act redundantly with to control spike development and their elite haplotypes may improve wheat grain yield.

Wheat is a staple crop for the world's population, and there is constant pressure to improve grain yield, which is largely determined by plant architecture. SQUAMOSA promotor-binding protein-like (SPL) genes have been widely studied in rice, including their effects on plant architecture, grain development, and grain yield. However, the function of homologous genes in wheat has not been well investigated. In this study, and , wheat's closest orthologous of , were functionally investigated using gene-editing assays, revealing that these genes redundantly influence plant height, tiller number, spike length, and thousand-grain weight (TGW). Bract outgrowth was frequently observed in the hexa-mutant, occasionally in the quintuple mutant but never in the wild type. Transcriptome analysis revealed that the expression of many spike development-associated genes was altered in hexa-mutants compared to that in the wild type. In addition, we analyzed the sequence polymorphisms of and among wheat germplasm and found superior haplotypes of and with significantly higher TGW, which had been positively selected during wheat breeding. Accordingly, dCAPS and KASP markers were developed for and , respectively, providing a novel insight for molecular marker-assisted breeding in wheat. Overall, our results highlight the role of in regulating plant architecture and their potential application for wheat grain yield improvement through molecular breeding.