Final answer:
The initial localized response of a resistant plant to pathogen invasion is the hypersensitive response (HR), which involves the rapid production of reactive oxygen species and programed cell death around the infection site.
Step-by-step explanation:
The initial localized response of a resistant plant to pathogen invasion is called the hypersensitive response (HR). During this response, the plant rapidly generates reactive oxygen species (ROS), such as superoxide anion, hydrogen peroxide, and nitric oxide, which cause programed cell death around the infection site. This response is an attempt by the plant to stop pathogen invasion.