Genetic control of rooting ability of stem cuttings from loblolly pine

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Abstract
Stem cuttings from 546 loblolly pine (Pinustaeda L.) seedlings were set for rooting during each of three separate trials over time. The seedlings arose from 54 full-sib families derived from four factorial mating designs. Phenotypic variation in rooting percentage was partitioned into genetic variance, environmental variance, and genotype × environment interaction variance. Virtually all genetic variance was due to additive gene effects, with little evidence for dominance gene effects and with no epistasis present. Genetic control of rooting percentage was weak with narrow-sense and broad-sense heritabilities of 0.15 and 0.13, respectively. Selection based on either family means or clone means represented a better strategy than mass selection, as evidenced by narrow-sense and broad-sense heritabilities of 0.46 and 0.40, respectively. Predicted genetic gain in rooting percentage was estimated using two population improvement alternatives. Selection of the best 10% of the clones would increase overall rooting percentage to 53.6% in the current generation, an increase of 11.3%; whereas selection of the best individual within the best 24 of the 54 families and intermating the select trees would increase rooting percentage of the next generation to 54.1 %, an increase of 11.8%.