Agrobacterium-Mediated Transformation in Monocots
Although, during early 1980s, transformation mediated by Agrobaeterium tumefaciens had been successfully achieved in many dicotyledonous crops, initially it could not be used in monocotyledonous crops like maize, wheat, rice, barley, oats, etc. In these monocots, biolistics and direct gene transfer to protoplasts by electroporation and polyethyleneglycol (PEG) mediated uptake were often utilized successfully. However, Agrobaeterium-mediated transformation was later (in 1990s) successfully achieved in several cereal crops including maize, rice, wheat and barley. Agrobaeteriummediated gene transfer was preferred over other methods of gene transfer, since it offered a number of advantages including the following: (i) defined transgene integration; (ii) integration of low copy number; (iii) preferential integration into transcriptionally active region. In view of this, concerted efforts were made and success was achieved in Agrobaeteriummediated transfer of genes in monocots, which was increasingly utilized during 1994-2000.