Micron blowout: heritability and genetic correlations with fibre diameter and secondary follicle diameter

1999 ◽  
Vol 50 (8) ◽  
pp. 1375 ◽  
Author(s):  
J. A. Hill ◽  
R. W. Ponzoni ◽  
J. W. James
Keyword(s):  
Genetic Correlation ◽  
Scale Effect ◽  
Genetic Variance ◽  
Genetic Correlations ◽  
Fibre Diameter ◽  
The Other ◽  
Follicle Diameter ◽  
The Difference ◽  
Biased Estimates ◽  
Practical Implications

Calculation of micron blowout as the difference between fibre diameter records taken at different ages can produce ‘biased’ estimates of the heritability and genetic correlations due to a scale effect. In some instances, standardisation of the fibre diameter records to a common genetic variance (i.e. removal of the scale effect) changed the heritability and the genetic correlation estimates. The effect of standardisation on the heritability of micron blowout was determined to a large extent by the difference in the genetic variance between the 2 fibre diameter measurements, whereas in the case of the genetic correlation between micron blowout and another trait, it was also dependent on the genetic correlation between the other trait and the two fibre diameters. It is recommended that heritabilities and genetic correlations involving micron blowout be calculated after standardising the fibre diameter measurements to a common genetic variance. The practical implications of the results are briefly discussed.

Selection for fertility in Australian Merino sheep

1963 ◽  
Vol 14 (4) ◽  
pp. 460 ◽  
Author(s):  
SSY Young ◽  
HN Turner ◽  
CHS Dolling
Keyword(s):  
Body Weight ◽  
Genetic Correlations ◽  
Fibre Diameter ◽  
Likelihood Method ◽  
Mass Selection ◽  
Genetic Progress ◽  
Subsequent Performance ◽  
Fertility Trait ◽  
Selection For ◽  
The Difference

Phenotypic and genetic parameters for fertility in sheep, in terms of number of lambs born and number weaned, have been estimated in a flock of medium Peppin Merinos. Repeatability of fertility traits over all ages is low, but there is an age effect, the record at 3 years of age having a higher value than those at 2 or 4 years. The regression of subsequent performance on a difference of 1 lamb at the initial lambing was higher for the difference between 1 and 2 lambs than between 0 and 1 lamb, which indicated that selection for twins is likely to raise fertility in the current flock more rapidly than selection against barrenness. The estimate of heritability for 2 years of age was negligible for each fertility trait, but the estimates for the 3-year-old record were higher, the value for lambs born being over 0.3. Mass selection for number of lambs born at 3 years of age would thus be expected to lead to appreciable genetic progress, while there would be at least some progress in number of lambs weaned. Phenotypic and genetic correlations were also estimated between fertility at different ages and 10 sheep and wool traits measured at 15–16 months of age. Phenotypically, fertility is positively correlated with body weight and negatively with skin wrinkle score. Genetically, it is suggested from the estimates that fertility is positively correlated with body weight and staple length and negatively correlated with fibre diameter, clean scoured yield, and wrinkle score. No phenotypic or genetic correlation was found between greasy or clean wool weight and either measure of fertility. The application of the findings to breeding for higher fertility is discussed. In an appendix, a maximum likelihood method of estimating heritability for all-or-none traits in half-sib data is presented.

scholarly journals Genetic Variation and Correlation among Resin Yield, Growth, and Morphologic Traits of Pinus massoniana

2013 ◽  
Vol 62 (1-6) ◽  
pp. 38-43 ◽  
Author(s):  
Qinghua Liu ◽  
Zhichun Zhou ◽  
Huihua Fan ◽  
Yurong Liu
Keyword(s):  
Genetic Correlation ◽  
Genetic Correlations ◽  
Tree Height ◽  
Pinus Massoniana ◽  
The Other ◽  
Breeding Programs ◽  
Family Effects ◽  
Breast Height ◽  
Sib Families ◽  
The Individual

AbstractIn breeding programs, the variations and relationships among main traits need to be understood to develop selection and breeding strategies. Resin is considered as one of most important non-timber production of P. massoniana which can privides terpenes used in the chemical industry. The present study assessed the genetic variations in growth, morphologic traits, and resin yield, as well as the phenotypic and genetic correlations between these traits of 45 half-sib families of eight-year-old Pinus massoniana trees. All traits show highly significant family effects. The individual heritability for diameter at breast height (DBH) was the highest (hi2=0.55). Heritabilities for resin yield, tree height, crown depth, and the height to the live crown were slightly lower than DBH, ranging from 0.32 to 0.45. The other traits were under weak genetic control and heritabilities ranged from 0.17 to 0.20. All growth and morphologic traits were significantly correlated genetically with resin yield. Number of living branches had the highest genetic correlation with resin yield (rg=0.99), followed by DBH and number of living whorls (rg=0.73 and 0.70). Only a moderate positive genetic correlation with resin yield was found with the other traits (rg=0.47-0.57), except for height under the living branches (rg=-0.45). The results of this study indicate that both resin yield and growth can be improved simultaneously in the next generation. Of the traits assessed DBH was the optimum trait for indirectly selecting high-yielding resin trees.

scholarly journals Genetic parameter and genetic trend estimates for reproductive traits in Wistar rats

2020 ◽  
Vol 72 (4) ◽  
pp. 1479-1486
Author(s):  
G. Taroco ◽  
J.T. Paiva ◽  
G.B. Mourão ◽  
J.B.S. Ferraz ◽  
E.C. Mattos ◽  
...  
Keyword(s):  
Genetic Correlation ◽  
Wistar Rats ◽  
Genetic Parameter ◽  
Genetic Correlations ◽  
Reproductive Traits ◽  
Wistar Rat ◽  
The Other ◽  
Genetic Trend ◽  
Genetic Progress ◽  
Genetic Trends

ABSTRACT The aim of this study was to estimate genetic parameters and genetic trends for reproductive traits in Wistar rats. A total of 1,167 data records from 283 females over six generations of monogamous mating pairs was used. Heritability and genetic correlation were estimated through Bayesian inference and genetic trends were calculated by linear regression of breeding values over generations. Heritability estimates for litter size at birth (LS), calving interval (CI), pup mortality (PM) and maternal cannibalism (CAN) presented low magnitude, ranging from 0.01 to 0.13. CAN presented high and positive genetic correlation with LS and PM (0.77 and 0.78, respectively). On the other hand, all the other estimated genetic correlations were not significant. Genetic trend was positive for LS (+0.0900 pups per generation), and negative for PM and CAN (-1.0085 and -0.5217 pups per generation, respectively). For CI the genetic trend was not significant. It is recommended to increase selection intensity on dams in this Wistar rat population in order to accelerate the genetic progress.

Genetic parameters for Australian maternal and dual-purpose meatsheep breeds. III. Liveweight, fat depth and wool production in Coopworth sheep

1994 ◽  
Vol 45 (2) ◽  
pp. 481 ◽  
Author(s):  
LD Brash ◽  
NM Fogarty ◽  
AR Gilmour
Keyword(s):  
Genetic Correlation ◽  
Fixed Effects ◽  
Genetic Correlations ◽  
Fibre Diameter ◽  
Dual Purpose ◽  
Management Group ◽  
Derivative Free ◽  
Fleece Weight ◽  
Group Sex ◽  
Birth Type

Heritability was estimated for weaning liveweight of 7030 Coopworth sheep from 10 flocks representing 92 sires by derivative-free restricted maximum likelihood procedures using an animal model. Similar analyses were used for yearling liveweight and greasy fleece weight with over 4000 animals, fat depth on 2184 animals and fibre diameter on 966 animals. The fixed effects of flock-year-management group, sex, birth type, rearing type and age were significant for most traits. Estimates of heritability were 0.45 � 0 - 07 for weaning liveweight, 0.38 � 0.07 for yearling liveweight, 0 28 � 0.05 for greasy fleece weight, 0.18 � 0 08 for fibre diameter and 0.13 � 0.04 for ultrasonic fat depth at the C site. The genetic correlations of liveweights with greasy fleece weight were positive, but close to zero with fibre diameter. The genetic correlation between greasy fleece weight and fibre diameter was 0.422 � 0.25. Fat depth was highly genetically correlated with liveweights at weaning (0.53 � 0.22) and yearling (0.64 � 0- 20) ages, was highly negatively correlated with fibre diameter (-0.55 � 0.28) and had a small positive genetic correlation with greasy fleece weight (0.15 � 0.34).

scholarly journals Evolution of genetic variability in a spatially heterogeneous environment: effects of genotype–environment interaction

1987 ◽  
Vol 49 (2) ◽  
pp. 147-156 ◽  
Author(s):  
Sara Via ◽  
Russell Lande
Keyword(s):  
Genetic Variability ◽  
Genetic Correlation ◽  
Genetic Variance ◽  
Genetic Correlations ◽  
Covariance Structure ◽  
Genetic Models ◽  
Quantitative Character ◽  
Disruptive Selection ◽  
Environment Interaction ◽  
The Mean

SummaryClassical population genetic models show that disruptive selection in a spatially variable environment can maintain genetic variation. We present quantitative genetic models for the effects of disruptive selection between environments on the genetic covariance structure of a polygenic trait. Our models suggest that disruptive selection usually does not alter the equilibrium genetic variance, although transient changes are predicted. We view a quantitative character as a set of character states, each expressed in one environment. The genetic correlation between character states expressed in different environments strongly affects the evolution of the genetic variability. (1) If the genetic correlation between character states is not ± 1, then the mean phenotype expressed in each environment will eventually attain the optimum value for that environment; this is the evolution of phenotypic plasticity (Via & Lande, 1985). At the joint phenotypic optimum, there is no disruptive selection between environments and thus no increase in the equilibrium genetic variability over that maintained by a balance between mutation and stabilizing selection within each environment. (2) If, however, the genetic correlation between character states is ± 1, the mean phenotype will not evolve to the joint phenotypic optimum and a persistent force of disruptive selection between environments will increase the equilibrium genetic variance. (3) Numerical analyses of the dynamic equations indicate that the mean phenotype can usually be perturbed several phenotypic standard deviations from the optimum without producing transient changes of more than a few per cent in the genetic variances or correlations. It may thus be reasonable to assume a roughly constant covariance structure during phenotypic evolution unless genetic correlations among character states are extremely high or populations are frequently perturbed. (4) Transient changes in the genetic correlations between character states resulting from disruptive selection act to constrain the evolution of the mean phenotype rather than to facilitate it.

Modelling genetic covariance structure across ages of mean fibre diameter in sheep using multivariate and random regression analysis

2012 ◽  
Vol 52 (11) ◽  
pp. 1019 ◽  
Author(s):  
M. Asadi Fozi ◽  
J. H. J. Van der Werf ◽  
A. A. Swan
Keyword(s):  
Genetic Correlations ◽  
Fibre Diameter ◽  
Covariance Structure ◽  
Multivariate Model ◽  
The Other ◽  
Random Regression ◽  
Multivariate Models ◽  
Genetic Covariance ◽  
Merino Sheep ◽  
Parsimonious Model

Mean fibre diameter measurements from yearling to 5-year-old Australian fine- and medium-wool Merino sheep were analysed using several multivariate models that varied in covariance structure. A pre-structured multivariate model was found to be the most parsimonious model in comparison with the other models fitted such as banded, autoregressive and random regression. In the preferred model, the ages of mean fibre diameter for fine-wool data were genetically partitioned into yearling, 2 years, 3 years and later ages and for medium-wool data into hogget, 2 years and later ages. The estimates of genetic correlations between mean fibre diameter measured at different ages for medium-wool sheep were higher (0.89–1.00) than those for fine-wool Merino (0.75–1.00).

Direct and maternal genetic (co)variances for hogget liveweight and fleece traits in Western Australian Merino sheep

2002 ◽  
Vol 53 (3) ◽  
pp. 271 ◽  
Author(s):  
S. W. P. Cloete ◽  
J. C. Greeff ◽  
R. P. Lewer
Keyword(s):  
Genetic Correlation ◽  
Coefficient Of Variation ◽  
Genetic Correlations ◽  
Fibre Diameter ◽  
Phenotypic Variance ◽  
Selection For ◽  
Fleece Weight ◽  
Variance Estimates ◽  
Western Australian ◽  
Australian Merino

(Co)variance estimates for hogget liveweight, greasy fleece weight, clean fleece weight, clean yield, fibre diameter, and the coefficient of variation of fibre diameter were obtained for a Western Australian Merino resource flock. The flock encompassed 16 medium wool bloodlines and data were available for the period 1982–93. Direct additive genetic variances (h2) — expressed as a ratio of the total phenotypic variance within bloodlines — were estimated at 0.52 for hogget liveweight, 0.44 for greasy fleece weight, 0.42 for clean fleece weight, 0.63 for clean yield, 0.71 for fibre diameter, and 0.62 for coefficient of variation of fibre diameter. Maternal genetic variance estimates were significant (P < 0.05) only in hogget liveweight and fibre diameter, but components within bloodlines were low (0.05 for liveweight and 0.02 for fibre diameter). Direct within-bloodline genetic correlations of hogget liveweight as well as greasy and clean fleece weight with fibre diameter were positive (0.17, 0.31, and 0.31, respectively), suggesting that selection for bigger and heavier cutting sheep would generally lead to a broader fibre diameter. Liveweight was unrelated to clean yield and negatively related to coefficient of variation of fibre diameter (–0.17). Greasy fleece weight was negatively related to clean yield (–0.20). The genetic correlation of clean fleece weight with clean yield was positive (0.37). Wool quantity was, in general, positively related to coefficient of variation of fibre diameter, although the estimated genetic correlations were low (0.12 for greasy fleece weight and 0.07 for clean fleece weight). The genetic correlation between fibre diameter and coefficient of variation of fibre diameter was negative, and fairly low (–0.10). These results are discussed with reference to sheep breeding.

Calculation of the heritability of spinning fineness from phenotypic and genetic parameters of the mean and CV of fibre diameter

1992 ◽  
Vol 43 (6) ◽  
pp. 1441 ◽  
Author(s):  
KL Butler ◽  
M Dolling
Keyword(s):  
Genetic Correlation ◽  
Coefficient Of Variation ◽  
Selection Criteria ◽  
Genetic Parameters ◽  
Genetic Correlations ◽  
Fibre Diameter ◽  
Diameter Distribution ◽  
The Mean

In sheep selection programmes where fibre diameter distribution measurements are available, such as when using the FDA method of assessing fibre diameter, spinning fineness (as defined by Anderson, S.L. (1976), J. Text. Inst., 67, 175-80) might be preferable to using mean fibre diameter as a sheep selection criteria. This paper uses a Taylor's expansion to obtain an approximation to the heritability of spinning fineness when the phenotypic and genetic parameters of only the mean and the coefficient of variation of fibre diameter are available. The approximation assumes that the mean and coefficient of variation of fibre diameter are both phenotypically and genetically independent. Approximations are also obtained for the genetic correlation between spinning fineness and mean fibre diameter, and between spinning fineness and coefficient of variation. Using the approximations, estimates of heritability of spinning fineness and of the two genetic correlations are calculated for published studies.

scholarly journals 303 ASAS-EAAP Talk: On the estimation of genetic parameters from molecular data

2020 ◽  
Vol 98 (Supplement_4) ◽  
pp. 33-33
Author(s):  
Miguel Toro Ibáñez
Keyword(s):  
Linkage Disequilibrium ◽  
Genetic Correlation ◽  
Genomic Selection ◽  
Genetic Parameters ◽  
Genetic Variance ◽  
Genetic Correlations ◽  
Molecular Data ◽  
Snp Markers ◽  
Directional Selection ◽  
Recombination Rates

Abstract We deal with several problems that arise when inferring genetic parameters at the level of quantitative trait loci (QTL) from molecular data such as SNP markers. Linkage Disequilibrium (LD) is recognized as a factor creating ambiguity in the partition of genetic variance. Here, using a simple model with three loci (one QTL and two markers), it is shown that the markers generate apparent AxA and DxD epistasis, even if only third order disequilibrium exists and the QTL is dominant. The problem of “phantom epistasis” is not alleviated by larger sample sizes (de los Campos et al., 2019). We also show that markers can give a distorted picture of the genetic correlation between traits: The genomic correlation could be greater, lower or even of opposite sign than the true genetic correlation. Therefore, speculating about genetic correlations and even about their causes (e.g., pleiotropy) using genomic data is often conjectural. Thirdly, we examine the problem of directional selection generating negative linkage disequilibrium (“Bulmer effect”) in the short term from a genomic selection perspective. It seems that the reduction in response due to the Bulmer effect is the same for genomic selection as for selection based on traditional BLUP. However, the reduction in response with genomic selection is greater than when selection is based directly on phenotypes only (Van Grevenhof et al. 2012). It is also expected that directional selection for a polygenic trait should increase recombination rate, provided there is genetic variance for recombination. It is then of relevance to ask whether recombination rates could be manipulated in order to increase selection response (Battagin et al., 2016). Finally, we consider that recombination and epistasis are closely intertwined: Epistasis generate LD and recombination break them up. Then, we should expect genomes to be modular: regions with low recombination containing functionally related genes loosely linked to other regions.

scholarly journals Moderating Effect of Materialism on the Inaction Inertia Phenomenon

2018 ◽  
Vol 7 (3.34) ◽  
pp. 611
Author(s):  
Seongsoo Lee ◽  
. .
Keyword(s):  
Statistical Analysis ◽  
Behavioral Intention ◽  
Point Of View ◽  
The Other ◽  
Inertia Effect ◽  
Price Difference ◽  
Mixed Design ◽  
Manipulation Check ◽  
The Difference ◽  
Practical Implications

Background/Objectives: This study aims to investigate whether materialism tendency will act as a moderating variable for the inaction inertia phenomenon.Methods/Statistical analysis: A total of 121 college students were randomly assigned to 2 (difference in attractiveness condition: large vs. small) × 2 (materialism: high vs. low) mixed design. Respondents read two-part scenario and responded to several questions: manipulation check item to assess perceived attractiveness, some questions related to regret (immediate regret, recalled experienced regret, anticipated inaction regret, anticipated action regret), behavioral intention, and demographics.Findings: First, the manipulation of the perception of difference in attractiveness (manipulated with price difference) was as the researcher intended. Immediate regret after missing the initial opportunity, recalled experienced regret, and anticipated action regret were found to be varied on the level of materialism. The level of recalled experienced regret, anticipated action regret, and anticipated inaction regret varied according to the difference in attractiveness conditions. The interaction effects of the level of materialism and difference in attractiveness conditions appeared only for anticipated action regret and anticipated inaction regret. Anticipated action regret and inaction regret were found to have a significant effect on behavioral intention regardless of the level of materialism. On the other hand, recalled experienced regret had a significant impact on behavioral intention only in low-materialist group.Improvements/Applications: This study has theoretical and practical implications from the point of view of how the various kinds of regrets vary according to materialism in the area of inaction inertia effect.  

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