scholarly journals Selection for Increased Budbreak in Apple

2003 ◽  
Vol 128 (3) ◽  
pp. 363-373 ◽  
Author(s):  
Iwan F. Labuschagné ◽  
J.H. Louw ◽  
Karin Schmidt ◽  
Annalene Sadie
Keyword(s):  
Genetic Variance ◽  
Screening Method ◽  
Selection Response ◽  
Significant Response ◽  
Correlated Response ◽  
Realized Heritability ◽  
Early Screening ◽  
Adult Trees ◽  
Selection For ◽  
Combined Selection

Significant response to selection for budbreak number (NB) based on data recorded on 1-year-old shoots of young apple (Malus sylvestris (L.) Mill var. domestica (Borkh.) Mansf.) seedlings (Expt. I) and branches from adult seedling trees (Expt. II) has been demonstrated in clonally propagated seedling trees. Between family variation for NB was low and masked by year × family interaction effects. Realized heritability for NB was estimated as 40% to 60%. Correlated response in uniformity and position of budbreak, and in the number and length of side shoots, was found. Association between the time of budbreak (TB) and NB, according to midparent and cross groupings, and according to the parental means, indicate a positive genetic correlation between these traits. Where data on adult trees were used as a measure of selection response and tested on young clonal trees, significant response and genetic variation was shown, confirming the presence of utilizable genetic variance and that this procedure may be successfully applied as an early screening method for increased budbreak in adult trees. Combined selection utilizing genetic variance between crosses as well as within crosses is proposed as the best procedure to increase the frequency of seedlings with increased budbreak and to improve adaptation to low winter chilling conditions.

scholarly journals EFFECTS OF POPULATION SIZE AND SELECTION INTENSITY ON SHORT-TERM RESPONSE TO SELECTION FOR POSTWEANING GAIN IN MICE

Genetics ◽  
1973 ◽  
Vol 73 (3) ◽  
pp. 513-530
Author(s):  
J P Hanrahan ◽  
E J Eisen ◽  
J E Legates
Keyword(s):  
Population Size ◽  
Selection Response ◽  
Selection Intensity ◽  
Realized Heritability ◽  
Family Selection ◽  
Effective Population ◽  
Population Sizes ◽  
Selection For ◽  
Selection Intensities ◽  
Term Response

ABSTRACT The effects of population size and selection intensity on the mean response was examined after 14 generations of within full-sib family selection for postweaning gain in mice. Population sizes of 1, 2, 4, 8 and 16 pair matings were each evaluated at selection intensities of 100% (control), 50% and 25% in a replicated experiment. Selection response per generation increased as selection intensity increased. Selection response and realized heritability tended to increase with increasing population size. Replicate variability in realized heritability was large at population sizes of 1, 2 and 4 pairs. Genetic drift was implicated as the primary factor causing the reduced response and lowered repeatability at the smaller population sizes. Lines with intended effective population sizes of 62 yielded larger selection responses per unit selection differential than lines with effective population sizes of 30 or less.

scholarly journals Selection for the length of the spermatozoan midpiece in the mouse

1970 ◽  
Vol 16 (3) ◽  
pp. 261-275 ◽  
Author(s):  
D. M. Woolley
Keyword(s):  
Electron Microscope Study ◽  
Selection Response ◽  
Sperm Cells ◽  
Realized Heritability ◽  
Family Selection ◽  
Selected Lines ◽  
Selection Programme ◽  
Proportionate Change ◽  
The Subject ◽  
Selection For

SUMMARYA subcellular dimension, the length of the spermatozoan midpiece, has been the subject of a two-way selection programme in mice. After thirteen generations of within-family selection the divergence between the selected lines amounted to 5·4 phenotypic standard deviations. The realized heritability was found to be 0·76 ± 0·02, dominance and commonenvironmental effects being apparently very small. The reality of the selection response was verified in measurements on live spermatozoa. Other measurements have shown that the change in the length of the midpiece has been independent of its width, and has occurred without a proportionate change in the length of the main-piece of the flagellum. An electron microscope study has shown that the selection has, in fact, brought about changes in the quantity of mitochondrial material in the sperm cells.

scholarly journals INTERACTION BETWEEN NATURAL SELECTION FOR HETEROZYGOTES AND DIRECTIONAL SELECTION

Genetics ◽  
1974 ◽  
Vol 76 (1) ◽  
pp. 163-168
Author(s):  
Margrith Wehrli Verghese
Keyword(s):  
Natural Selection ◽  
First Generation ◽  
Genetic Variance ◽  
Selection Response ◽  
Directional Selection ◽  
Simple Function ◽  
Small Populations ◽  
Gene Frequencies ◽  
Selection For

ABSTRACT When directional selection for an additively inherited trait is opposed by natural selection favoring heterozygous genotypes a selection plateau may be reached where genetic variance is present. The amount of response when this plateau is reached is a simple function of the selection response in the first generation and the intensity of natural selection. When selection is practiced in small populations, the sizes of the initial equilibrium gene frequencies are at least as important as the intensity of natural selection in determining the probability of fixing desirable alleles.

CORRELATED RESPONSE IN BIRTH WEIGHT, GROWTH RATE AND CARCASS MERIT UNDER SINGLE-TRAIT SELECTION FOR YEARLING WEIGHT IN BEEF SHORTHORN CATTLE

1974 ◽  
Vol 54 (2) ◽  
pp. 117-125 ◽  
Author(s):  
B. BECH ANDERSEN ◽  
H. T. FREDEEN ◽  
G. M. WEISS
Keyword(s):  
Birth Weight ◽  
Selection Response ◽  
Correlated Response ◽  
Weight Growth ◽  
Cumulative Selection ◽  
Selection For ◽  
Carcass Merit ◽  
Least Squares Estimates ◽  
Daily Gain

Data for male calves from the most recent 5 yr of a long-term (11 yr) selection experiment with beef Shorthorn cattle were analyzed to calculate the direct and correlated response of intensive selection for yearling weight on growth and carcass characteristics. Least squares estimates of line differences (select vs. control) for the final year indicated cumulative selection responses [Formula: see text] of 41.5 and 46.2 kg in yearling weight for the two herds. Associated with this selection response in the two herds were increases in birth weight (3.6 and 3.0 kg; [Formula: see text]) in weaning weight (16.2 and 7.8 kg; [Formula: see text] and NS) and daily gain from birth to 10 mo of age (104 and 118; [Formula: see text]). The indirect effects on carcass merit were higher percentage of bone (0.6 and 0.7; [Formula: see text]), and a reduced lean/bone ratio (−0.19 and −0.11; [Formula: see text] and NS). Other differences were not statistically meaningful. The heritabilities for growth characters calculated as son/sire regressions were: birth wt 0.30 ± 0.13; weaning wt 0.34 ± 0.22; yearling wt 0.47 ± 0.23; weaning wt/yearling 0.38 ± 0.21; and daily gain 0.22 ± 0.16. For the most important carcass merit measurements the heritabilities, calculated as half-sib correlations, were: % lean 0.03 ± 0.21; % bone 0.86 ± 0.29; % fat (ext.) 0.01 ± 0.21; % fat (int.) 0.19 ± 0.23; lean/bone 0.72 ± 0.28; and hindquarter wt/forequarter wt 0.24 ± 0.24.

Measurement of fleece wettability in sheep and its relationship to susceptibility to fleece rot and blowfly strike

1982 ◽  
Vol 33 (1) ◽  
pp. 141 ◽  
Author(s):  
L Pascoe
Keyword(s):  
Genetic Variance ◽  
Additive Genetic Variance ◽  
Genetic Correlations ◽  
Economic Importance ◽  
Correlated Response ◽  
Response To Selection ◽  
Significant Incidence ◽  
The Mean ◽  
Selection For ◽  
The One

Fleece wettability in sheep is a character believed to be related to susceptibility to fleece rot and blowfly strike. The present study was undertaken to investigate that hypothesis and to assess wettability as a possible character for a selection program. Wool samples were taken from two flocks which had been subject to selection for wool quality and resistance to fleece rot and a third flock which was unselected. The wettabilities of about 800 samples were determined. The results were found to be repeatable and the technique was capable of distinguishing between sheep. Some problems of measurement are discussed. In the one flock with a significant incidence of fleece rot, susceptibility to fleece rot was found to be associated with higher wettabilities. The mean wettability and the variance were found to be significantly higher in the unselected flock than in the two selected flocks. The heritability of wettability was estimated in the two selected flocks and was found to be low. It is argued that there is likely to be more additive genetic variance in the unselected flock and that the observed difference in wettability was due to a correlated response to selection for resistance to fleece rot. It is considered that further work on the heritability of wettability and its genetic correlations with other characters of economic importance could be fruitful.

scholarly journals Response in Genotypic and Breeding Value to a Single Generation of Divergent Selection for Fresh Fruit Color in Strawberry

1995 ◽  
Vol 120 (2) ◽  
pp. 270-273 ◽  
Author(s):  
Douglas V. Shaw ◽  
Erik J. Sacks
Keyword(s):  
Genetic Variance ◽  
Breeding Population ◽  
Selection Response ◽  
Fruit Color ◽  
Divergent Selection ◽  
Fresh Fruit ◽  
Breeding Value ◽  
Genetic Variances ◽  
Selection For ◽  
Genotypic Selection

Four sets of selected strawberry (Fragaria ×ananassa Duch.) genotypes were generated from within a single breeding population to evaluate the correspondence between predicted and realized selection response for fresh fruit color traits. Genotypes were selected for extreme phenotypes, dark or light, of either internal or external color value (CIELAB L*). Genotypic selection response was evaluated empirically by scoring fruit from the clonal derivatives of these selected genotypes, and response for breeding value was estimated by scoring the offspring of crosses performed among a subset of the genotypes within each selected set. Realized selection response was slightly larger than predicted for internal and external L* when calculated for selected genotypes. Also, more than half of the selected genotypes had genotypic values for L* outside the range of the original parents, providing evidence for transgressive segregation. Realized selection response for breeding value in exterior and interior color was slightly less than predicted. Compared in a different way, genotypic selection response for external color was significantly greater than selection response for breeding value, whereas genotypic and breeding value responses did not differ for internal color. These observations suggest the presence of some nonadditive genetic variance for external color but support the conclusion that the heritabilities predicted previously were reasonably accurate. Estimates of variance components within each of the offspring populations demonstrated that genetic variances were modified substantially by one generation of selection. Selection for dark fruit color reduced genetic variance to nonsignificant levels, with internal color more affected than external color. The total genetic variances within both of the offspring populations from parents selected for light color were changed little by one generation of selection, but substantial dominance variance was detected that had not been found in the original population. The rapid response to selection and large changes in the distribution of genetic variances may indicate the presence of a few genes with comparatively large effect in strawberry color expression. Additional divergent selection response can be expected, but primarily in the direction of light fruit color.

scholarly journals Genetic Variability And Selection Response To Heat Tolerance Through Membrane Thermostability In Spring Wheat (Triticum Aestivum L)

1970 ◽  
Vol 23 (2) ◽  
pp. 15-22
Author(s):  
NCD Barma ◽  
MA Islam ◽  
MA Hakim ◽  
DKR Sarker
Keyword(s):  
Genetic Variability ◽  
Heat Tolerance ◽  
Selection Response ◽  
Research Centre ◽  
Direct Selection ◽  
Realized Heritability ◽  
Response To Selection ◽  
Early Generation ◽  
Membrane Thermostability ◽  
Selection For

The present investigation was undertaken to study the genetic variability and selection response of heat tolerance measured through membrane thermostability (MTS) in F2 derived F4 and F5 generations of five wheat crosses: Kanchan × Gourab, Gourab × Fang 60, Kanchan × Pavon 76, Gourab × Pavon76 and Fang 60 × Pavon76. Each cross was consisted of 65, 60, 77, 72 and 64 F4 bulks including two parents. The study was conducted both in the field and laboratory of Wheat Research Centre, Dinajpur during 2002-03 and 2003-04. A completely randomized design for laboratory experiment and randomized complete block design for field experiments was followed with three replications. Acquired thermal tolerance through Membrane Thermo-stability assay was performed in controlled environment as per method described by Ibrahim and Quick (2001). Other morpho-physiological traits were measured from field experiment. The crosses Kanchan × Gourab, Kanchan × Pavon 76 and Fang 60 × Pavon76 showed high genetic variability with high population mean for MTS in F4 bulks. These crosses also exhibited high-observed response to selection, realized heritability and heritability in standard unit indicating expected good gain through early generation selection. Direct response to selection for this trait was significant in these crosses in F5 generation. Direct selection for MTS significantly improved biomass, grain yield, thousand grain weight, grain filling rate and canopy temperature depression in crosses Kanchan × Pavon 76, Gourab × Pavon76 and Fang 60 × Pavon76 with few exceptions. Direct selection of MTS also improved chlorophyll retention at 21 days after anthesis in crosses Gourab × Fang 60 and Gourab × Pavon76. Significant intergeneration correlations (F4 vs. F5) were observed for MTS in all five crosses studied indicating possibility of effective improvement of this trait through selection in early generation.   Key words: Membrane thermostability; selection response; realized heritability; intergeneration correlation.DOI: http://dx.doi.org/10.3329/bjpbg.v23i2.9320 Bangladesh J. Pl. Breed. Genet., 23(2): 15-22, 2010

Estimation of Genetic Parameters and Selection Response for Reproductive and Growth Traits in Rideau-Arcott sheep

2020 ◽  
Author(s):  
Mohammed Naser Boareki ◽  
Luiz Brito ◽  
Angela Cánovas ◽  
V.R. Osborne ◽  
Flavio S Schenkel
Keyword(s):  
Litter Size ◽  
Genetic Parameters ◽  
Growth Traits ◽  
Reproductive Traits ◽  
Selection Response ◽  
Direct Selection ◽  
Correlated Response ◽  
Response To Selection ◽  
Weaning Weight ◽  
Selection For

The goal of this study was to estimate genetic parameters and predict direct and correlated response to selection for lamb growth traits and ewe reproductive traits, based on single trait selection or combining multiple traits in an optimum index that targets total litter post-weaning weight in the first lambing as the main selection goal. Heritability estimates ranged from 0.04 to 0.19. Genetic correlations between growth and reproductive traits ranged from -0.24 to 0.15. The indirect response to selection for reproductive traits in later lambings, by selecting on first lambing performance, was 11 to 25% greater than direct selection. The response to indirect selection for composite reproductive traits, i.e. total weaning weight or total post-weaning weight, by selecting on individual lamb weaning weight or post-weaning weight was 1 to 69% greater than direct selection, but it was accompanied by a negative response on litter size. However, combining alternate growth and reproductive traits in optimum selection index resulted in correlated response of up to 96% greater than direct selection response for reproductive traits without a negative response on litter size. Therefore, multiple trait selection using an index of component traits was more effective than direct selection for a composite trait.

The effects of alternated cycles of full-sib and random mating on selection for pupa weight in Tribolium castaneum

1985 ◽  
Vol 27 (2) ◽  
pp. 251-254 ◽  
Author(s):  
Nicole Dion ◽  
Francis Minvielle
Keyword(s):  
Mating System ◽  
Tribolium Castaneum ◽  
Random Mating ◽  
Selection Response ◽  
Inbred Lines ◽  
Pupal Weight ◽  
Realized Heritability ◽  
Differential Selection ◽  
Selection For

Individual responses to selection for high pupal weight in Tribolium castaneum under two types of mating, cyclic full-sib random-mating system and random mating, were observed for 15 generations. No significant differences have been observed between the two types of mating for the selection response, differential selection, realized heritability, and the number of larvae per generation. Realized heritability of the pupal weight was 0.33 ± 0.02 and 0.42 ± 0.02 for the inbred lines and for the random-mated lines, respectively.Key words: inbreeding, pupa weight, Tribolium.

CHANGES IN BEEF CATTLE PERFORMANCE AFTER TEN YEARS OF YEARLING WEIGHT SELECTION

1990 ◽  
Vol 70 (4) ◽  
pp. 1017-1028 ◽  
Author(s):  
J. C. OLTHOFF ◽  
G. H. CROW ◽  
G. W. RAHNEFELD
Keyword(s):  
Beef Cattle ◽  
Average Daily Gain ◽  
Age Distribution ◽  
Selection Response ◽  
Correlated Response ◽  
Control Line ◽  
Short Period ◽  
Selection For ◽  
The Difference ◽  
Daily Gain

Selection for yearling weight, a trait with relatively high heritability, in beef cattle should lead to a significant response in a short period of time. Changes should also occur in correlated and component traits. Data from 10 yr of yearling weight selection in beef Shorthorn cattle were used to quantify the response in correlated calf and cow traits. Selection response was measured as the difference between the performance of the select line and a corresponding control line. Annual response to selection for bull and heifer calves, respectively, averaged 5.1 and 4.3 kg for yearling weight, 2.1 and 1.6 kg for weaning weight, 0.3 and 0.2 kg for birth weight, 0.016 and 0.014 kg d−1 for post-weaning average daily gain and 0.010 and 0.007 kg d−1 for preweaning average daily gain. There were no significant changes in calf survival or cow reproductive performance. Cow weights increased 4.5 kg yr−1 for 2-yr-old heifers, similar to the yearling weight response, but only 1.3 kg yr−1 for all cows because of the time delay caused by the age distribution of the breeding herd. Yearling weight increases were brought about by increases in the individuals genetic potential for gain, primarily postweaning. Response to yearling weight selection would be relatively easy to achieve for beef producers. Some additional costs would be incurred, however, and the environmental effects, which were large, would have to be monitored. Key words: Beef cattle, yearling weight, selection response, correlated response

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