Hd1是控制水稻感光性和抽穗期的一个核心基因。Hd1感光基因感光作用的丧失，是对长日照下早熟的重要适应性，但其遗传基础尚甚不清楚。我们的前期研究发现，早籼品种珍汕97中Hd1强感光等位基因的感光作用对遗传背景存在依赖性，本申请项目拟针对可能与Hd1途径中识别日照长度有关的生物钟和光受体相关基因，构建在珍汕97遗传背景下的近等基因系，比较感光和非感光材料在基因编码区和启动子区域的序列，分析基因表达变化及其与Hd1感光性的关系，并研究上述变化对产量性状和光合相关性状的影响；同时，分析主要早籼品种和杂交稻亲本、代表性中籼品种和杂交稻亲本在Hd1基因、生物钟基因和光受体基因上的等位变异。通过研究，揭示早籼品种Hd1感光基因丧失感光性的分子遗传学基础，并确定中国南方稻区早籼和中籼品种在相关基因上的主要等位变异及其特点，为拓宽早稻育种资源、提高不同类型稻种资源的育种通用性提供理论依据和技术手段。

Hd1 is one of the key genes in the regulation of photoperiod response and heading date in rice. Losing photoperiod sensitivity of functional Hd1 alleles provides an important adaption for rice varieties that require early maturing under the long-day conditions. We have previously found that a strong functional allele possessed by early indica rice variety Zhenshan 97 changed its photoperiod response depending on the genetic background. This proposal intends to investigate the molecular and genetic basis underlying the elimination of photoperiod response of the functional alleles carried by early indica rice varieties. Near isogenic lines (NILs) differing at gene loci for circadian clock and phytochrome that may affect the day-length recognization in the Hd1-regulation pathway will be constructed in the Zhenshan 97 background. Sequences in the coding regions and promoter regions, as well as the expression levels, will be compared between photoperiod sensitive and insensitive NILs. Influence of these variations on the yield traits and photosynthesis-related traits will also be analyzed. Commercial inbred varieties and parental lines of hybrid rice grown in the early season and single season rice cropping regions in Southern China will be tested for haplotypes regarding Hd1 gene, circadian clock genes and phytochrome genes targeted in the this study. Results are expected to provide new knowledge for the regulation network of photoperiod response and heading date in rice and facilitate the utilization of a diverse germplasm for the breeding of early indica rice.