Herbicide-resistant weeds exploit kinship to reduce allelopathy from crops

Kin recognition enables plants to optimize growth strategies when competing with heterospecific neighbors, yet its prevalence in herbicide-resistant weeds and how herbicide-resistant weeds exploit kinship to interact with allelopathic crops remain largely unknown. Here, we experimentally demonstrate that kin recognition occurred in 4 out of 10 tested herbicide-resistant weed biotypes from wheat and paddy fields. Root segregation treatments confirmed that kin recognition was mediated by root-secreted chemical signals. When interacting with allelopathic rice and wheat, kin-recognition-enabled weed biotypes exhibited striking plasticity. Kinship-based pairing reduced root allocation but accelerated flowering and increased seed production. Crucially, herbicide-resistant weed biotypes growing with kin lowered exudation of the signaling (-)-loliolide, which reduced allelochemical production in crops and minimized crop-mediated growth inhibition. This cascade allowed weeds to reallocate resources toward reproduction and to reduce defense investment in crops-revealing a novel "signal-mediated mutual de-escalation" strategy. The findings suggest that kin recognition is an adaptive trait in herbicide-resistant weeds, reducing allelopathy from crops through (-)-loliolide-mediated chemical interactions. By modulating crop signaling systems, herbicide-resistant weeds exploit kinship for population expansion in agroecosystems, highlighting the role of kinship strategy in shaping weed adaptation to develop integrated weed management approaches.