Genotype-dependent reductions of competition are associated with yield maintenance in a modern common wheat Triticum aestivum L. cultivar

Modern crop breeding has increased yield under monoculture stands, but the mechanisms underlying this improvement remain incompletely understood. We tested whether genotype-dependent reduction of competition, whereby plants adjust competitive responses according to neighbor genetic identity, contributes to yield maintenance in modern common wheat cultivars. We conducted a root-exudate application experiment and two competition experiments using three common wheat (Triticum aestivum L.) landraces and one modern cultivar, Norin 61. Norin 61 exhibited little change in shoot-to-root allocation in response to root exudates from the same cultivar compared with distilled water, whereas it increased shoot-to-root allocation exposed to root exudate from different cultivars. Moreover, shoot-to-root allocation increased with decreasing genetic relatedness between neighboring cultivars in common wheat plants. In competition experiments, greater shoot-to-root allocation was associated with stronger suppression of competitors. Norin 61 maintained grain biomass under the same-cultivar competition compared to solitary conditions but exhibited substantial yield reductions when competing with different cultivars, whereas these patterns were weaker or absent in landraces. These results suggest that genotype-dependent reduction of competition may contribute to yield maintenance in modern wheat cultivars and provide a new perspective on how crop breeding has shaped plant-plant interactions in monoculture stands.