In cross-pollinated crops a number of open-pollinated populations are in cultivation either as endemic cultivars or improved varieties. The major categories of such open-pollinated cultivars, sometimes referred to as open-pollinated varieties (OPVs), are endemic landraces, products of selection, synthetic varieties and composites. Because random mating is sustained in these population through open pollination the genetic structures of these populations are similar or close to Hardy-Weinberg populations and are, therefore, highly heterozygous and heterogeneous.