Although we have not found the ancestor of wild onion, the first center of domestication could be southwest Asia. This is certainly one of the oldest cultivated vegetables in the world, even if it did not become popular in Europe until the Middle Ages. It was also one of the first European plants to be cultivated in America, where Christopher Columbus introduced it. In the seventeenth century, it was established in the northern United States and Canada, where it was grown by both settlers and Native Americans. Today, onion can be found in all temperate regions of the globe, and testing to implement it in the semi-arid regions are underway. The main producing countries are China, India, the United States, Mexico, Brazil and Spain.