Fluorescent Pseudomonas spp. as biocontrol agents against forage legume root pathogenic fungi

Abstract

Native fluorescent pseudomonads isolated from the rhizosphere of Lotus corniculatus were screened in vitro for their antagonistic activity against the phytopathogenic fungi Pythium ultimum and Rhizoctonia solani. About 12% of the bacterial isolates inhibited one or both fungi in vitro. Isolates which exhibited the greatest antagonistic activity were assayed in vivo against the pathogens. Three Pseudomonas fluorescens strains were selected from these assays: UP61, UP143 and UP148. These strains produced HCN and siderophores, but addition of iron to the medium did not affect the antagonistic activity. Lytic enzymes such as chitinase and β-1,3-glucanase were not detected. The simultaneous inoculation of Pseudomonas strains and Rhizobium loti B816 did not affect nitrogen fixation efficiency in L. corniculatus plants. Sterile peat was successful as a carrier for these P. fluorescens strains.