Fungal plant diseases are a major concern in agricultural food production worldwide. Soil borne pathogenic fungi such as Pythium, Fusarium, Rhizoctonia and Phytopthora attack most of the economically important crop plants resulting in heavy losses. So there is a pressing need to control fungal diseases to ensure a steady and constant food supply to ever increasing world population. In recent years, biological control of plant pathogens has received increasing attention as a promising supplement to chemical control. Trichoderma - a genus under Deuteromycotina has gained immense importance as a biological control agent. However, the identification of isolates to species level is difficult due to the complexity and closely related characters of the species. Therefore, developing method to precisely identify species of Trichoderma and analysis of their molecular diversity among different isolates are important. This book give valuable information on biological control of plant diseases and molecular characterization of species identification and thus helps in evolving best performing isolates.