Pseudomonas fluorescens 134 as a Biological Control Agent (BCA) Model in Cell Immobilization Technology

Antifungal activity against Rhizoctonia solani was achieved in vivo through the application of Pseudomonas fluorescens strain 134 encapsulated in sodium alginate beads of different sizes (0.5, 1, and 2 mm). The activity was compared to that obtainable with chemical treatments and bead-derived liquid formulations. The latter was obtained by dissolving alginate beads of 1 and 0.5 mm in 1% Na-citrate solution before application, without any significant (P < 0.05) reduction of bacterial numbers during the dissolution process. The dry bead formulations were applied next to the seeds in plant inoculation experiments, resulting in a reduction of disease symptoms, which were markedly reduced when the liquid formulation was applied. Moreover, the rate of disease symptoms related to liquid formulations from both 1 and 0.5 mm beads was comparable (near to 10%) to that of chemical treatment. Pseudomonas fluorescens strain 134 delivered as both dry and liquid formulations was able to colonize cotton root at a population density of about 108 CFU/g fresh root, 15 days after sowing.