共查询到20条相似文献,搜索用时 15 毫秒
1.
Jon Hallander Patrik Waldmann 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2009,118(6):1133-1142
Development of selection methods that optimises selection differential subject to a constraint on the increase of inbreeding
(or coancestry) in a population is an important part of breeding programmes. One such method that has received much attention
in animal breeding is the optimum contribution (OC) dynamic selection method. We implemented the OC algorithm and applied
it to a diallel progeny trial of Pinus sylvestris L. (Scots pine) focussing on two traits (total tree height and stem diameter). The OC method resulted in a higher increase
in genetic gain (8–30%) compared to the genetic gain achieved using standard restricted selection method at the same level
of coancestry constraint. Genetic merit obtained at two different levels of restriction on coancestry showed that the benefit
of OC was highest when restriction was strict. At the same level of genetic merit, OC decreased coancestry with 56 and 39%
for diameter and height, respectively, compared to the level of coancestry obtained using unrestricted truncation selection.
Inclusion of a dominance term in the statistical model resulted in changes in contribution rank of trees with 7 and 13% for
diameter and height, respectively, compared to results achieved by using a pure additive model. However, the genetic gain
was higher for the pure additive model than for the model including dominance for both traits. 相似文献
2.
E. W. Andersson L. Sánchez Rodríguez B. Andersson 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1999,99(1-2):73-80
Integer Linear Programming was used to maximize genetic gain from selection at a given level of relatedness. Variances and
breeding values for total height were available for 296 plus-trees of Pinus sylvestris which had been evaluated by open-pollinated progeny testing at a single test site in northern Sweden. Second-generation breeding
and selection scenarios for this breeding population were evaluated using simulated data derived deterministically from normal
distributions of estimated breeding values of progeny around mid-parent family means. The study considered two mating designs,
assortative and non-assortative single-pair mating, and two selection criteria, individual phenotype and performance of half-sib
progeny. Relatedness (group coancestry) was restricted to a level equivalent to that given by within-family selection of 2
trees per family from each of 25 families (the current standard in Sweden). Selection that allows the best-performing families
to contribute a greater number of progeny was superior, both when the breeding population size was limited to 50 individuals
and when it was allowed to be larger. The selected set giving the greatest average breeding value under restricted group coancestry
included the best individual from families that would have been rejected under application of standard within-family selection.
We made a comparison of the present value on retrieved gain between phenotypic selection and evaluation by progeny testing.
Received: 24 November 1998 / Accepted: 14 December 1998 相似文献
3.
Michael Stoehr Alvin Yanchuk Chang-Yi Xie Leopoldo Sanchez 《Tree Genetics & Genomes》2008,4(2):193-200
Sublines are used in the third-generation breeding and testing of coastal Douglas-fir in British Columbia, with the original
intent of selecting only one genotype per subline for production populations (e.g., seed orchards) to eliminate relatedness
among parents (therein called “1/SL”). We evaluated three additional selection scenarios that did not consider the subline
structure. One of the scenarios strictly selected on the basis of the highest breeding values of the trees (“TOP”); another
scenario used the TOP selections, but assigned the number of ramets per selection proportionally to the selection breeding
value (“LIND”); lastly, a simulated annealing technique was applied to maximize gain under explicit constraints on coancestry
(“OPTS”). All three alternative selection scenarios resulted in some relatedness and coancestry among selections, but the
last two provided increases in average breeding values compared to those obtained by the 1/SL scenario. Effective population
sizes (and consequently inbreeding coefficients) varied among the three selection scenarios. Effects of the various selections
on merchantable volume at rotation age were determined using a linear regression model based on an individual tree model (TASS),
which was first run to determine the relationship between merchantable volume and inbreeding (f). LIND and TOP selections yielded the highest breeding values but, due to the increased coancestry among selections, paid
a penalty in the merchantable volume determination. OPTS maximized merchantable volume at rotation age 60 after including
more than 13 selections with an increase of around 3% over that obtained by the 1/SL selection scenario, with an associated
increase in Ne of 50%. Other implications of the three alternative selection scenarios are discussed. 相似文献
4.
Silvia Teresa Rodríguez-Ramilo Jesús Fernández Miguel Angel Toro Delfino Hernández Beatriz Villanueva 《PloS one》2015,10(4)
Estimates of effective population size in the Holstein cattle breed have usually been low despite the large number of animals that constitute this breed. Effective population size is inversely related to the rates at which coancestry and inbreeding increase and these rates have been high as a consequence of intense and accurate selection. Traditionally, coancestry and inbreeding coefficients have been calculated from pedigree data. However, the development of genome-wide single nucleotide polymorphisms has increased the interest of calculating these coefficients from molecular data in order to improve their accuracy. In this study, genomic estimates of coancestry, inbreeding and effective population size were obtained in the Spanish Holstein population and then compared with pedigree-based estimates. A total of 11,135 animals genotyped with the Illumina BovineSNP50 BeadChip were available for the study. After applying filtering criteria, the final genomic dataset included 36,693 autosomal SNPs and 10,569 animals. Pedigree data from those genotyped animals included 31,203 animals. These individuals represented only the last five generations in order to homogenise the amount of pedigree information across animals. Genomic estimates of coancestry and inbreeding were obtained from identity by descent segments (coancestry) or runs of homozygosity (inbreeding). The results indicate that the percentage of variance of pedigree-based coancestry estimates explained by genomic coancestry estimates was higher than that for inbreeding. Estimates of effective population size obtained from genome-wide and pedigree information were consistent and ranged from about 66 to 79. These low values emphasize the need of controlling the rate of increase of coancestry and inbreeding in Holstein selection programmes. 相似文献
5.
S. Maenhout B. De Baets G. Haesaert 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2009,118(6):1181-1192
Molecular markers allow to estimate the pairwise relatedness between the members of a breeding pool when their selection history
is no longer available or has become too complex for a classical pedigree analysis. The field of population genetics has several
estimation procedures at its disposal, but when the genotyped individuals are highly selected inbred lines, their application
is not warranted as the theoretical assumptions on which these estimators were built, usually linkage equilibrium between
marker loci or even Hardy–Weinberg equilibrium, are not met. An alternative approach requires the availability of a genotyped
reference set of inbred lines, which allows to correct the observed marker similarities for their inherent upward bias when
used as a coancestry measure. However, this approach does not guarantee that the resulting coancestry matrix is at least positive
semi-definite (psd), a necessary condition for its use as a covariance matrix. In this paper we present the weighted alikeness
in state (WAIS) estimator. This marker-based coancestry estimator is compared to several other commonly applied relatedness
estimators under realistic hybrid breeding conditions in a number of simulations. We also fit a linear mixed model to phenotypical
data from a commercial maize breeding programme and compare the likelihood of the different variance structures. WAIS is shown
to be psd which makes it suitable for modelling the covariance between genetic components in linear mixed models involved
in breeding value estimation or association studies. Results indicate that it generally produces a low root mean squared error
under different breeding circumstances and provides a fit to the data that is comparable to that of several other marker-based
alternatives. Recommendations for each of the examined coancestry measures are provided. 相似文献
6.
We examined gene models for two traits with and without antagonistic pleiotropy using a locus-based simulation model to investigate
the effects of different population sizes, heritabilities and economic weights, using index selection, and index selection
with optimum selection (OS), over 10 generations. Gene models included additive and dominance gene action, with equal and
varying initial allele frequencies with and without pleiotropy for a fixed level of resources (i.e. founder sizes each generation
of 40, 80 and 160 with progeny arrays that totaled 800 per generation). Pleiotropy (with an initial r
g of −0.5), reduced gain by ~8–10% when heritabilities for both traits were the same (0.2), relative to non-pleiotropic cases.
When traits had different heritabilities (i.e. 0.2 and 0.4), gains in the lower heritability trait were substantially lower,
especially with pleiotropy present. In general, OS with slightly larger population sizes could offset losses in gain, but
rarely overrode the large effects of different heritabilities or economic weights. Pleiotropy increased response variance
among traits, which was magnified when heritabilities were different. Identifying an appropriate weight on relatedness in
the OS process is important to manage coancestry expectations around the loss of alleles (or fixation of recessive alleles)
and to minimise response variance. The dynamics of selection intensity, drift, rate of coancestry build-up, response variance,
etc. are complex for multi-trait selection; however, a few economically viable strategies could reduce the adverse effects
of selecting against genetic correlations without drastically impairing gain. 相似文献
7.
Optimization of selection contribution and mate allocations in monoecious tree breeding populations 总被引:1,自引:0,他引:1
Background
The combination of optimized contribution dynamic selection and various mating schemes was investigated over seven generations for a typical tree breeding scenario. The allocation of mates was optimized using a simulated annealing algorithm for various object functions including random mating (RM), positive assortative mating (PAM) and minimization of pair-wise coancestry between mates (MCM) all combined with minimization of variance in family size and coancestry. The present study considered two levels of heritability (0.05 and 0.25), two restrictions on relatedness (group coancestry; 1 and 2%) and two maximum permissible numbers of crosses in each generation (100 and 400). The infinitesimal genetic model was used to simulate the genetic architecture of the trait that was the subject of selection. A framework of the long term genetic contribution of ancestors was used to examine the impacts of the mating schemes on population parameters.Results
MCM schemes produced on average, an increased rate of genetic gain in the breeding population, although the difference between schemes was small but significant after seven generations (up to 7.1% more than obtained with RM). In addition, MCM reduced the level of inbreeding by as much as 37% compared with RM, although the rate of inbreeding was similar after three generations of selection. PAM schemes yielded levels of genetic gain similar to those produced by RM, but the increase in the level of inbreeding was substantial (up to 43%).Conclusion
The main reason why MCM schemes yielded higher genetic gains was the improvement in managing the long term genetic contribution of founders in the population; this was achieved by connecting unrelated families. In addition, the accumulation of inbreeding was reduced by MCM schemes since the variance in long term genetic contributions of founders was smaller than in the other schemes. Consequently, by combining an MCM scheme with an algorithm that optimizes contributions of the selected individuals, a higher long term response is obtained while reducing the risk within the breeding program. 相似文献8.
N. G. Ehiobu M. E. Goddard J. F. Taylor 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1990,80(3):321-325
Summary The aim of the experiment was to determine if the estimated genetic distance between two populations could be used to predict the amount of heterosis that would occur when they were crossed. Eight lines of known relatedness to each other were produced by eight generations of sib mating and sub-lining. This produced lines that varied in coefficient of coancestry from zero to 0.78. Fourteen reciprocal crosses of these lines were used to measure heterosis for larval viability and adult fecundity. Gene frequencies at six polymorphic enzyme loci were used to estimate the genetic distances between lines, which were then compared with the known degrees of coancestry. The estimated genetic differences were poorly correlated with the known coancestry coefficients (r=0.4), possibly due to the small number of loci typed. Also genetic distances were only about 1/3 of what was expected. Selection acting on blocks of genes linked to the enzyme loci probably prevented the expected increase in homozygosity. Coancestry coefficient was correlated with heterosis (r=0.44–0.71). This level of correlation implied differences in heterosis among parent lines with the same level of coancestry. This variability is expected if a small number of loci explain most of the heterosis. The average level of heterosis was less than expected after eight generations of sib mating. This is most likely due to selection opposing the increase in homozygosity caused by inbreeding. The combination of these two imperfect correlations resulted in no significant correlation between genetic distance estimated from markers and heterosis. 相似文献
9.
The success of BNF in soybean in Brazil 总被引:6,自引:1,他引:5
Approximately forty years after commercial cropping of soybean in Brazil began, the total area under this crop has reached over 13 M ha with a mean productivity of 2400 kg ha–1. Soybean varieties introduced from the USA and varieties rescued from early introductions in Brazilian territory were part of the Brazilian soybean-breeding programme which spread the crop from high to low latitudes. Disease-resistance, pest-resistance, tolerance to low fertility soils, as well as production of plants with pods sufficiently high above the ground for efficient mechanical harvesting, were all aims of the programme. Although BNF was not explicitly considered as a trait for selection in the breeding/selection programme, maximisation of biological nitrogen fixation (BNF) was favoured by conducting selection and breeding trials on soils low in N, in which the seeds were inoculated with efficient Bradyrhizobium inoculants but without N fertiliser application. Several efficient imported Bradyrhizobium strains were found to be unable to compete with native soil micro-flora and other previously-introduced Bradyrhizobium strains. Surprisingly, after being in the soil for many years one or two of these strains had become more competitive while maintaining their high BNF capacity. Today, these strains are included amongst the recommended Brazilian inoculants and have promoted significant improvements in grain yields. The breeding of soybeans in conditions that made grain yield highly dependent on BNF, and the continuous attention paid to the selection of Bradyrhizobium strains appropriate for the newly released varieties, have been the main contributors to today's high yields and their great benefit to the Brazilian economy. There seems to be no reason why this ongoing research programme should not serve as an appropriate model to improve BNF inputs to grain legumes in other countries of the world. 相似文献
10.
Identification of molecular markers associated with linoleic acid desaturation in Brassica napus 总被引:6,自引:0,他引:6
D. J. Somers K. R. D. Friesen G. Rakow 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,96(6-7):897-903
Linolenic acid is a component of canola oil that is readily oxidized, which results in a reduced frying stability and shelf
life of the oil. The reduction of linolenic acid in canola seed has therefore been an important breeding objective for many
years. The inheritance of linolenic acid concentrations in seed oil is polygenic and is also strongly influenced by the environment.
For these reasons, molecular markers are sought to assist in early and reliable selection of desired low linolenic acid genotypes
in breeding programmes. Molecular markers associated with low linolenic acid loci were identified in a doubled-haploid population
derived from a cross between the Brassica napus lines, ‘Apollo’ (low linolenic)×YN90-1016 (high linolenic) using RAPDs and bulked segregant analysis. A total of 16 markers
were distributed over three linkage groups, which individually accounted for 32%, 14% and 5% of the phenotypic variation in
linolenic acid content. The rapeseed fad3 gene was mapped near the locus controlling 14% of the variation. The mode of inheritance appeared to be additive, and a
QTL analysis showed that collectively the three loci explained 51% of the phenotypic variation within this population. PCR
fragments for low linolenic acid ‘Apollo’ alleles (3% linolenic acid) were identified at all three loci. Simultaneous selection
for low linolenic acid ‘Apollo’ alleles at each locus resulted in a group of DH lines with 4.0% linolenic acid. The use of
these makers in the breeding programme will enhance the breeding of low linolenic acid B. napus cultivars for production in Canada.
Received: 23 September 1997 / Accepted: 21 October 1997 相似文献
11.
Selection and mating methods for controlling inbreeding in selection programmes are based on relationships obtained from pedigrees. The efficiency of these methods has always been tested by studies using genetic models of independent loci. However, under linkage the rate of inbreeding obtained from pedigrees can be different from the probability of identity by descent of genes. We simulated a quantitative trait under artificial selection controlled by a large number of genes spread on genome regions of different sizes. A method to control inbreeding based on minimising the average coancestry of selected individuals with a restriction in the loss of selection response, and a mating procedure to control inbreeding were applied. These methods, that use coancestry relationships, were not effective in controlling inbreeding when the genome sizes were smaller than five morgans or so. However, for larger genome sizes the methods were sufficiently efficient. For very tight linkage, methods that utilise molecular information from markers should be used. We finally discuss the effects of the selection of individual major genes on the neutral variability of adjacent genome regions. 相似文献
12.
Methods for assigning individuals to population of origin are widely used in ecological genetics, resources management, and
forensics. Characteristics of genetic data obtained from putative source populations that enhance accuracy of assignment are
well established. How non-independence within and among unknown individuals to be classified [i.e., gene correlations within
individual (inbreeding) and gene correlations among individuals within group (coancestry)] affect assignment accuracy is poorly
understood. We used empirical data for six microsatellite loci and offspring from full-sib crosses of hatchery strains of
lake trout (Salvelinus namaycush; Salmonidae) representing known levels of coancestry (mean θ = 0.006 and 0.06) within families to investigate how gene correlations can affect assignment. Additional simulations were
conducted to further investigating the influence of allelic diversity (2, 6 or 10 alleles per locus) and inbreeding (F = 0.00, 0.05, and 0.15) on assignment accuracy for cases of low and high inter-population variance in allele frequency (mean
F
st = 0.01 and 0.1, respectively). Inbreeding had no effect on accuracy of assignments. In contrast, variance in assignment accuracy
across replicated simulations, and for each empirical case study increased with increasing coancestry, reflecting non-independence
of probabilities of correct assignment among members of kin groups. Empirical estimates of assignment error rates should be
interpreted with caution if appreciable levels of coancestry are suspected. Additional emphasis should be placed on sampling
designs (spatially and temporally) that define or minimize the potential for sampling related individuals. 相似文献
13.
Minimization of the average coancestry in a population has been theoretically proven to be the most efficient method to preserve
genetic diversity. In the present study, based on a population genetic model, two methods to minimize the average coancestry
in populations with overlapping generations were developed. For a given parental coancestry structure, the first method (OG)
minimizes the average coancestry in the next generation, and the second method (LT) is designed to minimize the long-term
accumulation of coancestry. The efficiencies of the two methods were examined by stochastic simulation. Compared to random
choice of parents, the annual effective population sizes under the two proposed methods increased 2–3 folds. The difference
among the two methods was small in a population with short generation interval. For populations with long generation intervals,
the OG method showed a slightly larger annual effective size in an initial few years. However, in the subsequent years, the
LT method gave a 5–15% larger annual effective size than the OG method. From these results, it is suggested that the LT method
would be preferred to the OG method in most practical situations. 相似文献
14.
Said Ahmaidi Janick Masse-Biron Brigitte Adam Dominique Choquet Michel Freville Jean-Pierre Libert Christian Prefaut 《European journal of applied physiology and occupational physiology》1998,78(2):170-176
This study assessed clinical and cardiorespiratory responses after an interval training programme in sedentary elderly adults
using the ventilatory threshold (V
th) as the index of exercise training intensity. A selection of 22 subjects were randomized into two groups: 11 subjects served
as the training group (TG) and the others as controls (CG). Maximal exercise tests were performed on a treadmill before (T0), each month (T1, T2) and after the 3-month interval training programme period (T3). The TG subjects were individually trained at the heart rate corresponding to V
th measured at T0, T1 and T2 as the breakpoint in the oxygen uptake-carbon dioxide production relationship. Their training programme consisted of walking/jogging
sessions on a running track twice a week. The sessions consisted of varying durations of exercise alternating with active
recovery in such a way that the subjects slowly increased their total exercise time from an initial duration of 30 min to
a final duration of 1 h. During training the heart rate was continuously monitored by a cardiofrequency meter. Compared with
the daily activities of the controls, no training programme-related injuries were observed in TG. Moreover, programme adherence
(73%) and attendance (97.3%) were high. The maximal oxygen uptake and V
th were increased in TG, by 20% (P<0.05) and 26% (P<0.01), respectively. Interval training at V
th also significantly increased maximal O2 pulse (P<0.05) and maximal ventilation (P<0.01). A significant decrease in submaximal ventilation (P<0.05) and heart rate (P<0.01) was also noted. These results would suggest that for untrained elderly adults, an interval training programme at the
intensity of V
th may be well-tolerated clinically and may significantly improve both maximal aerobic power and submaximal exercise tolerance.
Accepted: 6 January 1998 相似文献
15.
Richard M. Kliman 《Journal of molecular evolution》1999,49(3):343-351
Evidence from a variety of sources indicates that selection has influenced synonymous codon usage in Drosophila. It has generally been difficult, however, to distinguish selection that acted in the distant past from ongoing selection.
However, under a neutral model, polymorphisms usually reflect more recent mutations than fixed differences between species
and may, therefore, be useful for inferring recent selection. If the ancestral state is preferred, selection should shift
the frequency distribution of derived states/site toward lower values; if the ancestral is unpreferred, selection should increase
the number of derived states/site. Polymorphisms were classified as ancestrally preferred or unpreferred for several genes
of D. simulans and D. melanogaster. A computer simulation of coalescence was employed to derive the expected frequency distributions of derived states/site under
various modifications of the Wright–Fisher neutral model, and distributions of test statistics (t and Mann–Whitney U) were derived by appropriate sampling. One-tailed tests were applied to transformed frequency data to assess whether the
two frequency distributions deviated from neutral expectations in the direction predicted by selection on codon usage. Several
genes from D. simulans appear to be subject to recent selection on synonymous codons, including one gene with low codon bias, esterase-6. Selection may also be acting in D. melanogaster.
Received: 15 April 1998 / Accepted: 13 May 1999 相似文献
16.
The effect of non-random mating on genetic response was compared for populations with discrete generations. Mating followed a selection step where the average coancestry of selected animals was constrained, while genetic response was maximised. Minimum coancestry (MC), Minimum coancestry with a maximum of one offspring per mating pair (MC1) and Minimum variance of the relationships of offspring (MVRO) mating schemes resulted in a delay in inbreeding of about two generations compared with Random, Random factorial and Compensatory mating. In these breeding schemes where selection constrains the rate of inbreeding, ΔF, the improved family structure due to non-random mating increased genetic response. For schemes with ΔF constrained to 1.0% and 100 selection candidates, genetic response was 22% higher for the MC1 and MVRO schemes compared with Random mating schemes. For schemes with a less stringent constraint on ΔF or more selection candidates, the superiority of the MC1 and MVRO schemes was smaller (5–6%). In general, MC1 seemed to be the preferred mating method, since it almost always yielded the highest genetic response. MC1 mainly achieved these high genetic responses by avoiding extreme relationships among the offspring, i.e. fullsib offspring are avoided, and by making the contributions of ancestors to offspring more equal by mating least related animals. 相似文献
17.
A. H. D. Brown J. Daniels N. D. Stevenson 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1970,41(4):174-180
Summary A method is proposed which extends the mass reservoir technique to the breeding of clonally propagated crops. The first phase produces a diverse array of clones by sexual recombination. Then the selection phase is conducted in one genotypically heterogeneous population. Such a population is termed a mass selection reservoir (MSR). In each generation of agricultural bulk planting, competitive ability is supplemented with a regime of artificial selection among propagules for fixing the rate at which each component genotype is advanced.A MSR programme has been initiated in sugarcane in Fiji. An analysis of the variation in selection characters demonstrated significant clonal effects at the single stalk (propagule) level. Sugar concentration was particularly repeatable on this basis. After two generations of selection, the MSR's performance at the population level at least equalled that of the best current commercial clone, Ragnar. It is therefore likely to include superior isolates of one or more clones.Two possible artificial selection methods are compared. These arise from either a linear (L) or multiplicative (M) combination of the two major selection criteria, sugar concentration and stalk weight. Although the M series differs genotypically from the L series, there is little difference to date in their respective population performances. 相似文献
18.
Gene and QTL detection in a three-way barley cross under selection by a mixed model with kinship information using SNPs 总被引:1,自引:0,他引:1
Malosetti M van Eeuwijk FA Boer MP Casas AM Elía M Moralejo M Bhat PR Ramsay L Molina-Cano JL 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2011,122(8):1605-1616
Quantitative trait locus (QTL) detection is commonly performed by analysis of designed segregating populations derived from
two inbred parental lines, where absence of selection, mutation and genetic drift is assumed. Even for designed populations,
selection cannot always be avoided, with as consequence varying correlation between genotypes instead of uniform correlation.
Akin to linkage disequilibrium mapping, ignoring this type of genetic relatedness will increase the rate of false-positives.
In this paper, we advocate using mixed models including genetic relatedness, or ‘kinship’ information for QTL detection in
populations where selection forces operated. We demonstrate our case with a three-way barley cross, designed to segregate
for dwarfing, vernalization and spike morphology genes, in which selection occurred. The population of 161 inbred lines was
screened with 1,536 single nucleotide polymorphisms (SNPs), and used for gene and QTL detection. The coefficient of coancestry
matrix was estimated based on the SNPs and imposed to structure the distribution of random genotypic effects. The model incorporating
kinship, coancestry, information was consistently superior to the one without kinship (according to the Akaike information
criterion). We show, for three traits, that ignoring the coancestry information results in an unrealistically high number
of marker–trait associations, without providing clear conclusions about QTL locations. We used a number of widely recognized
dwarfing and vernalization genes known to segregate in the studied population as landmarks or references to assess the agreement
of the mapping results with a priori candidate gene expectations. Additional QTLs to the major genes were detected for all
traits as well. 相似文献
19.
Maria João Gaspar Ana I. de-Lucas Ricardo Alía Jorge Almiro Pinto Paiva Elena Hidalgo José Louzada Helena Almeida Santiago C. González-Martínez 《Tree Genetics & Genomes》2009,5(4):609-616
The management of a genetic improvement program is based on the knowledge of the genetic parameters and their relationships
to determine the genetic gains. Knowledge of the coefficient of coancestry (θ) is a requirement for efficient progeny testing scheme and for estimating additive variance components for any quantitative
trait. When using open-pollinated families, most authors assume that the seedlings are related as half-sibs, but this is not
always true. Our aim was to estimate a mean value of the coancestry coefficient of the families present in a maritime pine
Pinus pinaster Ait. (maritime or cluster pine) progeny trial originating from seed collected in a clonal seed orchard and to study how deviations
from the standard assumption of θ = 0.125 affect heritability estimations. Five highly polymorphic microsatellite markers were scored in 125 offspring from
a subsample of five families from the progeny trial. The mean value of the coancestry coefficient of the families present
in this progeny trial was 0.130. Differences between the unadjusted and adjusted heritability estimates were more pronounced
in wood density (0.609 and 0.586, respectively) than in diameter (0.166 and 0.154, respectively). We conclude that in the
trial, the associated error in heritability estimates due to the inclusion of full-sibs, when assuming a standard coefficient
of relationship among open-pollinated sibs of 0.250, was low and that this result is robust with respect to the number of
families sampled, given unbiased estimates of average relationship among offspring within sib families. 相似文献
20.
Fernando Gómez-Romano Beatriz Villanueva María ángeles Rodríguez de Cara Jesús Fernández 《遗传、选种与进化》2013,45(1):38