Multigenerational exposure of spring wheat to weed competition and the role of memory response in crop‐weed interaction

Abstract Competitiveness is essential for plants to survive abiotic and biotic stressors. Studies reveal that plants can store and recall stress memories, influencing their future responses—known as the plant memory response. This study explored how multigenerational weed exposure affects the phenotypic plasticity of spring wheat. Wheat was grown in 3 L pots, surrounded by 8 kochia, 8 Italian ryegrass, 8 wheat, or no surrounding plants, with 15 replicates. Seeds harvested from generation 1 were used to plant generation 2, and this process was repeated through generation 5. Seed yields in generation 3 showed increases of 385% (wheat‐only), 123% (wheat‐kochia), 9% (wheat‐ryegrass), and 35% (wheat‐wheat) compared to generation 1. Conversely, generation 2 saw yield reductions of 59%, 64%, and 28% in the wheat‐kochia, wheat‐ryegrass, and wheat‐wheat treatments, respectively. The yield improvements observed in generation 3 were not sustained in generations 4 and 5, possibly due to the erasure of somatic stress memory. Wheat‐ryegrass and wheat‐wheat treatments caused the greatest reductions in yield and biomass relative to kochia competition. The wheat‐only treatment consistently produced the most spikes, biomass, and yield, peaking in generation 3 or 4, with seed numbers tripling compared to generation 1. These results indicate a possible positive effect of multigenerational stress memory on wheat in generation 3, followed by a maladaptive response to weed competition in later generations.