Molecular marker-assisted pyramiding of broad-spectrum disease resistance genes, Pi2 and Xa23, into GZ63-4S, an elite thermo-sensitive genic male-sterile line in rice

Abstract

The two-line system of hybrid rice seed production based on thermo-sensitive genic male-sterile (TGMS) lines is much more cost-effective, simple and efficient than the three-line system with cytoplasmic male sterility. In this study, we report the introgression of a rice blast resistance gene Pi2 from VE6219 and a bacterial blight (BB) resistance gene Xa23 from HBQ810 into Guangzhan63-4S (GZ63-4S), an elite TGMS rice line, through marker-assisted pyramiding, leading to the development of Hua1015S, a blast- and BB-resistant pyramided line. The newly developed TGMS line Hua1015S and its derived hybrids showed resistance to rice blast and BB. Hua1015S had a similar critical temperature point of fertility–sterility alteration to GZ63-4S and similar key agronomic and grain quality traits. However, Hua1015S gave higher hybrid seed yields on account of increased outcrossing rates due to better floral traits, e.g. spikelet dehiscence, angle of glume opening, and stigma exsertion. The newly developed TGMS parental line Hua1015S with Pi2 and Xa23 is currently being utilized for heterosis breeding of broad-spectrum blast- and BB-resistant two-line rice hybrids and as an improved disease donor source for further TGMS parental line improvement.