Growth promoting influence of siderophore-producing Pseudomonas strains GRP3A and PRS9 in maize (Zea mays L.) under iron limiting conditions

Maize seeds were bacterized with siderophore-producing pseudomonads with the goal to develop a system suitable for better iron uptake under iron-stressed conditions. Siderophore production was compared in fluorescent Pseudomonas spp. GRP3A, PRS9 and P. chlororaphis ATCC 9446 in standard succinate (SSM) and citrate (SCM) media. Succinate was better suited for siderophore production, however, deferration of media resulted in increased siderophore production in all the strains. Maximum siderophore level (216.23 microg/ml) was observed in strain PRS9 in deferrated SSM after 72 h of incubation. Strains GRP3A and PRS9 were used for plant growth promotion experiments. Strains GRP3A and PRS9 were also antagonistic against the phytopathogens, Colletotrichum dematium, Rhizoctonia solani and Sclerotium rolfsii. Bacterization of maize seeds with strains GRP3A and PRS9 showed significant increase in germination percentage and plant growth. Maximum shoot and root length and dry weight were observed with 10 microM Fe3+ along with bacterial inoculants suggesting application of siderophore producing plant growth promoting rhizobacterial strains in crop productivity in calcareous soil system.