When the cells were cultured in KB medium and directly added
to the system, the growth of the plants was significantly lower than
in the control irrespective of pathogen presence in the system.
Lettuce weight was similar to that of the infected control and the
weight of the roots was significantly lower than in the infected foaming when living strains are used. The strain used in this study,
P. koreensis 2.74, was originally isolated from a hydroponic system
(Hultberg et al., 2008b) and could be expected to be capable of
surviving and growing in the system. However, a rapid decrease in
viable cells of fluorescent pseudomonads in the nutrient solution
was observed after addition. After six days the amount of fluorescent
pseudomonads in treatments with addition of washed cells
did not differ significantly from that in the control treatment.
Repeated addition of the biocontrol strain is most probably needed
to ensure a consistent effect.