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1.5 Consequences of introgression
Introgression after h ybridization be tween G M c rops a nd t heir w ild r elatives m ay result i n
increasing: (1) genetic variation that promotes adaptive evolution (Rattenbury 1962; Postma
and Noordwijk 2005), (2) weediness of wild species (Darmency 1994; Pilson and Prendeville
2004), ( 3) c ompetitiveness or c olonization a bilities t hrough h ybrid vi gor or ne w t raits
(Ellstrand e t a l. 1999; Ramachandran e t al. 20 00), ( 4) i nvasiveness vi a e nhanced fitness
(Vacher e t a l. 2004) , a nd ( 5) t he a bility t o m atch ne w e nvironment ( Campbell e t a l. 2006;
Whitney e t a l. 2006) . While t ransgenes i ntrogressed f rom G M c rops t o w ild r elatives, t he
effects of novel genes on receiving wild plants would be detected at several levels, including
possible genetic assimilation of morphologic traits, and population dynamics.
1.5.1 Consequences of interspecific introgression on the morphological traits
As the introgression alters the genetic structure of receiving individuals, their forms and
behavior types, such as plant size, leaf size, petal color, fruit/ seed size, seed dormancy, etc.,
might be altered. There could be a directly relationship to transgenes (pleiotropy) or indirectly
via t he s uccessive e volution of a dvanced ge nerations ( for i nstance b y gene hi tch-hiking or
dramatic abundance of hybrids protected by herbicide and insect resistance). Crops are often
sexually compatible with their wild relatives and yet exhibit obviously different life history
traits, thus crop-to-wild gene flow and introgression may serve as a model system to evaluate
the r apid e volution of l ife hi story and ot her f itness-related tr aits d ue t o th e h ybridization
between c rops a nd wild r elatives. Indeed, i n s ome s tudies, m orphology i s us ed a s on e of
techniques to measure introgression (Table 1.5, Jarvis and Hodgkin 1999).
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