scholarly journals The effects of inbreeding and artificial selection on reproductive fitness

1962 ◽  
Vol 3 (1) ◽  
pp. 110-138 ◽  
Author(s):  
B. D. H. Latter ◽  
Alan Robertson
Keyword(s):  
Artificial Selection ◽  
Large Population ◽  
Theoretical Models ◽  
Base Population ◽  
Selected Lines ◽  
Index Method ◽  
Competitive Index ◽  
Sib Mating ◽  
Selection For ◽  
Rate Of Decline

The competitive-index method of measurement of over all fitness in Drosophila has been used to measure the effect of inbreeding and of artificial selection for metric characters in a large population of Drosophila melanogaster. The technique itself was examined in detail with particular reference to its repeatability and to the effect on it of the modification of various environmental variables.With continued full-sib mating the decline in the competitive index was very rapid (it was reduced to a half by a single generation of full-sib mating) and there were no indications that interactions between deleterious genes at different loci were important in determining the rate of decline of fitness as inbreeding increased. Other unselected lines with ten pairs of parents in each generation were carried to serve as a control for the lines under artificial selection. At the same theoretical degree of inbreeding the control lines had a much higher average fitness than the lines produced by continued full-sib mating.From the base population lines were selected in both directions for abdominal bristles, sternopleural bristles and for wing length, there being two replicates in all cases. Four control lines were kept with the same number of parents as the selected lines. In all cases the selected lines declined in fitness below the value for the base population. However, in three of the lines the fitness was not significantly below the value for the control lines. The effect of artificial selection on fitness was asymmetrical, the decline being greater with down selection for all characters.The relevance of these results to various theoretical models is discussed. If the variation in these characters is actively maintained in the base population by the selection of heterozygotes then the results are consistent with an average selection disadvantage of homozygotes relative to heterozygotes of about 0·5%.

scholarly journals The limits to artificial selection for body weight in the mouse: III. Selection from crosses between previously selected lines

1967 ◽  
Vol 9 (1) ◽  
pp. 73-85 ◽  
Author(s):  
R. C. Roberts
Keyword(s):  
Body Weight ◽  
Artificial Selection ◽  
General Feature ◽  
Base Population ◽  
Response To Selection ◽  
Selected Lines ◽  
Large Size ◽  
Selection For ◽  
Linkage Of Genes

1. Four lines selected for large size were crossed to form a base population for further selection for high 6-week weight; three small lines were crossed similarly, and the crossbred population was selected for low 6-week weight.2. In every case, a cross between two selected lines resulted in heterosis increasing body weight. This shows that all of the selected lines were differentiated with respect to genes affecting body weight.3. Further selection for large size produced a stock whose mean weight was 25% higher than the largest of the original lines at its limit. But the response to selection for small size was slow, and after twenty-four generations of selection, the low weights of two of the original lines had not been recovered.4. The evidence points to linkage of genes affecting body weight in the mouse. It is suggested that this is a particular feature of crosses between previously selected lines, rather than a general feature of mouse populations.

scholarly journals Artificial selection with differing population structures

1980 ◽  
Vol 36 (2) ◽  
pp. 117-131 ◽  
Author(s):  
K. A. Rathie ◽  
F. W. Nicholas
Keyword(s):  
Close Agreement ◽  
Large Population ◽  
Additive Model ◽  
Directional Selection ◽  
Base Population ◽  
Average Response ◽  
Response To Selection ◽  
Bristle Number ◽  
Population Structures ◽  
Selection For

SUMMARYThe effect of subdivision of a population on response to artificial directional selection for abdominal bristle number in Drosophila melanogaster was compared using large, replicated lines. Three different population structures were compared: (i) selection in an Undivided, large population with 50 pairs of parents (treatment U); (ii) selection in each of 10 sublines which were reconstituted every 6th generation by Crossing after Culling the 5 lowest sublines (treatment CC); and (iii) selection in each of 10 sublines which were reconstituted every 6th generation by Crossing after Retaining all 10 sublines (treatment CR). At the end of three cycles of selection and crossing, neither CR nor CC was superior to U; sublining did not increase response to selection. These results agree with the predictions arising from an entirely additive model and provide no evidence for the presence of epistasis.A comparison of 50-pair lines (U) with several 5-pair lines was made over 31 generations. For the 50-pair lines, there was close agreement between response predicted from the base population (using ih2σp) and observed response throughout all 31 generations of selection. Although the best of the 5-pair lines exceeded the 50-pair lines in the early generations, average response to directional selection in the 5-pair lines soon fell behind that predicted from ih2σp, and soon reached a plateau.

Mating frequency in male Japanese quail: crosses among selected and unselected lines

1983 ◽  
Vol 25 (5) ◽  
pp. 450-456 ◽  
Author(s):  
D. E. Bernon ◽  
P. B. Siegel
Keyword(s):  
Genetic Variation ◽  
Mating Behavior ◽  
Japanese Quail ◽  
Mating Frequency ◽  
Base Population ◽  
Selected Lines ◽  
Gland Size ◽  
Parental Lines ◽  
Selection For ◽  
Cloacal Gland

The genetics of mating behavior in Japanese quail was investigated in replicated lines selected for high or low number of completed matings and the random bred control which served as the base population for the selected lines. Comparisons involved the parental lines, F1, F2, and backcross generations. Results indicate that mating frequency is influenced by additive and nonadditive genetic variation with the former being the primary heritable influence. The relationships between mating behavior, cloacal gland size, and relative aggressiveness suggest that selection for mating frequency influences factors commonly affecting these traits.

TWO-WAY SELECTION ON PUPAL WEIGHT WITH DIFFERENT DEGREES OF INBREEDING IN TRIBOLIUM CASTANEUM

1974 ◽  
Vol 16 (4) ◽  
pp. 765-775 ◽  
Author(s):  
P. Y. Jui ◽  
G. W. Friars
Keyword(s):  
Tribolium Castaneum ◽  
Linear Response ◽  
Significant Interaction ◽  
Pupal Weight ◽  
Base Population ◽  
Significant Progress ◽  
Selected Lines ◽  
Selection Limit ◽  
Selection For ◽  
Seven Generations

Responses to selection for high and low pupal weight in Tribolium castaneum under four different inbreeding systems and two different relative humidities (40 and 70%) were observed for seven generations. By the seventh generation, the coefficients of inbreeding ranged from 0.79 in the full sib lines to 0.12 in the control lines.Heritability of pupal weight estimated by mid-parent offspring regression from the base population was around 0.30 which is lower than the estimates obtained by Bell (1969). However, realized heritabilities were around 0.50. Significant progress was observed for both upward and downward selection. A linear response in pupal weight was observed for most of the selected lines, suggesting that the selection limit had not been reached.Inbreeding caused a reduction of approximately two offspring per 10% increment in the inbreeding coefficient.Asymmetric responses were noted in conjunction with the significant interaction of the degree of inbreeding and the direction of selection.

EFFECT OF SELECTION FOR GROWTH AND FOR BREAST DEVELOPMENT ON KEEL DEFECTS IN BROILERS

1962 ◽  
Vol 42 (2) ◽  
pp. 203-210 ◽  
Author(s):  
E. S. Merritt ◽  
M. Zawalsky ◽  
R. D. Crawford ◽  
S. B. Slen
Keyword(s):  
Lower Incidence ◽  
Breast Development ◽  
Base Population ◽  
Control Strain ◽  
Selected Lines ◽  
The Third ◽  
Definite Relationship ◽  
Rate Of Growth ◽  
Selection For

Data from the third and fourth generations of a number of lines selected exclusively for growth, and of a number selected solely for breast angle, showed that selection for these traits had an effect on the incidence of crooked keels and breast blisters in 63-day-old broilers. The base population of these selected lines was a meat-control strain and a sample of this strain was reared with each hatch of the selected lines.Lines selected for growth had the highest incidence of both crooked keels and breast blisters. The lines selected for breast angle had a lower incidence of these defects than the controls, even though they did not differ from the controls in 63-day weight. It was concluded that there is a definite relationship between rate of growth, breast development and the incidence of keel defects. Market grading data on a sample of birds from these lines reflected these differences in keel defects. The market grades for conformation were lowest in the growth lines and highest in the breast lines.

scholarly journals The number of loci affecting a quantitative trait in Drosophila melanogaster revealed by artificial selection

1983 ◽  
Vol 42 (2) ◽  
pp. 137-149 ◽  
Author(s):  
Araceli Gallego ◽  
Carlos López-Fanjul
Keyword(s):  
Initial Response ◽  
Selection Method ◽  
Base Population ◽  
Response To Selection ◽  
Family Selection ◽  
Selected Lines ◽  
Additive Variance ◽  
Bristle Number ◽  
Selection Limit ◽  
Selection For

SUMMARYIndividual and within-full-sib family selection for low sternopleural bristle number was carried out for 17 generations, with six replicate lines for each selection method. Our results can be summarized as follows: (1) the response to selection was exhausted very quickly, (2) the additive variance of the selected lines declined rapidly, (3) the variation in response to selection decreased as selection progressed, (4) genetic differences among replicates at the selection limit were small, (5) individual selection resulted in a higher initial response than within-family selection, but similar limits were achieved with both procedures. These observations are consistent with the hypothesis that the pattern of response to selection is due to the segregation in the base population of only a few loci with large effects, at intermediate frequencies.

scholarly journals The Response to Artificial Selection Due to Autosomal Genes of Large Effect II. The Effects of Linkage on Limits to Selection in Finite Populations

1965 ◽  
Vol 18 (5) ◽  
pp. 1009 ◽  
Author(s):  
BDH Latter
Keyword(s):  
Artificial Selection ◽  
Simulation Technique ◽  
Linkage Equilibrium ◽  
Base Population ◽  
Finite Populations ◽  
Selection For ◽  
Definition Of

The limits to artificial selection for pairs of linked additive loci of equal proportionate effect, starting from a base population in linkage equilibrium, have been studied by means of a simulation technique on a CDC 3600 computer. Particular attention has been paid to the case of genes of large effect, making use of the definition of the selective value of a genotype given in the first paper of this series.

scholarly journals The limits to artificial selection for body weight in the mouse II. The Genetic Nature of the Limits

1966 ◽  
Vol 8 (3) ◽  
pp. 361-375 ◽  
Author(s):  
R. C. Roberts
Keyword(s):  
Body Weight ◽  
Natural Selection ◽  
Artificial Selection ◽  
Sharp Increase ◽  
Genetic Variance ◽  
Additive Genetic Variance ◽  
Base Population ◽  
Relaxed Selection ◽  
Genetic Nature ◽  
Selection For

1. The effects of long-continued selection for body weight in two lines of mice, one large and one small, are described.2. The large line showed a sharp increase in weight after remaining at an apparent limit for twenty generations. A rare combinational event is suggested as the most likely explanation.3. Reversed and relaxed selection from the large line at the limit failed to yield any response. This indicates that effectively, the additive genetic variance in this line had been exhausted.4. In contrast, the small line at the limit regressed slightly towards the base population when selection was relaxed. Reversed selection yielded a ready response until a new limit was apparently reached. Loci affecting body weight in this line had therefore not been fixed by selection.5. Natural selection, operating on viability between conception and the time when the selection was made, appears to explain best the lack of fixation in the small line.6. Attention is drawn to the necessity of more experimental work to elucidate the genetic nature of the limits to artificial selection.

Differential responses to selection for aluminium stress tolerance in triticale

2002 ◽  
Vol 53 (12) ◽  
pp. 1295 ◽  
Author(s):  
X. G. Zhang ◽  
R. S. Jessop ◽  
the late F. Ellison
Keyword(s):  
Stress Tolerance ◽  
Acid Stress ◽  
Directional Selection ◽  
Base Population ◽  
Al Tolerance ◽  
Selected Lines ◽  
Root Regrowth ◽  
Tolerance Response ◽  
Selection For ◽  
Nutrient Solutions

A directional selection program was initiated to select triticale genotypes with improved aluminium (Al) tolerance and presumably acid-stress tolerance. Two consecutive cycles of 2-way selection for either high or low apparent Al tolerances from a base population, Tahara, resulted in the production of 6 selected lines, whose progenies were tested for Al tolerance response in terms of root regrowth characteristics in nutrient solutions to assess selection effectiveness. In addition, 1 cycle of 2-way selection from 2 other base populations, Empat and 19th ITSN 70-4, resulted in 4 selected lines.Selective responses differed among selected lines, depending largely on the direction of the selection made and, to a lesser extent, on the genetic background of the original population. Upward selection for longer root regrowth produced progeny with more highly Al-tolerant plants. Although varying estimates of realised heritability were generated, the 2 cycles of upward selection resulted in an enhanced Al tolerance of 14.5% in the progeny A9701 derived from the base population Tahara. These results suggest that directional selection based on longer root regrowth in nutrient solutions was effective in improving Al tolerance. A pot-culture experiment showed that the second selection generation (S2) Al-tolerant lines were more productive than their moderately Al-tolerant counterparts, further implicating the effectiveness of directional selection in enhancing Al stress tolerance and plant productivity.

ESTIMASI NILAI HERITABILITAS BOBOT IKAN MAS VARIETAS PUNTEN DALAM PROGRAM SELEKSI INDIVIDU

2016 ◽  
Vol 11 (3) ◽  
pp. 217
Author(s):  
Estu Nugroho ◽  
Budi Setyono ◽  
Mochammad Su’eb ◽  
Tri Heru Prihadi
Keyword(s):  
Body Weight ◽  
Selection Response ◽  
Base Population ◽  
Breeding Programs ◽  
Male And Female ◽  
Body Weight Trait ◽  
Population Selection ◽  
Selection For ◽  
Weight Trait ◽  
Selection Of

Program pemuliaan ikan mas varietas Punten dilakukan dengan seleksi individu terhadap karakter bobot ikan. Pembentukan populasi dasar untuk kegiatan seleksi dilakukan dengan memijahkan secara massal induk ikan mas yang terdiri atas 20 induk betina dan 21 induk jantan yang dikoleksi dari daerah Punten, Kepanjen (delapan betina dan enam jantan), Kediri (tujuh betina dan 12 jantan), Sragen (27 betina dan 10 jantan), dan Blitar (15 betina dan 11 jantan). Larva umur 10 hari dipelihara selama empat bulan. Selanjutnya dilakukan penjarangan sebesar 50% dan benih dipelihara selama 14 bulan untuk dilakukan seleksi dengan panduan hasil sampling 250 ekor individu setiap populasi. Seleksi terhadap calon induk dilakukan saat umur 18 bulan pada populasi jantan dan betina secara terpisah dengan memilih berdasarkan 10% bobot ikan yang terbaik. Calon induk yang terseleksi kemudian dipelihara hingga matang gonad, kemudian dipilih sebanyak 150 pasang dan dipijahkan secara massal. Didapatkan respons positif dari hasil seleksi berdasarkan bobot ikan, yaitu 49,89 g atau 3,66% (populasi ikan jantan) dan 168,47 g atau 11,43% (populasi ikan betina). Nilai heritabilitas untuk bobot ikan adalah 0,238 (jantan) dan 0,505 (betina).Punten carp breeding programs were carried out by individual selection for body weight trait. The base population for selection activities were conducted by mass breeding of parent consisted of 20 female and 21 male collected from area Punten, eight female and six male (Kepanjen), seven female and 12 male (Kediri), 27 female and 10 male (Sragen), 15 female and 11 male (Blitar). Larvae 10 days old reared for four moths. Then after spacing out 50% of total harvest, the offspring reared for 14 months for selection activity based on the sampling of 250 individual each population. Selection of broodstock candidates performed since 18 months age on male and female populations separately by selecting based on 10% of fish with best body weight. Candidates selected broodstocks were then maintained until mature. In oder to produce the next generation 150 pairs were sets and held for mass spawning. The results revealed that selection response were positive, 49.89 g (3.66%) for male and 168.47 (11.43%) for female. Heritability for body weight is 0.238 (male) and 0.505 (female).

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