Browsing by Author "Pereira, Sandra"
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- Genetic variation, mating patterns and gene flow in a Pinus pinaster Aiton clonal seed orchardPublication . Fernandes, Lúcia; Rocheta, Margarida; Cordeiro, Jorge; Pereira, Sandra; Gerber, Sophie; Oliveira, Maria M.; Ribeiro, M.M.A.Relatedness among parents, variation in clonal fertility and background pollination deviate the realized genetic gain and the gene diversity of open pollinated seed orchard from expectation, in particular in wind pollinated species such as Pinus pinaster Aiton. • This work investigates the genetic variation, the mating system and the pollen contamination in a P. pinaster clonal seed orchard (CSO), by screening the 60 clones from the CSO and the seeds collected from 21 mother-trees with three nuclear microsatellites. • The expected diversity was similar, but the observed heterozygosity decreased 20% in the progenies compared with the parental trees. The outcrossing rate was 90.1%, the biparental inbreeding 21.7% computed through a multilocus approach, and the observed selfing 3.9%. The observed gene flow from outside the CSO was 52.4%. • From the results we concluded that the observed gene flow and the biparental inbreeding were high, and care should be taken in the implementation and management of future CSO, in particular clones should be checked for relatedness and the ramet number could be directly proportional to their breeding value.
- Pollen contamination in a maritime pine clonal seed orchard using microsatellitesPublication . Fernandes, Lúcia; Rocheta, Margarida; Cordeiro, Jorge; Pereira, Sandra; Ribeiro, M.M.A.Pollen contamination is a serious problem in seed orchards, which may reduce genetic gain considerably. High levels of pollen contamination can be reached even when the stands are isolated by several hundred of meters from natural populations. Recently, molecular markers have been used to trace details of reproductive processes. The efficiency and utility of estimating mating system, gene flow and pollen contamination are greatly increased by using microsatellite markers, which are ideal for parentage studies and fingerprinting, due to their high discrimination power. The aim of the present study was to estimate the pollen contamination in a clonal seed orchard (CSO). Three nuclear microsatellites were used to screen the 60 different clones from the CSO and the 206 seeds collected from 7 trees from each one of the three plots distributed according to the main winds direction. The 3 loci distinguished the 60 clones genotypes, but 2 pairs. Minimum and maximum estimates of pollen contamination were 46% and 56%, respectively. Those values could be explained by the presence of a P. pinaster stand at a distance lower than 2 Km and the existence of natural regeneration of this species on the orchard’s isolation zone. External plots pollen contamination was higher than in the inner plot. Only 20% of the clones contributed for the next generation, which may lead to a reduction of seeds’ genetic variability. However, an asymmetrical sampling from the orchard (3 plots) was made, which might have biased the results, and the effective number of clones participating in the next generation might be higher. The outcross pollination rate was found to be very high - 90.2%. The minimum estimate of biparental inbreeding was 21.2%, a not so high value if we consider the number of seeds sampled and the orchard size.