1.The effects of thyme essential oil at different concentrations on the inhibition rates of three main pathogenic bacteria causing root rot of Astragalus mongholicus 2.Data related to pathogen identification

1.The mycelial discs with a diameter of 6 mm were inoculated in PDA medium with thyme essential oil concentrations of 0.5, 1.0, and 1.5 μL/mL respectively, and the antibacterial effects of the essential oil at different concentrations were analyzed (see Figure 6). After 72 h of in vitro contact, when the thyme essential oil concentration was 0.5 μL/mL, the average inhibition rates of the three pathogenic fungi from high to low were: Penicillium chrysogenum (35.2%) > Fusarium solani (30.1%) > Fusarium oxysporum (28.4%). When the concentration was 1.5 μL/mL, the inhibition rate against Penicillium chrysogenum reached the highest (72.1%), indicating that the inhibitory effect on Penicillium chrysogenum was stronger at this concentration. After 120 h of in vitro contact, when the concentration was 1.5 μL/mL, the average inhibition rate of the three pathogenic fungi was 82.67%. After 168 h of in vitro contact, when the thyme essential oil concentration was 0.5 μL/mL, the inhibition rate against Fusarium oxysporum was the lowest at 35.4%. When the concentration was 1.5 μL/mL, the average inhibition rates of the three pathogenic fungi were Penicillium chrysogenum (88.3%) > Fusarium solani (78.1%) > Fusarium oxysporum (73.5%).2.Isolation and purification of pathogenic bacteriaThe treated lesion tissue was placed on a sterilized PDA medium and incubated in a constant temperature incubator at 28°C for 48 hours. The colony morphology was observed on the plate, and colonies with distinct morphological differences, neat edges, and rapid growth were selected for re-isolation and repeated purification. The selected colonies were separated on a new agar plate using the streaking method until a single colony was obtained [15].Observation of pathogenic bacteria morphologyA 6 mm fungal colony was taken from the edge of the purified fungal plate and placed on a new PDA medium, and then incubated in the dark at 27°C for observing the colony and conidial characteristics. A fluorescence microscope was used for observation and photography. The fungi were identified according to the "Manual of Fungal Identification" [16].Molecular identification of pathogenic bacteriaDNA was extracted from the mycelium cultured for 6 days. Using DNA as the template, PCR amplification was performed with the fungal identification primers ITS1: 5'-TCCGTAGGTGAACCTGCGG-3' and ITS4: 5'-TCCTCCGCTTATTGATATGC-3'. The reaction process was as follows: pre-denaturation at 96°C for 2.5 min; denaturation at 96°C for 30 sec; annealing at 55°C for 30 sec; extension at 72°C for 1 min 30 sec; 30 cycles; extension at 72°C for 5 min. The products were detected by 1.5% agarose gel electrophoresis, and the target fragment was observed under blue light and purified from the gel. Then, DNA sequencing was performed using a sequencer, and the spliced sequence file was compared with the database using the NCBI Blast program to obtain the comparison results. Finally, a phylogenetic tree was constructed using MEGA7.0 software [17].