The condition of a plant such that it is likely to succumb to attack by a pathogen. Extreme susceptibility, in which the host cells die soon after invasion by a pathogen, is termed *hypersensitivity
and this reaction in fact confers considerable resistance. Susceptibility is often found where a crop cultivar has relied on one major-gene for resistance to a particular pathogen. If a mutant of the pathogen develops that can overcome this major-gene resistance then the cultivar is often seen to have no other means of preventing the invasion and spread of the pathogen. Susceptibility, like *resistance
, varies according to environmental conditions. For example, excessive application of nitrogen fertilizer may lead to lavish growth that is more easily invaded by a pathogen.