ABSTRACT
Plant-pathosystems are complex systems composed of host, pathogen, environment, and human beings. Pathogens belonging to kingdom fungi are notorious, destructive, and are known for epidemics and starvation they have caused globally. Among all phytopathogens, fungi are the most destructive and cause huge losses in terms of productivity and environmental deterioration. Fungi have been the causal agents of many widespread epiphytotics, which have changed the outlook and course of human civilization toward the science of plant pathology. Adaptation to biotic or abiotic stress in the environment may play a key role in increasing the fitness of pathogens. There are two methods used for the measurement of the fitness: based on the contribution of an individual in a generation, known as "Predicted fitness method" and based on the multi generation changes in phenotype frequency and/or gene frequency where these observed changes are translated to single generation fitness which is known as "Realized fitness method".
