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This research (paper No. 8082, Journal Series of the N.C. Agricultural Research Service, Raleigh, NC 27650) was supported in part by NCSU Research Service Project No. NC05724 and the North Carolina Agricultural Foundation, Inc. Special thanks are extended to J. Baker, G. Rock, and C. R. Unrath for help in preparation of the manuscript; to Perry Lowe for the use of his orchards; and to S. Bambara, G. Kuhn, K. Kuhn, B. Lord, and P. Schillaci for technical assistance.