PR proteins are proteins encoded by the host plant which are
specifically formed in response to pathogen attacks or comparable
Based on their primary amino acid structure, their serological
relation and/or their enzymatic or biological activities, PR
proteins are classified into 14 groups.
PR proteins do not only accumulate in the leaf inoculated by the
pathogen. In connection with what is referred to as systemic
acquired resistance (SAR), the formation of PR proteins is also
As a consequence of SAR, the plants are largely or fully protected
against later infections with the same or even another pathogen.