Activity of Common Thyme ( L.), Greek Oregano ( L. ssp. ), and Common Oregano ( L. ssp. ) Essential Oils against Selected Phytopathogens.

The aim of this study was to determine the activity of common thyme ( L.), Greek oregano ( L. ssp. ), and common oregano ( L. ssp. ) essential oils (EOs) against selected phytopathogenic microorganisms in relation to their chemical profile. The EOs were obtained from the herbs of 2-year-old plants cultivated in the organic farming system in a temperate climate in Central Europe. The EOs' composition was determined by GC/MS and GC/FID. The investigated species were represented by the following three chemotypes: 'thymol' for common thyme, 'carvacrol' for Greek oregano, and mixed 'caryophyllene oxide + β-caryophyllene' for common oregano. The antimicrobial activity of the EOs was assessed based on minimum inhibitory concentration (MIC) and minimum bactericidal/fungicidal concentration (MBC/MFC) values. The plant pathogenic bacteria , , , and fungi: , , , , , , and were tested. The EOs revealed a stronger inhibitory effect against fungal growth in comparison to bacterial growth (MIC: 0.016-2 µL/mL for fungi and 0.125-4 µL/mL for bacteria). Common thyme and Greek oregano EOs indicated stronger antimicrobial power than common oregano EO. These results were associated with the chemical profile of the analysed EOs. The growth of examined bacteria and fungi strains (in particular, , , and ) were negatively correlated with the content of phenolic monoterpenes and monoterpene hydrocarbons. Among the tested strains, turned out to be the most sensitive (MIC 0.016 µL/mL) and the most resistant (MIC 0.250-4 µL/mL) to all investigated EOs.