What are the common non-radioactive detection techniques used for Southern blot detection?

In an alternative to radioactive detection, nucleotide probes can be labeled with digoxigenin or biotin. These labeled probes are then indirectly detected using an antibody labeled with digoxigenin or streptavidin, respectively. Another alternative is using chemiluminescent substrates that produce light when they react with an enzyme conjugated to the probe. The emitted light is then captured on X-ray film. For example, there is reaction between horseradish peroxidase (HRP) and luminol. This chemical reaction can produce a luminescent signal that indicates the presence of the target nucleic acids on the membrane. Fluorescent markers can also be used as a non-radioactive detection technique. Fluorescent probes, such as fluorescein, are used to label the DNA probes. After hybridization, the fluorescence emitted by the bound probes.