Received for publication 26 Sept. 1983. A contribution of the Georgia Agricultural Experiment Station, College Station, Athens, and the ARO, The Volcani Center, No. 1198-E, 1984 series. This research was supported by State and Hatch funds awarded to the Georgia Agricultural Experiment Station, College Station, Athens and by grant no. 1-43-79 awarded by the U.S.-Israel Binational Agricultural Research and Development Fund (BARD). 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.