scholarly journals Estimation of Genetic Variance and Covariance Components for Little Size and Little Weight in Danish Landrace Swine Using a Multivariate Mixed Model

1999 ◽  
Vol 12 (7) ◽  
pp. 1015-1018 ◽  
Author(s):  
C. D. Wang ◽  
C. Lee
Keyword(s):  
Genetic Variance ◽  
Mixed Model ◽  
Covariance Components ◽  
Variance And Covariance Components

scholarly journals Estimates for Genetic Variance Components in Reciprocal Recurrent Selection in Populations Derived from Maize Single-Cross Hybrids

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Matheus Costa dos Reis ◽  
José Maria Villela Pádua ◽  
Guilherme Barbosa Abreu ◽  
Fernando Lisboa Guedes ◽  
Rodrigo Vieira Balbi ◽  
...  
Keyword(s):  
Plant Height ◽  
Genetic Variance ◽  
Recurrent Selection ◽  
Reciprocal Recurrent Selection ◽  
Additive Variance ◽  
Lattice Design ◽  
Single Cross ◽  
Covariance Components ◽  
Variance And Covariance Components ◽  
Single Cross Hybrids

This study was carried out to obtain the estimates of genetic variance and covariance components related to intra- and interpopulation in the original populations (C0) and in the third cycle (C3) of reciprocal recurrent selection (RRS) which allows breeders to define the best breeding strategy. For that purpose, the half-sib progenies of intrapopulation (P11and P22) and interpopulation (P12and P21) from populations 1 and 2 derived from single-cross hybrids in the 0 and 3 cycles of the reciprocal recurrent selection program were used. The intra- and interpopulation progenies were evaluated in a10×10triple lattice design in two separate locations. The data for unhusked ear weight (ear weight without husk) and plant height were collected. All genetic variance and covariance components were estimated from the expected mean squares. The breakdown of additive variance into intrapopulation and interpopulation additive deviations (στ2) and the covariance between these and their intrapopulation additive effects (CovAτ) found predominance of the dominance effect for unhusked ear weight. Plant height for these components shows that the intrapopulation additive effect explains most of the variation. Estimates for intrapopulation and interpopulation additive genetic variances confirm that populations derived from single-cross hybrids have potential for recurrent selection programs.

scholarly journals Mixed model approaches for diallel analysis based on a bio-model

1996 ◽  
Vol 68 (3) ◽  
pp. 233-240 ◽  
Author(s):  
Jun Zhu ◽  
Bruce S. Weir
Keyword(s):  
Mixed Model ◽  
Diallel Analysis ◽  
Worked Examples ◽  
Genetic Effects ◽  
Unbiased Estimation ◽  
Paternal Effects ◽  
Covariance Components ◽  
Variance And Covariance Components ◽  
Parameter Values ◽  
Estimation Of Variance

SummaryA MINQUE(l) procedure, which is minimum norm quadratic unbiased estimation (MINQUE) method with 1 for all the prior values, is suggested for estimating variance and covariance components in a bio-model for diallel crosses. Unbiasedness and efficiency of estimation were compared for MINQUE(l), restricted maximum likelihood (REML) and MINQUE(θ) which has parameter values for the prior values. MINQUE(l) is almost as efficient as MINQUE(θ) for unbiased estimation of genetic variance and covariance components. The bio-model is efficient and robust for estimating variance and covariance components for maternal and paternal effects as well as for nuclear effects. A procedure of adjusted unbiased prediction (AUP) is proposed for predicting random genetic effects in the bio-model. The jack-knife procedure is suggested for estimation of sampling variances of estimated variance and covariance components and of predicted genetic effects. Worked examples are given for estimation of variance and covariance components and for prediction of genetic merits.

PRETEST HERD EFFECTS ON STATION PERFORMANCE TEST

1986 ◽  
Vol 66 (4) ◽  
pp. 925-935 ◽  
Author(s):  
A. K. W. TONG ◽  
J. A. NEWMAN ◽  
G. W. RAHNEFELD
Keyword(s):  
Fixed Effects ◽  
Mixed Model ◽  
Performance Test ◽  
Average Daily Gain ◽  
Research Station ◽  
Environmental Correlations ◽  
Warm Up ◽  
Covariance Components ◽  
Variance And Covariance Components ◽  
Daily Gain

Effects of herd of origin and the relationships between pretest and station test environments were examined from pre- and postweaning performance records of 1675 crossbred male and female calves of Hereford, Angus and Shorthorn dams, sired by 20 Charolais, 12 Simmental and 15 Limousin sires. The calves were born during 1969–1972 and raised to weaning in 45 herds from Manitoba, Saskatchewan and Alberta, and were then transported to the Brandon or the Lacombe Research Station for a 140-d postweaning performance test. Fixed effects and variance and covariance components were estimated from a mixed model which included fixed effects of herd-year, sex of calf and breed of sire and random sire effects. Herd-year effects were significant (P < 0.01) for all performance traits studied. Herd-year mean squares expressed as a percentage of the corrected total sum of squares accounted for 25.81% in the pretest period to a maximum of 54.26% in the warm-up period and then decreased to 6.78% in the 140-d period. Herd-year differences were relatively small in the later part of the test. Correlations of herd-year solutions ranged from −0.10 to 0.05 and of environments ranged from −0.09 to 0.02 between pretest average daily gain (ADG) and ADG at various test intervals. The low environmental correlations suggest that the performance of calves centrally tested at the Brandon and Lacombe Research Stations were not affected by the pre-test herd environment. Key words: Beef cattle, station test, pretest herd effects, environmental correlation

scholarly journals Genetic variance and covariance components related to intra- and interpopulation recurrent selection in maize (Zea mays L.)

1998 ◽  
Vol 21 (4) ◽  
pp. 537-544 ◽  
Author(s):  
Carlos Alberto Arrabal Arias ◽  
Cláudio Lopes de Souza Júnior
Keyword(s):  
Zea Mays ◽  
Genetic Variance ◽  
Recurrent Selection ◽  
Zea Mays L ◽  
Inbred Lines ◽  
Additive Effects ◽  
Covariance Components ◽  
Per Se ◽  
Variance And Covariance Components ◽  
Variance Estimates

New genetic variance and covariance components related to intra- and interpopulational recurrent selection methods have been theoretically developed by Souza Jr. (Rev. Bras. Genet. 16: 91-105, 1993) to explain the failure of these methods to concomitantly develop hybrid and per se populations. Intra- and interpopulation half-sib progenies of 100 genotypes were sampled from maize (Zea mays L.) populations BR-106 and BR-105 to estimate variance and covariance components and to compare the expected responses to reciprocal (RRS), intrapopulational (HSS), and modified (MRS) recurrent selection in interpopulation hybrid, populations per se, and to determine heterosis. Four sets of 100 progenies, two intra- and two interpopulational, were evaluated in partially balanced 10 x 10 lattices arranged in split-blocks with two replications in two years (1991/92 and 1992/93) and two locations in Piracicaba, SP. Data for ear weight, plant and ear height, and ear by plant height ratio were recorded. Populations and interpopulation crosses were high yielding and showed high breeding potential for production of hybrids from inbred lines. Mid parent and the highest parent heterosis were relatively high, but lower than values reported for these populations under other environmental conditions. Additive variance estimates of populations per se and interpopulation crosses confirmed the high potential of these materials. The magnitude of the variance estimates for the deviations from intra- and interpopulation additive effects (<img src="http:/img/fbpe/gmb/v21n4/1918f1.jpg" alt="1918f1.jpg (1262 bytes)" align="middle"> for BR-106 and <img src="http:/img/fbpe/gmb/v21n4/1918f3.jpg" alt="1918f3.jpg (1259 bytes)" align="middle">for BR-105) and covariance between additive effects with these deviations (<img src="http:/img/fbpe/gmb/v21n4/1918f2.jpg" alt="1918f2.jpg (2022 bytes)" align="middle"> for BR-106 and <img src="http:/img/fbpe/gmb/v21n4/1918f4.jpg" alt="1918f4.jpg (1995 bytes)" align="middle"> for BR-105) indicated that these new components can significantly influence the effectiveness of breeding methods. Genetic component estimates for BR-105 had relatively small errors, with <img src="http:/img/fbpe/gmb/v21n4/1918f4.jpg" alt="1918f4.jpg (1995 bytes)" align="middle"> negative for all traits. Estimates of <img src="http:/img/fbpe/gmb/v21n4/1918f1.jpg" alt="1918f1.jpg (1262 bytes)" align="middle">and <img src="http:/img/fbpe/gmb/v21n4/1918f2.jpg" alt="1918f2.jpg (2022 bytes)" align="middle"> had relatively larger errors for BR-106. The MRS method was more effective than the RRS and HSS methods in producing hybrids from inbred lines. The choice of a population tester for the MRS method based on population means per se may be incorrect. The additional use, when possible, of intra- and interpopulation additive genetic variances from each population would be more appropriate.

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