James R. BallingtonDepartment of Horticultural Science, North Carolina State University, Raleigh, NC 27250 and U.S. Department of Agriculture, Science and Education Administration Federal Research, Beltsville Agricultural Research Center, Beltsville, MD 20 705
Gene J. GallettaDepartment of Horticultural Science, North Carolina State University, Raleigh, NC 27250 and U.S. Department of Agriculture, Science and Education Administration Federal Research, Beltsville Agricultural Research Center, Beltsville, MD 20 705
The comparative self-compatibility, intra-, and interspecific crossability of representative clones of V. atrococcum (Gray) Heller, V. caesariense Mackenzie, V. darrowi Camp, and V. tenellum Aiton was determined. The number of germinated seeds and number of vigorous seedlings proved to be the best criteria for evaluation of crossability. The 4 species were largely self-incompatible. Generally, intraspecific and interspecific crossability levels were singificantly higher than those of the self-pollinations. Interspecific crossability was significantly lower than intraspecific crossability. Crossability levels within species and the range in crossability in individual combinations among species were extremely variable. Although F1 hybrids were produced in each of the 6 species hybridizations attempted, the rate of success was highly variable, and the direction in which the cross was made was usually critical. Specific combining ability was considerably more important than general combining ability in achieving species hybridizations. The hypothesis of complete homoploid interfertility in Vaccinium was not valid for these 4 species. The ranking of species crossability (number of vigorous seedlings per 100 pollinations) from highest to lowest was: V. atrococcum – V. caesariense, V. atrococcum – V. darrowi, V. darrowi – V. tenellum, V. caesariense – V. tenellum, V. caesariense – V. darrowi, and V. atrococcum – V. tenellum.
Received for publication April 17, 1976. Paper No. 4896 of the Journal Series of the North Carolina Agricultural Experiment Station, Raleigh, NC. Part of a thesis submitted in partial fulfillment of the Doctoral of Philosophy degree, Department of Horticultural Science.
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Assistant Professor and Research Geneticist, respectively. The authors gratefully acknowledge the suggestion of Dr. A. D. Draper, USDA Research Geneticist, that the X2 test of independence might be applicable to this data, and the advice of Dr. J. E. Koch, USDA Biometrician, for advising on the partitioning and genetic interpretation of the X2 data.