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Tillering is a crucial agronomic trait of wheat; it determines yield and plant architecture. Strigolactones (SLs) have been reported to inhibit plant branching. D14, a receptor of SLs, has been described to affect tillering in rice, yet it has seldomly been studied in wheat. In this study, three <i>TaD14</i> homoeologous genes, <i>TaD14-4A</i>, <i>TaD14-4B</i>, and <i>TaD14-4D</i>, were identified. <i>TaD14-4A</i>, <i>TaD14-4B</i>, and <i>TaD14-4D</i> were constitutively expressed, and <i>TaD14-4D</i> had a higher expression level in most tissues. TaD14 proteins were localized in both cytoplasm and nucleus. An SNP and a 22 bp insertion/deletion (Indel) at the exon regions of <i>TaD14-4D</i> were detected, forming three haplotypes, namely <i>4D-HapI</i>, <i>4D-HapII</i>, and <i>4D-HapIII</i>. Due to the frameshift mutation in the coding region of <i>4D-HapII</i>, the interaction of 4D-HapII with TaMAX2 and TaD53 was blocked, which led to the blocking of SL signal transduction. Based on the two variation sites, two molecular markers, namely <i>dCAPS-250</i> and <i>Indel-747</i>, were developed. Association analysis suggested that haplotypes of <i>TaD14-4D</i> were associated with effective tillering number (ETN) and thousand kernel weight (TKW) simultaneously in four environments. The favorable haplotype <i>4D-HapIII</i> underwent positive selection in global wheat breeding. This study provides insights into understanding the function of natural variations of <i>TaD14-4D</i> and develops two useful molecular markers for wheat breeding.