Plant bears its own defense mechanism (s) against the development of diseases caused by various fungi, bacteria, viruses, nematode and other microorganisms. The attribution of the hosts that reduce the chances of infection or the further development of the pathogen are considered to be defense mechanism'. The defense may be used against pathogen at any stage of infection i.e. during pre-penetration, penetration or post penetration. In nature disease resistance seems to be the rule rather than the exception. Plants also have induced structural and biochemical defense like histological defense structure, hypersensitive response, PR protein, phytoalexine and systemic acquired resistance. All these defense mechanism are slow down or inhibit the initial attack of pathogens.