Plants do not have an immune system as vertebrate do, they
do possess a very sophisticated system to monitor and react when
facing a biotic stress (Jones and Dangl, 2006). Coevolution of plants
and pathogens has created a multifaceted relationship, resulting
from the exchange of molecular information between the species
(Benhamou, 1996). Based on this, plants have developed a complex surveillance system with an array of defense mechanisms.
Pathogens, on the other hand, possess strategies to overcome the
defense system and colonize plants. The difference between success
and failure of plant defense is most likely dependent on the
time it takes for the plant to recognize a potential pathogen and subsequently
activate the defense system (Garcia-Brugger et al., 2006).
Once the defense is alarmed a wide range of proteins is induced in
the plant, among these the pathogenesis-related proteins (PR) (van
Loon et al., 2006).