I would like to express my sincere thanks to Mr. Minas K. Papademetriou, Senior Plant Production and Protection Officer, FAO Regional Office for Asia and the Pacific, Bangkok, Thailand, for his valuable assistance and encouragement in the preparation of this publication. Thanks are also due to Dr. N.B. Lutaladio, Agricultural Officer (Root and Tuber Crops), AGPC, FAO, Rome, for reviewing the manuscript.
