Tall fescue Festuca aurudinace Schrab is one of the most important forage species worldwide. Development of synthetic varieties is the most common breeding approach in this plant. The first synthetic generation is obtained through multi-parental random crossing. Selecting parental genotypes is mostly based on morphological traits that are highly influenced by environmental conditions. Molecular markers are not affected by environment and may help selecting diverse parental genotypes more precisely. Present study was conducted to assess the molecular diversity of two syn2 populations, one derived from parental genotypes with high molecular distance and the other from parents with high morphological distance. From each population sixty random genotypes were evaluated using 23 ES T - SSR primers. From the 23 tested primers, 18 were selected based on polymorphic band development. Totally 80 bands were produced in which 71 showed polymorphism. Within population genetic similarity coefficient ranged from 0.51 to 0.95 for the syn2 population having molecularly diverse parental genotypes. This value ranged from 0.48 to 0.96 for the syn2 population derived from morphologically diverse parents. Results of cluster analysis at similarity coefficient of 0.62 and 0.69 divided population 1 and 2 into 10 and 21 groups respectively. For both populations, principle component analysis partially confirmed the results obtained for cluster analysis. Analysis of molecular variance was conducted between these two populations. Based on this, 74.17 percent of observed diversity was related to within population and just 25.83 percent was related to between population diversity respectively. The Euclidian distance between the two syn2 populations was 0.19 which was higher than what it was 0.13 for the syn1 populations. Results showed that using molecular markers in parental selection it is possible to eliminate environmental effects that are evident in morphological characteristics and the selected diversity in the parents is transmitted to the subsequent generations. Keywords: tall fescue, molecular markers, synthetic varieties
