Trends in Productivity of U.S. Crops and Long-term Selection

2010 ◽  
pp. 89-108
Author(s):  
William F. Tracy ◽  
Irwin L. Goldman ◽  
Allison E. Tiefenthaler ◽  
Margaret A. Schaber
Keyword(s):  
Term Selection

Developing twinning cattle for commercial production

2008 ◽  
Vol 48 (7) ◽  
pp. 930 ◽  
Author(s):  
L. J. Cummins ◽  
C. A. Morris ◽  
B. W. Kirkpatrick
Keyword(s):  
United States ◽  
Production Systems ◽  
The United States ◽  
Research Centre ◽  
Commercial Application ◽  
Term Selection ◽  
Calf Survival ◽  
Potential Benefits ◽  
Meat Animal

Long-term selection programs in the United States and New Zealand have developed twinning herds. In Nebraska, the United States Meat Animal Research Centre population had a calving rate of 1.56 per parturition in 2004. They have shown that the location of ovulation has an important effect on the success of pregnancy and that ovulations ≥3 are probably undesirable. These cattle have issues associated with calving difficulty and calf survival, which present challenges for commercial application. Intensive management using existing technology and/or future genetic improvement to address these traits are required to realise the potential benefits to beef production systems.

Long-Term Selection in Hybrid Sorghum Breeding Programs

Crop Science ◽  
2019 ◽  
Vol 59 (1) ◽  
pp. 150-164 ◽  
Author(s):  
Brian K. Pfeiffer ◽  
Dennis Pietsch ◽  
Ronnie W. Schnell ◽  
William L. Rooney
Keyword(s):  
Breeding Programs ◽  
Term Selection ◽  
Sorghum Breeding

scholarly journals LONG-TERM SELECTION RESPONSE FOR 12-DAY LITTER WEIGHT IN MICE

Genetics ◽  
1972 ◽  
Vol 72 (1) ◽  
pp. 129-142
Author(s):  
E J Eisen
Keyword(s):  
Body Weight ◽  
Genetic Correlation ◽  
Half Life ◽  
Selection Process ◽  
Selection Response ◽  
Exponential Model ◽  
Correlated Response ◽  
Term Selection ◽  
Litter Weight

ABSTRACT Long-term selection for increased 12-day litter weight in two replicate lines (W2, W3) of mice resulted in an apparent selection limit at about 17 generations. Quadratic polynomial and exponential models were fitted to the data in order to estimate the plateaued response and half-life of the selection process. Using the polynomial results, the half-life estimates were 4.5 and 8.6 generations for W2 and W3, respectively. The plateaued responses were 5.1 and 5.8 g which, when expressed in phenotypic standard deviation units, became 1.1 and 1.3. The exponential model provides similar estimates. A negative association between 12-day litter weight and fitness was not considered to be an adequate explanation for the plateau since there was no decrease in fertility of the selected lines. Evidence that exhaustion of genetic variability was not the cause of the plateau came from the immediate response to reverse selection. It was proposed that the plateau may be due to a negative genetic correlation between direct and maternal genetic effects, which would be expected to occur after many generations of selection. There were positive correlated responses in both replicates for adult body weight, which was in agreement with the positive genetic correlation between preweaning and postweaning body weight. The expected positive correlated response for number born was realized in only one of the replicates.

scholarly journals Mutant alleles differentially shape cattle complex traits and fitness

2021 ◽  
Author(s):  
Ruidong Xiang ◽  
Ed Breen ◽  
Sunduimijid Bolormaa ◽  
Christy Vander Jagt ◽  
Amanda Chamberlain ◽  
...  
Keyword(s):  
Somatic Cell ◽  
Cell Count ◽  
Complex Traits ◽  
Somatic Cell Count ◽  
Protein Concentration ◽  
Opposite Effect ◽  
Gestation Length ◽  
Hybrid Vigour ◽  
Term Selection

Classical mutations tend to be deleterious to traits and fitness. Is this the case for mutations with polygenic effects? Here, we infer ancestral and mutant alleles (MAs) for 8 million sequence variants in 113k cattle and quantify the effects of MA on 37 complex traits. Heterozygosity at sites conserved across 100 vertebrates increase fertility, stature, and milk production, positively associating these traits with fitness. MAs decrease fat and protein concentration in milk and stature but increase gestation length and somatic cell count in milk indicative of mastitis. However, the frequency of MAs that decrease fat and protein concentration and stature and increase gestation length and somatic cell count is lower than the frequency of MAs with the opposite effect. These results suggest bias in the direction of effect of mutation (e.g. towards reduced protein in milk), but selection operating to reduce the frequency of these MAs. MAs with a large-effect decrease protein and milk yield, while small-effect MAs increase the two traits. These results imply two classes of genomic sites subject to long-term selection: sites conserved across vertebrates show hybrid vigour while sites subject to less long-term selection show a bias in mutation towards alleles that are selected against.

Individuals, hierarchies and processes: towards a more complete evolutionary theory

Paleobiology ◽  
1984 ◽  
Vol 10 (2) ◽  
pp. 146-171 ◽  
Author(s):  
Elisabeth S. Vrba ◽  
Niles Eldredge
Keyword(s):  
Downward Causation ◽  
Species Selection ◽  
Process Selection ◽  
Term Selection ◽  
Hierarchical Levels ◽  
Character Variation ◽  
Long Term Trend ◽  
Interlevel Causation ◽  
Selection Of

Hierarchy is a central phenomenon of life. Yet it does not feature as such in traditional biological theory. The genealogical hierarchy is a nested organization of entities at ascending levels. There are phenomena common to all levels: (1) Entities such as genomic constituents, organisms, demes, and species are individuals. (2) They have aggregate characters (statistics of characters of subparts), but also emergent characters (arising from organization among subparts). Character variation changes by (3) introduction of novelty and (4) sorting by differential birth and death. Causation of introduction and sorting of variation at each level may be (5) upward from lower levels, (6) downward from higher levels, or (7) lodged at the focal level. The term “selection” applies to only one of the possible processes which cause sorting at a focal level. Neo-Darwinian explanations are too narrow, both in the levels (of genotypes and phenotypes) and in the directive process (selection) which are stressed. The acknowledgment of additional, hierarchical phenomena does not usually extend beyond lip service. We urge that interlevel causation should feature centrally in explanatory hypotheses of evolution. For instance, a ready explanation for divergence in populations is “selection of random mutants.” But upward causation from genome dynamics (or downward causation from the hierarchical organism) to the directed introduction of mutants may be more important in a given case. Similarly, a long-term trend is traditionally explained as additive evolution in populations. But sorting among species may be the cardinal factor, and the cause may not be species selection but upward causation from lower levels. A general theory of biology is a theory of hierarchical levels—how they arise and interact. This is a preliminary contribution mainly to the latter question.

Long-Term Selection for Pupal Weight in Tribolium castaneum

2010 ◽  
pp. 211-224
Author(s):  
W. M. Muir ◽  
D. Miles ◽  
A. E. Bell
Keyword(s):  
Tribolium Castaneum ◽  
Pupal Weight ◽  
Term Selection ◽  
Selection For
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