Similar genetic diversity but increased differentiation revealed among a 58-year-old Pinus massoniana seed-tree stand and its progenies generated at different ages

Abstract

The genetic diversity and mating status of seed production stands are crucial factors impacting the genetic quality and ecological stability of progeny plantations. The genetic homogeneity of seeds collected from a seed production population in different years has not yet been clearly described. In this study, the genetic diversity and differentiation of a seed-tree stand of 58-year-old Pinus massoniana (P1959) and four-open pollinated plantations of its progeny (OS1996, OS2000, OS2006 and OS2015) were determined by using microsatellite markers. The results showed that similar high genetic diversity was preserved in the seed-tree stand and its four progenies. This implied that current artificial seed harvesting from the seed-tree stand for reforestation does not lead to a significant reduction in genetic diversity; the F index across most loci was significantly greater than zero, indicating population homozygote excess. The pairwise genetic differentiation of the five populations ranged from 0.035 to 0.075, among which OS2015 was the most differentiated from the parent. The differentiation between the parental population and its progeny seemed to increase with increasing age of the seed-trees. This implied that a limited pollination coupled with variable within-stand pollen availability has created opportunities for both self- and foreign pollination to be successful in various periods, resulting in a seemingly paradoxical scenario of both high selfing and gene flow, ultimately resulting in gradually increasing differences in the gene frequency composition between the parental population and its progeny. Management considerations in addressing these problems in similar seed production stands were discussed.