Anti-oomycete ability of scopolamine against Phytophthora infestans, a terrible pathogen of potato late blight

BACKGROUNDPhytophthora infestans causes late blight, threatening potato production. The tropane alkaloid scopolamine from some industrial plants (Datura, Atropa, etc.) has a broad-spectrum bacteriostatic effect, but its effect on P. infestans is unknown. RESULTSIn the present study, scopolamine inhibited the mycelial growth of phytopathogenic oomycete P. infestans, and the half-maximal inhibitory concentration (IC50) was 4.25 g L-1. The sporangia germination rates were 61.43%, 16.16%, and 3.99% at concentrations of zero (control), 0.5 IC50, and IC50, respectively. The sporangia viability of P. infestans was significantly reduced after scopolamine treatment through propidium iodide and fluorescein diacetate staining, speculating that scopolamine destroyed cell membrane integrity. The detached potato tuber experiment demonstrated that scopolamine lessened the pathogenicity of P. infestans in potato tubers. Under stress conditions, scopolamine showed good inhibition of P. infestans, indicating that scopolamine could be used in multiple adverse conditions. The combination effect of scopolamine and the chemical pesticide Infinito on P. infestans was more effective than the use of scopolamine or Infinito alone. Moreover, transcriptome analysis suggested that scopolamine leaded to a downregulation of most P. infestans genes, functioning in cell growth, cell metabolism, and pathogenicity. CONCLUSIONTo our knowledge, this is the first study to detect scopolamine inhibitory activity against P. infestans. Also, our findings highlight the potential of scopolamine as an eco-friendly option for controlling late blight in the future. & COPY; 2023 Society of Chemical Industry.