Population transcriptome and phenotype analyses reveal that Rht-D1b contributed a larger seedling root to modern bread wheat

Abstract The Green Revolution (GR) dramatically increased the yield of bread wheat (Triticum aestivum L.); however, whether and how GR reshaped the wheat root system remains largely unknown. Here, a large-scale transcriptomic and phenotypic investigation was performed on seedling roots of 406 worldwide bread wheat accessions, and this analysis revealed differences in the transcriptomes and phenotypes between landraces and modern cultivars. The GR allele Reduced height (Rht)-D1b was the main genetic factor driving this phenotypic diversity, and it conferred a significantly larger seedling root to modern cultivars by increasing cell length and root meristem size. In this case, the translational reinitiation of TaRht-D1 underlies the genetic effects of Rht-D1b. In contrast, another GR allele, Rht-B1b, has no significant effect on root-related traits, although both alleles have similar genetic effects on reducing plant height. This unexpected effect of Rht-D1b on root systems, coupled with its effect on plant height, contributes to a substantially larger root-shoot ratio in modern wheat cultivars. These findings reveal previously overlooked benefits of GR alleles in modern wheat cultivars and provide clues for their future application in enhancing the seminal root system.