## 2 Materials and Methods
### Plasma Sources and Treatment of Seeds  
Two plasma sources were employed in this study, a volumetric dielectric barrier discharge (volume-DBD, [32]) and a corona discharge (CD, [33]) reactor. The volume-DBD reactor has a coaxial configuration and has been previously reported in [32]. The reactor consists of a borosilicate glass tube with one end closed and a copper tape glued around it in a spiral shape serving as the high-voltage electrode (Figure 1A). The second electrode comprises a grounded copper rod placed at the central axis and forming a gap of 13 mm. Because of the relatively large gap size for operation in ambient air, the reactor operates with argon using a gas flow of 2 slm. To ensure a homogeneous treatment of the seeds, the reactor was mounted on top of a vortex mixer, allowing the constant shaking of the seeds.  
The CD reactor consists of an upside-down borosilicate glass funnel mounted on top of a glass Petri dish (Figure 1B), inside of which the seeds are placed. This configuration was reported in [33] for the treatment of seeds from rapeseed. The reactor is set up on top of a 5.85 mm thick glass plate with a grounded copper tape attached on the lower bottom. The high-voltage electrode comprises a tungsten pin inserted in the straight part of the funnel. With a distance between the pin electrode and the Petri dish of more than 10 cm, argon was fed into the reactor via the HV-electrode holder (top part) to facilitate discharge formation. Applying a flow rate of 4 slm helps with the corona filaments' propagation throughout the funnel, homogenizing their distribution.  
Both reactors were operated with an AC power supply (AL-1400-HF-A, Amp-Line, West Nyack, NY, USA) at a frequency of 10 kHz using amplitude-modulated voltage with a repetition period of 100 ms. The voltage amplitude was defined for each reactor separately and chosen as the minimum operating voltage to ignite the discharge when seeds were placed inside of it. Therefore, a voltage of 12 kV p-p and duty cycle of 30% were chosen for the volume-DBD configuration and a voltage of 20 kV p-p and voltage duty cycle of 50% were selected for the corona discharge.  
Incubation times of seeds with plasma on were 2, 5 and 10 min. After five minutes of operation with the respective parameters, the temperature in the reactor at the seed position was measured to be around 50 \({}^{\circ}\)C in both cases. To avoid the influence of high temperatures potentially originating from the plasma, the 10 min treatments for both reactors were split into 3 phases while the reactor was filled constantly with argon: 5 min induced plasma, 5 min without induced plasma and 5 min induced plasma without opening the reactor.  
More details on the temperature increase inside of the reactor during seed treatment are reported in [32; 33].  
In addition, two different control sets for each treatment and crop were implemented for the two plasma sources. The first control sample (control) encompassed artificially contaminated seeds without contact with the plasma sources inoculated with the spore suspension. This control enabled calculation of log reduction after CAPP treatment and served as a reference for total viable spores. The second control sample was a gas control with artificially contaminated seeds inside the plasma device which was filled with argon gas without plasma on for 2 min (Cg 2 min). This control elucidated whether gas flow of argon alone displayed decontaminating properties. A pre-test on the decontamination efficiency of argon gas only (gas flow 2 slm) applying treatment times of two minutes was carried out using the volume-DBD and lupine as a model.  
For each parameter, the treatment was established with three biological parallels and four technical replicates each.