Abstract: IDEAL PLANT ARCHITECTURE1 (IPA1) is a pivotal gene controlling plant architecture and grain yield. However, little is known about the effects of Triticum aestivum SQUAMOSA PROMOTER‐ BINDING‐LIKE 14 (TaSPL14), an IPA1 ortholog in wheat, on balancing yield traits and its regulatory mechanism in wheat (T. aestivum L.). Here, we determined that the T. aestivum GRAIN WIDTH2 (TaGW2)‐TaSPL14 module influences the balance between tiller number and grain weight in wheat. Overexpression of TaSPL14 resulted in a reduced tiller number and increased grain weight, whereas its knockout had the opposite effect, indicating that TaSPL14 negatively regulates tillering while positively regulating grain weight. We further identified TaGW2 as a novel interacting protein of TaSPL14 and confirmed its ability to mediate the ubiquitination and degradation of TaSPL14. Based on our genetic evidence, TaGW2 acts as a positive regulator of tiller number, in addition to its known role as a negative regulator of grain weight, which is opposite to TaSPL14. Moreover, combinations of TaSPL14‐7A and TaGW2‐6A haplotypes exhibit significantly additive effects on tiller number and grain weight in wheat breeding. Our findings provide insight into how the TaGW2‐TaSPL14 module regulates the trade‐off between tiller number and grain weight and its potential application in improving wheat yield.

Key words: grain weight, TaGW2, TaSPL14, tiller number, wheat