As a staple food crop for more than one half of the world's population and a major model system in cereal genome research, rice (Oryza sativa L.) is the first grass species to be sequenced. The two draft sequences of the rice subspecies japonica and indica have been completed and were publicly available (Goff et al., 2002; Goff et al., 2002; Yu et al., 2002). A fine physical map of the chromosome 4 and two high quality finished sequences of chromosome 1 and 4 have been produced (Feng et al., 2002; Yu et al., 2002; Sasaki et al., 2002; Zhao et al., 2002). With the completion of the rice genome sequencing, attention is turning increasingly to characterize the functions of a large number of genes. Reverse genetics aims to determine the function of a gene ((Maes et al., 1999).