Genetic effects of rooting loblolly pine stem cuttings from a partial diallel mating design

More than 239 000 stem cuttings from nearly 2200 clones of loblolly pine (Pinus taeda L.) were set in five rooting trials to estimate genetic parameters associated with rooting. Overall rooting success across the five trials was 43%, and significant seasonal effects were observed. Differences among clones within full-sib families accounted for approximately 10%-17% of the total variation. On the binary scale, individual-tree narrow-sense heritability ((h) over cap (2)(0,1)) ranged from 0.075 to 0.089 for rooting across the five separate settings, while broad-sense heritability ((H) over cap (2)(0,1)) ranged from 0.15 to 0.22. Narrow- and broad-sense heritability estimates on the observed binary scale were transformed to their underlying normal scale ((h) over cap (2)(N), (H) over cap (2)(N)). When all of the data from the five trials were analyzed together, (h) over cap (2)(N) (+/- SE) was 0.081 (0.027), (H) over cap (2)(N) was 0.16 (0.013), the type B additive correlation was 0.68 (0.23), and the type B dominance correlation was 0.61 (0.27). Narrow- sense family mean heritability was 0.83 (0.24), while broad-sense clonal mean heritability was 0.82 (0.074). These moderate to high family and clonal mean heritabilities, moderate type B correlations, and substantial among-family and among-clone genetic variation indicate the potential for increasing rooting efficiency by selecting good rooting families and clones or culling poor rooters.