TN5 INSERTION MUTANTS OF PSEUDOMONAS SP 267 DEFECTIVE IN SIDEROPHORE PRODUCTION AND THEIR EFFECT ON CLOVER (TRIFOLIUM PRATENSE) NODULATED WITH RHIZOBIUM LEGUMINOSARUM BV TRIFOLII

摘要

Pseudomonas sp. strain 267 isolated from soil promoted growth of different plants under field conditions and enhanced symbiotic nitrogen fixation in clover under gnotobiotic conditions. This strain produced pyoverdine-like compound under low-iron conditions and secreted vitamins of the B group. The role of fluorescent siderophore production in the beneficial effect of strain 267 on nodulated clover plants was investigated. Several non-fluorescent (Pvd(-)) Tn5 insertion mutants of Pseudomonas sp. strain 267 were isolated and characterized. The presence of Tn5 insertions was confirmed by Southern analysis of EcoRI digested genomic DNA of each derivative strain. The siderophore-negative mutants were compared to the parental strain with respect to their growth promotion of nodulated clover infected with Rhizobium leguminosarum by. trifolii 24.1. We found that all isolated Pvd(-) mutants stimulated growth of nodulated clover plants in a similar manner to the parental strain. No consistent differences were observed between strain 267 and Pvd(-) derivatives strains with respect to their plant growth promotion activity under gnotobiotic conditions.