IRBB21 is widely used for
the improvement of bacterial blight resistance in Asia. It confers
resistance to all Indian and Philippine races of Xoo tested (Ikeda
et al., 1990; Khush, 1981). Singh et al. (2001) reported that the
Xa21 gene showed resistance against 17 Xoo strains from Punjab. In
China, Xa21 has been introduced into the widely used restorer line
Minghui 63, and the introgression lines showed a resistant reac-tion to Chinese strains.