Genomics Meets Biodiversity: Advances in Molecular Marker Development and Their Applications in Plant Genetic Diversity Assessment

Genetic diversity is the fundamental source of biodiversity – the total number of genetic characters contributing to variation within species. In other words it is the measure that quantifies the variation found within a population of a given species. 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 (Laikre et al., 2009). Since the beginning of the 20th century, the study of genetic diversity has been the major focus of core evolutionary biology. The theoretical metrics developed, such as genetic variance and heritability (Fisher, 1930; Wright, 1931), provided the quantitative standards necessary for the evolutionary synthesis. Further research has focused on the origin of genetic diversity, its maintenance and its role in evolution. Simple questions such as “who breeds with whom” initiated studies on the relatedness of populations. These investigations led to the formation of metapopulation theory, where a group of spatially separated populations of the same species interact at some level and form a coherent larger group (Hanski, 1998). The discovery of spatial structure in populations was a key element in the early concepts and models of population ecology, genetics and adaptive evolution (Wright, 1931; Andrewartha & Birch, 1954). How different levels of genetic variance affect the rate of evolutionary change within populations has also been intensively studied. Such changes were originally studied using phenotypic markers: variation among individual plants in traits, such as leaf shape or flower color (Ward et al., 2008). Subsequently the detection of genetic variation has become more sensitive, firstly through the utilization of variation in enzymes (allozymes) and then through PCR-based marker systems allowing direct examination of DNA sequence variation. The precise detection of genetic variation/diversity has greatly enhanced studies of evolution. There is