Siderophore Detection assay v1

This protocol describes the detection and quantification of siderophore production by'Biocontrol bacteria' using the Chrome Azurol S (CAS) agar assay, adapted from Schwyn and Neilands (1987). CAS agar was prepared by incorporating a dye complex of CAS, HDTMA, and FeCl₃ into LB agar. Bacterial suspensions were spotted onto CAS agar plates at different dilutions and incubated at 28 °C. Siderophore activity was visualized as yellow-orange halos surrounding bacterial colonies, and the siderophore production index (SPI) was calculated. This method enables reproducible, semi-quantitative screening of siderophore production by bacterial isolates.