Study on the Genetic Variation of Triadica sebifera (Linnaeus) Small Populations Based on SSR Markers

Abstract

Triadica sebifera (Linnaeus) Small is a tree species native to China. The seeds of T. sebifera are rich in oil and are widely used in industrial fields. To explore the genetic diversity and genetic differentiation of T. sebifera germplasm resources, 10 pairs of microsatellite markers were applied to 203 samples collected from eight populations. Forty-three alleles were detected. The average expected heterozygosity (He = 0.491) revealed a low level of genetic diversity. The genetic differentiation among T. sebifera populations was low (Fst = 0.026), which might be related to high gene flow (average Nm = 11.151). Genetic distance and structure results further confirmed that the genetic compositions of the eight populations were quite similar. One of the possible reasons for this phenomenon is that the early introduction and cultivation of T. sebifera were common, so gene exchange was frequent among populations. However, UPGMA clustering results indicated that the eight T. sebifera populations could still be divided into three categories. The classification was related to their geographical location: the southwestern group (ZY), central group (HG and XY) and eastern group (LS, HS, LX, XZ and LY). The reason for this differentiation might be severe deforestation following the decline in T. sebifera economic status. In addition, the central XY population had the largest number of rare alleles (4). In conclusion, although T. sebifera germplasm resources had a low level of genetic diversity, several rare alleles were detected in the central populations, which are valuable for breeding. These resources should be conserved to maintain genetic diversity in the T. sebifera populations. Moreover, geographical distances were important reasons for the limited genetic variations among the populations.