Extracts of the carriers were collected in a series of weight-towater
volume ratios (1:25, 1:10, 1:5, and 1:2) in 250-mL flasks after
shaking in a rotator at 200 rpm for 1 h at room temperature. The
extracts were filtered through two layers of cheesecloth, and the
resulting filtrate was centrifuged at 10,000 g for 10 min. The
supernatant was then filtered through a 0.22-mm filter and stored at
4 C until further use. Next, the inhibitory effect of the cell-free
carrier extract on the growth of R. solanacearum QL-Rs1115 was
evaluated. After spreading 200 mL of a suspension (108 CFU mL1 in
0.01 mol L1 phosphate buffer, as determined by the plate count
method with CPG medium) of R. solanacearum QL-Rs1115 onto CPG
medium plates, 100 mL of cell-free carrier extract was added using
the Oxford cup method (Fig. S2). There were three replications for
each extract. The plates were then kept at 30 C, and the zones of
inhibition we