Pedigree reconstruction and genetic parameter estimation in a hybridization orchard of Eucalyptus camaldulensis and E. urophylla

Pedigree construction using molecular markers in open pollinated bulk seeds is proven to be one of the effective approaches in providing robust information about mating dynamics in the seed orchard. In addition, pedigree construction combined with phenotypic pre-selection of the progeny trees will eventually reduce the cost of genotyping and time. In the present study, we used highly informative microsatellite markers to construct half-sib and full-sib families from phenotypically pre-selected individuals for growth in an open pollinated hybridization seed orchard consisting of E. camalulensis and E. urophylla. All the progenies were assigned with their respective female parents, while 84 % of the progenies were assigned with their candidate male parents. Both single locus (t̂_s) and multi- locus (t̂_m) outcrossing estimates revealed high level of outcrossing rate in the seed orchard. Intra-specific combinations in the progenies were found to be high compared to inter-specific hybrids. Variance components estimates using half-sib and full-sib based model revealed high heritability (h2) for diameter at breast height (DBH) and height in the half sib model. We also found significant correlation between the breeding values estimated for parents and progenies in the half-sib and full- sib model using Best Linear Unbiased Prediction (BLUP) method. Present study demonstrates that molecular marker based pedigree construction combined with phenotypic pre-selection from open pollinated bulk seeds is an effective approach for identifying superior parents and studying mating dynamics in the seed orchard. In addition, breeding value estimates could eventually increase the efficiency and accuracy of forward, backward, and mixed selection models.