Preface

Genetic diversity is the fundamental source of biodiversity. In 1989, the World Wildlife Fund defined biodiversity as "the richness of life on Earth – millions of plants, animals and microorganisms, including the genes which they carry, and complex ecosystems that create the environment". Currently, the issue of maintaining genetic diversity as a component of the conservation of biodiversity has been accepted at an international level. FAO has included the issue of conservation, evaluation, and the use of animal genetic resources in its fields of interest since the 1970s. In this context, one of the main concerns of scientific research activities is conserving the genetic diversity of local breeds, especially those of economic interest. Genetic diversity among individuals reflects the presence of different alleles in the gene pool, and hence, different genotypes within populations. Genetic diversity should be distinguished from genetic variability, which describes the tendency of genetic traits found within populations to vary. There is a considerable genetic variability within or between natural populations. Population geneticists attempt to determine the extent of this variability by identifying the alleles at each locus and measuring their respective frequencies. This variability provides a genomic flexibility that can be used as a raw material for adaptation. On the other hand, one of the consequences of low genetic variability could be the inability to cope with abiotic and biotic stresses. From the growing knowledge on the genome sequences of organisms it becomes evident that all forms of diversity have their origin at genetic level. In this context, genetic diversity analysis provides vital and powerful data that helps for a better understanding of genetic variation and improved conservation strategies.

Plants are a distinct kingdom of organisms that possess unique properties of reproduction, development, physiology, and adaptation. Plant diversity refers to the variety of plants that exist on the Earth. Plants, in order to survive, have to compete with other plants and organisms in an ecosystem. Over time, they have developed various characteristics to help them survive, which leads to plant diversity. It is essential to have regular assessments of the conservation status of all plant species, in order to prioritize those in need of conservation action and to provide a measure of the success of actions being taken. The improvement of cultivated plants considerably depends on the extent of genetic variability available within the species. The genetic variation that exists among plant populations is a basic requirement for efficient development and improvement of such populations. It also indicates whether a population can withstand and live with changes in the environment, which are mostly altered in an unpredictable way. Molecular studies shed light on relationships and diversity among plant breeds. The extent and nature of genetic diversity of plants from all around the world has been investigated by typing DNA markers in a set of individuals belonging to several breeds. The most useful techniques for these studies have been micro-satellites, RFLP, RAPD, SSR, AFLP, SCAR and ISSR.

The purpose of *Plant Genetic Diversity* is to provide a glimpse into the dynamic process of genetic variation by presenting the thoughts of some of the scientists who are engaged in the development of new tools and ideas used to reveal genetic variation, often from very different perspectives. I would like to express my deepest gratitude to all the Authors who contributed to this book by sharing their valuable works with us. This book should prove useful to students, researchers, and experts in the area of conservation biology, genetic diversity and molecular biology. The year 2010 has been celebrated as the international year of biodiversity by the United Nations and it has been a unique opportunity to realize the vital role that biodiversity plays in sustaining the life on Earth. Let us all wish much success to all projects and initiatives dealing with the conservation of diversity of life because rich genetic resources are a prerequisite for future generations to be able to breed crop varieties and face new challenges.

> **Prof. Dr. Mahmut Caliskan**  Mustafa Kemal University, Department of Biology Hatay, Turkey
