Isolation of siderophore negative mutants of Azotobacter chroococcum and studies on the role of siderophores in mdstard yield

Six siderophore negative (Sid⁻) mutants were derived from Azotobacter chroococcum 111 after mitomycin C treatment. The mutants showed neither hydroxamate nor catechol type of siderophore pmduction. Pot experiments using three Sid⁺ strains of A. chroococcum (soil isolate 111, two metabolic analogue resistant mutants viz. Mac 27 and Mala 27) and one Sid⁻ mutant derived from 111 revealed that only Sid⁺ mutants caused significantly higher increase in plant growth and grain yield over Sid⁻ mutant on mustard.