Relative Efficiency Of Indirect Selection Research Articles

Genetic parameters for growth and morphological traits of the Pacific white shrimp Penaeus vannamei from a selective breeding programme in the industrial sector of Ecuador

This study aimed to estimate the genetic parameters of growth-related traits (weight and length), morphological traits (cephalothorax, abdomen, length, height, segment width and volume), and the correlated response of weight traits via the selection for morphological traits to evaluate the relative efficiency of indirect selection in P. vannamei from a selective breeding growth programme, PMG-BIOGEMAR®, under industrial production conditions in Ecuador. A total of 595 shrimps from 89 full-sibling families were reared under an extensive culturing system (estuaries) (PRODUMAR, Duran, Ecuador), and were evaluated for genetic parameters at harvest size. The heritability of growth traits was moderate-medium (0.25–0.34), whereas it was quite variable for morphological traits (0.01–0.77). Among the morphological traits, Sixth Segment Width (SW6) (0.77) and Sixth Segment Volume (SV6) (0.35) had medium-high heritability, and genetic correlations between almost all morphological and growth traits were high and positive, except those corresponding to the fourth segment. According to these genetic parameters, SW6 and SV6 as the correlated response to weight are 9.7% and 5.8%, respectively, being more efficient than direct selection for weight. Thus, the sixth segment should be considered an indirect selection criterion for growth in future breeding programmes as it is a precise, non-invasive, and low-cost morphological trait for growth improvement in the industrial sector.

Estimated genetic associations among reproductive traits in Nellore cattle using Bayesian analysis

Scrotal circumference of bulls is correlated with pubertal age of female offspring. Hormonal control of reproductive function is similar in males and females, which may result in genetic correlation among different reproductive traits measured in the two sexes. The estimation of heritability and genetic correlations allows for the computation of direct and correlated genetic gains which are important for predicting of outcomes as a result of genetic-based selection. The aim of this study was to estimate genetic parameters and relative efficiency of indirect selection for age at first calving (AFC), stayability (STAY) and scrotal circumference at 365 days of age (SC365) in Nellore cattle. The STAY variable can be defined as the probability of a cow remain in the herd enough time to raise a certain number of calves that pay for her development and maintenance costs. A bivariate Bayesian analysis was used to estimate variance components using a linear-animal model for SC365 and AFC and threshold-linear model for SC365 and STAY and for AFC and STAY. For STAY, the value of 1 was assigned to cows that calved at least three times by 76 months of age; otherwise, the value 0 was assigned. The posteriori means of heritability estimates were 0.29, 0.08 and 0.09 for SC365, AFC and STAY, respectively. Genetic correlations were favorable from a cow productivity perspective between SC365 and AFC, and SC365 and STAY (-0.45 and 0.12, respectively). Indirect selection approaches were more efficient than direct selection for AFC (ERS = 1.87) when animals were selected for SC365.

Use of spectral reflectance for indirect selection of yield potential and stability in Pacific Northwest winter wheat

The use of canopy spectral reflectance as a high throughput selection method has been recommended to augment genetic gain from yield based selection in highly variable environments. The objectives of this study were to estimate genotypic correlations between grain yield and spectral reflectance indices (SRIs), and estimate heritability, expected response to selection, relative efficiency of indirect selection, and accuracy of yield predictive models in Pacific Northwest winter wheat (Triticum aestivum L.) under a range of moisture regimes. A diversity panel of 402 winter wheat genotypes (87 hard and 315 soft) was grown in rain-fed and irrigated conditions across the eastern Washington in 2012 and 2013. Canopy spectral reflectance measured at heading, milk, soft dough, and hard dough stages were used to derive several SRIs which generally had higher broad sense heritability (H2) than yield per se. Grain yield and SRIs showed generally high genetic variability and response to selection in moist-cool rain-fed condition. Efficiency of indirect selection for yield using SRIs was high in drought environment and exceeded efficiency of yield-based selection in the soft winter subgroup. Normalized water band index (NWI) showed consistent response to selection across environments, higher genetic correlation with yield (0.51–0.80, p<0.001), and highest indirect selection efficiency (up to 143%). A yield predictive model with one or more SRIs explained 41–82% of total variation in grain yield (p<0.001). The repeatability of genotypic performance between years increased when selection was conducted based on both SRIs and grain yield compared to selection based on yield or SRI alone. The generally high heritability of SRIs and their significant genotypic correlation with grain yield highlight the possibility to improve yield and yield stability in winter wheat through remotely sensed phenotyping approaches.

Is low-input management system a good selection environment to screen winter wheat genotypes adapted to organic farming?

The move toward resilient and productive agriculture requires, among other innovations, the design of new sustainable farming systems in which the variety plays a main role. Plant breeding strategies adapted to organic farming conditions have to deal with limiting factors. Whereas in north-west France, it is known that trials carried out under high-input management do not give a good prediction of genotype performance in organic conditions, less is known about the relative stability of wheat genotypes between low-input (LI) and organic cropping systems. A retrospective analysis of 34 winter wheat trials conducted from 2004 to 2011 was performed to determine whether data obtained on genotypes grown under LI conditions can be used to predict genotype performance in organic (ORG) target conditions. Every year, ORG and LI (no fungicide or growth regulators, N balance sheet-60 kgN/ha, weed control with herbicides) trials including 25–30 genotypes describing a large range of genetic diversity were sown in three different agro-climatic regions across north-west France. Genotype performance in ORG management system was reduced from 25 to 40 % for yield and from 10 to 22 % for grain protein content. Estimates of genotypic values appeared to be more precise under LI than ORG conditions. Because of high genetic correlations between LI and ORG conditions, the relative efficiency of indirect selection from LI to ORG conditions was approximately 1. Spearman’s rank correlations were high (Rs = 0.54–0.92) and genotype rank inversions generally had a minor extent. However, in 2005 and 2010, almost 50 % of the lines had to be retained in LI to keep 80 % of the top 20 % of genotypes in organic conditions. Compared with previous results from high-input conditions, LI management provided a better prediction of genotype performance under ORG conditions but crossover genotype × management interactions could be observed between both systems. Overall, combining information provided from both LI and ORG crop management systems appears to be a good process for building efficient and adapted breeding schemes for ORG farming conditions.

Reprint of: Genetic parameters of in-vivo prediction of carcass, head and fillet yields by internal ultrasound and 2D external imagery in large rainbow trout (Oncorhynchus mykiss)

Selection to improve processing yields relies on sib selection, in which live candidates are ranked according to their family breeding value. This approach limits genetic progress, as it only exploits genetic variability between families and not within them. Indirect criteria measured on live candidates could overcome this limitation. The present study (I) proposes a procedure to identify indirect criteria to predict processing yields in rainbow trout (head, carcass and fillet yields), (2) estimates genetic parameters of these indirect criteria, and (3) predicts relative genetic gains in processing yields using full-sib selection or indirect individual selection on those indirect criteria. DNA-pedigreed all-female rainbow trout Oncorhynchus mykiss (n = 2029, 1631.0 +/- 355.6 g) from 600 families produced from 100 sires and 60 dams were characterized by external and internal non-lethal morphological measures using digital pictures and real time ultrasound tomography. Nineteen landmarks were recorded on the digital pictures to define the outline of the body, head and lateral line. Their coordinates were used to calculate different lengths, heights and areas. Five different internal thicknesses were measured by ultrasound tomography. In the first phase of this study, processing yields were predicted using multiple linear regressions including both external and internal morphometric variables. In a second phase, the heritability of the predicted values and their genetic correlations with real processing yields were estimated using animal models. Predicted yields exhibited intermediate heritabilities (0.25-0.28) that were half the value of heritabilities for real processing yields (0.47-0.55), but had high genetic correlations with these real yields (0.87-0.90). The relative efficiency of indirect selection (IS) on these indirect criteria was compared to theoretical mass selection (MS) or sib selection (FS) with different family sizes (10 or 100) and two different selection pressures (10% or 40%). At the same selection pressure (10%, with 100 sibs per family %), full-sib selection created genetic progress 49.6% to 60.5% higher than indirect selection according to the processing yield targeted. However, when sib-selection pressure was limited to a more realistic between family selection pressure (40% and 10 sibs per family), indirect selection with 10% selection pressure was 21.9% to 32.7% more efficient than sib selection.

Genetic parameters of in-vivo prediction of carcass, head and fillet yields by internal ultrasound and 2D external imagery in large rainbow trout (Oncorhynchus mykiss)

Selection to improve processing yields relies on sib selection, in which live candidates are ranked according to their family breeding value. This approach limits genetic progress, as it only exploits genetic variability between families and not within them. Indirect criteria measured on live candidates could overcome this limitation. The present study (1) proposes a procedure to identify indirect criteria to predict processing yields in rainbow trout (head, carcass and fillet yields), (2) estimates genetic parameters of these indirect criteria, and (3) predicts relative genetic gains in processing yields using full-sib selection or indirect individual selection on those indirect criteria.DNA-pedigreed all-female rainbow trout Oncorhynchus mykiss (n=2029, 1631.0±355.6g) from 600 families produced from 100 sires and 60 dams were characterized by external and internal non-lethal morphological measures using digital pictures and real time ultrasound tomography. Nineteen landmarks were recorded on the digital pictures to define the outline of the body, head and lateral line. Their coordinates were used to calculate different lengths, heights and areas. Five different internal thicknesses were measured by ultrasound tomography.In the first phase of this study, processing yields were predicted using multiple linear regressions including both external and internal morphometric variables. In a second phase, the heritability of the predicted values and their genetic correlations with real processing yields were estimated using animal models. Predicted yields exhibited intermediate heritabilities (0.25–0.28) that were half the value of heritabilities for real processing yields (0.47–0.55), but had high genetic correlations with these real yields (0.87–0.90). The relative efficiency of indirect selection (IS) on these indirect criteria was compared to theoretical mass selection (MS) or sib selection (FS) with different family sizes (10 or 100) and two different selection pressures (10% or 40%). At the same selection pressure (10%, with 100 sibs per family %), full-sib selection created genetic progress 49.6% to 60.5% higher than indirect selection according to the processing yield targeted. However, when sib-selection pressure was limited to a more realistic between family selection pressure (40% and 10 sibs per family), indirect selection with 10% selection pressure was 21.9% to 32.7% more efficient than sib selection.

Variation and covariation for Gibberella ear rot resistance and agronomic traits in testcrosses of doubled haploid maize lines

Gibberella ear rot (GER) of maize caused by Fusarium graminearum reduces grain yield and leads to contamination of the grains with deoxynivalenol (DON), a mycotoxin that adversely affects the health of humans and animals. The objectives of this study were to (1) analyze means and genotypic variances for line per se performance (LP) and testcross performance (TP) of doubled haploid (DH) lines for GER severity and DON concentration as well as for some agronomic traits, (2) examine correlations among these traits, (3) validate QTL for resistance detected in previous studies for LP and their effect on TP and (4) investigate the relative efficiency of indirect selection (RE) for LP to improve TP. Testcross progenies of 94 DH lines originating from four flint populations were developed using a susceptible dent tester as pollinator. Artificial inoculations with F. graminearum led to appreciable disease development. Average TP for GER severity and DON concentration were lower than the mean mid-parent values of the tester and DH lines, indicating mid-parent heterosis for resistance. Genotypic variation for resistance was significant for LP and TP. Genotypic correlations between LP and TP were low and resistance QTL for LP had no significant effects on TP. Accordingly, RE for resistance was low, suggesting to allocate resources mostly to the evaluation of testcrosses. Correlations of resistance to GER and DON contamination with grain yield (measured under non-inoculated conditions) were not significant, indicating that selection for resistance and higher grain yield can be carried out simultaneously.

Prediction of indirect selection for seed and forage yield of lucerne based on evaluation under spaced planting

AbstractPhenotypic selection under spaced planting is frequently used in forage species. This study aimed to compare the predicted efficiency of direct selection for lucerne seed or forage yield under dense planting with indirect selection based on the same traits or seed yield components evaluated under spaced planting. Sixteen genotypes randomly chosen from a representative sample of locally adapted germplasm were grown for two years as individual clones spaced at 75 cm (density =1.78 plants/m2) and in dense plots formed by one row of four clones spaced at 10 cm (density = 50 plants/m2) using a randomized complete block design with three replications. Indirect selection based on seed yield under spaced planting was just 19% less efficient than direct selection, owing to moderate genetic correlation between plant densities (rg = 0.66) and somewhat higher broad‐sense heritability under spaced planting than under dense planting. The relative efficiency of indirect selection for seed yield in density based on individual seed yield components under spaced planting ranged from modest to very low and was always below 45%. The efficiency of indirect selection for dry matter yield based on yield response under spaced planting was moderate for total yield (64%) and very low for second‐year yield (32%) relative to direct selection.

Indirect versus Direct Selection of Winter Wheat for Low‐Input or High‐Input Levels

Market prices and environmental concerns favor low‐input wheat (Triticum aestivum L.) production systems. This study assesses the efficiency of low‐input vs. high‐input selection environments to improve wheat for low‐input environments. Three standard cultivars, 11 parents, and 270 lines bred in INRA Mons‐Péronne were investigated for 2 yr (1998, 1999) in France at three INRA locations. Four agronomic treatments combining two levels of fungicides with two levels of nitrogen (N) were applied. Because of seed supply, only 10 year × treatment × location combinations were conducted. Broad‐sense heritabilities for grain yield (GY) ranged from 0.18 at low N without fungicide to 0.90 at high N without fungicide. Heritability estimates were higher at high N than at low N level. This was due to both an increase in error variance and a decrease in genetic variance at low nitrogen level. Heritabilities in treatments without fungicide were the same or higher than heritabilities measured in the corresponding controlled treatments. Broad‐sense heritabilities for grain N content (GNC) were similar between the controlled treatments with fungicide and the corresponding treatments without fungicide. They were lower at low N level and this was due to an increased error variance in both years. Genetic correlations between the 10 experiments were always positive for GY and N content: they ranged from 0.10 to 0.95 for yield and from 0.78 to 0.98 for GNC. The relative efficiency of indirect selection to direct selection for each pair of environments ranged from 0.15 to 0.99 indicating that indirect selection was never more efficient than direct selection. Therefore, breeding programs targeting low‐input environments should include low‐input selection environments to maximize selection gains.

Efficiency of drained selection environments for improving grain yield in faba bean under undrained target environments on vertisol

Waterlogging is a major constraint of faba bean (Vicia faba L.) production in the highland vertisols of Ethiopia. Genotypes are currently evaluated under both the drained conditions of Broad Bed and Furrow(BBF) and the undrained flatbeds. The objective of this research was to determine if selection of genotypes under BBF is efficient for identification of genotypes for the flatbed conditions. Yields under the flatbed conditions were lower by 20–50% (38% on average) than yields under the BBF. Genetic variation, heritability and predicted genetic gains for grain yield due to direct selection were also lower under the flatbeds than they are under the BBF. There were good levels of genetic correlation (r = 0.20–0.75 or0.45 on average) between yield performances under BBF and flatbeds, indicating that selection under BBF may identify good genotypes for flatbeds and vice versa. There was also high association (r =0.91) between relative yield reduction under flatbeds and the ratio of the predicted genetic gains from indirect selection under BBF to the predicted genetic gains from direct selection under flat beds. This indicates that indirect selection under BBF may be useful to identify better genotypes for flatbed conditions, but the relative efficiency of indirect selection was lower than direct selection under flatbeds themselves.

Efficiency of indirect selection at selection equilibrium

Efficiency of indirect selection compared with that of direct selection to increase the mean value of some trait has been usually studied by considering a single generation of indirect and direct responses to selection only. However, under continued selection, genetic variances and covariances, and therefore expected genetic responses, change each generation due to linkage disequilibrium. With directional and truncation selection, genetic parameters asymptote to limiting values after several generations. The efficiency of indirect selection is examined in this limiting situation. The ratio of correlated response to direct response for the trait to improve in the limit is compared with the ratio after the first generation of selection. For all initial parameter values for which indirect selection is more efficient than direct selection, relative efficiency of indirect selection is smaller in the limit than in the first generation. For some parameter values, indirect selection is more efficient than direct selection in the first generation, but less efficient in the limit. Expressions for minimum values of the initial genetic correlation and heritability of the alternative trait required for indirect selection to be preferred in the limit are derived. These values are higher when limiting responses are used instead of single generation responses. The loss in relative efficiency of indirect selection from changes in genetic parameters due to selection should be taken into account when applications of indirect selection are considered.

Heritabilities and Correlations for Pod Yield and Leafspot Resistance in Peanut (Arachis hypogaea L.): Implications for Early Generation Selection1

Abstract The purpose of this study was to investigate early generation selection methods for the identification of peanut (Arachis hypogaea L.) crosses with combined high yield and disease resistance. Eleven crosses were chosen in the S1 on the basis of yield and disease reaction. The S2 was evaluated under natural disease infection for pod yield and leafspot resistance, causal organisms Cercospora arachidicola Hori and Cercosporidium personatum (Berk. and Curt.) Deighton. Resistance was measured by leaf necrotic area and defoliation. Narrow sense heritabilities for all the traits were estimated by sib analysis and regression of S2 plant performance on S1 plant performance. Genetic correlations among traits and the relative efficiency of indirect selection for all the traits were also computed. The results suggest that selection among crosses for all the traits would be advantageous in the S1 (h2f = 67 to 79%) as compared to individual plant selection (h2 = 16 to 26%) or within family selection (h2w = 3 to 5%). Selection of genotypes within crosses would be the poorest strategy in early generations. Negative genetic correlations were noted between yield and leafspot severity. The expected progress in increasing resistance of peanut genotypes through selection for yield (30 to 40% of the response from direct selection for resistance) indicated that selection for yield under disease pressure may be advantageous for developing high yielding, leafspot tolerant genotypes.

Effect of the Biometrical Relationship among Total Milk Yield, Milk Constituent Yield, and Per Cent of Milk Constituent on Response to Selection

The biometrical interrelationships among total milk yield, milk constituent yield, and per cent of milk constituent are considered. Formulas are developed which express the parameters of per cent constituent in terms of the parameters of total milk yield and milk constituent yield. Genetic and phenotypic statistics calculated directly from dairy cattle data agree with those obtained by application of the formulas.Formulas are presented for genetic gain in milk constituent yield by indirect selection on either total milk yield or per cent of milk constituent. These formulas show that genetic gains in milk constituent yield by indirect selection are determined by the means and genetic standard deviations of total milk yield and per cent constituent, the genetic correlation between these two traits and the heritability of either milk yield or per cent milk constituent.Relative efficiencies of three methods of selecting for either SNF yield or fat yield are compared in the population studied. Selecting for SNF yield using total milk yield was slightly less efficient than direct selection. However, the relative efficiency of indirect selection using per cent SNF was considerably lower. Loss in efficiency of indirect selection for fat yield, using total milk yield, is not greatly different from that using per cent fat.