The colonization and plant growth promotion of PTS-394 in pots

The dynamic colonization of PTS-394 on the tomato rhizoplane and its plant growth-promoting ability were investigated by pot experiments, and the GFP-labeled strain (PTS-394G) was used for colonization analysis. Suspensions of B. subtilis PTS-394 and PTS-394G with an OD₆₀₀ = 1.0 were used. In both experiments, tomato seeds were surface-disinfected and sown into nursery soil containing a mixture of vermiculite and organic manure (1:1, w/w) for germination. Tomato seedlings at the 4-leaf stage were transplanted into pots filled with a mixture of vermiculite, rice field soil and organic manure (1:2:1, w/w). 20 mL of bacterial cell suspension was added to each plant and cultivation was continued in a greenhouse under natural conditions with temperatures ranging from 18 to 30 °C. Each treatment was performed on 30 plants and replicated three times in a completely randomized block design. In the colonization experiment, tomato root samples were collected from three PTS-394G plants at 0, 1, 2, 3, 5, 7, 9, 11, 14, and 21 days after transplantation and the amount of PTS-394 on the root surface was determined, as described previously. Meanwhile, tomato roots were examined at 1, 3, 7 and 14 days using fluorescent microscopy in order to detect colonization with PTS-394G. At 30 days after treatment with PTS-394, the fresh weight of the root and the plant height were measured in order to evaluate the growth-promoting effect of PTS-394.