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large-seeded plants did, and there was no di fference for thousand-seed weight (Fig. 2.2). At
low d ensity, s mall-seeded pl ants of GT pr oduced l ower bi omass a nd thousand-seed weight
than l arge-seeded pl ants, but f lowering t ime and s eed num ber w as not di fferent. The
percentage of large, medium and small seeds produced was not different among the three seed
categories for all four plant types at both high and low density.
Fitness c omparison of f our pl ant t ypes All f itness c omponents, e xcept of t he
emergence rate, were significantly different in the four plant types: trF1, ntrF1, mustard and
GT (Tables 2.2, 2.3). Wild mustard flowered the earliest, trF1 and GT the latest, and ntrF1 was
intermediate. T ransgenic F 1 and nt rF1 produced hi gher bi omass, l ower s eed num ber a nd
weight a nd reproductive a llocation t han m ustard a nd G T, w ith l owest bi omass a nd hi ghest
seed number and allocation in mustard and highest seed weight in GT (Table 2.3). Thousandseed
weight of trF1 and ntrF1 was higher than that of mustard but lower than that of GT. The
percentage o f l arge s eeds, m edium s eeds a nd s mall s eeds pr oduced b y t he f our pl ant t ypes
was significantly different, and trF1 and ntrF1 produced 77% and 72% large seeds, 54% for
GT and 1% for wild mustard (Table 2.3).
At small seed size level, the seed number and seed weight of small-seeded plants of trF1
were not significantly different compared with their parents, mustard and GT, in high density
population, and they were lower than their parents at low density level.
Discussion
Growth and reproduction of various plant types
Fitness o f h ybrids b etween t ransgenic cr ops an d w ild r elatives i nfluences t he eco logical
consequences of transgene flow from GM crops to their wild relatives (Ellstrand et al. 1999;
Pilson & Prendeville 2004; V acher et a l. 2004). S everal f itness components of t wo
interspecific hybrids (trF1 and ntrF1) and the parent plants--transgenic oilseed rape (GT) and B.
juncea (mustard), ar e d escribed at al l g rowth stages f rom s eedling e mergence t o s eed
production i n t he c urrent s tudy. T he h ybrids s howed h igher v egetative f itness b ut lo wer
reproductive fitness than their parents, which is consistent with the results of Di et al. (2009).
There are some cases in which wild-crop hybrids may be as fit (Lefol et al. 1995; Arriola &
Ellstrand 1997) , l ess f it (Hauser et a l. 1998; G ueritaine et a l. 2002; A llainguillaume et a l.
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