Molecular mapping of a novel non-canonical gibberellin-sensitive dwarfing gene Rht29 in wheat (Triticum aestivum)

Breeding semi-dwarf cultivars has long been a major objective for wheat improvement due to the inseparable association between plant height (PH) and grain yield. Although the utilization of Rht-B1b and Rht-D1b genes successfully achieved semi-dwarfism in the 1960s, these genes were associated with undesirable traits. The current wheat breeding urgently requires continuously exploring PH-controlling genes and their regulatory mechanisms, which will expand the genetic diversity of the PH gene pool to achieve precise PH regulation while maintaining or even increasing the grain yield potential. In this study, we identified a gibberellin (GA)-sensitive dwarf mutant, designated wph3 (wheat plant height 3). It showed GA biosynthesis deficiency and had pleiotropic effects on PH, spike length, grain weight, and grain number per spike. Using Exome Capture Sequencing for Bulked Segregant Analysis and molecular marker mapping, a novel recessive nuclear dwarfing gene was identified and localized into a ~ 3.9 Mb physical interval on chromosome 2B, designated Rht29 (Reduced height 29). Transcriptome analysis and candidate gene mining indicated that Rht29 may not encode a canonical key enzyme for GA biosynthesis, but participate in the GA biosynthesis by regulating the expression level of GA3ox. This study enriches the genetic resources available for wheat dwarfing breeding and establishes a foundation for further molecular characterization of phenotypic regulation by Rht29.