1. Chang (2000) made exhaustive review on the pattern for rice evolution was suggested as from perennial wild to annual wild and then to cultivated. Therefore, the evolution for O. sativa is O. rufipogon to O. nivara to O. sativa in Asia. In parallel, the evolution for O. glaberrima is O. longistaminata to O. barthii and then to O. glaberrima in Africa.
2. It is believed that rice originated in the marsh areas and spread toward the dry lands and hills. The domestication of rice, including such cultural practices as puddling and transplanting, might have first taken place in China.