COFFEE LEAF RUST ( CLR ) AND DISEASE TRIANGLE : A CASE STUDY

Leaf rust in coffee is the major fungal disease caused by Hemileia vastatrix that devastates the coffee plantations at its peak incidence levels. Present study reveals the relationship of the three components of disease triangle viz. host, environment and pathogen involved in coffee-leaf rust disease complex. Results indicated that, in the case of coffee; the host disease resistance is more influencing than the other two factors i.e. pathogen and environmental variables. This is clearly elucidated by the fact that with the prevalence of almost 37 races in Indian coffee tracts the evolution one predominant race is not observed, i.e. races I and II that were prevalent in 1930s continue to be predominant even now. With the changing climatic conditions shifts in patterns are observed in the factors that influence the climate but not much effect on disease development as disease develops whenever favourable conditions occur, i.e. spore germination that requires lower temperatures (15-20C) and diffuse light. Therefore, the ability of the host plant to tolerate the pathogen attack should be given prime importance in breeding approaches for sustainable coffee production.