New strains of genetically modified corn will play a key role in meeting soaring demand as U.S thirst for ethanol fuel cuts into supplies, a top seed company scientist said on Friday. Dupont’s Bill Niebur, the firm’s vice president for genetics research and development, said demand for ethanol means the race is on to rapidly ramp up grain yields. ”We doubled average yields in North America in 41 years. We don’t have that much time to make the next step,” Niebur said at a gathering of grain exchanges, traders and consumers in Mexico. ”The challenge for our plant breeders is to move that curve significantly faster.”