The spikelet number and heading date are two crucial and correlated traits for yield in wheat. Here, a quantitative trait locus (QTL) analysis was conducted in F₈ recombinant inbred lines (RILs) derived from crossing two common wheats with different spikelet numbers. A total of 15 stable QTL influencing total spikelet number (TSN) and heading date (HD) were detected. Notably, FT-D1, a well-known flowering time gene in wheat, was located within the finely mapped interval of a major QTL on 7DS (QTsn/Hd.cau-7D). A causal indel of one G in the third exon of FT-D1 was significantly associated with total spikelet number and heading date. Consistently, CRISPR/Cas9 mutant lines with homozygous mutations in FT-D1 displayed an increase in total spikelet number and heading date when compared with wild type. Moreover, one simple and robust marker developed according to the polymorphic site of FT-D1 revealed that this one G indel had been preferentially selected to adapt to different environments. Collectively, these data provide further insights into the genetic basis of spikelet number and heading date, and the diagnostic marker of FT-D1 will be useful for marker-assisted pyramiding in wheat breeding.

中文翻译：

---

FT-D1 第三个外显子中的单核苷酸缺失增加了小麦 (Triticum aestivum L.) 的小穗数并延迟抽穗日期

小穗数和抽穗期是小麦产量的两个关键且相关的性状。_{在这里，对源自杂交具有不同小穗数的两种普通小麦的 F 8}重组自交系 (RIL)进行数量性状基因座 (QTL) 分析。共检测到15个影响总小穗数（TSN）和抽穗期（HD）的稳定QTL。值得注意的是，小麦中著名的开花时间基因FT-D1位于 7DS ( QTsn/Hd.cau-7D ) 上主要 QTL 的精细定位区间内。FT-D1的第三个外显子中一个 G 的因果插入缺失与总小穗数和抽穗日期显着相关。一致地，在FT-D1中具有纯合突变的 CRISPR/Cas9 突变系与野生型相比，总小穗数和抽穗日期有所增加。此外，根据FT-D1的多态性位点开发的一个简单而稳健的标记表明，这个 G indel 已被优先选择以适应不同的环境。总的来说，这些数据为小穗数和抽穗日期的遗传基础提供了进一步的见解，FT-D1的诊断标记将有助于小麦育种中的标记辅助金字塔化。