Often overlooked is the importance of early maturing rice varieties with their ability to escape droughts, avoid floods, and in some localities, open up the opportunity for double cropping. Most varieties grown in the tropics until the last half century matured in 150 to 180 days or longer and were photoperiod sensitive. However, non-photoperiod sensitive one-hundred-day varieties were grown in the Champa Kingdom in what is now Central Vietnam centuries ago. How these varieties moved into Song Dynasty China and the impact of the early ripening rice on population growth in South China is well documented. However, the origin of the Champa varieties is less clear. According to a recent DNA test (see below), the Champa varieties belong to the aus sub-population. The aus have the characteristics of both indica and japonica and originated in the hill areas of what are now Eastern India, Bangladesh, and Myanmar. Because the Champa Kingdom adopted the Indian language and religion, at least in the higher courts, it seems logical that the Champa rice must have been disseminated from the hilly areas in the Indian sub-continent to Central Vietnam and eventually to China—first Fujian and later to the Yangtze region during the Song Dynasty in the eleventh century.
Read the full paper here: The Origin and Spread of Early-Ripening Champa Rice