Over the past 20 years, researchers have developed increasingly sophisticated genome information and analytical platforms for rice (Oryza sativa) genetic research. The genetic controls of source capacity include photosynthesis capacity, leaf senescence, canopy architecture, and translocation. Details of these controls have been gradually elucidated using biotechnological approaches and studies of natural genetic resources. These advances have been accompanied by the development of phenotyping methodologies for use under both field and controlled conditions. However, a more comprehensive understanding of the genetic factors that regulate source capacity and their effects on rice yield is required to increase the efficiency of breeding to improve yield. In this review, we summarize the current understanding of the physiological and genetic factors that regulate source capacity gained through biotechnology approaches. We also describe the development of phenotyping methods and recent improvements of our understanding of natural variant genes that regulate source capacity. We conclude that the next challenge to be addressed is closing the gap between understandings of genetic control of source capacity and rice productivity in the field.