 2003).
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