Although fruit breeding has been a major activity since early in the 20thcentury, the results have been uneven and vary from ineffectual to extraordinarily successful (Table 3). Many of the world fruit industries is still based on grower-selected clones. The reason for the lack of progress is two fold. First, vegetative propagation permits the genetic fixation of naturally occurring variation. Because of the vast populations involved in seedling orchards, the quality of the selected clones over hundreds and even thousands of years of selection is very high. Second, the difficulties and expense inherent in fruit breeding have inhibited long term breeding programs. Progress from breeding a number of fruit crops, however, has shown significant advances in the second half of the 20thcentury and selections form controlled crosses are increasingly important in many crops. In apple, although chance seedlings such as ‘Delicious’ and ‘Golden Delicious’
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