International Rice Research Institute, Los Banos, Philippines
Vitamin A Deficiency (VAD) remains a persistent problem in many developing countries, including many countries and regions in Asia where rice is the predominant staple. The development of the prototype transgenic Golden Rice in the year 2000 demonstrated against considerable scientific scepticism that provitamin A carotenoids could be produced at significant levels in the rice endosperm. This discovery opened up the possibility of providing this important provitamin for the first time in this staple and this approach would be complementary to ongoing VAD relief efforts. This initial discovery was followed by research that revealed that only the phytoene synthase and phytoene desaturase genes were required to complete the missing steps in the pathway in the endosperm, thereby simplifying the process from the original three genes that were used. Over the last few years, a number of advances have produced new Golden Rice events with much higher levels of provitamin A carotenoids – up to more than 20 times of those reported originally. A number of these new events have been grown in the field and show no apparent negative agronomic or quality effect of this high level of expression. Preliminary retention studies during cooking show only little losses – these and other retention studies are continuing. The new high expression events were produced in modern American varieties and the introgression of the these events into adapted germplasm has begun, with special focus on widely grown varieties in Asia and on those preferred for local cultivation and consumption in the most VAD-prone regions in a number of Asian countries. This process is being accelerated by the use on Marker Assisted Selection.