Received April 5, 1971. Paper No. 608 - Department of Vegetable Crops, Cornell University, Ithaca, New York.
One of us (M. J. Trudel) held a Quebec Agricultural Research Council Fellowship during his participation in this work. The excellent technical assistance of Miss S. Altschuller is gratefully acknowledged.
Present address: Department of Crop Science, Faculty of Agriculture, Laval University, Quebec 10e, Canada.