Control of plant diseases is crucial to the reliable production of food, and it provides significant reductions in agricultural use of land, water, fuel and other inputs. Plants in both natural and cultivated populations carry inherent disease resistance, but there are numerous examples of devastating plant disease impacts, as well as recurrent severe plant diseases. Disease control is achieved by use of plants that have been bred for good resistance to many diseases, and by plant cultivation approaches such as crop rotation, use of pathogen-free seed, appropriate planting date and plant density, control of field moisture, and pesticide use. The increased reflection on environmental concern over pesticide use has been instrumental in a large upsurge of biological disease control. Among the various antagonists used for the management of plant diseases, Trichoderma and Pseudomonas play a vital role. Development of crop varieties which are resistant against many economically important diseases is a major challenge for plant biotechnologists, worldwide. Plant diseases are a threat to world agriculture and general food security. Significant yield losses due to the attack of pathogen occur in most of the agricultural and horticultural crop species. The present book is primarily written for the use of students of graduate and postgraduate courses in plant pathology.