Genetic parameters for growth and Quambalaria shoot blight resistance in Corymbia citriodora subsp. variegata

In order to provide genetic parameters of growth and Quambalaria shoot blight (QSB) resistance in Corymbia citriodora subsp. variegata (CCV), two trials of 91 open-pollinated families from 10 provenances were established in southern China. Effects of variance components of provenance and/or family within provenance were significant ( p ≤ 0.05, 0.01, or 0.001) for most growth traits (tree height at seven, 12, 21, 29, and 46 months as well as breast-high diameter and single-tree volume at 21, 29, and 46 months) and QSB resistance (at 7 months) at each trial and across trials. Narrow-sense heritability estimates ranged from 0.04 to 0.46 in growth and 0.01 to 0.27 in QSB resistance, indicating generally low to moderate levels of additive genetic control of the traits studied. Proportions of provenance to phenotypic variance were also generally low, being 0.02–0.22 for growth and 0.01–0.23 for QSB resistance. Genetic correlations were significant and positive between growth traits and also between growth and QSB resistance, meaning that better growth at older ages could be expected from early-stage selection in growth and/or QSB resistance in CCV. Except for 29-month-old breast-high diameter, type-B correlations between trials were significant for all the traits, which suggested strong genotype by environment effects.