Present address: Department of Horticultural Science, North Carolina State University, Raleigh, NC 27650.
Received for publication December 14, 1982. Oregon Agricultural Experiment Station Technical Paper No. 6651. Data reported herein are from a dissertation by the senior author in partial fulfillment of the requirements for the PhD degree. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact.