An Assessment of Stabilizing Selection in Crop Variety Development

There is a limited amount of published information on the subject of stabilizing selection. The authoritative treatises on stabilizing selection do not, for the most part, contain data colIected from experiments designed to test the validity of the hypothesis (44, 49, 50, 52, 58-60). Papers that do deal directly with the subject have been limited to studies of one host and one pathogen (5, 12, 14-18, 32, 33, 36-38, 41, 46, 47, 53, 54, 57), from which it is difficult to draw conclusions with general applicability to the majority of host-pathogen interactions. Based solely upon proven scientific importance, there is inadequate information to justify the preparation of a review article on the subject of stabilizing selection. One has only to refer to the publications of Nelson (44, 45), Vanderplank (58-60), and Horsfall (31) to be familiar with the bulk of the information in print concerning stabilizing selection. The concept of stabilizing selection deals directly and inti­ mately with the production of food through the utilization of new varieties. The world press (television, radio, magazines, newspapers) has popularized these sub­ jects indirectly through news stories that deal with food production, and especially with the failures of food production systems around the globe. Every person exposed to the free-world press was made aware of the achievements of Norman Borlaug when he won the Nobel Peace Prize for developing new crop varieties. These new varieties provided the basis for the green revolution, which was intended to make the famine-stricken people of underdeveloped countries self-sufficient in food pro­ duction. Likewise, people everywhere were made aware of the sales of American grain to Russia when the Russian small grain crop production failed, and of the resultant rise in the price of wheat and bread in the USA. More recently, we were made very aware on a daily basis of the effects of the drought in Europe during the summer of 1976, and the effects of this on world food production. We are continu­ ously bombarded with news reports of the rise in the cost-of-living index and of the