The term 'MAJOR SOURCE OF WHEAT' can be summarized as the SUN being a major source of wheat. Wheat is a cereal grain that is a staple food for many cultures around the world and is one of the most widely produced crops. The SUN provides the energy needed for photosynthesis, which is essential for the growth of wheat. Without the SUN, wheat would not be able to grow and therefore would not be a major source of food.