A note on the use of inbreeding in progeny test schemes     

Toro MA 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》1993,110(1-6):234-240

SUMMARY: In this note some theoretical and simulated results are presented comparing the selection response in a progeny test scheme that utilizes inbred offspring for testing, with respect to a standard progeny test. The theory indicates a substantial increase in selection response, although the advantage decreases as the number of dams mated to a sire and the number of offspring per dam increases. The advantage is at a maximum when the variation of the trait is due to segregation of recessive alleles at low frequencies unfavourable to the direction of selection. Computer simulation confirmed the advantage of the method. ZUSAMMENFASSUNG: Verwendung von Inzuchttieren bei der Nachkommenschaftsprüfung Hier wurden theoretische und simulierte Selektionserfolge konventioneller Nachkommenschaftsprüfung mit Prüfung von Inzuchtnachkommen verglichen. Theoretisch zeigt sich ein erheblicher Vorteil der letzteren, wenn dieser auch mit steigende Zahl von Partnern und deren Nachkommen abnimmt und nach null tendiert. Der Vorteil der Nachkommenschaftsprüfung ingezüchteter Nachkommen ist am h?chsten, wenn seltene ungünstige rezessive Gene eine Rolle spielen. Rechner-Simulation best?tigt den Vorteil dieser Vorgangsweise.  相似文献   

A leaf spot disease of Nymphaea alba in the Netherlands     

H. A. van der AA 《European journal of plant pathology / European Foundation for Plant Pathology》1978,84(3):109-115

A destructive leaf spot disease was found onNymphaea alba in the lakes near Kortenhoef, Netherlands. After comparison of fresh material and herbarium specimens the causal agent is namedColletotrichum nymphaeae (Pass.) van der Aa, comb. nov. Synonymy, morphology and cultural characters of the fungus are described and discussed. Some remarks on the relationship with several host plants are given and the provisional conclusion is that the species is a widespread parasite, but that the destructive attack in the Kortenhoef region is probably caused by a combination of various factors.  相似文献   

Review: The strobilurin fungicides     

DW Bartlett  JM Clough  JR Godwin  AA Hall  M Hamer  B Parr‐Dobrzanski 《Pest management science》2004,60(3):309-309

The original article to which this Correction refers was published in Pest Management Science 58 (7): 649–662 (2002).Copyright © 2004 Society of Chemical Industry  相似文献   

Influence of organic phosphorus on reproductive performance and metabolic profiles of anoestrous Farafra ewes in subtropics at the end of breeding season          下载免费PDF全文

W Senosy  AY Kassab  HA Hamdon  AA Mohammed 《Reproduction in domestic animals》2018,53(4):904-913

The effect of organic phosphorus on metabolic, haematological and hormonal status, restoration of ovarian functions and conception rate in anoestrous Farafra ewes in subtropics were evaluated. Anoestrous Farafra ewes (n  = 24; 34.72 ± 0.52 kg body weight) were allocated into two equal groups: control and phosphorus groups. The ewes of phosphorus group were treated with sodium 4‐dimethylamino‐2‐methyl‐phenyl‐phosphonate as an organic bound phosphorous twice a week for successive 3 weeks. Ovarian follicle development and corpora lutea were checked three times a week till occurrence of oestrus using ultrasonography while pregnancy was confirmed at 30 days post‐service. Plasma metabolites, reproductive hormones, thyroid hormones and minerals were detected at weeks ?2, ?1, 0 (mating day) and + 4 weeks post‐oestrus. Phosphorus group had significantly (p  < .05) short interval to oestrous resumption if compared to control ewes (2.1 ± 0.8 weeks vs . 4.6 ± 1.1 weeks). In addition, phosphorous supplementation significantly (p  < .05) increased the number of antral follicles (developed and their sizes in addition to sizes of corpora lutea (8.72 ± 0.3 mm vs . 7.46 ± 0.9 mm) as well. Number of services per conception (2.6 vs . 1.4; p  < .01) was higher in control group than that of phosphorus group. Pregnancy rate (80 vs . 50%) was significantly (p  < .01) higher in phosphorus group when compared to control. White blood cells in treated ewes (10.8 ± 0.44; p  < .05) and monocytes (2.93 ± 0.13; p  < .01) were higher than that of control group (white blood cells; 9.53 ± 0.50 and monocytes; 2.24 ± 0.14). Metabolic parameters did not differ between phosphorus and control groups during different times of treatment. It could be concluded that phosphorous administration to anoestrous Farafra ewes in subtropics could improve reproductive performance and restore ovarian activity at the end of spring and early summer.  相似文献   

Emerging issues in genomic selection     

Ignacy Misztal  Ignacio Aguilar  Daniela Lourenco  Li Ma  Juan Pedro Steibel  Miguel Toro 《Journal of animal science》2021,99(6)

Genomic selection (GS) is now practiced successfully across many species. However, many questions remain, such as long-term effects, estimations of genomic parameters, robustness of genome-wide association study (GWAS) with small and large datasets, and stability of genomic predictions. This study summarizes presentations from the authors at the 2020 American Society of Animal Science (ASAS) symposium. The focus of many studies until now is on linkage disequilibrium between two loci. Ignoring higher-level equilibrium may lead to phantom dominance and epistasis. The Bulmer effect leads to a reduction of the additive variance; however, the selection for increased recombination rate can release anew genetic variance. With genomic information, estimates of genetic parameters may be biased by genomic preselection, but costs of estimation can increase drastically due to the dense form of the genomic information. To make the computation of estimates feasible, genotypes could be retained only for the most important animals, and methods of estimation should use algorithms that can recognize dense blocks in sparse matrices. GWASs using small genomic datasets frequently find many marker-trait associations, whereas studies using much bigger datasets find only a few. Most of the current tools use very simple models for GWAS, possibly causing artifacts. These models are adequate for large datasets where pseudo-phenotypes such as deregressed proofs indirectly account for important effects for traits of interest. Artifacts arising in GWAS with small datasets can be minimized by using data from all animals (whether genotyped or not), realistic models, and methods that account for population structure. Recent developments permit the computation of P-values from genomic best linear unbiased prediction (GBLUP), where models can be arbitrarily complex but restricted to genotyped animals only, and single-step GBLUP that also uses phenotypes from ungenotyped animals. Stability was an important part of nongenomic evaluations, where genetic predictions were stable in the absence of new data even with low prediction accuracies. Unfortunately, genomic evaluations for such animals change because all animals with genotypes are connected. A top-ranked animal can easily drop in the next evaluation, causing a crisis of confidence in genomic evaluations. While correlations between consecutive genomic evaluations are high, outliers can have differences as high as 1 SD. A solution to fluctuating genomic evaluations is to base selection decisions on groups of animals. Although many issues in GS have been solved, many new issues that require additional research continue to surface.  相似文献   

Pathogenesis of infectious bronchitis virus in vaccinated chickens of two different major histocompatibility B complex genotypes     

Joiner KS  Hoerr FJ  Ewald SJ  van Santen VL  Wright JC  van Ginkel FW  Toro H 《Avian diseases》2007,51(3):758-763

Infectious bronchitis (IB) disease progression in vaccinated chickens after challenge was evaluated in a single commercial line of layer chickens presenting two different major histocompatibility complex (MHC) B complex genotypes. MHC B genotypes were determined by DNA sequence-based typing of BF2 alleles. In total, 33 B2/B15 and 47 B2/B21 chickens were vaccinated with an Ark-type IB virus (IBV) attenuated vaccine and challenged with Ark-type IBV field isolate AL/4614/98 14 days later. Additional chickens of both genotypes served as unvaccinated/challenged and unvaccinated/nonchallenged controls. Clinical signs, histopathologic analysis, detection of IBV genomes in tears, and IBV-specific immunoglobulin A (IgA) in tears were used to evaluate disease progression and immune response. The incidence of IBV respiratory signs was significantly higher in B2/21 than in B2/B15 MHC genotype birds. However, neither the severity and duration of respiratory signs nor the severity and incidence of histologic lesions differed significantly with MHC genotype. The levels of IBV-specific IgA in tears of vaccinated and challenged chickens did not differ significantly between MHC genotypes. IBV genomes were present in the tears of vaccinated and challenged birds, and the incidence of detectable IBV genomes did not vary significantly with MHC B genotype. From an applied perspective, these results indicate that vaccinated commercial outbred chickens with these MHC genotypes are equally resistant to IBV.  相似文献   

Quantitative trait locus mapping for meat quality traits in an Iberian x Landrace F2 pig population   总被引：2，自引：0，他引：2  

Ovilo C  Clop A  Noguera JL  Oliver MA  Barragán C  Rodriguez C  Silió L  Toro MA  Coll A  Folch JM  Sánchez A  Babot D  Varona L  Pérez-Enciso M 《Journal of animal science》2002,80(11):2801-2808

An experimental F2 cross between Iberian and Landrace pig strains was performed to map quantitative trait loci (QTL) for diverse productive traits. Here we report results for meat quality traits from 369 F2 animals with records for pH 24 h postmortem (pH 24 h), muscle color Minolta measurements L* (lightness), a* (redness), and b* (yellowness), H* (hue angle), C* (chroma), intramuscular fat (IMF) and haematin pigment content measured in the longissimus thoracis. Pigs were genotyped for 92 markers covering the 18 porcine autosomes (SSC). Results of the genome scan show evidence for QTL for IMF (SSC6; F = 27.16), pH 24 h (SSC3; F = 7.73), haematin pigments (SSC4 and SSC7; F = 8.68 and 9.47 respectively) and Minolta color measurements L* (SSC4 and SSC7; F =16.42 and 7.17 respectively), and a* (SSC4 and SSC8; F = 8.05 and 7.36 respectively). No QTL were observed for the color measurements b*, H*, and C*. Alternative models fitting epistasis between QTL were also tested, but detected epistatic interactions were not significant at a genome-wise level. In this work we identify genomic regions related with meat quality traits. Improvement by traditional selection methods is complicated, and finer mapping would be required for their application in introgression programs.  相似文献   

Between-founder heterogeneity in inbreeding depression for production in Jersey cows     

D. Gulisija  D. Gianola  K.A. Weigel  M.A. Toro 《Livestock Science》2006,104(3):244-253

Severity of inbreeding depression depends on the hidden (i.e., recessive) genetic load carried by a population. If the load is distributed unevenly among founder genomes, or founder-lines were exposed to variable amounts of selection, descendants from different founders may be differentially affected by inbreeding. Between-founder heterogeneity in inbreeding depression for production traits and somatic cell score in milk (SCS) was studied using records from 59,788 Jersey cows. Inbreeding coefficients (F) were partitioned into components due to four founders, plus a remainder. A two-stage statistical analysis was performed. First, empirical best linear unbiased predictions (EBLUP) of residuals for milk, fat and protein yield, and for SCS, were computed using linear models including fixed effects of herd–year–season, age at calving and days in milk, and random additive genetic effects of individual cows. Second, models with total and partial inbreeding coefficients as predictor variables were fitted to EBLUP residuals, for each trait. Tests of differences between slopes indicated that regressions of milk, fat and protein yield on partial inbreeding coefficients were heterogeneous; SCS did not exhibit inbreeding depression. Hence, alleles contributing to inbreeding depression for production in this Jersey population seem to be associated with specific founders. This indicates that a homogeneous effect of inbreeding on production may be an incorrect statistical specification in genetic evaluation models that attempt to account for inbreeding depression. Furthermore, the observed variability between effects of partial inbreeding due to different founders implies that inbreeding effects on yield traits may be due to alleles with major effects.  相似文献   

Assessing genetic diversity between breeds for conservation   总被引：1，自引：0，他引：1  

Miguel Angel Toro 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2006,123(5):289-289

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Effect of Food Ration and Temperature on Length of Brooding Period, Larval Development and Size of Pediveligers Released in the Chilean Oyster Ostrea chilensis     

Jorge E.  Toro P. R. Morandé 《Journal of the World Aquaculture Society》1998,29(2):267-270

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