Thirty Years of Genetic Gains in Rice.

From 1981 to 2011, U.S. rice yields have increased 47% (2.5 t ha^-1) at an average of 86 kg ha^-1 y^-1. Reilly and Fuglie in their paper on future yield growth in crops projected U.S. rice yields for 2011 to be approximately 8 and 11 t ha^-1 for the linear and exponential growth rates, respectively.  The average U.S. rice yield for 2009-2011 was 7.8 t ha^-1, which was close to the linear growth prediction but well below the exponential model. Their annual increment for rice yield with the linear prediction was 85 kg ha^-1 y^-1, almost identical to the actual calculated value of 85.9 kg ha^-1 y^-1 for the U.S. Yield advancement and genetic gain in U.S. rice production has been very dramatic since the 1980’s, estimates from regional varietal testing range from 25 to 87 kg ha^-1 y^-1.  In the Southern U.S. this trend is continuing.  Rice yield increases in California, although higher, have slowed indicating a yield plateau may have been reached. U.S. rice breeding programs have historically been public sector and grower supported efforts.  Changes have occurred with commercially available privately developed F₁ hybrids.  Genetic yield gains have been associated with improved traits like; semidwarf habit, diseases resistance, specific cultivars, herbicide tolerance, and F₁ hybrids. Herbicide tolerant cultivars (non-transgenic) and F₁ hybrids have become very popular and successful and are currently exclusive to the Southern U.S. Yield genetic gains have not been made through the adaption of transgenic rice because it is not commercially or politically acceptable in the U.S. or anywhere in the world to date.  Genetic markers have become routine in many U.S. breeding programs. The relatively high yields produced in the U.S. make achieving yield increases more challenging as the maximum yield potential of rice is approached.