What are the regularities of the geographical location of the centers of diversity and origin of cultivated plants?

Plants need for normal functioning: sun, water and minerals.
In tropical areas, there is a lot of sun and high humidity. Also in these areas are soils rich in minerals for plants.
As you move away from the equator, the climate becomes more severe.
For example, in the Tundra zone it is very cold and there is no water in the soil (permafrost layer).