An agronomist hailed as a Chinese national hero for helping develop hybrid rice and easing hunger for millions worldwide died yesterday at the age of 90, state-run Xinhua news agency said. Yuan Longping, known in China as the "father of hybrid rice", is credited with cultivating the world's first high-yield hybrid rice strain in 1973. Hybrid rice, which can yield 20 percent above conventional varieties according to experts, was subsequently widely planted in China and rice-growing areas around the world.