33S为晚稻专用型两用核不育系，配合力好，所配系列组合表现出生育期短、产量高、抗倒性好等特点，深受市场欢迎。田间鉴定33S感染的叶瘟与穗瘟均为9级，稻米直链淀粉含量达到24.9%，大大限制了该不育系在生产上的配组应用。本研究利用定向回交和分子标记辅助选择相结合的技术，快速聚合稻瘟病抗性基因Pigm和直链淀粉含量调控基因Wx^b，获得了2个携带双基因的33S改良株系。经抗性鉴定和稻米品质分析，改良系HS4和HS5的稻瘟病综合抗性指数分别为3.5、2.3，稻米直链淀粉含量分别为11.7%、11.6%。用同一父本分别与改良系和33S配组，所配组合的其他主要农艺性状无显著差异。全基因重测序比较显示，改良系HS4和HS5的背景回复率分别达到96.67%和97.79%。本研究结果表明，聚合Pigm和Wx^b基因能显著提高稻瘟病抗性、改善稻米品质，实现对33S抗性和优良食味的定向改良。

33S is a thermo-sensitive genic male sterile (TGMS) line special for late hybrid rice, which known for its good combining ability, the series of hybrid combinations derived from 33S are widely popular in the market due to its short growth period, high yield potential, and excellent lodging resistance. However, its practical application in hybrid breeding is constrained by poor resistance to rice blast, both leaf blast and panicle blast reaching severity level 9, and a high amylose content of 24.9%. This study combined directional backcrossing and molecular marker-assisted selection to introduce the rice blast resistance gene Pigm and the amylopectin-regulating gene Wx^b into 33S, successfully developing two improved lines, HS4 and HS5, harboring both target genes. Resistance evaluations and grain quality analyses revealed that the comprehensive blast resistance indices of HS4 and HS5 were 3.5 and 2.3, corresponding amylose contents were 11.7% and 11.6%, respectively. When the same paternal line was crossed with the improved strain and 33S, there were no significant differences in the main agronomic traits of the resulting combinations. Furthermore, whole-genome resequencing indicated that the genetic background recovery rates of HS4 and HS5 were 96.67% and 97.79%, respectively. The results revealed that pyramiding Pigm and Wx^b significantly enhances both blast resistance and grain quality, achieving targeted improvement in both disease resistance and palatability of the 33S rice line.