Introduction: Establishing a seed orchard not only ensures the supply of reproducible seeds and high-quality seedlings but also plays a crucial role in providing sufficient genetic diversity for future research. Acer cappadocicum Gled., known as Cappadocian Maple, is a native tree in Iran and an important species in the Hyrcanian forests. This study evaluated the genetic distances of maternal bases of Cappadocian Maple planted for the purpose of establishing a seed orchard. The main goal of this research was to avoid inbreeding depression and genetic uniformity in the population derived from these maternal bases.
Material and Methods: The number of 21 maternal trees with suitable phenotypes was identified in two populations in a forest with an approximate area of 100,000 hectares and seeds were collected and transformed into seedlings. The DNA was extracted using a modified CTAB technique, and the polymerase chain reaction was carried out with SSR markers. The amplified markers, genetic indices, the similarity matrix of Jaccard coefficients, and the cluster analysis of 21 chosen trees, were performed using the UPGMA. To produce seedlings and transfer them to the Maple seed orchard, 21 maternal bases with suitable phenotypes were identified from three populations in a forest area with area of approximately 100,000 hectares. Seeds were collected from these bases, converted into seedlings, and leaf samples were collected. After DNA extraction, polymerase chain reaction (PCR) was performed using SSR markers to amplify DNA bands. According to the results, amplification occurred at 15 SSR loci.
Results: For 15 SSR markers, 63 polymorphic alleles were identified in 21 selected genotypes for 15 pairs of SSR primers. The highest genetic diversity indices were estimated for the Dahmian population and the lowest for the Kilijkola population. Heterozygosity (H) varied between 0.23 (Dahmian population) and 0.16 (Kilijkola population). In addition, these two populations (Dahmian and Kilijkola) showed the highest (1.38) and the lowest (1.08) Shannon coefficient, respectively. The Jaccard genetic similarity between genotypes ranged from 0.001 to 0.52, indicating the low similarity of trees within each of the groups. Therefore, selection for seed collection should be from bases with less genetic affinity that are placed in separate clusters to prevent genetic regression.
Conclusion: In this study the genetic diversity of two populations, the molecular markers used were highly efficient in distinguishing maternal trees. The genetic diversity between the two populations was less than the genetic diversity within both populations. However, the genetic distances were calculated based on the relevant criteria, and considering the similarity coefficient, maternal trees were placed in three main clades. Trees with high similarity such as KilijKala 3, 7, and 5, as well as Dahmian 9 and Kilijkola 7 were observed. Finally, the information obtained from this research was used to manage the planted bases in the seed orchard, arranging the bases, and avoiding planting bases with high genetic affinity next to each other to prevent inbreeding depression.