Abstract: Blast is one of the most serious diseases of rice worldwide, which usually leads to a sharp decline in rice production and even results in no yield. Breeding blast-resistant varieties is one of the most effective and economical ways to control the disease. In this study, the BL122 contained two blast resistance genes Pi-1 and Pi-2 was used as gene donor to be crossed and then backcrossed with the TGMS line GD-7S. Five improved TGMS lines with Pi-1 and Pi-2 homozygous genotype were successfully developed through molecular marker-assisted selection. The resistance frequency of the improved TGMS lines ranged from 94.12% to 97.06%, much higher than that of the check GD-7S, which was only 17.65%, by artificially inoculating 34 representa-tive blast isolates collected in Guangdong Province. The improved TGMS lines also displayed high resistance to leaf and neck blast in the epidemic areas. The critical temperature of fertility transformation for the improved TGMS lines from fertile to sterile was preliminarily identified in the phytotron with the regime of 12.5 h/23℃ and natural conditions. The results showed that the critical temperature point for the improved TGMS lines was likely consistent with that of the check GD-7S. The statistical analysis showed there was no significant difference in the agronomic traits between improved TGMS lines and GD-7S except the flag leaf length and number of panicles per plant. Moreover, there was also no significant difference in most of the agronomic traits be-tween the F1s derived from the crosses of the same restorer line L38 with both the check GD-7S and the improved TGMS lines, respectively. All these indicated that the improved TGMS lines retained almost the same agronomic traits and combining ability as the check.

Key words: Molecular marker-assisted selection, Gene pyramiding, Pi-1, Pi-2, TGMS line, Blast resistance