Role of siderophores in chickpea ( Cicer arietinum L.) — Rhizobium symbiosis

Abstract

Strains of Rhizobium ciceri (wild type as well as mutants) were screened for their ability to produce siderophores under cultural conditions.All strains except a mutant Ca40lRW5 were found to be siderophore producers.A standard strain Cal81 which is being used for large scale production as inoculant for chickpea, found to be a siderophore producer, was used for standardization of conditions for siderophore production.Only hydroxamate type of siderophores were detected under cultural conditions.The level of hydroxamate production increased linearly during log phase of growth up to 8 days.Addition of iron in the medium resulted in decrease in hydroxamate production and at 500 pM iron level, the hydroxamate level decreased by 40%.In other strains tested, decrease in hydroxamate production varied from 30 to 75% whereas in one strain Ca85AZ3 this level of iron completely inhibited hydroxamate production.Strain Cal 81 was most effective in terms of symbiotic nitrogen fixation in absence as well as added iron.Addition of iron stimulated nodule fresh weight in almost all the strains tested.It also resulted in increased symbiotic effectivity in terms of nitrogen gain per plant although the response varied with the bacterial strain.