Genetic Variation In Growth Traits Research Articles

Age trends of genetic variation and early selection for growth traits in Cunninghamia lanceolata open-pollinated families

Abstract The present study measured the growth traits of 98 open-pollinated half-sibling families from the second-generation clonal seed orchard of Chinese fir for 6 consecutive years from age 2 to 7, the change patterns of genetic variation in growth traits and genetic parameters were analyzed, and best linear unbiased prediction (BLUP) was used for early selection to determine the excellent families. The growth traits of Chinese fir revealed highly significant differences between families, indicating that there was significant genetic variation at the family level, which serves as the foundation for exceptional family selection. The heritabilities of family and individual for H (height) ranged from 0.61 to 0.65 and 0.41 to 0.46, respectively; for DGH (the diameter at ground height)/DBH (the diameter at breast height), they were 0.55 to 0.66 and 0.35 to 0.46, respectively; and for V (tree volume), they were 0.66 to 0.70 and 0.48 to 0.49, respectively. The growth traits of genetic control were at a greater level at age 5. The findings of the coefficient of variation analysis demonstrated that the phenotypic variation coefficient were larger than the genetic variation coefficient for three growth traits at various ages. The juvenile-mature genetic and phenotypic correlations revealed an increasing tendency with age, and mainly controlled by genetic factors. Compared to other age groups for growth traits, age 5 had greater phenotypic and genetic association coefficients, as well as greater efficiency of early selection. Based on the selection method of breeding value, nine families were selected with a 9.2 % selection rate.

First genetic evaluation of growth traits in Larimichthys polyactis to guide the formulation of selective breeding programs

Growth is an economically important trait in aquaculture. For the genetic improvement of growth traits in Larimichthys polyactis, a relatively new aquaculture species with great potential in large-scale farming, a genetic evaluation of these traits is necessary. In the present study, 34 families of L. polyactis were used to estimate genetic parameters for body weight, total length, and body length at the age of 11 months. Heritability estimates for the three growth traits including body weight, total length, and body length were 0.17 ± 0.06 to 0.23 ± 0.07 and were significantly different from zero (P < 0.05). The genetic correlation coefficients among the three traits were highly positive (i.e., 0.88–0.96). A selection ratio of 30% can result in an expected genetic gain (ΔG) of 3.41% and relative genetic gain (ΔG′) of 5.31% per generation for body weight in L. polyactis. There were significant differences in the response to selection when using parents selected by estimated breeding values (EBVs) and by phenotypic values (PVs). The concordance rate of individuals selected by the two methods was only 42.72%–46.02%. The average breeding value of the individuals selected based on EBVs (6.87 for body weight) was much higher than that for individuals selected based on PVs (3.48 for body weight). Environmental factors had a substantial impact on the growth phenotype of L. polyactis; accordingly, the EBV selection method is more efficient than the PVs method for breeding. The results of this study confirm that L. polyactis shows genetic variation for growth traits and highlight the enormous potential for improvements in growth by selective breeding based on EBVs.

Genetic variation in height, diameter and second flushing in four-year old maritime pine progeny tests in Türkiye

Abstract A maritime pine (Pinus pinaster Ait.) breeding program was initiated in Türkiye by selecting plus trees from plantations across the country. Quantifying genetic variation in growth traits is essential for this program. Four-year old trees from 140 open-pollinated maritime pine families were assessed for height (HT), root collar diameter (D) and number of shoots in the fourth growing season (S) in three progeny test plantations (Kefken, Gebze and Çatalca) in northwest Türkiye. Growth was greater in Kefken, followed by Gebze and Çatalca. Both individual tree (h i 2) and family mean (h f 2) heritability estimates were greatest for HT (h i 2=0.22 and h f 2 =0.77) followed by D (0.16 and 0.59) and S (0.08 and 0.45). While genetic correlation between HT and D was strong (r A =0.72), S was correlated moderately with HT (0.56) and weakly with D (0.11). Genotype × environment interaction was significant only for D. While modest genetic gains (up to 15.20 % over the average of family means) from selections at age four seem possible for growth, changes in patterns of genetic variation and interrelationships among the traits as the trees age remains to be explored in the future.

Age trends in genetic parameters for growth performance across country-wide provenances of the iconic conifer tree Araucaria angustifolia show strong prospects for systematic breeding and early selection

Understanding the growth patterns of long-lived conifer tree species is important to devise breeding and early selection strategies, predict future biomass productivity and assess adaptive tree fitness for long term conservation efforts. We investigated the genetic variation for growth traits of Araucaria angustifolia, the grandiose renowned “Paraná pine” tree, in a trial involving 122 families across 15 provenances covering the entire natural range of the species in Brazil. Measurements at ages 7, 24, 32, 33 and 35 were used to adjust continuous growth curves based on nonlinear mixed-effect models for all 2158 trees, providing annual estimates for unmeasured ages in the 7-to-35-year interval. Estimated values closely matched observed ones and a reduction of the coefficient of residual variation was observed in the estimated data, possibly due to removal of random error in the observed measurements, making the estimated curves more reliable to predict growth patterns. Genetic variation for growth within provenances was greater than between, with a trend of increasing heritabilities over time for most provenances. Substantial genetic variation found both within and between families could drive efficient early selection at both levels. All provenances included individual trees and families with good potential to be selected for shorter rotations. Growth curves show that trees invest first in height and later in diameter growth. Considerable variation was observed across provenances for the optimal age and optimal tree volume at which annual growth increment peaks, a tipping point that could be used as a predictor of the optimal rotation age and expected tree volume. The data clearly indicate potential for early selection for growth at age 7–10 with an 85% prediction accuracy of growth at age 35. Additionally, growth data indicate potential of shortening harvest age from 30–35 to 15–20 years by selecting the best individuals and families. These results underscore the potential of expanding investments in breeding and plantation forestry of A. angustifolia, which in parallel could contribute to enhancing conservation efforts of this iconic subtropical conifer.

Genetic test and early selection in full-sib families of Pinus koraiensis

ABSTRACT To understand the reliability of genetic determination and early selection of Pinus koraiensis, the genetic variation of growth traits of 34 full-sib families in different growth year were investigated and analyzed. The results showed significant differences in female and male parents and their interaction at different ages, and genetic variance components of growth traits between families accounted for over 50% of the total genetic variation. The phenotypic and genotypic coefficients of variation ranged from 8.61% to 27.29%, and from 6.71% to 19.96%, respectively. Meanwhile, broad-sense heritability and narrow-sense heritability ranged from 0.951–0.999, and from 0.566–0.681, respectively. Correlation analysis shown significant positive correlation coefficients between H, DBH, and V at different ages. Using the multiple-traits comprehensive evaluation method, seven families were selected in different ages. The estimated results of combining ability shown that female parent, male parent and parental combination were F 4, M 11 and F 9 × M 14, respectively. Therefore, the early genetic determination and selection of P. koraiensis could greatly shorten the breeding cycle, improve breeding efficiency, which could provide references for the early genetic determination of other tree species with long rotation age.

Inheritance of growth traits and impact of selection on carcass and egg quality traits in Vanashree, an improved indigenous chicken.

The present study was carried out to assess the inheritance of growth traits and to study the effect of selection on carcass characteristics and egg quality traits in Vanashree, an improved indigenous chicken. Estimates of heritability were high for body weights recorded at 4, 5 and 6weeks of age and 8th week shank length, while it was moderate for 8th week body weight. Estimates of heritability on sire component of variance declined as age increased from 4 to 8weeks of age. The genetic and phenotypic correlations among various growth traits were positive and high in magnitude. The body weight continued to increase up to 40weeks of age particularly in male birds, while there was little increase in shank length from 20 to 40weeks of age particularly in hens. There was no significant change in carcass characteristics and egg quality traits except that there was some improvement in dressing percentage over the generations. Sex effect was significant on relative weights of the breast, legs, gizzard, liver and heart and abdominal fat percentage. There was increase in Haugh unit and albumen index, yolk percentage, yolk to albumen ratio and yolk colour in the present generation. The results suggest that there is adequate additive genetic variation for growth traits in the population and that Vanashree chicken could continue to be improved so as to make it a promising dual purpose purebred indigenous chicken for increasing the productivity of free range or semi-intensive systems of production.

Preliminary study on genetic variation of growth traits and wood properties and superior clones selection of Populus ussuriensis Kom.

In this study the genetic variation of growth traits and wood properties was assessed in 45 clones of Populus ussuriensis Kom. grown in a 10-year-old experimental forest located in Northeastern China and a preliminary selection of superior clones was performed based on multi-trait selection index. The following traits were analyzed: tree height, H; diameter at breast height, DBH; volume, V; basic wood density, BWD; fiber length, FL; fiber length-width ratio, FL/W; microfibril angle, MA; cell wall percentage, CWP; fiber double wall thickness, FWT; vessel proportion, VP; wood fiber proportion, FP; wood ray proportion, RP; holocellulose content, HC. The results revealed significant differences (P<0.05) in DBH, V, BWD, FWT, VP and FP among different clones. Broad-sense heritabilities for growth traits and wood properties ranged from 0.020 to 0.749, therefore growth traits and wood properties are moderately or weakly controlled. Negative correlations between growth traits and most wood properties were also found. According to the multi-trait selection index at a selected rate of 10% and survival rates, 3 superior clones (I18, H16, C13) were selected, and the DBH, V, BWD, FL and FP of superior clones were higher than those of all clones by 2.83%, 9.81%, 3.40%, 6.59% and 0.31%, the MA, FWT, VP were lower than those of all clones by 7.54%, 0.39%, 2.12%, respectively. These superior clones could be used as starting breeding material for P. ussuriensis.

Genetic parameters of a snakeskin gourami (Trichopodus pectoralis, Regan 1910) base population created from crossing three hatchery stocks

A base population with a broad genetic background is a prerequisite for a successful selection program. In the present study, a synthetic base population of snakeskin gourami (Trichopodus pectoralis) was established by crossing three farmed stocks following a nested mating scheme. At 120 days after hatching (DAH), after being separately reared in hapas, all 79 full-sib families (16 half-sibs) obtained were tagged using elastomer tags and communally reared in cages until 270 DAH. Heritability, estimated using an animal model, was low for all traits at 120 DAH (0.0002–0.0514 for growth traits and 0.01 for the condition factor, K). At harvest age (270 DAH), heritability was moderate for growth traits (0.3016–0.3644) but low for K (0.2119). All heritability estimates were associated with low SE, while common environmental effect (c2) was also low. Most of the genetic correlations (rg) among traits were extremely low at 120 DAH, while at 270 DAH, rg approached 1 among growth traits and was moderate between K and growth traits. Thus, due to sufficient additive genetic variation of growth traits in this synthetic population with minimal effects from genetic variation other than additive, sufficient selection response is expected.

Genetic Variation of Growth Traits and Genotype-by-Environment Interactions in Clones of Catalpa bungei and Catalpa fargesii f. duclouxii

Clones of Catalpa bungei and Catalpa fargesii f. duclouxii were studied over several years in central China to explore genetic variation in growth traits and to identify clones of high wood yield and high stability. The genetic parameters for height, diameter at breast height (DBH), and stem volume of clones, were estimated. The effect of clone × year on the increment of stem volume in the two species was analyzed by genotype and genotype × environment (GGE) biplot methods. Significant differences in growth traits among clones and between species were found. The growth of C. bungei exceeded that of C. fargesii f. duclouxii after 4 years. Furthermore, from the 5th year, the repeatability and genetic variation coefficient (GCV) of the C. bungei clones were higher than those of the C. fargesii f. duclouxii clones in most cases. The phenotypic variation coefficient (PCV) of the C. fargesii f. duclouxii clones was significantly lower than that of the C. bungei clones. The repeatability of stem volume was intermediate or high in the two species. ANOVA revealed significant effects of the clone by year interaction in these two species. GGE biplot analysis revealed that wood yield and stability were largely independent in C. bungei; clones 22-03, 19-27, and 20-01 were the optimal clones in this species. In contrast, the optimal clones 63 and 128 of C. fargesii f. duclouxii combined the desired characteristics of high yield and high stability. In conclusion, our results indicated that the height and stem volume of C. bungei was under strong genetic control, whereas that of C. fargesii f. duclouxii was influenced by the environment more than by genetic effects. Genetic improvement by clone selection can be expected to be effective, as the repeatability of stem volume was high. Francis and Kannenberg’s method and GGE biplot analysis were used in combination to evaluate the clones. C. bungei clone 22-03 and C. fargesii f. duclouxii clones 63 and 128 were identified as the optimal clones, which exhibited both a high increment of stem volume and high stability.

Genetic variation in silvicultural traits and carbon stock content in a provenance-progeny test of Genipa americana L. (Rubiaceae)

Abstract The aim of this study was to determine the genetic variation of growth traits, wood basic density, dry mass of crown, leaf, and stem, and carbon stock within and between two Genipa ameri­cana L. provenances. The provenance and progeny test was installed in the Teaching, Research and Extension Farm, located in Selvíria, Mato Grosso do Sul, Brazil. The test was established using a randomized block design with two provenances and 36 progenies, a spacing of 3 x 2 m, four replicates, and six plants per plot. At 11 years of age, height and diameter at breast height (DBH) were measured. To estimate wood basic density, biomass, and carbon stock, 45 plants were thinned. Growth traits for crown, leaf, and stem, as well as wood basic specific gravity showed significant differences. Both provenances pre­sent high carbon storage, demonstrating the potential of this species to be included in carbon credit programs that help to minimize the effects of global warming. In general, heritability values were low, suggesting limited genetic control of the eva­luated traits. However, the traits presented a high coefficient of genetic variation, indicating adequate sampling among popu­lations; these results are promising for ex situ conservation and for future breeding programs.

Genetic parameters estimates for growth performance traits at harvest in Japanese flounder (Paralichthys olivaceus)

Despite Japanese flounder (Paralichthys olivaceus) is of importance in aquaculture of Northeast Asia, selective breeding programs for growth performance traits remain limited. The aim of this study was to estimate parameters of growth performance traits in this species. The heritabilities, genetic and phenotypic correlations, and breeding values were estimated for body weight (BW), total length (TL), condition factor (K), and average daily gain (ADG). The genetic analyses were performed on a total number of 186 full-sib families (108 sires and 146dams, 16,807 individuals with integrated pedigree information) from 4 year-classes based on three mixed animal models with tank and year-class as fixed effects, mean family trait values at tagging as a covariate, and additive genetic effect as a random effect using the restricted maximum likelihood method. For all growth traits the maternal and sir-dam interaction effects in proportion to phenotypic variance were very low (0.00–0.05). The heritability estimates for growth traits ranged from 0.12 to 0.39, which is in a low to moderate level. These results indicated that there is a considerable additive genetic variation in growth traits, and the ongoing selective breeding project will produce considerable genetic improvement in growth traits of Japanese flounder. The genetic and phenotypic correlations among BW, TL and ADG were high and positive (0.87–0.94, P < .001). However, the correlations between K and other three traits were low to moderate (−0.10–0.58, P < .001). These data indicate that these traits (except K) could be selected and enhanced simultaneously and also imply that direct selection of TL, which is an easily measurable trait, will be more favorable than selection on BW and ADG. The estimated breeding values of parents and individuals and the average family breeding values for 4 traits were obtained. In summary, all the findings in this study will be of significance to optimize the flounder selective breeding program. Statement of relevanceThis paper offers guidelines to select breeding strategy in Japanese flounder.

Genetic and variation analyses of growth traits of half-sib Larix olgensis families in northeastern China

To gain a better understanding of genetic variation of growth traits in Larix olgensis, we investigated the progeny of 60 half-sib families of L. olgensis grown in a seed orchard in northeastern China. Tree height (H), basal diameter, and diameter at breast height (DBH) were measured at four different ages (i.e., at 4, 6, 8 and 10 years of growth). Significant differences among all the variation sources were observed during the different growth years. During the four measured years, phenotypic coefficients of variation (PCVs) of all traits ranged from 17.83 to 33.01 %, with heritabilities varying from 0.531 to 0.798. A correlation analysis uncovered extremely significant positive correlations among all traits within or among years. These high heritabilities and large PCVs were beneficial for the early selection of superior families. Using a comprehensive evaluation method, different families were selected as superior on the basis of different selection rates during each measured year, with families L78, L64, L63, L48, L13 and L14 selected across all measured years. At the 10th growth year, the optimal time to identify superior L. olgensis families, the selected families (L78, L64, L63, L48, L13 and L14) displayed higher H and DBH values, which corresponded to genetic gains of 8.31 and 16.82 %, respectively. In addition to the identification of superior female parents for improved seed orchard establishment, the findings generated by our study can serve as a theoretical foundation for early selection of L. olgensis families.

Genetic parameter estimates for growth of grass carp, Ctenopharyngodon idella, at 10 and 18 months of age

The aim of this study was to estimate the growth trait parameters in grass carp, Ctenopharyngodon idella, which is one of the major freshwater aquaculture species in China. The heritability, genetic and phenotypic correlations were estimated for body weight, standard length, body height and body thickness measurements of 10 and 18month old fish. Analyses were performed on a total of 41 and 104 full-sib families of grass carp including 937 and 2454 individuals at 10 (first spring) and 18months (second winter) of age, respectively. The families were reconstructed using the molecular pedigree based on twelve microsatellite loci, and 97.6% of the offspring were unambiguously assigned to single parent pairs. Unbalanced contributions to progeny were found among families and parents (P<0.01). Variance components and genetic parameters were estimated using the restricted maximum-likelihood algorithm with animal models. For all growth traits across two stages of grass carp, the common environment/maternal effect in proportion to phenotypic variance was very low (0.00–0.06), and not significant (P>0.05). The heritability estimates for growth traits ranged from 0.24 to 0.38, and were significantly different from zero (P<0.01). These results indicated that the breeding population had considerable additive genetic variation in growth traits, and the ongoing selective breeding program should produce considerable genetic improvement in the growth traits of the grass carp. High genetic and phenotypic correlations were found among growth traits (0.81–0.99, P<0.01). These data indicate that selection for improved standard length will have a favorable effect on body weight in grass carp which is the key economic parameter for production yield. High and positive genetic correlations between growth traits at 10 and 18months of age were also detected in grass carp (0.87–0.95, P<0.01), which indicated that individuals with higher growth performance at 10months also grew to be better at 18months. The results showed that genetic differences in growth traits among grass carp progeny could be determined earlier by measuring indicator traits predictive of long-term genetically determined growth. Statement of relevanceOur article comply with the Policy Statement for submission of manuscripts to the Genetic Section.In this study, we aim to estimate the genetic parameters of growth traits in grass carp, Ctenopharyngodon idella, which is one of the major freshwater aquaculture species in China.The heritability, genetic, and phenotypic correlations were estimated for growth traits of grass carp at 10 and 18months. Our study is an essential report on the quantitative genetic analysis of growth traits in sub-adult grass carp.This paper has not been submitted to any other journal for publication. The authors can confirm that the study has no actual or potential conflicts of interest to report. All authors have read and agreed the contents of the manuscript and consent to its publication.

Genetic variation in growth traits and stem–branch characteristics and their relationships to Eucalyptus clones

Eucalyptus has become an important genus in China because it displays adaptability to a wide range of site conditions and produces pulp wood and veneer on short rotations. The aim of this study was to estimate genetic parameters and relationships and consider implications for development of clonal forestry. We assessed growth traits, stem–branch characteristics, crown diameter and height of fresh branch for 20 Eucalyptus hybrid clones in China measured at the age of 44 months. Analysis of variance showed that there were significant differences in growth traits, height of fresh branch and stem straightness among clones. Significant differences in height, volume, crown diameter, height of fresh branch and branch size among replicates were also recorded. Coefficients of variation ranged from 9.84 to 28.54 % for growth traits, 12.03 to 17.25 % for stem–branch characteristics, 18.26 % for crown diameter and 11.73 % for height of fresh branch. Estimates of repeatabilities for height, diameter at breast height over bark, volume, crown diameter, height of fresh branch, stem straightness and branch size at clone mean level were 0.86, 0.80, 0.80, 0.54, 0.85, 0.77 and 0.44 respectively. Diameter at breast height over bark and height had strongly positive phenotypic and genotypic correlations with volume, ranging from 0.96 to 1.00. The positive genotypic and phenotypic correlations between growth traits and other studied traits suggested that fast growing clones always had bigger crown diameter, higher height of fresh branch, straighter stems and relatively smaller branches.

Genetic variation for growth and selection in adult plants of Eucalyptus badjensis.

The aim of this study was to evaluate Eucalyptus badjensis concerning the genetic variation for growth traits and the potential of the species in supporting a breeding programme. The field trial was a provenance/progeny test established in Campina da Alegria, Santa Catarina, Brazil (latitude 26°52′05.1″ S, longitude 51°48′47.5″ W, altitude 1,015 m) in a soil classified as Latossolic Alumino-Ferric Brown Nitosol. The experiment comprised 60 open-pollinated progenies from the provenances Glenbog and Badja State Forest, New South Wales, Australia. Ten replicates and plots with six plants in row were used. At the age of 17 years, 279 trees were assessed for diameter of the bole at breast height (DBH), total tree height (H) and volume of wood with bark (Vol). After submitting the data to statistical genetic analysis, the overall means for DBH, H and Vol were 45.17 cm, 33.30 m and 2.84 m3, and the estimates of additive coefficient of variation [(%)] were 12.59%, 5.91% and 26.51%, respectively. Heritability coefficients of additive effects () were also estimated and the following values were found: 0.443, 0.312 and 0.358. Thirty-nine trees from 25 different progenies were selected. The expected means of the provenances after improvement were 50.02 cm, 34.35 m and 3.47 m3 for DBH, H and Vol, respectively.

Genetic Variation Observed in Composite Seedling Seed Orchard of Acacia mangium Willd. at Central Java, Indonesia : Implications for Increasing Genetic Gain and Seed Production

As part of multiple-population breeding scheme using sub-lining system, a composite seedling seed orchard of was established at Central Java, Indonesia. The orchard comprises a combination of the best 40 plus tree families selected from four sub-lines in the first-generation of Acacia mangium progeny trial. The design of orchard is randomized complete block laid-out as four line tree-plot of six replications with a spacing of 2 x 4 meter. Variation among sub-lines and families within sub-line, and genetic parameters for height, dbh and volume were investigated at age of 24 months. The aim of this study was to investigate genetic variation for growth traits in a composite seedling seed orchard and to discuss the implication for increasing genetic gain and seed production. In general, trees derived from two sub-lines of Papua New Guinea (PNG) provenance showed better growth than those from Far North Queensland, Australia (FNQ). Analysis of variance revealed significant differences among sublines and families within sub-line for height, dbh and volume. Variation of the traits among families within sub-line accounted for 1.1% to 5.0%, and trees within family 43.8% to 65.8%. Heritability varied from 0.044 to 0.201 for individual, 0.060 to 0.229 for within-family and 0.098 to 0.383 for family. Withinfamily selection promoted high genetic gain for all traits, ranging from 1.3% to 4.4%. In order to increase genetic gain and seed productivity, it is recommended that:(1) the best plus trees included in the orchard should be selected based on their progeny test, (2) the design of plot size should be single treeplot, (3) the final density of seed trees should be twice greater than the number of trees intended for seed collection, which is about 300 trees per hectare.

VARIASI GENETIK UJI PROVENAN MERBAU SAMPAI UMUR 3 TAHUN DI BONDOWOSO, JAWA TIMUR

Merbau (Intsia bijuga) is one of high economic value timbers. Establishment of seed source of merbau is essential tosupply qualified seeds for plantation. Center for Forest Biotechnology and Tree Improvement has established provenance test of merbau at Sumberwringin Research Forest in Bondowoso, East Java. The objectives of this study are to know survival and genetic variation of growth traits in provenance test plot of merbau. This provenance test was designed as Randomized Complete Block Design with single factor of provenance consisted of Halmahera Timur, Waigo, Oransbari, Wasior, Nabire and Seram. Each provenance comprises 3 blocks as replication and 60 treeplots of each block. The result showed high survival rate of all provenances (above 90 %). Moreover, genetic variation of height and stem diameter among provenances was also high. The best provenance for survival, and height for all observation years was Wasior. The best provenance for diameter for all observation years was Halmahera Timur. Meanwhile, provenance having the best value of survival, height and diameter for all observation years was Halmahera Timur. The provenance having the worst value of height and diameter for all observation years was Seram. Whereas, the worst provenance of survival at 1, 2 and 3 years old were Waigo, Halmahera Timur dan Seram, respectively.

Genetic parameter estimates for live weight and daily live weight gain obtained for Nellore bulls in a test station using different models

The objective of this study was to estimate (co)variance components and genetic parameters for live weight (LW) and daily live weight gain (LWG) of Nellore bulls in a test station using multi-trait and random regression models. In addition, breeding values for these traits were predicted by multi-trait and random regression analyses, and the rank of animals based on breeding values was compared with the current selection criterion of the test station (own performance). A total of 4758 Nellore bulls tested in a central station of the Beef Cattle Research Center (CPPC) between 1978 and 2007, including 2211 bulls from the CPPC herd and 2547 from commercial herds, were used. During the test, four LWs were recorded at intervals of 56days (LW1d, LW56d, LW112d and LW168d). LWG was calculated as the difference between two consecutive weights for three periods: 1 to 55 (LWG1), 56 to 111 (LWG2), and 112 to 168 (LWG3) days on test. For LW and LWG, the multi-trait model included the fixed effects of contemporary group (year-month of birth), dam age class, and animal age at recording as covariate. For random regression analysis, direct additive genetic and animal permanent environmental effects were modeled using linear, quadratic and cubic polynomial functions. Residual variances for LW and LWG were modeled using a step function with 1 or 3 classes, respectively. Contemporary group (year-month of birth and month of recording) and dam age class were included as fixed effects. The (co)variance components were estimated by the Restricted Maximum Likelihood method using the WOMBAT software. According to model comparison criterion, the model including cubic and quadratic Legendre polynomials to fit genetic and animal permanent environmental effects, respectively, was the most appropriate to describe the covariance structure of LW. For LWG, the BIC value indicated that the model including quadratic and linear Legendre polynomials was the most appropriate to fit genetic and animal permanent environmental effects, respectively. The variance component and genetic parameter estimates for LW and LWG obtained by random regression and multi-trait analyses were similar. Random regression on Legendre polynomials of days on test was more appropriate than multi-trait models to describe the genetic variation of growth traits in station-tested Nellore bulls. Selection based on breeding values for LWG during the test would result in the selection of bulls different from those chosen if final weight is applied as a selection criterion.

Genetic variation in tree growth, stem form and mortality of Guazuma crinita in slower- and faster-growing plantations in the Peruvian Amazon

Abstract Guazuma crinita is an important timber tree with a rotation age of 6–12 years in the Peruvian Amazon. A provenance/progeny test containing 200 families from seven locations (provenances) in the Aguaytía watershed of Peru was established in three zones in the Aguaytía watershed that differ in mean annual rainfall and soil fertility. Farmers managed the replications as plantations. Replications were divided into two groups at 24 months: faster- and slower-growing plantations. The faster-growing plantations were thinned at 32 months. The objectives of this paper are to determine if genetic variation in growth traits (tree height, stem diameter) is relatively greater in the faster-growing plantations, and if there are significant differences in tree mortality and stem bifurcations among provenances and families at 24, 36 and 48 months. Variation due to provenances and families and heritability of growth traits were consistently greater in the faster-growing plantations. At 48 months, heritability of growth traits was about twice as large in the faster- than in the slower-growing plantations. There were no significant interactions between zones and either provenances or families. Tree mortality and stem bifurcations in the faster-growing plantations generally did not differ significantly among families, but did differ significantly among provenances. Based on these results and considering its rotation age, we recommend that G. crinita families/trees could be selected at 48 months in the faster-growing plantations, the plantations could be transformed into seed orchards and the seed could be used for reforestation throughout the Aguaytía watershed. Results are compared with other tropical hardwoods.

Genetic variation in growth traits and morphological characteristics of Eastern cottonwood (Populus deltoides Bartr.) hybrids at nursery stage.

Eastern cottonwood (Populus deltoides Bartr.) clones obtained from intraspecific and interspecific crosses were tested at A°zmit nursery in Turkey. Growth traits and various morphological characteristics were assessed after two growing seasons. Significant clonal differences were observed regarding height, diameter, volume index and survival rate. Ten intraspecific crosses had significantly better growth performances than control clones “Samsun” and “I-214” based on volume index values, but most of the clones showed poor survival rates in comparing control clones. High heritability values were found for the clone means of tree dimensions and survival rate, ranging from 0.51 to 0.65. Factor analysis was applied for 13 components and 71.46% of total variance was explained by the first five components. Volume index was determined as the most important variable in component 1. Groups of the clones were separated by discriminant functions and five highest groups were indicated with the most effective variable volume index. Key words: Eastern cottonwood, hybrid clone, genetic variation, growth trait, morphological characteristic, heritability, tree dimensions.