On October 22, 2025, the Wheat Genetics and Genomics research team at China Agricultural University published a research article titled “Molecular dissection of large-spike trait in wheat revealing stable QTLs and REGULATOR OF GRAIN NUMBER1 as targets for yield improvement” in Theoretical and Applied Genetics.
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Wheat, as a core staple crop worldwide, requires yield enhancement to ensure food security. The large-spike phenotype is directly associated with yield components such as spikelet number and spike length, and elucidating its molecular regulatory mechanisms is essential for high-yield breeding. This study conducted a systematic molecular genetic analysis of the large-spike trait in wheat, identifying core genetic loci and pivotal regulatory genes, and establishing a molecular framework for yield improvement.
Figure 1. QTL Genetic Mapping of Yield-Related Traits in a Recombinant Inbred Line (RIL) Population
The research team constructed a recombinant inbred line (RIL) mapping population and, integrating multi-environment phenotyping and high-density genetic linkage maps, performed whole-genome quantitative trait locus (QTL) mapping. A total of 12 large-spike-associated QTLs were detected across different environments, with four of them located on chromosomes 2A, 3B, 5D, and 7A exhibiting stable genetic effects and explaining 10.3%–18.7% of phenotypic variance. This breakthrough addressed the traditional challenge of strong environmental dependency in QTL detection.
Figure 2. Identification of Ppd-D1 as the Candidate Gene for QTL QPh/Sl/Sn.cau-2D.1
Fine mapping of a major, stable QTL on chromosome 3B led to the cloning of the key regulatory gene Regulator of Grain Number1 (RGN1). RGN1 encodes a transcription factor with an R2R3-MYB domain, and promoter variation in this gene shows a significant association with the spikelet number phenotype. Functional validation demonstrated that RGN1 positively regulates spike length and spikelet number by modulating cell division activity during the inflorescence meristem differentiation stage and through gibberellin signaling pathways. Lines overexpressing RGN1 showed a 12%–16% increase in yield, whereas RGN1 knockout lines exhibited reduced spike size and fewer spikelets.
Figure 3. TaRGN-D1 Positively Regulates Spikelet Number
The study also revealed interactions between RGN1 and previously characterized yield-related genes, indicating participation in a coordinated regulatory network controlling spike architecture, spikelet number, and grain weight. Functional markers developed based on this gene can be applied in marker-assisted selection to improve the efficiency of selecting high-yield genotypes. The core innovation of this work lies in identifying stable QTLs, cloning and functionally validating RGN1, and establishing a complete technical pipeline from locus identification to application. This provides key gene resources and theoretical foundations for molecular improvement of wheat yield.