ABSTRACT
Rice is an important cereal crop of the world. It serves as a major food grain to nearly 2 billion people, equating to one third of global population. Globally, rice is grown on 161.4 m ha. Its production in 2009 amounted to 704.4 MT paddy, i.e., 476 t milled rice [1] at an average productivity of 4.2 t/ha. Asians produce and consume nearly 95% of the global rice. The rice agroecosystem of the world thrives on variety of soils and climatic conditions experienced in over 115 countries situated between 53° N to 35° S. China, India and other South-east Asian nations support a very large Rice Agroecosystem. Rice belt of India extends into 44.6 m ha and contributes about 86 m t of rice grains annually. Historically, domestication of rice and its culture for regular consumption as carbohydrate source occurred in north-east of Indian subcontinent. Rice was associated with Chinese and Indian civilizations since 6000 years [2]. Archeological samples of rice from Chalcolithic period were estimated between 6570 and 4530 B.C. [3, 4]. Rice cultivation began in Gangetic plains around 2000 to 1500 B.C. Rice culture spread to South India around 1400 B.C. Archaeological studies on Neolithic sites in North Karnataka and Andhra Pradesh, in India indicate that rice cultivation occurred in these locations around 1500 B.C. [5]. Fuller et al. [5] believe that rice may have also been independently domesticated in South India around 1st millennium B.C. Randhawa [6] states that rice spread into Southern Indian plains during Iron Age.
