About Lesson
Defense mechanisms of host against pathogen/parasite
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