Rapid generation advance of rice at the International Rice Research Institute

Short generation is also necessary in low-temperature areas where only one crop can be grown each year. The rapid generation advance (RGA) method shortens rice plant growth duration by using high-temperature close-spacing short-day treatments to make three generations possible each year. This report describes cultural methods evolved to obtain optimum growth, shortest possible growth duration, and maximum use of space. Various characteristics that can be screened during RGA and the general breeding procedure are discussed. Besides shortening crop duration, RGA allows many crosses to be processed in limited space and time. Environment can be controlled, and problems such as bad weather, rats, and other disease and insect pests minimized; limited selection and screening is also possible using RGA. The method can help shorten breeding periods at national programs in rainfed wetland areas where photoperiod sensitivity is important. Although few new photoperiod-sensitive rice varieties have been named in the last 20 years, due to the greater length of time needed to develop such varieties in comparison with high-yielding breeds, they are grown on more than 20 million ha; Japanese rice breeders have used RGA increasingly since 1958. In photoperiod-sensitive rice breeding, selection for maturity date is site-specific. Through RGA, however, fixed bulk materials from the International Rice Research Institute can be sent to different sites where primary selections, especially flowering dates, are made. (Author abstract, modified)