Majority of the high yielding varieties of Indian rice have been developed by cross between
Oryza sativa japonica and Oryza sativa indica
Oryza sativa indica and Oryza nivara
Oryza nivara and Oryza sativa japonica
Oryza nivara and Oryza rufipogon
Plant breeding is a technique used by agricultural scientist and botanist across the world for creation of varieties of plants and trees. While, this is a manipulation of plant species to get varieties with desired characteristics, this is the basics of green revolution which led to the development of high yielding varieties of rice, wheat and other crop plants. A majority of the high yielding rice varieties were derived by cross breeding of various species of japonicas and indicas since 1960 e.g., Oryza sativa japonica and Oryza sativa indica.