THE GENETIC VARIANCE FOR VIABILITY AND ITS COMPONENTS IN A LOCAL POPULATION OF DROSOPHILA MELANOGASTER

ABSTRACT Two hundred and ninety second chromosomes extracted from a natural population of Drosophila melanogaster were analyzed to estimate the genetic variance of viability and its components by means of a partial diallel cross (Design II of Comstock and Robinson 1952). The additive and dominance variances are estimated to be 0.009 and 0.0012. Using the dominance variance and the inbreeding depression, the effective number of overdominant loci contributing to the variance in viability is estimated to be very small, a dozen or less. Either the actual number of loci is small, or the distribution of viabilities is strongly skewed with a large majority of very weakly selected loci. The additive variance in viability appears to be too large to be accounted for by recurrent harmful mutants or by overdominant loci at equilibrium with various genetic parameters estimated independently. The excess might be due to frequency-dependent selection, to negative correlations between viability and fertility, or possibly to the presence of a mutator. The selection for viability and fertility, or possibly to the presence of a mutator. The selection for viability at the average polymorphic locus must be very slight, of the order of 10-3 or less.

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Variance component analysis for viability in an isolated population of Drosophila melanogaster

Genetics Research ◽

10.1017/s0016672300021662 ◽

1983 ◽

Vol 42 (2) ◽

pp. 207-217 ◽

Cited By ~ 7

Author(s):

Hidenori Tachida ◽

Muneo Matsuda ◽

Shin-Ichi Kusakabe ◽

Terumi Mukai

Keyword(s):

Drosophila Melanogaster ◽

Genetic Variance ◽

Balancing Selection ◽

Additive Genetic Variance ◽

Diallel Cross ◽

Variance Component Analysis ◽

Logarithmic Scale ◽

Dominance Variance ◽

Diversifying Selection ◽

Partial Diallel

SUMMARYUsing the 602 second chromosome lines extracted from the Ishigakijima population of Drosophila melanogaster in Japan, partial diallel cross experiments (Design II of Comstock & Robinson, 1952) were carried out, and the additive genetic variance and the dominance variance of viability were estimated. The estimated value of the additive genetic variance is 0·01754±0·00608, and the dominance variance 0·00151±0·00114, using a logarithmic scale. Since the value of the additive genetic variance is much larger than expected under mutation–selection balance although the dominance variance is compatible with it, we speculate that in the Ishigakijima population some type of balancing selection must be operating to maintain the genetic variability with respect to viability at a minority of loci. As candidates for such selection, overdominance, frequency-dependent selection, and diversifying selection are considered, and it is suggested that diversifying selection is the most probable candidate for increasing the additive genetic variance.

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Corrigendum - Response to selection in Australian Merino sheep. II. Estimates of phenotypic and genetic parameters for some production traits in Merino ewes and an analysis of the possible effects of selection on them

Australian Journal of Agricultural Research ◽

10.1071/ar9680303c ◽

1968 ◽

Vol 19 (2) ◽

pp. 303

Author(s):

GH Brown ◽

HN Turner

Keyword(s):

Genetic Parameters ◽

Genetic Variance ◽

Statistical Significance ◽

Additive Genetic Variance ◽

Genetic Correlations ◽

Production Traits ◽

Average Value ◽

Selection History ◽

Order Of Magnitude ◽

Selection For

Estimates of heritabilities and of phenotypic and genetic correlations are given, based on extensive measurements on medium Peppin Merino ewes at 15–16 months of age. In general these substantiate results obtained by other workers and, in particular, confirm the high heritabilities of the traits measured. An effort has been made to try to detect possible changes in additive genetic variance for the trait under selection (clean wool weight). Estimates are obtained for data from animals at different stages of selection: (A) either unselected, or with little selection history, and (B and C) with varying amounts of selection. For stage A data the average estimated additive genetic variance was 0.31. There are problems involved in estimating from stage (B+C) data but an upper limit average value of 0.22 was obtained. Thus, although a decrease in additive genetic variance has occurred, its statistical significance is unknown and conclusions about the decrease must necessarily be tentative. In practically all cases the estimates of phenotypic and genetic correlations are of the same order of magnitude, and for the genetic correlations may be summarized as: See PDFAll other combinations of traits have negligible genetic correlations (in the range –0.20 to + 0.2).

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The genetic structure of natural populations of Drosophila melanogaster. XXIV. Effects of hybrid dysgenesis on the components of genetic variance of variability.

Genetics ◽

10.1093/genetics/127.3.545 ◽

1991 ◽

Vol 127 (3) ◽

pp. 545-552

Author(s):

D S Suh ◽

T Mukai

Keyword(s):

Drosophila Melanogaster ◽

Population Genetic ◽

Genetic Parameters ◽

Genetic Variance ◽

Additive Genetic Variance ◽

Natural Populations ◽

Deleterious Mutations ◽

Degree Of Dominance ◽

Population Genetic Parameters ◽

P Type

Abstract Eight hundred second chromosomes were extracted from the Ishigakijima population, one of the southernmost populations of Drosophila melanogaster in Japan. Half of them were extracted in Native cytoplasm (P-type), and half in Foreign cytoplasm (M-type). Various population-genetic parameters, including the frequency of lethal-carrying second chromosomes (Q = 0.235 for the Native; 0.218 for the Foreign), the allelism rate of lethal second chromosome (Ic = 0.0217 for the Native; 0.0134 for the Foreign), the homozygous detrimental and lethal loads (D = 0.179 for the Native; 0.270 for the Foreign; L = 0.262 for the Native; 0.240 for the Foreign), the average degree of dominance of mildly deleterious mutations (ĥE = 0.244 for the Native; 0.208 for the Foreign), and the components of genetic variance for viability [additive (sigma A2) and dominance (sigma D2)](ŝigma A2 = 0.0187 for the Native; 0.0172 for the Foreign; ŝigma D2 = 0.0005 for the Native; 0.0009 for the Foreign) were estimated. The data indicate that D was significantly larger and hE was significantly smaller in the Foreign cytoplasm. However, the estimates of additive and dominance variances were not significantly different between the two cytoplasms. The additive genetic variance for viability in the Ishigakijima population was greater than expected on the basis of mutation-selection balance confirming previous studies on papers of D. melanogaster in warm climates.

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A CHROMOSOMAL ANALYSIS OF X-RAY INDUCED GENETIC VARIANCE OF WING LENGTH IN DROSOPHILA MELANOGASTER

Canadian Journal of Genetics and Cytology ◽

10.1139/g71-086 ◽

1971 ◽

Vol 13 (3) ◽

pp. 600-606

Author(s):

J. F. Kidwell ◽

M. L. Tracey ◽

P. Glaser ◽

M. M. Kidwell

Keyword(s):

Sex Differences ◽

Drosophila Melanogaster ◽

Genetic Variation ◽

Genetic Variance ◽

Wing Length ◽

Chromosomal Analysis ◽

Isogenic Line ◽

Additive Variance ◽

X Ray

A chromosomal analysis of genetic variation in wing length of Drosophila melanogaster was done using an isogenic line and a single derived irradiated line which differed significantly in wing length. Partitioning of the variance indicates no difference between X-ray induced genetic variance and that from other sources. Furthermore, the amount of additive variance is strongly dependent on chromosome frequency, and sex differences are present in all components.

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Genetic architecture and genomic selection of female reproduction traits in rainbow trout

10.21203/rs.3.rs-21280/v1 ◽

2020 ◽

Author(s):

Jonathan D’Ambrosio ◽

Romain Morvezen ◽

Sophie Brard-Fudulea ◽

Anastasia Bestin ◽

Charles Poncet ◽

...

Keyword(s):

Rainbow Trout ◽

Genomic Selection ◽

Genetic Architecture ◽

Egg Size ◽

Genetic Parameters ◽

Genetic Variance ◽

Female Reproduction ◽

Egg Number ◽

Reproduction Traits ◽

Selection For

Abstract Background Rainbow trout is a significant fish farming industry under temperate climates. Female reproduction traits play an important role in the economy of breeding companies with the sale of fertilized eggs. The objectives of this study are threefold: to estimate the genetic parameters of female reproduction traits, to determine the genetic architecture of these traits by the identification of quantitative trait loci (QTL), and to assess the expected efficiency of a pedigree-based selection (BLUP) or genomic selection for these traits. Results A pedigreed population of 1,343 trout were genotyped for 57,000 SNP markers and phenotyped for seven traits at 2 years of age: spawning date, female body weight before and after spawning, the spawn weight and the egg number of the spawn, the egg average weight and average diameter. Genetic parameters were estimated in multi-trait linear animal models. Heritability estimates were moderate, varying from 0.27 to 0.44. The female body weight was not genetically correlated to any of the reproduction traits. Spawn weight showed strong and favourable genetic correlation with the number of eggs in the spawn and individual egg size traits, but the egg number was uncorrelated to the egg size traits. The genome-wide association studies showed that all traits were very polygenic since less than 10% of the genetic variance was explained by the cumulative effects of the QTLs: for any trait, only 2 to 4 QTLs were detected that explained in-between 1 and 3% of the genetic variance. Genomic selection based on a reference population of only one thousand individuals related to candidates would improve the efficiency of BLUP selection from 16 to 37% depending on traits. Conclusions Our genetic parameter estimates made unlikely the hypothesis that selection for growth could induce any indirect improvement for female reproduction traits. It is thus important to consider direct selection for spawn weight for improving egg production traits in rainbow trout breeding programs. Due to the low proportion of genetic variance explained by the few QTLs detected for each reproduction traits, marker assisted selection cannot be effective. However genomic selection would allow significant gains of accuracy compared to pedigree-based selection.

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COMBINING ABILITY ANALYSIS, ESTIMATION OF HETEROSIS AND SOME GENETIC PARAMETERS USING PARTIAL DIALLEL CROSS IN COMMON WHEAT (Triticum aestivum. L)

Mesopotamia Journal of Agriculture ◽

10.33899/magrj.2011.30467 ◽

2011 ◽

Vol 39 (2) ◽

pp. 132-141

Author(s):

Mohammed Ali Hussein

Keyword(s):

Triticum Aestivum ◽

Common Wheat ◽

Combining Ability ◽

Genetic Parameters ◽

Diallel Cross ◽

Triticum Aestivum L ◽

Combining Ability Analysis ◽

Partial Diallel

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Recombination load associated with selection for increased recombination

Genetics Research ◽

10.1017/s0016672300033450 ◽

1996 ◽

Vol 67 (1) ◽

pp. 27-41 ◽

Cited By ~ 70

Author(s):

B. Charlesworth ◽

N. H. Barton

Keyword(s):

Transposable Elements ◽

Direct Effect ◽

Quantitative Traits ◽

Genetic Variance ◽

Genetic Recombination ◽

Additive Genetic Variance ◽

Directional Selection ◽

Additive Variance ◽

Linkage Disequilibria ◽

Selection For

SummaryExperiments on Drosophila suggest that genetic recombination may result in lowered fitness of progeny (a ‘recombination load’). This has been interpreted as evidence either for a direct effect of recombination on fitness, or for the maintenance of linkage disequilibria by epistatic selection. Here we show that such a recombination load is to be expected even if selection favours increased genetic recombination. This is because of the fact that, although a modifier may suffer an immediate loss of fitness if it increases recombination, it eventually becomes associated with a higher additive genetic variance in fitness, which allows a faster response to directionselection. This argument applies to mutation-selection balance with synergistic epistasis, directional selection on quantitative traits, and ectopic exchange among transposable elements. Further experiments are needed to determine whether the selection against recombination due to trie immediate load is outweighed by the increased additive variance in fitness produced by recombination.

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INHERITANCE OF DRY MATTER YIELD IN A HETEROZYGOUS POPULATION OF ALFALFA

Canadian Journal of Plant Science ◽

10.4141/cjps81-044 ◽

1981 ◽

Vol 61 (2) ◽

pp. 313-318 ◽

Cited By ~ 7

Author(s):

STEVE R. BOWLEY ◽

B. R. CHRISTIE

Keyword(s):

Dry Matter ◽

Genetic Variance ◽

Total Yield ◽

Dry Matter Yield ◽

Response To Selection ◽

Additive Variance ◽

Growth Room ◽

Medicago Sativa L ◽

Selection For ◽

Made In

Additive and digenic variances for dry matter yield were estimated from a population of F1 lines of alfalfa (Medicago sativa L.). The F1 lines and their polycross (PX) progenies were both evaluated over three harvests in a simulated sward in a growth room. From the analyses of variance, the genetic variances of the F1 and PX lines were estimated and the covariance between the F1 and PX performance calculated for dry matter yield. Correlations between relatives were used to partition these variances into additive and digenic effects. Narrow-sense heritabilities and the expected response to selection were estimated for the F1 population and broad-sense heritabilities were calculated from the F1 and PX trials. The pooled estimates of additive variance were significantly greater than zero for the second harvest and total yield while all estimates of digenic variance were nonsignificant. This indicated that the genetic variance for dry matter yield was mainly additive. The expected response to selection for total dry matter yield, if the top 10% of the F1 lines were recombined, was 23% of the F1 population mean. Based on these results, it was concluded that selection gains for yield could be made in this population of alfalfa.

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Response to selection in Australian Merino sheep. II. Estimates of phenotypic and genetic parameters for some production traits in Merino ewes and an analysis of the possible effects of selection on them

Australian Journal of Agricultural Research ◽

10.1071/ar9680303 ◽

1968 ◽

Vol 19 (2) ◽

pp. 303

Author(s):

GH Brown ◽

HN Turner

Keyword(s):

Genetic Parameters ◽

Genetic Variance ◽

Statistical Significance ◽

Additive Genetic Variance ◽

Genetic Correlations ◽

Production Traits ◽

Average Value ◽

Selection History ◽

Order Of Magnitude ◽

Selection For

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Genetic analysis in the pasture grass Setaria sphacelata. II. Chemical composition, digestibility and correlations with yield

Australian Journal of Agricultural Research ◽

10.1071/ar9810311 ◽

1981 ◽

Vol 32 (2) ◽

pp. 311 ◽

Cited By ~ 3

Author(s):

RA Bray ◽

JB Hacker

Keyword(s):

Genetic Variance ◽

Additive Genetic Variance ◽

Seasonal Effects ◽

In Vitro Digestibility ◽

High Concentration ◽

Element Analysis ◽

Additive Variance ◽

Setaria Sphacelata ◽

Calcium And Magnesium ◽

Selection For

The progeny of a 7 x 7 diallel cross between plants randomly selected from a segregating tetraploid population (Setaria sphacelata var. sericea and var. splendida) was studied at Lawes, south-east Queensland, over a two year period, together with the parent clones. Plants were harvested at 6-week intervals (9-10 weeks in winter), dry weight was recorded, and family rows were bulked for analysis of in vitro digestibility (DMD) and for multi-element analysis. Concentrations of nitrogen, phosphorus, magnesium and calcium tended to be low in summer, and potassium concentration decreased during the two years of the experiment. In contrast magnesium, calcium and sodium increased. Genetic variance for digestibility was detected for only two of 14 harvests. Additive genetic variance was statistically significant, and generally consistent over harvests for nitrogen, potassium, sodium, calcium and magnesium. Family by season and family by year interactions were of a low order, showing that the expression of genetic variance was not strongly influenced by seasonal effects. Additive variance effects were erratic for phosphorus, sulfur, manganese, copper, zinc, silicon, iron, aluminium and boron, and selection for higher or lower concentrations of these elements would be unlikely to be successful. Nitrogen, potassium, calcium, magnesium and sodium were negatively and consistently correlated with dry matter yield. Over all harvests r was - 0.64, - 0.16, - 0.77, - 0.30 and - 0.44 respectively. With the possible exception of potassium, selection for higher concentrations of any of these minerals would result in a decrease in yield. Sodium was negatively correlated genetically with nitrogen, potassium, calcium and magnesium on an individual harvest or a season basis. For the total of all 15 harvests values for rg were -0.76, -0.88, -0.21 and -0.73 respectively. Nitrogen, potassium, calcium and magnesium were consistently positively correlated (for all harvests rg - 0.69 for all combinations), and selection for high concentration of any of these elements would result in an increase in the others, but a decrease in sodium. Significant genetic variation was detected for the mineral ratios K:(Ca + Mg) and calcium: phosphorus. However, these ratios are not known to adversely affect production in setaria pastures, and manipulation by breeding is not warranted. These examples show that there is the potential for breeding for mineral ratios in tropical forages.

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