The Monsanto company now doesn't grant the property of seeds for cultivations, which in the past were sold to farmers. The company sends their own inspectors to verify that the farmer doesn't resell the seeds to others. And they publish pages on papers to be payed by those who transgress their rules. This means that every year the farmer must buy the seeds again since the plants of the previous year are sterile, they don't produce seeds. The price is therefore practically imposed.
Biodiversity disappears with all the serious implications which follow.
Man runs the risk of genetic mutations whose consequences are not predictable.