Physiological basis of heterosis in rice

New plant types and hybrids are physiologically more efficient. They have a higher biomass than inbred varieties and a comparable harvest index. Increasing biomass yield and maintaining a high harvest index are the main breeding strategies for achieving another breakthrough in rice yield. Biomass is a complex trait governed by a number of morphophysiological components. We attempted to analyze the physiological components of biomass and to study the character association and path relationship among its components. A strategy to select parents for developing hybrids and pedigree breeding based on physiological efficiency are outlined.