pH-responsive manganese carboxymethyl chitosan hydrogel releases pesticide to promote rice tillering and suppress root-parasitic weeds

Abstract Strigolactone (SL) signaling is an important agricultural target for controlling plant branching and parasitic weeds. Here, based on the SL inhibitor KK094, we describe the design of 32 indole derivatives, of which DK6 exhibits optimal activity. To enhance solubility and bioavailability, we describe a pH-responsive manganese-coordinated carboxymethyl chitosan hydrogel (CMCS-DK6), showing sustained release under alkaline conditions. We demonstrate CMCS-DK6 strongly inhibits germination of parasitic weeds, especially Striga asiatica (IC 50 = 1.80 μM), while promoting rice tillering, reducing height, and increasing dry weight. Molecular simulations, along with microscale thermophoresis results, suggest that DK6 binds stably to SL receptors. Transcriptomics reveal DK6 suppresses SL signaling, modulates metabolic pathways, and interacts with hormone pathways to regulate tillering. This work offers a hydrogel delivery strategy and some potential mechanistic implications for improving crop architecture and weed control.