TAIPEI, Taiwan—Yuan Longping, a Chinese scientist who developed higher-yield rice varieties that helped feed China’s people, died Saturday at a hospital in the southern city of Changsha, the Xinhua News agency reported. He was 91. Yuan spent his life researching rice and was nicknamed “Father of Hybrid Rice” by Chinese media. Worldwide, a fifth of all rice now comes from species created by hybrid rice following Yuan’s breakthrough discoveries, according to the website of the World Food Prize, which he won in 2004. It was in the 1970s that Yuan achieved the breakthroughs he was known for. He developed a hybrid strain of rice that recorded an annual yield 20 percent higher than existing varieties—meaning it could feed millions more people a year. His work helped transform China from “food deficiency to food security” within three decades, according to the World Food Prize, which was created by Nobel Peace Prize …