Avirulence

Avirulence refers to a situation in plant-pathogen interactions where a pathogen, such as a fungi or bacteria, loses or lacks the ability to cause disease in a plant that it would normally infect. This often happens because the plant has developed specific defense mechanisms, like resistance genes, that recognize certain pathogen features and trigger an immune response. When the pathogen no longer carries these recognizable features—due to genetic changes—it becomes avirulent, meaning it cannot successfully infect or harm the plant. This concept helps explain how plants can sometimes resist pathogen attacks even if the pathogen is still present.