scholarly journals Additive Genetic Effects for Resistance to Foliar Powdery Mildew in Strawberry Revealed through Divergent Selection

2014 ◽  
Vol 139 (3) ◽  
pp. 310-316
Author(s):  
Colleen Kennedy ◽  
Luis F. Osorio ◽  
Natalia A. Peres ◽  
Vance M. Whitaker
Keyword(s):  
Powdery Mildew ◽  
Genetic Correlations ◽  
Breeding Population ◽  
Field Trials ◽  
Divergent Selection ◽  
Response To Selection ◽  
Additive Variance ◽  
Susceptible Population ◽  
High Heritability ◽  
Selection For

Powdery mildew (PM) of strawberry (Fragaria sp.) is a ubiquitous, wind-spread disease caused by the obligate parasite Podosphaera aphanis. To control PM, multiple fungicide applications are necessary each season, and none of the major cultivars in Florida have high levels of resistance. Therefore, the objectives of this study were to observe the response to selection and to estimate genetic parameters for PM and related traits in the University of Florida breeding population. In 2010, clonally replicated individuals from seven biparental crosses arising from 11 parents were included in a field trial in which clonally replicated seedlings were evaluated visually for percent coverage of PM mycelium using a modified Horsfall-Barratt scale of 0 to 6. Broad- (H2) and narrow-sense (h2) heritabilities for PM score were (mean ± se) 0.50 ± 0.08 and 0.40 ± 0.39, respectively, for the base population. After the second round of selection in the resistant population, no additive variance was detected, indicating that alleles for PM resistance had become fixed. In contrast, after two rounds of divergent selection in the susceptible population, there remained considerable additive variance (h2 = 0.42 ± 0.65). Moderate to high heritability estimates and a clear response to selection indicate that resistance to PM is genetically controlled through mostly additive effects. Selection of parents based on field trials with natural inoculum should result in good progress toward more resistant cultivars. The consistently moderate to strong genotypic and genetic correlations among PM and canopy density (CD) indicate that selection for PM resistance will result in reduced CD. Therefore, CD must be monitored over successive rounds of selection for low levels of PM to prevent CD falling below the commercially acceptable range.

Genetic loci responding to two cycles of divergent selection for grain yield under drought stress in a rice breeding population

Euphytica ◽  
2009 ◽  
Vol 167 (2) ◽  
pp. 261-269 ◽  
Author(s):  
R. Venuprasad ◽  
M. E. Bool ◽  
C. O. Dalid ◽  
J. Bernier ◽  
A. Kumar ◽  
...  
Keyword(s):  
Drought Stress ◽  
Grain Yield ◽  
Breeding Population ◽  
Divergent Selection ◽  
Rice Breeding ◽  
Genetic Loci ◽  
Selection For

Changes in resistance to powdery mildew in a barley composite cross

1990 ◽  
Vol 68 (4) ◽  
pp. 916-919 ◽  
Author(s):  
M. Reinhold ◽  
M. E. Bjarko ◽  
D. C. Sands ◽  
H. E. Bockelman
Keyword(s):  
Hordeum Vulgare ◽  
Powdery Mildew ◽  
Selection Pressure ◽  
Recurrent Selection ◽  
Erysiphe Graminis ◽  
Response To Selection ◽  
Multiple Alleles ◽  
Negative Effect ◽  
Selection For ◽  
Representative Samples

The response of barley composite cross XLII to selection for resistance to powdery mildew was evaluated. Representative samples from eight cycles of recurrent selection were inoculated with two isolates of Erysiphe graminis f.sp. hordei. Frequencies of resistant plants were determined for each cycle. The resistance in composite cross XLII increased with selection. Increased selection pressure in 1986 resulted in a more rapid increase in resistance than in previous years. Multiple alleles occurring in the Ml-a locus did not seem to have a negative effect on the accumulation of resistance in composite cross XLII. Key words: Hordeum vulgare, barley, Erysiphe graminis f.sp. hordei, powdery mildew, response to selection, recurrent selection.

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.

Direct response to selection for post-weaning net feed intake in mice and correlated responses in post-weaning growth, intake, gross digestibility and body composition

2004 ◽  
Vol 44 (5) ◽  
pp. 489 ◽  
Author(s):  
T. E. Hughes ◽  
W. S. Pitchford
Keyword(s):  
Body Composition ◽  
Feed Intake ◽  
Genetic Correlations ◽  
Heritability Estimate ◽  
Response To Selection ◽  
Correlated Responses ◽  
Direct Response ◽  
Selection For ◽  
Seven Generations ◽  
Daily Gain

Seven generations of divergent selection on a phenotypic index of net feed in mice produced a realised heritability estimate of 0.27 ± 0.07. Despite small negative genetic correlations of net feed intake with daily gain and liveweight, correlated responses in these economically important traits were negligible. Still, more efficient animals tended to be fatter during the early post-weaning phase. Gross digestibility was also affected, which may have implications for the overall energy balance of a biological system.

Heritability, correlated response, and indirect selection involving spectral reflectance indices and grain yield in wheat

2007 ◽  
Vol 58 (5) ◽  
pp. 432 ◽  
Author(s):  
M. A. Babar ◽  
M. van Ginkel ◽  
M. P. Reynolds ◽  
B. Prasad ◽  
A. R. Klatt
Keyword(s):  
Grain Yield ◽  
Spectral Reflectance ◽  
Genetic Correlations ◽  
Grain Filling ◽  
Indirect Selection ◽  
The Other ◽  
Correlated Response ◽  
Response To Selection ◽  
Selection For ◽  
Reflectance Indices

The objectives of this study were to assess the potential of using spectral reflectance indices (SRIs) as an indirect selection tool for grain yield in wheat under irrigated conditions. This paper demonstrates the genetic correlation between grain yield and SRIs, heritability and expected response to selection for grain yield and SRIs, correlated response to selection for grain yield estimated from SRIs, and efficiency of indirect selection for grain yield using SRIs in different spring wheat populations. Four field experiments, GHIST (15 CIMMYT globally adapted genotypes), RLs1 (25 random F3-derived families), RLs2 (36 random F3-derived families), and RLs3 (64 random F5-derived families) were conducted under irrigated conditions at the CIMMYT research station in north-west Mexico in 3 different years. Spectral reflectance was measured at 3 growth stages (booting, heading, and grain filling) and 7 SRIs were calculated using average values of spectral reflectance at heading and grain filling. Five previously developed SRIs (PRI, WI, RNDVI, GNDVI, SR), and 2 newly calculated SRIs (NWI-1 and NWI-2) were evaluated in the experiments. In general, the within- and between-year genetic correlations between grain yield and SRIs were significant. Three NIR-based indices (WI, NWI-1, and NWI-2) showed higher genetic correlations (0.73–0.92) with grain yield than the other indices (0.35–0.67), and these observations were consistent in all populations. Broad-sense heritability estimates for all indices were in general moderate to high (0.60–0.80), and higher than grain yield (0.45–0.70). The realised heritability for the 3 NIR-based indices was higher than for the other indices and for grain yield itself. Expected response to selection for all indices was moderate to high (0.54–0.85). The correlated response for grain yield estimated from the 3 NIR-based indices (0.59–0.64) was much higher than the correlated response for grain yield estimated from the other indices (0.31–0.46), and the efficiency of indirect selection for these 3 NIR-based indices was 90–96% of the efficiency of direct selection for grain yield. These results demonstrate the potential for using the 3 NIR-based SRI tools in breeding programs for selecting for increased genetic gains for yield.

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.

Genetic and environmental factors affecting temperament of zebu and zebu-derived beef cattle grazed at pasture in the tropics

2000 ◽  
Vol 51 (1) ◽  
pp. 155 ◽  
Author(s):  
H. M. Burrow ◽  
N. J. Corbet
Keyword(s):  
Bos Indicus ◽  
Genetic Correlations ◽  
Objective Measure ◽  
Divergent Selection ◽  
Gastrointestinal Parasites ◽  
Flight Speed ◽  
Production Costs ◽  
Subjective Tests ◽  
Speed Score ◽  
Selection For

Separate experiments were conducted in 2 zebu-derived herds grazed at pasture in the dry tropics of Central Queensland, to determine genetic and environmental effects on At Duckponds, temperament of crossbreed steers and heifers from 2 calf crops was assessed using an objective flight speed score and 2 subjective scores (a visual flight speed score and a crush score) to determine whether the subjective tests were useful as selection criteria for on-farm selection programs. At Belmont, temperament of bull and heifer calves from 7 calf crops was measured by recording objective flight speed scores of individual animals at weaning (6 months), 12 months, and 18 months. At Duckponds, heritabilities of average objective flight speed, visual flight speed, and crush scores were 0.35, 0.08, and 0.30, respectively. Phenotypic and genetic correlations between the different measures of temperament were moderate to low. Based on low correlations and re-ranking of fixed effect classes that occurred between subjective tests, it was concluded the subjective tests were not sufficiently correlated with the objective measure to justify their use. The objective flight speed score is recommended as the test of choice for use in breeding programs using Bos indicus or Bos indicus derived animals. At Belmont, even a single flight speed score was moderately heritable, but use of the average of 2 or 3 repeated flight speed scores substantially increased heritability. The realised heritability of average flight speed score was 0.48, almost identical to the estimated heritability of average flight speed score of 0.50. Direct responses to a single generation of divergent selection for single flight speed scores at different ages demonstrated that selection for flight speed was effective in modifying flight speed scores of progeny. Correlated responses to divergent selection for flight speed scores indicated that, under extensive grazing systems, the economic value of temperament arose mainly through a reduction in production costs. There were significant differences in temperament scores between sire breeds used in the crossbreeding experiment at Duckponds, but there were no differences between lines at Belmont. From these results, it is possible that Continental breeds either have specific, negative combining ability when crossed with Brahmans, or themselves have temperaments that are no better than those of Bos indicus. Treatment to control gastrointestinal parasites (worms) had a significant (P < 0.001) negative effect on flight speed.

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