ROLE OF SIDEROPHORES IN CHICKPEA (CICER-ARIETINUM L.) - RHIZOBIUM SYMBIOSIS

Strains of Rhizobium ciceri (wild type as well as mutants) were screen ed for their ability to produce siderophores under cultural conditions . All strains except a mutant Ca401RW5 were found to be siderophore pr oducers. A standard strain Cal81 which is being used for large scale p roduction as inoculant for chickpea, found to be a siderophore produce r, was used for standardization of conditions for siderophore producti on. Only hydroxamate type of siderophores were detected under cultural conditions. The level of hydroxamate production increased linearly du ring log phase of growth up to 8 days. Addition of iron in the medium resulted in decrease in hydroxamate production and at 500 mu M iron le vel, the hydroxamate level decreased by 40%. In other strains tested, decrease in hydroxamate production varied from 30 to 75% whereas in on e strain Ca85AZ3 this level of iron completely inhibited hydroxamate p roduction. Strain Ca181 was most effective in terms of symbiotic nitro gen fixation in absence as well as added iron. Addition of iron stimul ated nodule fresh weight in almost all the strains tested. It also res ulted in increased symbiotic effectivity in terms of nitrogen gain per plant although the response varied with the bacterial strain.