Progress in sour cherry breeding in the U.S. is severely hampered by the limited germplasm available. Importing Prunus germplasm into the U.S. as budwood from the center of diversity in Eastern Europe, is impractical because of the lengthy quarantine period required. Instead it is proposed that pollen collection and the use of a tester clone would be the most efficient way to import and use sour cherry germplasm. Sour cherry pollen can be imported and used directly without a quarantine period. When the pollen is used in crosses with an appropriate tester clone, the breeding value of the germplasm can be assessed relatively easily because both parents are known as opposed to one parent as is the case with open-pollinated seed. Once a germplasm source has been identified as having a desired breeding value, pollen can again be imported or requested from the Plant Introduction Station where presumably the clone is still in quarantine, and used in routine breeding crosses. For a clone to be a good tester, it must induce precocity in the progeny and behave in a recessive manner for traits of importance. Data is presented to illustrate the use of the sour cherry cultivar English Morello as a tester clone for sour cherry germplasm evaluation.
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