*2.4. Screening for Antagonistic Actinobacteria*

The phytopathogenic *S. sclerotiorum* strain used in this study was kindly provided by the Soybean Research Institute of Northeast Agricultural University (Harbin, China). Antagonistic activity of isolates were evaluated through the dual culture plate assay [45]. The isolates were point-inoculated at the margin of potato dextrose agar (PDA) [46] plates and incubated for three days at 28 ◦C, after which a fresh mycelial PDA agar plug of the fungus was transferred to the opposite margin of the corresponding plate. After additional days of incubation at 20 ◦C for seven days, inhibition of hyphal growth of the fungus was scored. The inhibition rates were calculated as follows:

$$\text{Inhibition rate (\%)}=\text{Wil/W}\times100\text{\%}\tag{1}$$

where *Wi* is the width of inhibition and *W* is the width between the pathogen and actinobacteria. Each test was repeated three times and the average was calculated.
