从缙恢10/R21的杂种后代中发现了一个抽穗期稳定遗传的迟熟恢复系N91(110~114 d)，以早熟不育系金23A(89~94 d)作为杂交和回交亲本，获得的F2和BC1F1群体抽穗期均表现双峰分布，χ2检测表明其抽穗期受一对主基因控制，暂命名为Hd(t)。在400多对SSR引物中筛选出5对在早熟基因池和迟熟基因池中表现差异的引物，进行单株验证，用回交群体进行基因定位，发现位于第7染色体长臂末端的SSR标记RM1364和RM3555与Hd(t)连锁，遗传距离分别为32.7 cM和22.5 cM。在目标区域进一步合成8对SSR引物，将Hd(t)基因定位在RM22143与第７染色体末端之间，与RM22143相距12.9 cM。该结果为Hd(t)基因的精细定位、分子标记辅助育种和基因克隆奠定了基础。
A restoring line N91 with late heading period (from 110 d to 114 d) was found from the offspring of a cross (Jinhui 10/R21), and N91 was crossed and backcrossed with Jin 23A, which was sterile line with early heading period (89–94 d). The frequency distribution of heading period showed double peaks in F2 and BC1F1 population and χ square test demonstrated the heading period was controlled by a major gene, which tentatively named as Hd(t), and other minor genes. Bulkled segregant analysis was used to map the Hd(t) by the backcross population, and 5 out of 400 SSR primer pairs showed polymorphism between late and early genome pools. Linkage analysis demonstrated the Hd(t) linked with two SSR loci (RM1364, RM3555) on chromosome 7. The Hd(t) were 32.7 and 22.5 cM from loci RM1364 and RM3555 respectively, and two SSR loci located at the same side of the Hd(t). Based on the targeted interval, 8 pairs of primers were selected from the public SSR primer pairs according to rice physical map. Through linkage analysis, RM22143 was added into the interval of the RM3555 and Hd(t) on the distal end of long arm of chromosome 7, and Hd(t) was 12.9 cM from RM22143. The present result establishes a basic for fine mapping, molecular marker assisted breeding and gene cloning of the Hd(t).
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