Monsanto plans to reassess the long-term targets for global penetration of genetically-modified seeds amid surging demand from farmers for its most sophisticated products. The rise in demand for US corn for use as food and fuel has forced farmers to plant in more hostile terrain and encouraged a drive for higher yields to take advantage of record crop prices. Hugh Grant, Monsanto’s chairman and chief executive, said the US group would evaluate how the current US harvest proceeds, but said the demand for seeds improving the yields of corn, soybeans and other crops was already ahead of its existing targets.