Why has it taken this long to develop Golden Rice?

The process of using modern breeding and biotechnology techniques to develop new plant traits such as Golden Rice and integrate them into existing varieties usually takes many years. The time for discovery, development, regulatory approval and marketing of a new biotechnology crop trait is estimated to be 13 years on average http://www.croplife.org/PhillipsMcDougallStudy

The development of Golden Rice is on pace with this timeframe. In 2006, IRRI and others began working with a new version of the Golden Rice trait that produces significantly more beta carotene than the 1999 prototype, and it is this version of Golden Rice that is still under development and evaluation. Golden Rice will only be made available broadly to farmers and consumers if it is approved as safe by national regulators and shown to reduce vitamin A deficiency in community conditions, a process that is likely to take another two to three years (see When will Golden Rice be available to farmers and consumers?)