Pure monoterpenes as precision tools against soft rot: Fast susceptibility screening of Pectobacterium carotovorum with relevance to crop protection

Abstract

Pectobacterium carotovorum, the causative agent of soft rot in vegetables, is responsible for substantial postharvest losses worldwide. This study assessed the antimicrobial activity of seven pure monoterpenes 3-carene, α-pinene, (−)-β-pinene, (−)-bornyl acetate, D-carvone, (S)-(−)-limonene, and sabinene against P. carotovorum using disk diffusion, determination of minimum inhibitory concentrations (MIC₅₀ and MIC₉₀), bacterial growth curve analysis, and MALDI-TOF MS Biotyper profiling after 3 and 6 h of exposure. In disk diffusion assays, (S)-(−)-limonene and sabinene produced the largest inhibition zones (6.33 mm), whereas α-pinene, β-pinene, D-carvone, and bornyl acetate showed weaker activity (2.67-3.67 mm). MIC₅₀ values ranged from 0.158 mg/mL for β-pinene to 7.426 mg/mL for bornyl acetate, indicating wide variation in potency. Growth kinetics revealed the strongest suppression by D-carvone (final OD₈₅₀ = 0.88), moderate inhibition by limonene and sabinene, and negligible effects of bornyl acetate and 3-carene. MALDI-TOF MS Biotyper spectra displayed compound-specific alterations in bacterial spectral profiles, confirming biochemical changes induced by monoterpene exposure. These in vitro results identify β-pinene, (S)-(−)-limonene, and D-carvone as promising candidates warranting further in vivo evaluation for managing soft rot in postharvest vegetables.