Synthesis and antagonistic evaluation of fluorinated imidazolium salt [1-(2,6-diisopropylphenyl)-3-(2-fluoro-benzyl)-1H-imidazol-3-ium bromide] against significant phytopathogens in agriculture

Abstract

The current investigation evaluated the in vitro bioefficacy of a newly synthesized unsymmetrical imidazolium salt [1-(2,6-diisopropylphenyl)-3-(2-fluoro-benzyl)-1H-imidazol-3-ium bromide] that contains the electron-withdrawing fluorine atom at the ortho position against agriculturally significant phytopathogens. The molecular structure of the imidazolium salt was characterized by various spectroscopic techniques such as ¹H, ¹³C, and ¹⁹F NMR, FTIR, and high-resolution mass spectrometry (HRMS). Antimicrobial bioassay of the compound has been tested against two Gram-negative, bacterial phytopathogens namely Ralstonia solanacearum (Rs) (Gen Bank accession no. OQ743450) [causal agent: bacterial wilt of solanaceous crops], and Xanthomonas citri pv. citri (Xcc) (Gen Bank accession no. OR7036310) [causal agent: citrus canker in citrus trees] and two fungal phytopathogens namely Fusarium solani (Gen Bank accession no. OR140825) [causal agent: Fusarium die-back in tea] and Pseudopestalotiopsis chinensis (Gen Bank accession no. OR140826) [causal agent: grey blight in tea]. Different concentrations of imidazolium salt was tested against the target phytopathogens using the in vitro antimicrobial bioassay through disc diffusion method. The imidazolium salt demonstrated a maximum percentage inhibition of 16.70 and 21.78 against the bacterial phytopathogens R. solanacearum, and X. citri pv. citri, respectively, at a concentration of 2000 ppm over negative control. Similarly, the compound demonstrated promising antagonism against the tea fungal pathogens F. solani and P. chinensis (percentage inhibition up to 61.43 and 80.84, respectively at 2000 ppm) over negative control. Five replications were maintained in each of the cases. The present investigation demonstrated the potential of fluorinated imidazolium salt as commercial antimicrobial agent in integrated disease management schedule to control significant phytopathogenesis in agriculture including in tea.