Rice feeds more than half the world's people. The long-leaved grass, which thrives in shallow wetlands, produces edible seeds that have sustained humans for generations. In the 1960s researchers bred rice plants to respond favorably to fertilizer, which helped prevent famine by allowing farmers to grow more rice per acre than ever before. Now scientists have improved rice once again, this time by stiffening the plant.

Tomoaki Sakamoto of the University of Tokyo and his colleagues tested 34 different varieties of rice plants in which individual genes had been removed--specifically avoiding an approach in which genetically desirable traits are imported from other plants. One such plant lacked the OsDWARF4 gene, which governs production of a steroid involved in growth. Eliminating this particular gene created a plant with stiff but normal leaves, yet the removal had no impact on flowering or the eventual grain, the researchers report in a paper that will be published online tomorrow in Nature Biotechnology.

Scientists have long sought such a stiff-leafed rice plant, believing that it would raise grain yields. A rigid rice plant allows sunlight to reach leaves on even the lowest parts of the plant, improving photosynthesis and therefore grain production; it also allows plants to be placed in closer proximity without interfering with each other's growth. But previous attempts to produce such strength by knocking out specific genes had stunted the plants or produced bad seeds.

The new rice also remedies one of the problematic legacies of the original "green revolution": over-use of fertilizer. The new plant produced more than 30 percent more grain than regular rice plants without the generous helpings of fertilizer commonly used today.

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