ABSTRACT
During the last two decades, genetic engineering has been progressing at a steady pace in the forest trees. Genetically modifi ed (GM) trees have been produced in a number of forest tree species (Ahuja 1988a, 2000, 2001, Tzfi ra et al. 1998, Peña and Séguin 2001, Tang and Newton 2003, Henderson and Walter 2006, Malbadi and Nataraja 2007). A number of target traits, including herbicide resistance, insect resistance, and reduced lignin (Table 1) have been engineered in forest trees (Campbell et al. 2003, Boerjan 2005, Sedjo 2006, White et al. 2007, Ahuja 2009, Harfouche et al. 2011). The current protocols for genetic engineering include transfer of recombinant genes by Agrobacterium-mediated and biolistic approaches to plant tissues followed by regeneration of plants by tissue culture technology. Both methods of genetic engineering have been successfully employed for transferring a large number of recombinant genes in forest trees. The fi rst phase of genetic engineering in trees included the transfer of foreign genes (mostly bacterial genes) used as reporter genes to monitor the integration patterns and expression of trangenes in the tree genome. This was followed by the second phase that marked the transfer of economically important genes (both bacterial and plant genes) to the forest trees. Since both types of
Table 1. Target traits for genetic engineering in forest trees (modifi ed from Sedjo 2006). These recombinant genes for these traits could be transferred singly or stacked by multi-gene co-transformation systems.
