Generation of marker-free, bacterial blight-resistant transgenic sterile line and hybrid rice with Xa21

Abstract

With 6 figures and 4 tables Abstract Bacterial blight (BB) of rice caused by Xanthomonas oryzae pv. oryzae (Xoo) is a major production constraint in commercial hybrid rice production because most of the parental lines used in hybrid production are susceptible to Xoo. In this study, the cloned BB resistance gene Xa21 was transferred into ‘D62B’, a maintainer line of three-line indica hybrid rice using the double right-border vector pDRBXa21 through an Agrobacterium tumefaciens-mediated system. Molecular and resistance analysis revealed that Xa21 was integrated into the genome of transgenic ‘D62B’, and the homozygous, single-copy and marker-free maintainer line D62B-Xa21 was obtained in the T2 generation. D62B-Xa21 was then backcrossed with ‘D62A’ to produce a homozygous transgenic sterile line D62A-Xa21. The introduction of Xa21 did not cause any obvious alteration to sterility and other agronomic traits of the sterile line through iodine–potassium iodide (I2/KI) staining of pollen grains and field observation. Reverse transcriptase–polymerase chain reaction revealed a normal expression pattern of the Xa21 gene in the transgenic lines. The hybrid combinations derived from D62A-Xa21 could inherit high resistance to BB.