scholarly journals A simplified calculation of the correlations between relatives

2020 ◽  
Author(s):  
Reginald D. Smith
Keyword(s):  
Path Analysis ◽  
Quantitative Genetics ◽  
Genetic Correlations ◽  
Genomic Data ◽  
Complex Task ◽  
Outbred Population ◽  
Common Task ◽  
Rapid Calculation ◽  
Simplified Calculation

AbstractThe correlations between relatives is one of the fundamental ideas and earliest success of quantitative genetics. Whether using genomic data to infer relationships between individuals or estimating heritability from correlations of phenotypes amongst relatives, understanding the theoretical genetic correlations is a common task. Calculating the correlations between arbitrary relatives in an outbred population, however, can be a careful and somewhat complex task for increasingly distant relatives. This paper introduces an equation based method that consolidates the results of path analysis and uses easily obtainable data from non-inbred pedigrees to allow the rapid calculation of additive or dominance correlations between relatives even in more complicated situations such as cousins sharing more than two grandparents and inbreeding.

scholarly journals Path analysis of yield components in tropical pumpkin

1969 ◽  
Vol 90 (3-4) ◽  
pp. 183-191
Author(s):  
Miguel Espitia-Camacho ◽  
Franco A. Vallejo-Cabrera ◽  
Diosdado Baena-Garcia ◽  
Linda Wessel-Beaver
Keyword(s):  
Path Analysis ◽  
Indirect Effects ◽  
Block Design ◽  
Genetic Correlations ◽  
Fruit Weight ◽  
Residual Effects ◽  
Path Coefficient ◽  
Direct Effects ◽  
Randomized Complete Block Design ◽  
Effect On Yield

Path coefficient analysis was carried out in tropical pumpkin (Cucurbita moschata Duchesne) for yield per plant as a function of number of fruit per plant and weight per fruit, using phenotypic and genetic correlations from two diallels: one using five varieties (variety diallel) and a second using five S1 lines derived from the varieties (line diallel). A randomized complete block design with five replications was used to evaluate 15 genotypes from each diallel, not including reciprocals. Direct effects were 300 to 500% greater than indirect effects in the line diallel. In contrast, direct effects were only 17 to 68% greater than indirect effects in the variety diallel. Effects (direct and indirect) were greater (17 to 500%) when genetic correlations rather than phenotype correlations (42 to 440%) were used in the path analysis. Fruit weight showed a greater effect on yield than did number of fruit, with values between 3.2 to 4.9 times the residual effects. Fruit weight and number of fruit can be used as selection criteria to increase yield in tropical pumpkin.  

Plasticity in novel environments induces larger changes in genetic variance than adaptive divergence

2021 ◽  
Author(s):  
Greg M. Walter ◽  
Delia Terranova ◽  
James Clark ◽  
Salvatore Cozzolino ◽  
Antonia Cristaudo ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Phenotypic Plasticity ◽  
Quantitative Genetics ◽  
Leaf Morphology ◽  
Genetic Variance ◽  
Genetic Correlations ◽  
Elevational Gradient ◽  
Adaptive Divergence ◽  
Genetic Constraints ◽  
Novel Environments

AbstractGenetic correlations between traits are expected to constrain the rate of adaptation by concentrating genetic variation in certain phenotypic directions, which are unlikely to align with the direction of selection in novel environments. However, if genotypes vary in their response to novel environments, then plasticity could create changes in genetic variation that will determine whether genetic constraints to adaptation arise. We tested this hypothesis by mating two species of closely related, but ecologically distinct, Sicilian daisies (Senecio, Asteraceae) using a quantitative genetics breeding design. We planted seeds of both species across an elevational gradient that included the native habitat of each species and two intermediate elevations, and measured eight leaf morphology and physiology traits on established seedlings. We detected large significant changes in genetic variance across elevation and between species. Elevational changes in genetic variance within species were greater than differences between the two species. Furthermore, changes in genetic variation across elevation aligned with phenotypic plasticity. These results suggest that to understand adaptation to novel environments we need to consider how genetic variance changes in response to environmental variation, and the effect of such changes on genetic constraints to adaptation and the evolution of plasticity.

scholarly journals Quantitative genetics and behavioural correlates of digit ratio in the zebra finch

2005 ◽  
Vol 272 (1581) ◽  
pp. 2641-2649 ◽  
Author(s):  
Wolfgang Forstmeier
Keyword(s):  
Zebra Finch ◽  
Quantitative Genetics ◽  
Mating Behaviour ◽  
Genetic Correlations ◽  
Relative Length ◽  
Digit Ratio ◽  
Laying Order ◽  
Egg Deposition ◽  
Offspring Sex ◽  
Choice Chamber

A recent study on a captive zebra finch population suggested that variation in digit ratio (i.e. the relative length of the second to the fourth toe) might be an indicator of the action of sex steroids during embryo development, as is widely assumed for human digits. Zebra finch digit ratio was found to vary with offspring sex, laying order of eggs within a clutch, and to predict aspects of female mating behaviour. Hence, it was proposed that the measurement of digit ratio would give insights into how an individual's behaviour is shaped by its maternal environment. Studying 500 individuals of a different zebra finch population I set out to: (1) determine the proximate causes of variation in digit ratio by means of quantitative genetics and (2) to search for phenotypic and genetic correlations between digit ratio, sexual behaviour and aspects of fitness. In contrast to the earlier study, I found no sexual dimorphism in digit ratio and no effect of either laying order or experimentally altered hatching order on digit ratio. Instead, I found that variation in digit ratio was almost entirely additive genetic, with heritability estimates ranging from 71 to 84%. The rearing environment (from egg deposition to independence) explained an additional 5–6% of the variation in digit ratio, but there was no indication of any maternal effects transmitted through the egg. I found highly significant phenotypic correlations (and genetic correlations of similar size) between digit ratio and male song rate (positive correlation) as well as between digit ratio and female hopping activity in a choice chamber (negative correlation). Rather surprisingly, the strength of these correlations differed significantly between subsequent generations of the same population, illustrating how quickly such correlations can appear and disappear probably due to genotype–environment interactions.

Short-term Changes in the Variance: 2. Changes in the Environmental Variance

2018 ◽  
Author(s):  
Bruce Walsh ◽  
Michael Lynch
Keyword(s):  
Quantitative Genetics ◽  
Directional Selection ◽  
Genetic Models ◽  
Direct Selection ◽  
Outbred Population ◽  
Short Term ◽  
Environmental Variance ◽  
Additive Variance ◽  
Indirect Response ◽  
Existing Data

While classical quantitative genetics usually assumes that all genotypes have the same environmental variance (the assumption of homoscedasticity), in reality, genotypes can show heteroscedasticity in the environmental variance. When such variation is heritable (i.e., has an additive variance in an outbred population), then the environmental variance can change under selection. This can either be due to an indirect response (such as during directional selection on a trait), or through direct selection to increase the homogeneity of a trait (such as for increased uniformity during harvesting). This chapter reviews the existing data on the heritability of the environmental variance and examines several different genetic models for predicting its response.

scholarly journals Correlations between characters and path analysis in sweet sorghum (Sorghum bicolor (L.) Moench) genotypes for juice production

2021 ◽  
pp. 290-296
Author(s):  
Taniele Carvalho de Oliveira ◽  
Marco Antonio Aparecido Barelli ◽  
Valvenarg Pereira da Silva ◽  
Rafhael Felipin- Azevedo ◽  
Danilo de Lima Gonçalves ◽  
...  
Keyword(s):  
Path Analysis ◽  
Genetic Correlation ◽  
Sweet Sorghum ◽  
Bootstrap Method ◽  
Genetic Correlations ◽  
Dry Mass ◽  
Soluble Solids ◽  
Flowering Plant ◽  
Phenotypic Correlation ◽  
Green Mass

Sweet sorghum presents stems with juice similar to that of sugar cane, rich in fermentable sugars, that may be used in off-season for sugar and ethanol production optimizing the sugar-ethanol sector. The objective of this work was to determine genetic correlations between characters and perform path analysis between juice volume and its components. Twenty-five sweet sorghum genotypes were evaluated in randomized blocks design with three repetitions and studied variables were: number of days to flowering; plant height; number of stems; weight of green mass; weight of dry mass; number of leaves; diameter of stems; volume of extracted juice and percentage of total soluble solids. In order to verify the existence of variability among the genotypes, data were subjected to variance analysis by F-test. Subsequently, genetic parameters were determined, as soon as genetic correlation estimator’s method, performed by t-test, to determine phenotypic correlation and bootstrap method for determining environmental and genetics correlation coefficient. Before performing path analysis a multicollinearity diagnosis was also conducted. The results of genetic correlation and path analysis point weight of green mass as the main variable influencing the juice volume, allowing these characters in indirect selection for increasing juice volume

scholarly journals The contribution of mutation and selection to multivariate quantitative genetic variance in an outbred population of Drosophila serrata

2021 ◽  
Vol 118 (31) ◽  
pp. e2026217118
Author(s):  
Robert J. Dugand ◽  
J. David Aguirre ◽  
Emma Hine ◽  
Mark W. Blows ◽  
Katrina McGuigan
Keyword(s):  
Genetic Variance ◽  
Genetic Correlations ◽  
Stabilizing Selection ◽  
Outbred Population ◽  
Drosophila Serrata ◽  
Slow Evolution ◽  
Multivariate Traits ◽  
Mutational Variance ◽  
Mutation And Selection ◽  
Multivariate Phenotypes

Genetic variance is not equal for all multivariate combinations of traits. This inequality, in which some combinations of traits have abundant genetic variation while others have very little, biases the rate and direction of multivariate phenotypic evolution. However, we still understand little about what causes genetic variance to differ among trait combinations. Here, we investigate the relative roles of mutation and selection in determining the genetic variance of multivariate phenotypes. We accumulated mutations in an outbred population of Drosophila serrata and analyzed wing shape and size traits for over 35,000 flies to simultaneously estimate the additive genetic and additive mutational (co)variances. This experimental design allowed us to gain insight into the phenotypic effects of mutation as they arise and come under selection in naturally outbred populations. Multivariate phenotypes associated with more (less) genetic variance were also associated with more (less) mutational variance, suggesting that differences in mutational input contribute to differences in genetic variance. However, mutational correlations between traits were stronger than genetic correlations, and most mutational variance was associated with only one multivariate trait combination, while genetic variance was relatively more equal across multivariate traits. Therefore, selection is implicated in breaking down trait covariance and resulting in a different pattern of genetic variance among multivariate combinations of traits than that predicted by mutation and drift. Overall, while low mutational input might slow evolution of some multivariate phenotypes, stabilizing selection appears to reduce the strength of evolutionary bias introduced by pleiotropic mutation.

scholarly journals Path analysis under multiple-trait BLUP: application in the study of interrelationships among traits related to cotton fiber length

2021 ◽  
Vol 53 (1) ◽  
pp. 1-10
Author(s):  
Rodrigo Alves ◽  
João Rocha ◽  
Larissa Teodoro ◽  
Luiz Carvalho ◽  
Francisco Farias ◽  
...  
Keyword(s):  
Path Analysis ◽  
Fiber Length ◽  
Mixed Model ◽  
Fiber Quality ◽  
Genetic Correlations ◽  
Residual Effects ◽  
Phenotypic Variance ◽  
Multiple Trait ◽  
Effect Relationship ◽  
Cause And Effect

Multi-trait best linear unbiased prediction (BLUP) is, generally, the most appropriate method to genetic evaluation because it considers the genetic and residual correlations among traits and conduct to higher selection accuracy. Thus, the present study aimed to identify traits correlated to the fiber length via path analysis under multi-trait BLUP for the cotton breeding. To this end, thirty-six elite lines were evaluated in three environments and phenotyped for many traits related to fiber quality and agronomic traits. Variance components were estimated via residual maximum likelihood (REML). The genetic correlation coefficients among traits were obtained through mixed model output, and to graphically express these results a correlation network was built. Subsequently, we performed path analysis considering fiber length as a principal dependent variable. Genetic parameters obtained by multi-trait BLUP model indicate that the phenotypic variance for most traits is mostly composed of residual effects, which reinforces the need for using more accurate statistical methods such as multi-trait BLUP. The results found for genetic correlations and path analysis under multi-trait BLUP reveal the difficulty of selection based on important fiber quality traits, especially fiber length, since most traits show very low cause-and-effect relationship, and other important traits present undesirable cause-and-effect relationship. Highlights Multiple-trait BLUP is the most appropriate method to predict genetic values. This is the first study in cotton to perform path analysis under multiple-trait BLUP. The findings of this study indicate that there is no genotype presenting all desirable traits.

Sign in / Sign up

Export Citation Format

Share Document