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Status number is a measure of effective population size that is based on current relatedness only. Formulae are developed for group coancestry (=average coancestry) and status number for seed orchard crops. The formulae consider (1) differences in reproductive success among orchard genotypes, (2) relatedness between pairs of orchard genotypes, (3) inbreeding of orchard genotypes, (4) influence of pollen contamination (considering its relatedness both to itself and to the genotypes in the orchard), and (5) gender differences and sexual asymmetries of orchard genotypes. Properties of status number and other measures of effective number are discussed. They may refer to rate or state, to the reference population or the development of an idealized population, and to different moments in the sexual cycle.

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Concepts and procedures are presented for the analysis of progeny trials that incorporate clonal replication as a means to resolve variance arising from nonadditive gene effects. Components of variance from the linear model may be expressed in terms of expected covariances among relatives, and these, in turn, may be used to derive approximations of additive, dominance, and epistatic components of genetic variance. In addition to the usual assumptions applied to conventional progeny trials, the use of this expanded genetic model in the analysis of tests with clonal replicates assumes that the greatest portion of the total epistasis is due to interactions involving groups of more than two or three loci. If this assumption is not satisfied, estimates of additive and dominance variance, including those from trials without clonal replicates, will be contaminated by a large fraction of epistasis, and total epistasis will be underestimated by a corresponding amount. Heritability and gain formulae for alternative selection and deployment schemes are developed and illustrate the use of genetic parameters in the comparison of seedling and clonal reforestation strategies.

Different methods for predicting clonal values were explored for diameter growth (diameter at breast height (DBH)) in a radiata pine clonal forestry program: (1) clones were analyzed with a full model in which the total genetic variation was partitioned into additive, dominance, and epistasis (Clone Only-Full Model); (2) clones were analyzed together with seedling base population data (Clone Plus Seedling (CPS)), and (3) clones were analyzed with a reduced model in which the only genetic term was the total genetic variance (Clone Only-Reduced Model). DBH was assessed at age 5 for clones and between ages 4 to 13 at the seedling trials. Significant additive, dominance, and epistatic genetic effects were estimated for DBH using the CPS model. Nonadditive genetic effects for DBH were 87% as large as additive genetic effects. Narrow-sense ( b h 2 ) and broad-sense ( b H 2 ) heritability estimates for DBH using the CPS model were 0.14 ± 0.01 and 0.26 ± 0.01, respectively. Accuracy of predicted clonal values increased 4% by combining the clone and seedling data over using clonal data alone, resulting in greater confidence in the predicted genetic performance of clones. Our results indicate that exploiting nonadditive genetic effects in clonal varieties will generate greater gains than that typically obtainable from conventional family-based forestry of radiata pine. The predicted genetic gain for DBH from deployment of the top 5% of clones was 24.0%-an improvement of more than 100% over family forestry at the same selection intensity. We conclude that it is best practice to predict clonal values by incorporating seedling base population data in the clonal analysis.

The principal aim of this investigation was to improve somatic embryogenesis initiation and to enhance representation of families and genotypes within those families of Pinus radiata D. Don. A total of 19 open-pollinated seed families, many with unrelated and weakly related parents, were tested. Optimum stage of cone maturity for initiation success was tested by five collections made at 1 week intervals, spanning the developmental period from pro-embryo to cotyledonary embryos. Two media were compared; embryo-development media (EDM6) and a modified Litvay medium (Glitz). Two zygotic embryo explant-preparation techniques were tested; embryos with retained megagametophytes and excised embryos. Proliferating embryogenic tissues were obtained from all four treatments (2850 explants per treatment, 570 per collection time) for the 19 families. The best initiation rates were achieved with a combination of Glitz medium with excised zygotic embryos, with 55% of explants from all collections and all families combined giving rise to proliferating embryogenic tissue. At the optimal collection time for each of the families, this treatment gave a range of 47%–97% initiation success with an average of 70% per family.

Genetic parameters were estimated for the diameter-height (d-h) relationship and three other tree stem-form characteristics (total height, breast height diameter, and total tree volume) for data from 10 diallel progeny trials of Scots pine (Pinus sylvestris L.), at about 30 years of age in Sweden. Linear mixed models were fit to the data, where adjustments for intertree competition and microsite heterogeneity were made by means of covariates in a nearest-neighbour analysis. The d-h relationship was analyzed with a covariate (tree height) adjusted model of diameter. Average estimates of the additive coefficient of variation and narrow-sense heritability for the d-h relationship were 7.4% and 0.22, respectively. Estimates of dominance were comparatively small (average dominance: phenotypic variance ratio of 0.04). The results indicate that there is scope to modify the d-h relationship by selection and breeding. Additive genetic correlations between the d-h relationship and height were negative, with a mean of -0.62. Selection for height would thus result in stems that are more slender than average, suggesting that tall trees allocate relatively more resources to height growth than to diameter growth. Selection based on height alone will negatively affect volume gain. Résumé :Les auteurs ont estimé les paramètres génétiques de la relation entre le diamètre et la hauteur (d-h) des arbres et de trois autres caractères de forme de la tige (hauteur totale, diamètre à hauteur de poitrine et le volume total de l'arbre) à partir des données de 10 tests de descendances diallèles de pin sylvestre (Pinus sylvestris L.) âgé d'environ 30 ans en Suède. Des modèles linéaires mixtes ont été ajustés aux données, incluant des ajustements pour la compétition entre les arbres et l'hétérogénéité des microsites effectués au moyen de covariables dans une analyse du plus proche voisin. La relation d-h a été analysée à l'aide d'un modèle de diamètre ajusté pour une covariable (la hauteur de l'arbre). Les estimations moyennes du coefficient de variation additive et de l'héritabilité au sens strict pour la relation d-h affichaient des valeurs respectives de 7,4 % et 0,22. Les estimations de dominance étaient comparativement faibles (le rapport moyen de la variance de dominance sur la variance phénotypique était de 0,04). Les résultats indiquent qu'il est possible de modifier la relation d-h par la sélection et les croisements. Les corrélations génétiques additives entre la relation d-h et la hauteur étaient négatives, avec une moyenne de -0,62. La sélection pour la hauteur produirait donc des tiges plus effilées que la moyenne, ce qui porte à croire que les grands arbres allouent relativement plus de ressources à la croissance en hauteur qu'à la croissance en diamètre. La sélection pour la hauteur uniquement aura un effet négatif sur le gain en volume.[Traduit par la Rédaction]