Extensive screening for the siderophore producing bacteria from the sugarcane rhizosphere was carried out.
Seven isolates were found to produce more than 85 % siderophore units. Amongst them S-11 was found be the
most efficient siderophore producer (96 % SU). S-11 was further characterized and identified as Pseudomonas
fluorescens. Physico-chemical parameters were evaluated for optimum for production of siderophores by
Pseudomonas fluorescens strain. It was found to produce maximum siderophore at pH 7 and 29OC. Tyrosine as
carbon source was found to stimulate bacterial growth as well as siderophore production. Maximum siderophore
yield was obtained with ammonium sulphate and urea as independent nitrogen source. Iron concentration up to
20 μM was found to optimum for siderophore production. Shake flask studies revealed that the siderophore production
starts after 6 h of growth and reached to maximum productivity of 96 % SU after 24 h. The present study
reveals Pseudomonas fluorescens strain as a promiscus candidate for crop improvement and protection due to
its PGPR activities.