Received for publication 2 Feb. 1988. Vegetable Crops Paper no. 860. This research was supported by Hatch Act Project NYS161-422, and grants from the Kimberly-Clark Corp. and E.I. du Pont de Nemours and Company. We gratefully acknowledge the technical assistance of K.E. Tripp and D. Bell. 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.