Systemic acquired resistance

While, it has been recognized since at least the 1930s that plants have some kind of induced immunity to pathogens, the modern study of systemic acquired resistance began in the 1980s when the invention of new tools allowed scientists to probe the molecular mechanisms of SAR.

[2] It was noticed in the early 1990s that levels of salicylic acid (SA) increased dramatically in tobacco and cucumber upon infection.

ETI often results in a form of programmed cell death (PCD), called hypersensitive response (HR).

SAR is characterized by accumulation of plant metabolites and genetic reprogramming both locally and systemically (surrounding tissues that were not infected).

Unusually, the synthetic fungicide acibenzolar-S-methyl is not directly toxic to pathogens, but rather acts by inducing SAR in the crop plants to which it is applied.