Improving bacterial blight resistance of‘6078′, an elite restorer line of hybrid rice, by molecular marker‐assisted selection

<jats:title>Abstract</jats:title><jats:p>Bacterial blight (BB), caused by <jats:italic>Xanthomonas oryzae</jats:italic> pv. <jats:italic>oryzae (X00)</jats:italic>, is one of the most devastating diseases of rice world‐wide; it is also a serious problem of hybrid rice production in China. In this study, a molecular marker‐assisted introgression of <jats:italic>Xa21</jats:italic>, a gene highly resistant to a broad spectrum of <jats:italic>Xoo</jats:italic> strains, from ‘IRBB21’ was performed to improve the BB resistance of‘6078′, a new restorer line with high yielding potential. The entire process took one generation of crossing followed by three generations of backcrossing and one generation of selfing. The presence of <jats:italic>Xa21</jats:italic> in each generation was determined by both polymerase chain reaction (PCR) and pathogen inoculation. Recombinations between <jats:italic>Xa21</jats:italic> and flanking markers were identified by PCR analysis. Background selection was conducted in BC<jats:sub>1</jats:sub>F<jats:sub>1</jats:sub> and BC<jats:sub>2</jats:sub>F<jats:sub>1</jats:sub> using amplified fragment length polymorphism (AFLP) markers detecting a total of 129 polymorphic bands between‘6078’ and ‘IRBB21′. The individual selected in BC<jats:sub>3</jats:sub>F<jats:sub>2</jats:sub>, or‘6078′(<jats:italic>Xa21</jats:italic>), carried a fragment of less than 3.8 cM from the donor line in the <jats:italic>Xa21</jats:italic> region on chromosome 11, and about 98.8% of the genetic background from the recurrent parent. The results showed that‘6078′(<jats:italic>Xa21</jats:italic>) had the same level and spectrum of BB resistance as the donor parent ‘IRBB21′, while maintaining the agronomic performance and combining ability of the original 6078. A significant increase in BB resistance was also achieved in the hybrid using 6078(<jats:italic>Xa21</jats:italic>) as the restorer line.</jats:p>