R Making Rice Disease-resistant

food. Almost two billion people—one third of the world’s population—depend primarily on rice for basic nourishment. Rice fields cover more than 360 million acres of land around the globe and yield 560 million tons of grain every year. But farmers plant much more rice than they harvest, because insects, bacteria, viruses and fungi often claim a substantial portion of each crop. One of the most devastating of these pestilences is blight, caused by bacteria common throughout Asia and Africa. These bacteria—Xanthomonas oryzae pv. oryzae (known as Xoo)—spread rapidly from rice plant to rice plant and from field to field in water droplets. Infected leaves develop lesions, yellow and wilt in a matter of days. In severely infected fields, bacterial blight can wipe out half of a farmer’s rice crop. And yet rice plants possess an amazing assortment of genes that offer protection from a host of diseases, including bacterial blight. The farmers’ predicament is that no single variety has every gene and that all plants are vulnerable to some diseases more than to others. Breeders have exploited disease-resistance genes in rice for nearly a century, redistributing this genetic wealth from hardy species to agriculturally useful varieties. But conventional breeding is painstaking and time-consuming; often a decade or more is needed to produce desired traits. With the advent of genetic engineering, we are now able to introduce isolated disease-resistance genes directly into rice plants, trimming years from the time required to develop a useful variety. My colleagues and I recently cloned the first such disease-resistance