A) Avoidance

• Reduces the possibility of contact between potential consumer and plants by morphology, phenology or smell
• Eg: Erect leaf habit in cereals reduces the deposition of rust inoculation

B) Tolerance

• host neither restricts parasitic contact nor the growth and development of the parasite after establishment.
• As a consequence, it does not affect the number of damage/symptoms per unit quantity of parasite present. However, there is little loss in the economic yield.

C) Resistance

• It is the ability of the host to reduce the growth and or development of the parasite or pathogen after contact have been initiated or established

➢ Race specific/vertical resistance/gene for gene resistance: A resistance that is effective to specific (avirulent) genotypes of a pathogen species.

➢ Race nonspecific/horizontal resistance/no gene for gene resistance: A resistance that is equally effective to all the genotypes of a pathogen species.

D) Immune:

• Host does not show the symptom of disease is known as immune reaction.
• Rate of reproduction of the pathogen is zero
• Immune plants generally show hypersensitive reaction