the chairman of his graduate committee, for his unusual ability to "Kai-chiau" (open the doors of thinking), and his patience as an educator. The author also expresses his thanks to Dr. Kenneth H. Quesenberry and his group of cytogenetic co-workers for the orientation and facilities generously provided. Thanks are extended to the faculty members, staff and all the graduate students of the Vegetable Crops Department for the good times experienced during the author's pursuit of knowledge at the University of Florida. Special thanks are extended to the Brazilian Ministry of Education and the Escola Superior de Agricultura de Lavras for financial support during the author's training.