The most important crop to the densely populated regions of east south and southeast asia is

The most important crop in East Asia, South Asia, and Southeast Asia, by far, is the rice. The rice is the basic food in these three heavily populated parts of the world, and is used daily by the majority of the population. It has a tradition of around 10,000 years of cultivation in East Asia, and it is the crop the feeds the two most populated countries in the world, which are also the biggest producers of this crop in the whole world.

Themes; subfields is the answer