The course deals with the concepts and nature of plant disease pathogenesis. It includes the study on the mechanism of ingress and establishment of plant pathogens, the effect of plant disease on biochemical and physiological processes namely photosynthesis, respiration, water and nutrient uptake and reproduction; and the mechanism on plant disease resistance as an important component in plant disease management. These processes are essential in analyzing the impact of plant pathogens on the crop productivity and in designing sustainable plant disease management approaches.