Graft compatibility emerges from the balance between regeneration and immunity: lessons from plant-plant interactions.

Plant grafting is a significant horticultural technique that enables the combination of desirable traits such as enhanced resilience, disease resistance, and productivity. Despite its widespread application, the mechanisms underlying graft compatibility remain poorly understood. Because grafting is largely an anthropogenic process, plants are unlikely to have evolved mechanisms specifically to recognize graft partners. Here, we propose that graft compatibility is not controlled by a dedicated recognition system, but instead emerges from the balance between existing tissue regeneration and immune surveillance pathways that evolved in other plant-plant interactions. We synthesize evidence from inter-plant communication, parasitic interactions, and damage-associated molecular pattern signaling (DAMPs) to show that these systems converge on conserved mechanisms regulating non-self perception, tissue regeneration, and long-distance communication. This evolutionary framework explains diverse observations across graft biology and provides a foundation for developing strategies to expand graft compatibility across economically important crops.