Many microorganisms, including phytopathogenic and non-pathogenic bacteria, landing on plant surfaces, enter the intercellular spaces of the mesophyll via open stomata or wounds. Plant pathogenic bacteria are able to invade the susceptible plants causing serious diseases or can induce a rapid hypersensitive response (HR) in disease resistant cultivars. The mechanism of the HR was first published by our laboratory (Nature, 1983).

Now another defence mechanism of plants was described by us as early induced resistance (EIR) which can inhibit not only the multiplication of pathogenic bacteria, but that of non-pathogenic bacteria as well. (J. Phytopathology, 1999). In nature this common non-specific local mechanism can defend plants from the invasion of microorganisms at the penetration site. At present we are investigating the pathological, biochemical and molecular aspects of the EIR.