Introgression of bacterial blight resistance genes Xa7, Xa21, Xa22 and Xa23 into hybrid rice restorer lines by molecular marker-assisted selection

Abstract

Four bacterial blight (BB) resistance genes, Xa7, Xa21, Xa22 and Xa23, were introgressed into an elite hybrid rice restorer line Huahui 1035, by marker-assisted selection (MAS). Ten promising BB resistant lines identified by MAS approach in Huahui 1035 restorer background and their respective F1 hybrids with a cytoplasmic male sterile line i.e. Jinke 1A, three BB resistant gene donors and their recurrent parent were evaluated for BB resistance by inoculating them with eleven representative races of Xanthomonas oryzae pv. oryzae (Xoo) in China. Further, the ten marker assisted selection of BB (MAS-BB) resistant restorer lines and their F1 hybrids were also characterized for agro-morphological traits and grain yield. Results revealed that restorer lines with Xa23 introgression i.e. HBQ809 and HBQ810 were found to be resistant to all eleven Chinese representative Xoo races, showing broad spectrum resistance to BB. However, the lines possessing Xa7 or Xa7+Xa21 were resistant to ten out of eleven Xoo races. While restorer lines with Xa21 were resistant to nine out of eleven Xoo races. Interestingly, the F1 hybrids with Xa23, Xa7 or Xa7+Xa21 were resistant to two severe epidemic Xoo races of China. Restorer lines i.e. HBQ807 and HBQ808 possessing Xa22 were only resistant to six or five out of inoculated eleven Xoo races. Lesion length comparisons between restorer lines and their F1 hybrids for the above four BB resistance genes showed them to be dominant in heterozygote genotype. Three promising high yielding F1 hybrids with BB resistance were identified for immediate exploitation for hybrid rice production in China.