It is also true that for upwards of the past century, mutation breeding has been used successfully in a wide variety of crops, for example:
[R]adiation breeding has produced thousands of useful mutants and a sizable fraction of the world’s crops...including varieties of rice, wheat, barley, pears, peas, cotton, peppermint, sunflowers, peanuts, grapefruit, sesame, bananas, cassava and sorghum...The mutations can improve yield, quality, taste, size and resistance to disease and can help plants adapt to diverse climates and conditions...Peanuts got tougher hulls. Barley, oats and wheat got better yields...In 1929, farmers stumbled on the Ruby Red grapefruit, a natural mutant. Its flesh eventually faded to pink, however, and scientists fired radiation to produce mutants of deeper color — Star Ruby, released in 1971, and Rio Red, released in 1985. The mutant offspring now account for about 75 percent of all grapefruit grown in Texas.
Source:
http://www.nytimes.com/2007/08/28/science/28crop.html?pagewanted=all&_r=0
So I think we should be cautious in our use of these techniques, but optimistically so in light of the successes that have been demonstrated.