Parental selection and deployment design in the second-generation seed orchard of Chinese pine in Shanxi Province

Seed orchard of Chinese pine in Shanxi Province is in the critical period from first-generation to advanced-generation. In this paper, issues related to the establishment of second-generation seed orchard, including elite family selection, within-family superior individual selection, phylogenetic analysis with SSR (simple sequence repeat) markers, genetic diversity analysis with SSR markers and field design, were investigated in the plus-tree open-pollinated progeny test of the first-generation seed orchard of Chinese pine in Shangzhuang, Shanxi Province, China. Results showed that there were significant differences in volume growth among the 77 investigated families and 20 families were selected as the elite families. One superior individual was selected in each of the 20 elite families and a total of 20 superior individuals were selected in the open-pollinated progeny test, with the mean volume dominance ratio and mean volume genetic gain of 0.25 and 0.13. There were varying genetic relationships among the 20 open-pollinated superior individuals. Individual No. 3 was distantly related with the other 19 individuals, however, individual No. 15 and No. 17 were closely related. Genetic diversity results revealed that there were relatively high genetic diversity levels among the 20 superior individuals, with the mean polymorphism information content (PIC) of 0.532 4. The 20 superior individuals were in a relatively stable state, with the mean heretability (H), expected heretability (He) and fixation index of 0.595 5, 0.570 3 and -0.018 4, respectively. Unbalanced, incomplete fixed block design was advised in the second-generation seed orchard of Chinese pine in Shangzhuang. The relative phylogenetic relationships among clones were considered and the best clones were represented with higher proportion, which had effectively increased the genetic gain. This study will lay an important theoretical foundation for the establishment of the second-generation seed orchard of Chinese pine in Shanxi province and provide important references for the application of molecular marker technology into the improvement of Chinese pine.