Hello I am woundering if it is possible to breed for disease ressitance in pigeons against this resiratory disease called coryza is it possible if so how .
Thank you

This depends on how much genetic variation for susceptibility there is within the pigeon population you want to breed from. Commonly there will be some genetic variation for disease traits meaning that artificial selection should be succesful to some degree. The more variation in the trait that is caused by genetic differences among individuals, the faster the improvement you could obtain.

In terms of how to do it, you need to identify birds that have high resistance and then preferentially breed from those (while making sure you avoid inbreeding too). This can be tricky with diseases caused by bacteria/viruses because unless you know all birds have had the same exposure (or you deliberately expose them - which raises ethical issues) its not possible to know whether a bird is healthy because it has good genes or because it was never exposed to infection.

Agreed with all of the above and also to note coryza in pigeons is a catch all that is not just one disease and includes a whole range of organisms including rapidly mutating influenza tyoe viruses which it almost impossible to breed resistance to.