Effects of parental genetic distance on offspring growth performance in Pinus massoniana: significance of parental-selection in a clonal seed orchard

Abstract

Pinus massoniana is the most widely cultivated tree in southern China and an important afforestation, timber species. Seed orchards are the main source of high-quality seeds of P. massoniana, and parental selection is key to seed orchard construction. In this study, the relationships among genetic-quality stability, growth-performance and parental genetic-distance (GD) were analyzed based on 18 shared half-sib families from 3 progeny tests (established in 1995, 1996 and 1997) of P. massoniana seed orchard. Based on the growth stability of the offspring among different years, the stable groups (SGs) (9 families with the lowest growth fluctuation) and unstable groups (USGs) (9 families with the greatest growth fluctuation) were selected. Using 27 simple sequence repeat markers, we identified the parental-combinations for the most individuals in SGs and USGs from 18 known females and 217 candidate males. The parental GDs in the SGs changed less than those in USGs. Furthermore, based on the growth-performance of offspring, the excellent group (EG) (4 families in the top level), middle group (MG) (4 families in the medium level) and worst group (WG) (4 families in the last level) were selected. Compared with the MG and WG, the EG contained more parental-combinations with GD > 0.6, indicating this group could produce more high-quality variation. Hence, parents with a small range of GDs should be selected to ensure the sustainable and stable production of seeds with excellent genetic quality in the construction of P. massoniana seed orchards, while hybrid parents with greater GDs should be selected in the breeding process of P. massoniana to obtain more offspring with excellent genetic quality.