## 2 Materials and Methods
### Effect of \(\beta\)-Caryophyllene & \(\beta\)-Caryophyllene Oxide on Plant Pathogenic Fungi  
Isolates of the plant pathogenic fungi _P. lingam_, _S. sclerotorium_ and _A. brassicicola_ were obtained from the Leibniz-Institut DSMZ (Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH, Braunschweig, Germany), while isolates of _F. oxysporum_, _R. solani_ were obtained from the INRES, Plant Diseases and Plant Protection, University of Bonn. All isolates were sub-cultured on potato dextrose agar (PDA) at 24 \({}^{\circ}\)C and were used in this study to evaluate the bioactivity of the compounds on hyphal growth.  
To test the bioactivities of \(\beta\)-caryophyllene and \(\beta\)-caryophyllene oxide, compounds were dissolved in a mixture of DMSO and Tween 20 (ratio of 1:2) to prepare differently concentrated stock solutions. These were mixed with PDA to gain the final concentrations 62.5, 125, and 250 \(\mu\)g mL\({}^{-1}\) and to prepare PDA agar plates with terpenoids. The final DMSO and Tween 20 concentrations were always 1% (\(v/v\)) and 0.5% (\(v/v\)), respectively. Fungal discs with a diameter of 0.5 cm were cut from the culture media of freshly grown agar plates without terpenoids and placed upside down in the middle of PDA plates containing the chemicals. PDA plates with 0.5% (\(v/v\)) DMSO and 1% (\(v/v\)) Tween 20 alone were used as control. All plates were incubated for 7 days at 24 \({}^{\circ}\)C. Subsequently, the diameter of the fungal colony was measured, and the percentage of growth inhibition compared to the solvent control was calculated. Differences between the treatments were statistically analyzed using SigmaPlot software by one-way analysis of variance (ANOVA) and multiple comparisons for significance were performed at (\(p<0.05\)) using the Holm-Sidak method.  
Determination of the Minimum Inhibitory Concentration (MIC) of \(\beta\)-Caryophyllene and \(\beta\)-Caryophyllene Oxide in Liquid Cultures of Bacteria  
The minimum inhibitory concentration of \(\beta\)-caryophyllene and \(\beta\)-caryophyllene was determined according to reference [89]. For the precultures, 10 mL Muller Hinton (MH) medium (Merck, Germany) was first inoculated in 100 mL flasks with four single bacterial colonies. For _R. capsulatus_, RCV was used. The liquid cultures were incubated for 18 h at 130 rpm and 37 \({}^{\circ}\)C (_R. capsulatus_ at 30 \({}^{\circ}\)C). For the main cultures, MH or RCV medium was supplemented with differently concentrated stock solutions of \(\beta\)-caryophyllene and \(\beta\)-caryophyllene oxide in a mixture of DMSO and Tween 20 (ratio 1:2) to gain final concentrations of 62.5, 125, and 250 \(\mu\)g mL\({}^{-1}\). All bacterial cultures were adjusted to a cell density corresponding to an optical density at 625 nm of 0.1 and then diluted 50-fold with medium for _B. subtilis_, _P. putida_, _P. fluorescens_, _R. rhizogenesis_ and _P. polymyna_ and _2_-fold for _R. capsulatus_. For the inoculation of 96-well microtiter plates (Greiner Bio-One GmbH, Frickenhausen, Germany), 50 \(\mu\)L MH medium with the corresponding concentration of the substance to be tested and the solvent controls were mixed with 50 \(\mu\)L of previously diluted bacterial culture, resulting in an end optical density at 625 nm of 0.001 and 0.025, respectively. The solvent control contained 1% (\(v/v\)) Tween 20 and 0.5% (\(v/v\)) DMSO. After inoculation, the microtiter plates (MTPs) were first shaken in a SpectraMax i3x (Molecular Devices, San Jose, CA, USA) plate photometer for 20 s to mix the solution and then incubated for 20 h at 37 \({}^{\circ}\)C. _R. capsulatus_ was incubated at 30 \({}^{\circ}\)C and 300 rpm. For subsequent determination of the MICs, the optical density of cell cultures was determined at 625 nm in a plate photometer. The MIC was defined based on the European Committee on Antimicrobial Susceptibility Testing (EUCAST) guidelines as the compound concentration at which an optical density at 625 nm minus the background absorbance equals 0 [90].