Plant hormones and their synthetic analogueues offer sustainable alternatives for crop protection, yet the direct antifungal activity of strigolactone (SL) and its analogues against necrotrophic pathogens remain largely unexplored. Here, we screened eight phytohormones and related analogues for treatments of Botrytis cinerea and identified the SL analogue rac-GR24 (racemic GR24) as a concentration-dependent growth inhibitor active at low micromolar concentrations. Given the stereochemical complexity of SLs and their analogues, we evaluated multiple enantiopure isomers and found that ent-5DS and GR24ent-5DS, which differ in configuration from natural SLs, exhibited the strongest inhibitory activity. This stereospecific response was further validated using another filamentous fungus, Sclerotinia sclerotiorum, which displayed an identical susceptibility profile. Combinatorial treatments with enantiopure isomers and double-concentration rac-GR24 revealed that the antifungal effect of the racemate is primarily attributable to the GR24ent-5DS enantiomer, whereas the opposite enantiomer GR245DS is almost inactive. Collectively, our findings uncover a stereospecific response in fungal pathogens, demonstrating that B. cinerea and S. sclerotiorum respond to exogenous SL analogues in a chirally selective manner. This work establishes a stereochemically defined framework for developing enantioselective fungicidal agents with potential applications in sustainable agriculture.
Huang et al. (Wed,) studied this question.