Since 1970, the rate has increased to 21.6 new wheat varieties and 3.4 new rice varieties per year. Comparison of experimental-plot yields of new varieties to those in production in 1970 indicates that in the absence of the new varieties, wheat yields would have been 33 percent lower in 1993, and rice yields 19 percent lower. Around 73 percent of the total U.S. rice acreage in 1993 was sown to varieties with IRRI ancestry. Cutbacks in research investments can undermine the benefits already gained through crop improvement research, as diseases mutate, pest problems recur, populations grow, and climatic conditions shift. Scientific research must continue apace in order to keep ahead of rapid population growth, shifting consumer demands, and other changing conditions that threaten crop yields.
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