Exogenous strigolactones selectively suppress redundant tillers to increase phenotypic plasticity and grain yield in high-density and strong-tillering winter wheat

The objective of this study was to identify how strigolactones (SLs) coordinate canopy architecture and yield plasticity in winter wheat at varying planting densities and genotypic tillering potentials. We examined whether exogenous SLs regulate tiller hierarchy and yield plasticity in winter wheat by conducting two-year field experiments at Jinan and Laizhou with a sowing-density gradient, contrasting tillering cultivars, and foliar application of a natural SL compound or the synthetic analog rac -GR24 at the jointing stage. SL application induced position-specific tiller suppression, reducing total tillers per plant and peak tiller number under high density stress. This adjustment in canopy structure favored assimilate allocation to grain, increasing grain yield under high-competition conditions. We conclude that SLs act as conditional regulators that increase phenotypic plasticity and could be used as a post-establishment agronomic intervention to mitigate overcrowding stress in intensive wheat cropping systems.