Age-age Correlations Research Articles

Climate response of radial growth and early selection of Larix olgensis at four trials in northeast China

The objective of this study was to evaluate the age trends of genetic variation in radial growth of different provenances and growth-climate relationship in different locations. Tree-ring cores of 10 L. olgensis provenances were sampled from four representative trials with different climatic conditions in 2019. The results of ANOVA show that significant differences for DBH at different ages were detected among provenances within sites, except for 10, 11, 37, and 38 years at LS. The phenotypic and genetic coefficient of variation in different sites were generally decreased with age. Although there were large fluctuations for provenance repeatability at different ages across sites, they all belonged to high repeatability. Age-age correlations show that the early selection for DBH could be made at the age of 10 years at the semi-arid area in Heilongjiang province and the southeast slope of Xiaoxing'an Mountains, while the ages for early selection at the southeastern slope of Daxing'an Mountains and the western slope of Zhangguangcai Mountain were 13 and 12 years old, respectively. The results of growth-climate relationships showed that temperature and precipitation played key roles in the radial growth of larch at each site. In the semi-arid area in Heilongjiang province, radial growth showed significant correlations with August temperature (positive) of the current year, and with previous May temperature (negative) and November temperature (positive), and previous December precipitation (positive). The current June temperature (negative) and precipitation (positive) were important factors affecting the radial growth at the southeastern slope of Daxing'an Mountains. July temperature of the current year had a negative relationship with larch growth at the southeast slope of Xiaoxing'an Mountains, while there were no significant correlations between radial growth and climatic factors at the western slope of Zhangguangcai Mountain. The results reported in this study provide a valuable insight about early selection for different sites and can serve as a reference for future breeding and improvement research.

Age-age correlations and prediction of early selection age for diameter growth in a 35-years old Pinus brutia Ten. Genetic experiment

Aim of study: Forest geneticists developed various methods to predict an early selection age for forest tree species in order to shorten the breeding cycles. This study aims to estimate age-age correlations among diameter growth of trees at different ages and predict early selection age for Pinus brutia Ten. Area of study: P. brutia populations in the study were sampled from the most productive distribution range of the species, which is an important forest tree in the eastern Mediterranean Basin. To understand genetic variation and determine early selection age for the species, a common garden experiment was established in two test sites near Antalya city, Turkey, in 1979. Material and methods: Wood increment cores at breast height were collected at age 30 years, and diameters (dbh) were measured for the ages 13, 15, 19, 21, 23, 25, and 27 years on the cores. Diameters at ground level (dgl) and dbh were also measured on live trees at age 35. Variance components, age-age correlations, heritability and selection efficiency were estimated for the diameters. Main results: Age-age genetic correlations for diameters were high (mostly > 0.90). Genetic correlations between dgl (at age 35) and dbh (at all measurement ages) ranged from 0.84 to 0.99. Regressions of genetic correlation on natural log of age ratio (LAR) of juvenile age to older age were significant (P < 0.0001). Selection efficiencies estimated by employing the prediction equation indicated that for rotation age 40, the optimum selection age would be between 3 to 5 years, and for rotation age 100 it would be between 5 to 9 years. Research highlights: The results of this study provide information that can be used to find early selection ages in P. brutia. On relatively poor test sites most trees may not attain enough height growth to have measurable dbh trait. In such cases, dgl and/or tree height traits (both of which are highly correlated with dbh traits of all ages) can be measured and used instead of dbh trait for evaluations. Keywords: Correlated response; selection efficiency; trait-trait correlations; brutian pine.

Estimation of genetic parameters associated with frosty pod rot (Moniliophthora roreri) and cacao production in Mexico

Genetic parameters were estimated for frosty pod rot resistance and yield components in cacao using a linear mixed model approach (restricted maximum likelihood and best linear unbiased prediction). Two progeny trials established in the Rosario Izapa Experimental Field of the INIFAP in Chiapas, Mexico, were evaluated for frosty pod rot incidence and yield components, including the number of pods per tree, bean dry weight per tree, number of beans per pod, bean dry weight per pod, seed index, and pod index, for 4 years. Genetic correlations, age-age correlations, and heritabilities were estimated. The narrow-sense heritability for frosty pod rot resistance was 0.46, and for the yield components, it ranged from 0.14 to 0.99. Backward selection, using UF-273 and Pa-169 as parents for new combinations, resulted in a reduction from −36.54 to −29.05% in frosty pod rot, respectively. The genetic correlations between bean dry weight per tree and frosty pod rot, number of pods per tree, number of beans per pod and pod index were −0.72, 0.89, 0.25, and 0.40, respectively (all significant at p < 0.01). Age-age correlations and heritabilities from data subsets indicated that the first 2 years of evaluation and evaluating for only two specific months (August to September) in the year should result almost in the same genetic estimates as using all 4 years data, for key traits, including frosty pod rot resistance, reducing the costs, and accelerating breeding decisions.

Phenotypical and genetic age-age correlations in progeny tests Scots pine

Phenotypical and genetic age-age correlations in progeny tests Scots pine

An analysis of age-age correlations in white spruce and lodgepole pine and how it applies to the growth and yield projection system (GYPSY) in Alberta

Tree improvement is considered an effective method to address the shrinking forest land-base in Alberta, Canada. It is also of great necessity to quantify the potential harvest from deployment of improved trees. However, the growth and yield models currently used in Alberta were originally developed based on growth measurements and projections from fire origin stands, and therefore, there is no widely accepted method to recognize the impact of managed stands, and even less information available to properly incorporate genetic gain in volume from tree improvement into managed stand models. Furthermore, there are considerable challenges associated with acceptance of an appropriate age-age correlation when selecting trees at a young age and projecting their anticipated increase in volume at rotations as long as 80–110 years.White spruce (Picea glauca (Moench) Voss) and lodgepole pine (Pinus contorta Dougl.) are the most important commercial tree species in Alberta, and the focus of this study. Based on the most recent and comprehensive datasets from progeny trials from both species, two available age-age correlation equations, one developed by Lambeth (1980) and another by Rweyongeza (2016), were compared and adjusted. This study also explored a new method for age-age correlation prediction based on a sigmoid parabolic branch (SPB) equation.The results show that the adjusted Lambeth equations, with re-estimated parameters for white spruce and lodgepole pine in Alberta, are the most robust for both species and should be further incorporated into the growth and yield models, based on cross-validation results at a relatively young age (7–31 years for white spruce and 6–30 years for lodgepole pine). The phenotypic age-age correlation shows no significant deviation from the genetic age-age correlation for white spruce and lodgepole pine in Alberta. The stand volume generated from the growth and yield projection system (GYPSY) using an age-age correlation from the adjusted Lambeth equations shows that white spruce has a higher age-age correlation and therefore, a higher percentage improvement in volume per hectare compared to lodgepole pine regardless of rotation age.

Genetic parameters of growth and quality traits in open-pollinated silver birch progeny tests

Genetic parameters of growth and stem quality traits were estimated for open-pollinated silver birch Roth progenies in Latvia at the age of 10 and 14 years. Tree height and stem volume were found to be under strong genetic control at both inventories (narrow-sense heritabilities varied from 0.41 to 0.66). Mainly low heritabilities were found for stem defects, yet genetic control of branch diameter, stem straightness and overall stem quality varied from low to high depending on study site. High additive genetic coefficient of variation was found for stem volume (25.3–32.5%). Genetic correlations among growth traits were strong and positive (0.90–0.99). Mainly weak genetic correlations between growth and quality traits implied simultaneous improvement. Still, strong negative correlations between branch angle and stem straightness might result in enlarged knot size for straighter logs. The genetic age-age correlations were strong. Weak genotype by environment interaction and stability of best genotypes over different sites was indicated by strong genetic correlations between trials. Each growth or quality trait alone showed substantial improvement in terms of estimated genetic gain (up to 62% over trial mean for stem volume). Therefore, selection index combining both growth and stem quality may be developed.Betula pendula

Repetibilidad de parámetros genéticos de las características de ramificación en progenies de Pinus patula

La ramificación de los árboles tiene un impacto económico importante en las plantaciones forestales, ya que afecta la calidad de la madera. La posibilidad de incorporar estas características en un programa de mejora genética depende de su heredabilidad y estructura genética con la productividad de los árboles. El objetivo del estudio fue estimar la repetibilidad de los parámetros genéticos de las características de ramificación en progenies de Pinus patula a 7 años y 10 años de edad, así como su relación genética con la tasa de crecimiento de los árboles. Las características de ramificación (número de verticilos, número, diámetro y ángulo de ramas, y presencia de defectos en la ramificación) y crecimiento (altura, diámetro y volumen del tronco) se evaluaron en 84 familias de polinización libre. Con estos datos se estimó la heredabilidad y las correlaciones genéticas, fenotípicas y edad-edad de las características. El control genético de las características de ramificación varío de nulo a moderado (0.00 ≤ h2i ≤ 0.23; 0.00 ≤ h2f ≤ 0.42), pero fue estable en las dos edades. Las características de ramificación con variación genética mostraron una estructura genética favorable con las de crecimiento. El número de verticilos y el diámetro de ramas ajustado tuvieron una correlación negativa (-0.60 ≤ rg ≤ -0.01), y el ángulo de ramas una correlación positiva (0.14 ≤ rg ≤ 0.47), con el crecimiento de los árboles. La repetibilidad de la estructura genética de las características de ramificación y crecimiento de los árboles fue alta, en términos de las correlaciones edad-edad (0.58 ≤ rg ≤ 0.94; 0.83 ≤ rpf ≤ 1.00) y del coeficiente de correlación entre las matrices de correlaciones genéticas y fenotípicas en las dos edades (r ≥ 0.86). La selección individual o familial para aumentar la productividad en esta población causaría mejoras en la ramificación (menor número de verticilos y ramas más delgadas, con ángulo mayor) y, por lo tanto, en la calidad de la madera.

Genetic parameter estimates for growth, stem-form and branching traits of Casuarina junghuhniana clones grown in Thailand

Casuarina junghuhniana is an emerging tropical plantation species that is increasingly being planted on tropical lowland and mid-altitude sites with moderate dry seasons. Field trials have been established to investigate genetic variation in the species with a view to identifying genetically improved planting material. In this study genetic parameters were estimated for nine growth traits using 29 novel clones of Casuarina junghuhniana planted in Thailand. Survival, height, diameter and stem volume were recorded annually for six consecutive years and compared with a commercially-deployed, Thai benchmark clone. Stem form (axis persistence and stem straightness) and branching habit (branch density, branch thickness and branch angle) were scored when the trees were 4years of age. Marked variation among clones was observed for all traits at each measurement. While the stand had attained a mean annual increment of 20.8 m3ha−1y−1 by year 6, the most productive clone was double the average and four times greater than the benchmark. Broad-sense heritability estimates (Ĥ2) for most traits were moderate (0.13–0.50), and there was a tendency for Ĥ2 to increase with age for survival, diameter and stem volume. There were no correlations between growth and stem form, but growth was negatively correlated with branch thickness and positively correlated with branch angle. Age-age correlation for growth was strong, suggesting that selection for stem volume need not be delayed beyond 3years. Based on the growth and stem form traits, up to 11 clones are considered suitable for commercial plantation establishment.

A new approach to prediction of the age-age correlation for use in tree breeding

Early selection in tree breeding requires a credible age-age correlation. Modelling height growth in provenance and progeny trials, we can predict age-age correlations suitable for use in operational breeding as described in this article. Tree breeding involves early selection, which is an indirect selection using a genetic correlation. This study describes a procedure of predicting an age-age phenotypic correlation as a surrogate for a genetic correlation. Although the predicted correlations are based on white spruce (Picea glauca) and lodgepole pine (Pinus contorta) data, they can be used in other coniferous species with similar mode of height growths. The aim of the study is to predict a correlation coefficient used to adjust breeding values at a measurement age to breeding values at a rotation age. This correlation is derived from the observed height growth trajectories of trees in progeny and provenance trials. Correlation prediction equations were developed using modelled height growth in provenance and progeny trials of lodgepole pine and white spruce. The time lag between successive tree ages was used as a correlation predictor variable. Correlations differed between spruce and pine but the differences narrowed as trees grew older. For example, a correlation between 20 and 100 years was 0.607 for spruce and 0.470 for pine, whereas that of 30 and 100 was 0.826 for spruce and 0.832 for pine. Based on the age-age correlation, the optimum selection age for a 100-year rotation age is 40–50 years. Parameters of the tree height growth function exhibited significant genetic variance and genotype × environment interaction. After the age of 40 years, age-age correlation for height may be less important for selection and genetic gain prediction than the correlation between height and diameter, which is declining with tree age.

Age trends of genetic parameters, early selection and family by site interactions for growth traits in Larix kaempferi open-pollinated families.

BackgroundJapanese larch (Larix kaempferi) as a successful exotic species has become one of the most important economic and ecological conifers in China. In order to broaden the genetic resource of Larix kaempferi, an effort was made in 1996 to introduce 128 families from seven seed orchards in Japan, with which to establish two progeny trials in climatically different environments. The experiment was aimed to determine the strategy of early selection, particularly important for long-rotated Japanese larch, and the optimal breeding program for specific environments.ResultGrowth trajectories revealed different growth performances of stem height (HGT) and diameter at breast height (DBH) in two different environments, Hubei and Liaoning. In both sites, there were marked variabilities in HGT, DBH and volume (VOL) among families at each year. The trends of individual and family heritability and age-age correlations were found to follow a certain dynamic pattern. Based on these trends, the optimum selection age was determined at four years for HGT and five years for DBH in Hubei and Liaoning. Genetic gains for VOL were 34.4 and 6.04 % in Hubei and Liaoning respectively when selection ratio was 10 % at age 16. Type-B correlations were less than 0.67 and rank correlations of breeding value were less than 0.4 for HGT, DBH and VOL between the two sites, revealing that there exist pronounced family-by-site interactions for the growth traits of Larix kaempferi.ConclusionsEarly selection for Larix kaempferi is an effective strategy to overcome its long rotation age. In early selection, dual growth trait selection is more effective than single one. Regionalization deployment should be considered in Larix. kaempferi breeding program based on different environmental factors.Electronic supplementary materialThe online version of this article (doi:10.1186/s12863-016-0400-7) contains supplementary material, which is available to authorized users.

Inheritance of growth and survival in two 9-year-old, open-pollinated progenies of an advanced breeding population of Chinese firs in southeastern China

Tree growth traits (tree height, DBH and stem volume) and survival from two 9-year-old, open-pollinated progeny tests of Chinese fir were investigated for heritability, genotype × environment interaction, age-age genetic correlation and selection efficiency. The 97 and 79 families planted at two sites were collected from the third-cycle seed orchard. Individual heritability was estimated between 0.05 and 0.21 for tree height, DBH, and volume and between 0.45 and 1.0 for survival. Family heritability was between 0.20 and 1.14. Significant genotype × environment interaction was observed for the three growth traits. Type B genetic correlation was between 0.41 and 0.67 with an increasing trend as tree grows. High age-age genetic correlation was observed with correlation reaching 0.9 after age 4 for height, DBH, and volume. The genetic gains were estimated at 3.26, 3.39 and 5.98 % for tree height, DBH, and volume with 10 % selection intensity. The implication for advanced tree breeding in Chinese fir is discussed.

Variation in Seedling Growth of Tamarindus indica (L.): A Threatening Medicinal Fruit Tree Species in Bangladesh

Seedling growth is a precondition for conservation and sustainable use of genetic resources which depends upon understanding of breeding system, genetic inconsistency, and evolutionary forces in forest tree improvement. The aim of this study was to determine variation in seedling growth and age-age correlations of Tamarindus indica at population level in Bangladesh. The study revealed significant (P&lt;0.05) differences of seasonal variation in seedling growth. Height and collar diameter growth showed significant (P&lt;0.05) positive correlation with mean monthly rainfall. The study also revealed significant difference (P&lt;0.05) of seedling growth among T. indica population. PCA illustrated rainfall, height growth, and diameter growth as the main characters in this study which defined drought as an additive character for this species. Cluster analysis of similarity showed how seedlings from 22.67°N latitude (origin) separated from others. An increasing trend of age-age correlation was identified in both cases of shoot height and diameter growth. The study concluded that seed collection for either ex situ conservation or seedling production can be done from 22.67°N latitude as seedlings from that area performed better than others, and early clonal selection of T. indica can be done at the age of 9 months.

The influence of age-age correlations on epidemic spreading in social network

On the basis of the experimental data concerning interactions between humans the process of epidemic spreading in a social network was investigated. It was found that number of contact and average age of nearest neighbors are highly correlated with age of an individual. The influence of those correlations on the process of epidemic spreading and effectiveness of control measures like mass immunizations campaigns was investigated. It occurs that the magnitude of epidemic is decreased and the effectiveness of target vaccination is increased.

Age-related trends in genetic parameters for Larix kaempferi and their implications for early selection.

BackgroundJapanese larch (Larix kaempferi) has been introduced in China at the end of the 19th century, and as one successful exotic species, is becoming the preferred coniferous in northern China and sub-tropical alpine region. The rotation age is about 25-28 years for L. kaempferi as pulpwood in Henan province. Waiting for even one-half rotation age for final evaluation will be inefficient due to accumulated testing costs and delayed return on investment, which suggests that selection at an early age is highly desirable for L. kaempferi improvement programs in Henan province. In this study, we determined age trends of genetic parameters and evaluated early selection efficiency for L. kaempferi in Henan province to find out the appropriate trait for early selection and its selection age.ResultsGrowth traits of 78 clones were measured periodically from age 2 to age 15 in a clonal trial of Larix kaempferi establishted at Son town, Henan Province. The genetic variation among clones, age-age correlations, and age trends in genetic parameters for growth traits were analyzed. Variant analysis revealed that tree height (HGT) and diameter at breast (DBH) were significant (1% level) among clones at every ages. The clonal repeatability of growth traits varied year-by-year, reaching the highest levels at different ages for different traits (0.77 at age 2 for HGT, 0.70 at age 5 for DBH and 0.66 from age 8 to age 10 for volume, respectively). The age-age genetic correlations ranged from 0.904 to 1.000 for HGT, and from 0943 to 1.000 for DBH. DBH at different ages was more genetically correlated to volume-15 than HGT. At the phenotypic level, HGT was always less correlated to volume-15 than DBH. With the estimates of efficiencies of early selection, the recommendation from present study was that the optimum age of early selection was age 2 for HGT and age 5 for DBH.ConclusionsOur study showed that there were significant (1% level) on growth traits among clones at every ages. The genetic parameters for growth traits varied from age to age. We found dual trait selection was more efficient than single trait selection for early selection.

Genetic Control of Growth Traits and Inheritance of Resistance to Bacterial Leaf Scorch in American Sycamore

AbstractOpen-pollinated progeny tests of American sycamore (Platanus occidentalis L.), which included 55 open-pollinated families selected from several prior Westva - co progeny tests and seed orchards and six control-pollinated families were established in 2002 and 2003. The half-sibling families were planted at two sites in western Kentucky and southeastern Missouri. The six full-sibling families, generated from selections based on exhibition of parental disease resistance and susceptibility to a variety of diseases, were also planted near Stoneville, MS at the US Forest Service Center for Bottomland Hardwoods Research. All full-sibling families planted at the Stoneville site were inoculated in the fall 2002 with the leaf-scorch-causing bacterium, Xylella fastidiosa. Diameter and height data for trees of both half- and full-sibling families were recorded at ages three, five, seven, and nine at the various sites. Bacterial leaf scorch disease presence was also recorded as symptomatic or asymptomatic/ mildly symptomatic. Average family heritability across ages was 0.58, 0.50, and 0.55 for height, diameter, and volume, respectively, indicating that increased growth traits can be gained from family selection. In conjunction with derived age-age correlations, selection based on age-five data results in the greatest gain per unit time for age nine gains for half-sibling families. Breeding for bacterial leaf scorch resistance can also be successfully undertaken if proper selection and breeding of two resistant parents are undertaken which can result in a 4.5 fold decrease in the probability in symptoms of offspring by age nine. Results indicate a large potential for increased growth and disease resistance in American sycamore through traditional breeding.

Phenotypic correlations among wood properties and growth in wild cherry plantations

Italy is one of the major users of cherry wood (Prunus avium L.), and its cultivation has been increasing since the early nineties, together with studies aimed at improving genotypes, with a selection usually based on growth, stem form, vigor, and tree adaptation. Here, the phenotypic correlations between growth rate and the physical and mechanical properties of wood are investigated in two wild cherry plantations. X-ray microdensitometry was also applied to analyze the age-age correlations of wood density. It was shown that growth rate did not affect wood properties, and density was confirmed to be the trait that best represents the main properties of wood. The absence of relationships between wood density and growth rate was confirmed by densitometric analysis, although an increase of wood density with an increase of ring width was detected for very narrow rings (less than 3 mm wide). The average density at age 7 to 8 was observed to be highly correlated (r &gt; 0.90) to the average density of a 19-year-old tree, allowing reliable estimation of the wood properties of older trees by early investigation of young trees.

Patterns of genetic parameters for height in field genetic tests of Picea abies and Pinus sylvestris in Sweden

We reviewed the genetic parameter estimates carried out from 1992 to 2006 for height increment in genetic tests of Norway spruce and Scots pine, to describe patterns of genetic variation, heritability, and genetic correlations. The material included seedling and clonal tests in Sweden, aged between 5 and 20 years. Multiple regression was used to explore relationships between parameter values and test environments. Results showed moderate narrow-sense heritabilities (\( {\hat{h}^2} \): mean =0.29 in Norway spruce; mean =0.23 in Scots pine) that decreased with test site latitude for both species. In Norway spruce, \( {\hat{h}^2} \) increased with better growth and decreased with tree age, while for Scots pine, \( {\hat{h}^2} \) increased with tree age and southward transfer. The additive genetic coefficient of variation (Open image in new window; mean 15%), in Norway spruce, decreased with growth as well as site latitude. Open image in new window in Scots pine (mean =8.5%) increased with southward transfer and more southerly test latitude. Additive and genotypic within-site genetic age-age correlations in Norway spruce were high, with mean rA and rG of 0.92 and 0.85, respectively. Corresponding across-sites estimates were on average lower. Genetic parameters were better expressed on favorable sites, at younger ages in Norway spruce and at older ages in Scots pine. The results imply that gain calculations should be based on different parameters in the two species. For maximizing genetic gain in the Swedish breeding program, testing times could be shorter for Norway spruce than for Scots pine. The investigation showed a large variation in parameter estimates from different field experiments, highlighting the importance of testing over multiple sites.

Genetic Parameters for Bud Flushing and Growth Characteristics of White Spruce Seedlings

Abstract We estimated heritabilities and correlations for bud flushing and growth traits of white spruce seedlings, and the correlations of seedling traits with 10- and 11- year height of the same families in the field. The seedling greenhouse experiment had a randomized complete block design with 30 replications, 58 open-pollinated families and single-tree plots. Individual tree heritability (hi 2) was 0.78 and 0.54 for 18 (H18) and 36 (H36)-week total height, respectively. The corresponding heritabilities for family means (hf 2) were 0.91 and 0.82. For root collar diameter, hi 2 were respectively, 0.61 and 0.22 at 24 and 54 weeks from germination. The corresponding hf 2 were 0.87 and 0.55. Heritability for bud flushing ranged from 0.13 to 0.46 (hi 2) and 0.44 to 0.83 (hf 2). The genetic correlation (ra) between H18 and H36 was 0.70 and that of D24 and D54 was 0.89, indicating a substantial change in family ranking in one growing season. The type B genetic correlation for H18 with field heights ranged from 0.22 to 0.30. Type B genetic correlations of field height with all other seedling traits were very low and largely negative. It can be concluded that: (1) age-age correlation of seedling height can be expected to decline drastically even in a stable environment of the greenhouse, (2) heritability for growth potential is meaningful when estimated on cumulative growth not on individual annual growth increments that are susceptible to short-term environmental variation, (3) dates of bud flushing did not influence variation in height and root collar diameter, and (4) field growth potential is better predicted by greenhouse growth potential than other morphological and shoot phenological traits.

PERTUMBUHAN DAN PARAMETER GENETIK UJI KETURUNAN SENGON (Falcataria moluccana) DI CIKAMPEK, JAWA BARAT

Genetically improved seed is one of the important factors in producing a high volume increment of sengon (Falcataria moluccana (Miq.) Barneby & J. W. Grimes) Plantation forest in Indonesia. A progeny test of sengon was established at Cikampek West Java in 2008. The plot was arranged in a randomized complete block design, consisting of 80 families, 4 tree line plot and 6 blocks. At 6 and 12 months of age the progeny test was measured for stem diameter and height growth. Seed source and family had significant effect on both stem diameter and tree height at six months old, but the seed source did not have significant influence on growth at one year old. Heritability estimate for stem diameter was low (h 2 i = 0.07) while that of height was moderate (h 2 i = 0.10). Genetic correlation between diameter and height was strong (rg = 0.90), while age-age correlation for diameter (-0.05) and height (0.04) were low.

Genetic variation and age-age correlations of Eucalyptus grandis at Dongmen Forest Farm in southern China

Summary Five seed source—family trials of Eucalyptus grandis were planted at Dongmen Forest Farm in southern Guangxi, China, between 1987 and 2001. Growth was assessed up to age 5 y on an annual basis for three trials and in 4 out of 5 y for two trials. In 2008 growth was assessed again, along with pilodyn penetration, at trial ages ranging from 7 to 21 y. These trials initially contained 386 families representing 49 seed sources, including a total of 97 families from four different improvement programmes. Two trials included small numbers of Dongmen second-generation families. Thinning was applied variously in all trials. Large significant differences between both seed sources and families within seed sources were observed at each assessment. At age 5 y, which approximates an average rotation for fibre plantations in southern China, the best seed sources included Ravenshoe, Windsor Tableland, Copperlode and Paluma areas of northern Queensland; Bellthorpe in southern Queensland; Aracruz, Brazil; and Florida, USA. Some families from local selections at Dongmen also performed very well. Sources from the Coffs Harbour region in New South Wales were markedly inferior for growth, as was a South African seed orchard source. Superiority of seed sources for growth at age 5 y was generally maintained through to the 2008 assessment. At the later-age assessments in 2008 (trial ages 7, 18 and 21 y), sources notable for combining superior volume growth with higher wood density (i.e. lower pilodyn penetration) included Ravenshoe, Queensland; Aracruz, Brazil; Florida, USA; and some from Dongmen, China. However, the 2008 growth results may have been biased by heavy selective thinning regimes. Within-seed-source heritabilities at single sites for height at age 1 y and then volume at ages 2,3,4 and 5 y ranged from 0.03 ± 0.02 up to 0.45 ± 0.10 and generally peaked at age 3–4 y in each trial. Genetic correlations between growth at early ages (height at 1 y, volume at ages 2, 3 and 4 y) with growth at rotation age (age 5 y volume) were moderate to very strong. Optimum selection efficiency for volume was generally reached at age 2 to 3 y but did not decline markedly between ages 3 and 5 y.