Submergence due to flash flooding is a major stress constraint to rice production, especially in rainfed lowland areas of the tropics. Developing rice cultivars with tolerance of submergence and with better agronomic traits acceptable to farmers is a feasible approach to address this problem. Research on the identification of new genetic sources tolerant to submergence/ flooding stresses is of great significance not only to utilize new gene sources to develop new cultivars tolerant to submergence but also to unravel the physiological and molecular mechanism. The present book describes the different physiological and molecular screening strategy for submergence tolerance in rice. This book should especially useful to researchers / scientists in agriculture and life science field for future development of submergence tolerant rice cultivars.