Genetic evaluation on growth and branching traits of 4-year-old half-sib families of loblolly pine

  Objective  Accurate genetic evaluation of loblolly pine progeny test plantation was conducted to improve the efficiency of breeding selection and genetic gain, and to determine the selected individuals for breeding population and reproduction population.

  Method  More than 1800 individuals from 53 half-sibling families of loblolly pine were selected as the objects for genetic evaluation using the R and ASReml software. The genetic gain was predicted based on family breeding value or individual breeding value.

  Result  There were significant genetic differences in height, DBH, volume, number of branches, mean diameter of branches and mean angle of branches among family lines of the torch pine, which showed great potential for selection. There was a positive genetic correlation among these traits (tree height, DBH, volume and mean diameter of branches), and the individual heritability was ranged from (0.118 9 ± 0.038 3) to (0.308 4 ± 0.053 2). There was a negative genetic correlation between the mean diameter of branches and the number of branches, and the individual heritability was (0.0316 ± 0.0272) and (0.0958 ± 0.0357), respectively. According to the family breeding value of volume, the offsprings of the top 10 female parents were selected as the selected population, and the predicted genetic gain was 4.63%−5.10%. However, the genetic gain was predicted to be 43.96%−48.43% based on the top 10 individuals, which were selected according to the breeding value of volume.

  Conclusion  The superior families and individuals can be used as candidate materials for the next generation breeding population. The top 10 individuals of volume breeding value have higher predicted genetic gain and could be afforested by asexual propagation.