An Agrobacterium tumefaciens-mediated transformation method has several advantages. However, this method has no example of success in perennial ryegrass (Lolium perenne L.). Since Lolium species are outcrossing, one cultivar consists of many genotypes. Each genotype can show a different ability for callus formation and plant regeneration (Takahashi et al., 2004). Thus, it is important to select a good genotype for efficient and stable transformation. If the plant is maintained in vitro, we can perform transformation using calli induced from shoot tips of the same genotype at any time. Our objective is to confirm an A. tumefaciens-mediated transformation method for perennial ryegrass and to screen for suitable genotype
