[A genetically modified japonica restorer line, C418-Xa21, and its hybrid rice with bacterial blight resistance].

The cloned bacterial blight (BB) resistance gene Xa21 was transferred into C418,a major restorer line of japonica hybrid rice in China,using an Agrobacterium-mediated system.The integrated single copy of transgene displayed a 3∶1 segregation ratio in T 1 generation in PCR and resistance analyses.The transgenic homozygous C418-Xa21 lines were selected in T 2 generation through PCR and resistance analyses.The selected transgenic restorer lines were then crossed with a commonly used sterile line,TijinA,to produce Xa21 transgenic hybrid rice.Molecular analysis revealed that the produced hybrid rice,named as Tiyou418-Xa21,inherited the transgene.Both C418-Xa21 and Tiyou418-Xa21 plants displayed high resistance with a broad spectrum to Xoo races and maintained their normal elite agronomic characters.We also observed that the resistance level of Tiyou418-Xa21 was obviously higher than that of C418-Xa21 which may be attributed to their differences in genetic background.The propagation of this BB resistant hybrid variety with the transgene Xa21 with extend hybrid rice production in north China.