Age-age Correlations Research Articles

Determining the Optimal Age For Selection by Modelling the Age-Related Trends in Genetic Parameters in Eucalyptus Hybrid Populations

Abstract Ten factorial mating designs using a combined total of 88 females, 107 males, 684 families and 37,206 individual trees were used to model the age-related trends in genetic parameters and genetic gain between four and 65 months in the Eucalyptus urophylla x grandis breeding population in Republic of Congo. Selection was either of pure species (as parents for continued breeding) or individual hybrids for commercial plantations based on clonal varieties. The variance components were significantly different from zero for female, male and female-by-male interaction effects for volume. The age-related trends in additive, dominance and environmental variances, modelled by nonlinear functions, showed three phases corresponding to different stages of competition and growth. Male and female narrow sense heritabilities were high (h2 Am= 0.70 and h2 Af = 0.90, respectively for highest estimates) compared with individual broad sense heritability (h2 ind= 0.45). They were modelled by polynomial functions that did not display specific trends with age. The age-age correlations, modelled by a response surface, were higher than 0.8 after 36 months. A similar trend with age was observed for additive and total genetic effects. Genetic gain was calculated by combining the different models. The genetic gain was higher for female than for male. Considerable gains can be achieved by clone selection. The efficiency of selection indicated an optimal age of 54 months for juvenile selection of males and females and a mature age for ortets. The trend in efficiency of selection per time unit showed that juvenile selection for volume is much more efficient than adult selection whatever the age.

Genetic Parameters of Growth Traits and Wood Density in Eucalyptus grandis Progenies Planted in Argentina

Abstract To determine the genetic parameters of growth traits and wood density (estimated by Pilodyn penetration) in a population of Eucalyptus grandis formed by families from 11 seed origins in NE Queensland, Australia and a local land race, 8.5-year-old progenies established in three sites in NE Argentina were evaluated. Local trees exhibited higher growth rate at two sites and better stem form, but also deeper Pilodyn penetration, at all sites; thus, there is potential to infuse new genetic variation into the current breeding population in the region. A significant amount of genetic variation was found for all traits assessed, with growth traits [diameter (DBH), height (HT) and volume (VOL)] showing different genetic structure and degree of genetic control as compared to stem straightness (FORM), bark thickness (BARK) and Pilodyn penetration (PILO). The effect of origin was negligible for growth traits while it was important for the other traits, so it should be considered in the selection strategy; in addition, individual heritability for growth traits (0.11-0.16 in the combined analyses) was generally lower than for the other traits (0.20-0.35). Genetic correlations between sites for all traits were high enough to indicate that genotype-environment interaction would not affect the selection program by using a single breeding population for this region. Genetic correlations between growth traits were high (rg > 0.80), and negligible between these and FORM; the only unfavorable genetic correlation was between PILO and BARK (rg = -0.44). Age-age correlations for growth traits and FORM were very high (rg > 0.90). Results suggest that all traits evaluated could be handled in a breeding program, either independently or combined, without negative correlated effects. Early selection for growth traits and stem form is also possible, with major savings in time.

Growth, Stem Quality and age-age Correlations in a Teak Provenance Trial in Tanzania

Abstract This study examines the growth and stem straightness variation between teak (Tectona grandis L. f.) provenances in a 30-year-old field trial in the coastal lowland of Tanzania. The results are compared with earlier results. The findings demonstrate that it is possible to find large height and yield differences between teak provenances. The best performing provenance grows some 10% (height) to 40% (volume) better than the average. The provenance Topslip, India, consistently proved to be outstanding in terms of growth and stem quality confirming earlier evaluations at age 5 and 17 years. Tanzanian land races also proved to be superior, especially as regards stem straightness.

Genetic Performance and Maximizing Genetic Gain Through Direct and Indirect Selection in Cherrybark Oak

AbstractIn 1987, an open-pollinated test of cherrybark oak (Quercus pagodae Raf.) was established on a loess site in Carlisle County, Kentucky. The test contained 37 half-sib families representing eight provenances from Louisiana, Mississippi, Tennessee, and Virginia. Height measurements were taken at ages one, three, five, ten, and fifteen, and diameter at ages five, ten, and fifteen. Significant differences existed among provenances and among families within provenances. Seed sources from the west-central Mississippi area performed better for both diameter and height, yet no overall geographic trend was apparent. The top three families were all from the Warren Co., Mississippi source while two of the top three diameter families were from Washington Co., MS and the third was from Warren Co., Mississippi. Survival among the eight provenances was constant from age one to ten. A drop in survival was shown between ages 10 and 15, probably a result of inter-tree competition. Height and diameter growth between ages five and 10 was nearly double that prior to age five and between ages 10 and 15. Family heritabilities for height and diameter were calculated for each measurement year. Family heritabilities for diameter ranged from 0.55 to 0.70 while height ranged from 0.50 to 0.70. Strong age-age correlations for height, diameter, and volume were found indicating good trait predictability from early measurements. Genetic gain equations were used to identify the optimum selection age and trait for maximizing age 15 volume. Early selection of families within provenances should yield gains in height, diameter, and volume.

Age-age correlation for early selection of rubber tree genotypes in São Paulo State, Brazil

In a field trial involving 68 rubber tree (Hevea spp.) clones calculation of genotypic correlation coefficients revealed significant age-age correlation from age 1 to 6 (immature period) for girth A and for age 7 to 12 (mature period) for girth B and for age 7 to 12 (production of latex) for yield. Rank correlation coefficients between all immature ages of girth (girth A), all ages of mature girth (girth B) and all annual rubber production (yield) were significant for the three traits, with the coefficients decreasing with increasing age. Selection of the sets of best 30, 15, 10 and 5 clones from the available 68 clones at a given age was generally accompanied by a descending order of percentage success. It was suggested: (a) to have the best 30 clones of age 6, select the set of best 36 clones at age 2, (b) to have the best 15 clones of age 6, select the set of best 20 clones at age 3, (c) to have the best 5 clones of age 6, select the set of best 8 clones at age 4, and (d) to have the best 3 clones of age 6, select the set of best 3 clones at age 5. More than 80% of the targeted clones on girth A or girth B basis and more than 76.7% clones on yield basis were found to get selected at steps (a) through (d). For achieving early multiplication of the most productive clone for deployment, multiplication should be started with the best 36 (i.e. 60%) clones selected at age 2.

Early Assessment of First Year Height Data from Five Acacia mearnsii (black wattle) Sub-populations in South Africa using REML/BLUP

Abstract Recent research has shown, Acacia mearnsii (black wattle) to be a source of high quality pulp. This led to a change in the emphasis in the breeding programme at the Institute for Commercial Forestry Research, from improving bark yield and quality, to improving timber yield and quality while maintaining an acceptable bark quality. A Multiple Population Breeding Strategy was implemented to cater for these changes. Five sub-populations were established across different sites in KwaZulu- Natal and were determined by origin of seed. Each sub-population was established as a progeny trial with a seedling seed orchard adjacent to it. The management of the seed orchards will be determined according to the performance of the families within the progeny trials. This paper reports on the first year height measurements taken from the five sub-populations. The intention of this paper is not to base any selections from this data but rather to establish a set of analyses using REML/BLUP which will be used for future data analysis. This will also allow for future assessment of age-age correlations for the various traits being assessed and provide an appropriate decision-making tool, for selecting individuals for future generations.

Genetic Control of Growth Traits in Shortleaf Pine in Missouri

Abstract Genetic parameters for height (HT), diameter (diameter at breast height [dbh]), and volume for a shortleaf pine (Pinus echinata Mill.) population in Missouri were estimated from a single progeny test comprising 44 half-sibling families assessed at 3, 5, 7, 10, and 17 years. Individual tree heritability estimates for growth traits at age 10 years and younger were high (0.30–0.43), and those at age 17 years were low (0.11–0.24). Heritability estimates for dbh were lower than those for HT. Family mean heritability estimates were moderate to high (0.32–0.66). Genetic correlations were higher than their phenotypic counterparts for all growth traits. Age-age genetic correlations for growth traits were moderate to high (0.68–0.98), indicating opportunity for early selection. Genetic correlations between different growth traits were high (0.81–1.00). Indirect selection on age 5- or 7-year HTs may be expected to produce over 25% more volume at 17 years compared with direct selection for volume at age 17 years. Efficiencies of selection suggest that early HT is a better selection criterion for volume at older ages than dbh because of the high heritability at young ages and strong juvenile-mature genetic correlations. Genetic gain in an unrogued seed orchard was predicted to be 6.7 and 27.2% for 10- and 17-year volume, respectively. These results suggest that growth traits in shortleaf pine in Missouri have high genetic variation, and genetic improvement was effective. South. J. Appl. For. 29(4):200–204.

Performance of Green Ash Seed Sources at Four Locations in the Great Plains Region

Abstract Green ash trees from 10 seed sources were planted in a test in 1961 in four states of the Great Plains Region. After more than 20 years, height growth indicates a strong interaction between seed source and plantation location. Larger trees were from southerly sources within about three degrees of latitude of the plantation site. Beyond those limits, cold injury may result. Height and dbh age-age correlations were highly significant at 8 and 20+ years. Height and dbh correlated negatively with a decrease in latitude. North. J. Appl. For. 22(1):54–58.

Time Trends in Genetic Parameters for Height and Optimal Age for Parental Selection in Scots Pine

Abstract Data used to estimate time trends in genetic parameters and the optimal age for parental selection were obtained from 13 Scots pine (Pinus sylvestris L.) progeny tests in southern Sweden. The final age at measurement was between 24 and 39 yr, corresponding to approximately half the rotation age in southern Sweden. Trees in each test have been measured for height 4–6 times, covering ages from 5 to 39 yr. Individual tree heritability for height averaged 0.16, and increased slightly over time, although there were differences among tests. The average additive coefficient of variation for height (CVA), which decreased with age, was 6.0% while the average nonadditive coefficient of variation (CVD) was 3.8% and did not show any significant trend over time. A model based on the natural logarithm of the ratio between the two ages at measurement was used to predict genetic age-age correlations. The efficiency of early selection was also examined, in an analysis considering total height at age 30 as the target trait. The optimal age for parental selection based on gain per unit time peaked at 11 yr, with a time lag for breeding of 10 yr. In the southern tests, the peak came some years earlier than in the northern tests. Selection efficiency based on present value with an interest rate of 5% showed the optimum at 11 yr.

Early selection in eucalypt breeding in Australia: optimum selection age to minimise the total cost of kraft pulp production

Optimum ages for early combined-trait selection were derived for a breeding objective of reducing the total cost of unbleached eucalypt kraft pulp, assuming typical heritabilities and age-age genetic correlations for basic density and growth. The optimum biological selection age, the selection age where average annual gain is maximised, was four years for an assumed rotation age of 15 years. The optimum economic selection age, the selection age where the present value of all future gains is maximised, was three years. These conclusions were relatively robust to changes in assumptions used in analysis.

Age-age and trait-trait correlations for Eucalyptus grandis Hill ex Maiden and their implications for optimal selection age and design of clonal trials.

Previous results from seven locations of Eucalyptus grandis clonal trials in Colombia supported the a priori contention of sub-dividing them into three different environmental zones for testing and deployment. Within these zones, the determination of age-age genetic correlations for both height and mean annual increment (MAI) showed that strong age-age correlations are present for a rotation age of 6 years starting at 3 years age and, thereafter, suggesting this age as appropriate for selection. This biological selection age coincides with an "economical" age for selection based on discounted selection efficiency in perpetuity, considering a range of interest rates between 10% and 20%. High genetic correlations between wood density at 3 years and 6 years as well as the lack of genetic correlation between this trait and growth traits, also favors selection at age 3 and facilitates breeding strategies that consider the utilization of both traits for improvement. A simulation of optimal clonal test designs indicated that by using six locations and six blocks per location in a single-tree plot design, between 80% and 90% of the maximum selection efficiency could be obtained. This type of design allows testing of a large number of genotypes across a reasonable number of locations in a cost-effective manner.

Genetic Parameter Estimates of Growth and Survival of Pinus sylvestris with Mixed Model Multiple-trait Restricted Maximum Likelihood Analysis

To improve adaptation and production of forest trees in areas with a harsh climate, it is important to consider survival ability in addition to growth traits. For breeding decisions, parameters such as heritabilities and genetic correlations between such traits need to be estimated. Multitrait, restricted maximum likelihood (REML) estimation was used in a full-sib Scots pine ( Pinus sylvestris L. ) progeny trial in northern Sweden to utilize all available information regarding survival and growth on the individual tree level and to avoid bias due to selection caused by mortality. The trial was evaluated at the ages of 6, 11 15 and 27 yrs, including estimation of age-age genetic correlations, which were high. During the period, the mortality reached 36%, the heritability of survival increased from 0.02 to 0.05, and heritability of tree height varied between 0.06 and 0.13. The genetic correlation estimates between survival and height were all positive and varied between 0.03 and 0.65.Univariate estimation, considering only growth and ignoring survival, resulted in much higher heritabilities of tree height. This should be an effect due to the mortality and thus a bias caused by selection.

Predicting age-age genetic correlations in tree-breeding programs: a case study of Pinus taeda L.

A meta-analysis of 520 parents and 51,439 individuals was used to develop two equations for predicting age-age genetic correlations in Pinus taeda L. Genetic and phenotypic family mean correlations and heritabilities were estimated for ages ranging from 2 to 25 years on 31 sites in the southern U.S. and Zimbabwe. Equations for predicting age-age correlations based on P. taeda populations from west and east of the Mississippi River proved statistically different. Both predictive equations proved conservative for validation datasets consisting of younger tests in the U.S. and Zimbabwe. Age-dependent log-linear predictive equations were favored over growth-dependent equations. All P. taeda predictive equations based on genetic correlations favored earlier selection when compared to a generalized conifer predictive equation based on phenotypic correlations. The age-age correlations structure showed stability independent of planting density and across a wide range of family sizes.

Age trends in genetic parameters of wood density in young Norway spruce

Age trends of phenotypic, environmental, and additive genetic variance and heritability were estimated for overall density and its components earlywood and latewood densities and latewood proportion. The objective was to acquire information for both individual and cumulated rings from ring number 3 to 12 counted from the pith. Age-age correlations were calculated for cumulated density traits only. The wood density data were obtained with X-ray analysis of increment cores from 47 open-pollinated families of Norway spruce (Picea abies (L.) Karst.). The families had earlywood and latewood with significant differences in density for individual and cumulated rings and consequently for overall density. The latewood proportion had significant family variation for cumulated rings but not for all individual rings. Large fluctuations in environmental variance caused fluctuations in heritability estimates for successive rings. A strong decrease in environmental variance for all cumulated traits, especially from ring 3 to 5, resulted in a steady increase in heritability estimates. The latewood density had the highest heritability estimates and latewood proportion the lowest for both individual and cumulated rings. Overall density and the cumulated components at cambial age 12 showed strong genetic correlations with their respective traits at all younger ages.

Age-age correlations for tracheid length and wood density in Pinus sylvestris

The existence of strong genetic correlations between traits at an early age and at an adult age should shorten the generation turnover of tree breeding populations and render forest tree breeding more effective. Genetic age-age correlations for tracheid length and wood density were estimated in Scots pine (Pinus sylvestris L.) and the efficiency of early selection for these traits was evaluated. Increment cores of 10-mm diameter were collected from trees of 106 full-sib families in a progeny trial located in southeastern Sweden and consisting of controlled matings between 30 parent trees. The additive genetic age-age correlations were consistently close to unity for all traits and ages studied. The additive genetic variance differed significantly from zero for all traits. The dominance variance was zero for tracheid length and small and insignificant for wood density. The heritabilities varied between 0.3 and 0.5. The genetic gain per year for both tracheid length and wood density was largest if selection was carried out at tree age 11, the lowest age studied, indicating that early tests for these traits will be efficient.

Age-age correlations for tracheid length and wood density in <I>Pinus sylvestris</I>

The existence of strong genetic correlations between traits at an early age and at an adult age should shorten the generation turnover of tree breeding populations and render forest tree breeding more effective. Genetic age-age correlations for tracheid length and wood density were estimated in Scots pine (Pinus sylvestris L.) and the efficiency of early selection for these traits was evaluated. Increment cores of 10-mm diameter were collected from trees of 106 full-sib families in a progeny trial located in southeastern Sweden and consisting of controlled matings between 30 parent trees. The additive genetic age-age correlations were consistently close to unity for all traits and ages studied. The additive genetic variance differed significantly from zero for all traits. The dominance variance was zero for tracheid length and small and insignificant for wood density. The heritabilities varied between 0.3 and 0.5. The genetic gain per year for both tracheid length and wood density was largest if selection was carried out at tree age 11, the lowest age studied, indicating that early tests for these traits will be efficient.

Variation Among Green Ash of Differing Geographic Origins Outplanted in Kansas

Green ash trees from 18 provenances were planted in a seed-source test in 1971 near Manhattan, Kansas, in the central part of the Great Plains Region. Most seed sources were from north of the planting site. After 20 years, growth measurements revealed that the tallest trees were from more southerly sources and/or those near the plantation site. Trees from moderate distances north (150 miles) of the planting site also showed adequate growth. Height and dbh age-age correlations were highly significant and increased when compared to age measurements of earlier intervals.

Age-age correlation and early selection in radiata pine I. Family x environment interactions in plantation and greenhouse

Summary Ten open-pollinated families of radiata pine (Pinus radiata D. Don) were grown under greenhouse conditions in an attempt to emulate conditions in a field trial on 11 sites across southern Australia. Two levels of each of water, nitrogen and phosphorus (ie 8 factorial combinations) were applied to seedlings for a period of 145 days with the intention of relating seedling growth of families in the greenhouse to later-age growth of the same families in the field. Families reacted differently depending on whether they changed rank frequently from site to site in the field trial (“interactive”) or not (“stable”). Seedling size was not a good indicator of family field performance, but the ratio by weight of stem wood to needle tissue provided good relationships with field data on many sites.

Predictions of age-age correlations of total height based on serial correlations between height increments in Maritime pine (Pinus pinaster Ait.)

Successive annual height increments (AHIs) are considered to be elements of a time series. Empirical data in Maritime pine (Pinus pinaster Ait.) show that genetic correlations between successive AHIs (serial correlation) decrease when the lag between corresponding growing seasons increases. When separated by more than 13 years AHIs are no longer genetically correlated. It is shown that age-age correlations between total heights depend on three components: the serial correlation structure between AHIs, the genetic coefficient of variation of AHIs, and the phenotypic growth curve of AHIs. Age-age correlations are computed in various combinations of the three components. Serial correlation structure and the genetic coefficient of variation had the more pronounced effect on age-age correlations. The genetic correlation between height at age 10 and height at age 50 varies between 0.764 and -0.136 according to the different combinations. Results obtained by simulations are comparable to those issued from previous empirical methods. mplications on early selection procedures and on optimal selection age are discussed.

Age-Age Correlations and Early Selection for Wood Density in Young Coastal Douglas-Fir

Abstract Age-age correlations and age-associated changes in the genetic control of wood density and its components (earlywood density, latewood density, and latewood proportion) were investigated in 15-yr-old trees of 60 open-pollinated families of coastal Douglas-fir (Pseudotsuga menziesii var. menziesii (Mirb.) Franco). The possibility of using wood density components as secondary traits to increase the efficiency of early selection for overall wood density was also explored. Heritability estimates for overall density and its components increased with age, mainly because of a decrease in the error variance as the number of rings in the core sample increased. Overall density and its components at age 15 had strong genetic correlations with their respective traits at all younger ages analyzed. Moreover, with few exceptions, age-age genetic correlations were greater than phenotypic correlations. Early selection to improve overall density at age 15 was quite efficient (relative efficiency above 79%), even when selection was based on core density at the youngest age (age 7). Using wood density components as secondary traits produced a slight increase in the efficiency of early selection only at the youngest ages, presumably because age-age correlations for overall core density were already strong, limiting the possibility of additional improvement. For. Sci. 38(2):467-478.