Characterization of Pseudomonas spp. isolated from sewage irrigated soils and their plant growth promoting traits in vitro

PGPR serve several functions for plants. They fix atmospheric nitrogen and supply it to plants, or they synthesize siderophores that can solubilize and sequester iron from the soil and provide it to plant cells. PGPR also synthesize several different phytohormones, including auxins (IAA) and cytokinins, which enhance plant growth. In the present study efficient PGPR strains with multiple plant growth promoting activities belonging to Pseudomonas spp were isolated from domestic sewage irrigated rhizospheric soil samples. These test isolates were biochemically characterized and screened in vitro for their plant growth promoting traits like production of Indole acetic acid (IAA), Siderophore, ammonia, HCN and catalase production. most of the isolates were able to produce IAA. Production of ammonia was commonly detected in all the isolates. 60 % test isolates produce Siderophore but none of the isolates produced HCN and Phosphate Solubilization. On the basis of multiple plant growth promoting activities, test bacterial isolates of pseudomonas genus, were tolerant to multiple heavy metals. Among these isolates, Pseudomonas spp isolate YSY S-1, YSY S-3, YSY S-4 showed tolerance in concentrations (100μg/ml, 200μg/ml) . whereas YSY-26 and YSY-27 were tolerant to all heavy metals (50 to 100 μgml-1). YSY S-2 isolate showed tolerance in (50μg/ml, 100μg/ml, 200μg/ml ) whileas isolate (YSY S-5 showed tolerance in (50μg/ml, 100μg/ml) .