Genetic control of adventitious rooting on stem cuttings in two Pinus elliottii × P. caribaea hybrid families

Genetic control of adventitious rooting was characterised in two unrelated Pinus elliottii ×P. caribaea families, an outbred F₁ (n=287) and an inbred F₂ (n=357). Rooting percentage was assessed in three settings and root biomass was measured on a sub-set of clones (n=50) from each family in the third setting. On average, clones in the outbred F₁ had a higher rooting percentage (mean ± SE; 59 ± 1.9%) and biomass (mean ± SD; 0.41 ± 0.24 g) than clones in the inbred F₂ family (mean ± SE; 48 ± 1.8% and mean ± SD; 0.19 ± 0.13 g). Genetic determination for rooting percentage was strong in both families, as indicated by high individual setting clonal repeatabilities (e.g. Setting 3; outbred F₁ 0.62 ± 0.03 and inbred F₂ 0.68 ± 0.02 (H² ± SE)) and the moderate-to-high genetic correlations amongst the three settings. For root biomass, clonal repeatabilities for both families were lower (outbred F₁ 0.35 ± 0.09 and inbred F₂ 0.44 ± 0.10 (H2 ± SE)). Weak positive genetic correlations between rooting percentage and root biomass in both families suggested a concomitant gain in root biomass would be insignificant when selecting solely on the more easily assessable rooting percentage.