mammals. Most fruit crops are highly cross-pollinated, and tree fruits generally have long juvenility and long-life. Some fruit crops have the ability to propagate vegetatively. Subsequent progress in the improvement of fruit cultivars resulted from continual selection of seedling populations, and from intercrosses among elite clones or with wild or introduced clones, that vastly speeded up the process. This process has been very efficient and in spite of progress in plant breeding replacing grower-selected clones has not been easy (Table 5). A review of the fruit crops discussed above indicates that the origins of fruit growing evolved from an interaction of genetic changes and cultivation technology, often unique for each species. Some idea of how this has occurred can best be inferred from the history of two recent domesticates: cranberry and kiwifruit. What occurred in these crops probably occurred in the
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