The contributions of plant genetics to the production of higher yielding crops of superior quality are well documented. These successes have been realized through the application of plant breeding techniques to a diverse array of genetically controlled traits. Such highly effective breeding procedures will continue to be the primary method employed for the development of new crop cultivars; however, new techniques in cell and molecular biology will provide additional approaches for genetic modification. There has been considerable speculation recently concerning the potential impact of new techniques in cell and molecular biology on plant improvement. These genetic engineering techniques should offer unique opportunities to alter the genetic makeup of crops if applied to existing breeding procedures. Many questions must be answered in order to identify specific applications of these new technologies. This search for applications will require input from plant scientists working on various aspects of crop improvement. This volume is intended to assess the interrelationships between conventional plant breeding and genetic engineering.