Within-population variances (ô2
) and narrow-sense heritabilities (h2
) were estimated in a Pinus radiata
D.Don provenance-progeny trial. Samples from the five natural populations and two New Zealand "land-race" populations were included, each as 50 wind-pollinated progenies, on two sites in Kaingaroa Forest in the central North Island of New Zealand. Assessments were made to around 8 years throughout and to 11-12 years in a sample. Estimates of heritabilities provisionally assumed random mating to give "apparent" heritabilities, but a basis was developed for revising estimates in the light of information or assumptions on departures from random mating.
Natural populations usually gave higher apparent h2 than New Zealand plantation material, especially for growth traits in island material and when the trees were younger. Population differences in apparent h2 mainly reflected differences in between-family ô2, but the New Zealand material also showed less within-family ô2 for growth traits. These higher estimates of heritabilities and variances in natural populations appear to reflect appreciable non-randomness of mating, including significant inbreeding, and presumably associated contributions of non-additive gene effects. Allowing for likely biases arising from population differences in mating patterns, the different populations appeared to have generally similar variances (or coefficients of variation) and heritabilities for individual traits.
Genotype-site interaction appeared unimportant for the two sites, but there was some obscure family-block interaction which tended to erode the overall heritabilities for the less heritable traits, notably early heights. Pooling subpopulations within natural populations was usually immaterial to h2 and ô2.
The results indicated the following h2 values around age 8: forking and current leader dieback, 0-0.05; stem diameter (and stem volume), butt sweep score, and current retarded leader, 0.1; branch habit quality score, 0.1-0.15; height, 0.1-0.2; stem straightness score, 0.2; branching angle score, 0.2; branching frequency score, 0.2-0.25; branch cluster counts, >0.4; sealed bud scores, 0.5. Coefficients of variation declined with age for height but increased for stem diameter, recent increments tended to be less heritable than cumulative values for height but more so for diameter, and various heritabilities appeared to rise with age. Although experimental conditions were not ideal the 7-9 year h2 values concur well with those in other reports, particularly in respect of comparative heritabilities among traits. Heritabilities in select material thus appear to have been similar to those in both native populations and the New Zealand land races that haveserved as base populations.