The impact of molecular genetics on plant breeding and, consequently, agri- culture, is potentially enonnous. Understanding and directing this potential im- pact is crucial because of the urgent issues that we face concerning sustainable agriculture for a growing world population as well as conservation of the world's rapidly dwindling plant genetic resources. This book is largely devoted to the applications of genetic markers that have been developed by the application of molecular genetics to practical problems. These are known as DNA markers. They have gained a certain notoriety in foren- sics, but can be used in a variety of practical situations. We are going through a period of accelerated breakthroughs in molecular ge- netics. Therefore, the authors of each chapter were encouraged to speculate about both current bottlenecks and the future of their subfields of research. We can cer- tainly apply molecular genetic tools and approaches to help resolve crucial ge- netic resource problems that face humanity. However, little has been discussed with respect to when or how we should use such tools, nor to who specifically should use them; therefore, social and economic analyses are important in the planning stages of projects that are aimed at practical results.