Selfing and sibship structure in a two-cohort stand of maritime pine (Pinus pinaster Ait.) using nuclear SSR markers

Abstract

The genetic relatedness between pairs of trees was analyzed in an adult stand of maritime pine with abundant advanced natural regeneration using three highly polymorphic microsatellites (EP > 90%). Only five possible self-pollinated offspring were found, thus meaning a maximum selfing rate based on dispersed progeny of 3.8%. Likelihood ratios were used to detect sib relationships in both mature trees and natural regeneration. The percentage of half-sib and full-sib links in the adult trees was 19.09% and 1.82%, respectively, thus indicating a low level of genetic relatedness due to sib relationships (≈ 3%). Similar results were obtained for the natural regeneration but with a higher percentage of full-sibs (2.37%) and a greater family size. A high amount of pollen gene flow from outside the plot is suggested to explain the low genetic relatedness found. Collection of seedlots in this stand seems adequate as a low level of inbreeding is expected.