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Marker-assisted selection for quantitative traits
Schuster, Ivan;
Crop Breeding and Applied Biotechnology , 2011, DOI: 10.1590/S1984-70332011000500008
Abstract: although thousands of scientific articles have been published on the subject of marker-assisted selection (mas) and quantitative trait loci (qtl), the application of mas for qtl in plant breeding has been restricted. among the main causes for this limited use are the low accuracy of qtl mapping and the high costs of genotyping thousands of plants with tens or hundreds of molecular markers in routine breeding programs. recently, new large-scale genotyping technologies have resulted in a cost reduction. nevertheless, the mas for qtl has so far been limited to selection programs using several generations per year, where phenotypic selection cannot be performed in all generations, mainly in recurrent selection programs. methods of mas for qtl in breeding programs using self-pollination have been developed.
Marker-assisted selection for quantitative traits
Ivan Schuster
Crop Breeding and Applied Biotechnology , 2011,
Abstract: Although thousands of scientific articles have been published on the subject of marker-assisted selection (MAS) andquantitative trait loci (QTL), the application of MAS for QTL in plant breeding has been restricted. Among the main causes for thislimited use are the low accuracy of QTL mapping and the high costs of genotyping thousands of plants with tens or hundreds ofmolecular markers in routine breeding programs. Recently, new large-scale genotyping technologies have resulted in a costreduction. Nevertheless, the MAS for QTL has so far been limited to selection programs using several generations per year, wherephenotypic selection cannot be performed in all generations, mainly in recurrent selection programs. Methods of MAS for QTL inbreeding programs using self-pollination have been developed.
标记辅助选择改良数量性状的研究进展 Advances on Marker-Assisted Selection in the Improvement of Quantitative Traits
刘鹏渊,朱军LIU Peng-yuan,ZHU Jun
遗传 , 2001,
Abstract: 本文系统地介绍了近年来有关标记辅助选择改良数量性状的研究进展,主要包括标记辅助回交、指数选择与最佳线性无偏预测的理论和应用研究概况.理论与计算机模拟表明标记辅助选择比常规表型选择更有效,但在实际育种中并不理想.同时本文还就当前标记辅助选择存在的问题和前景进行了讨论。 Abstract:Recent advances on marker-assisted selection (MAS) in the improvement of quantitative traits are reviewed.These include theoretical researches and applications of marker-assisted backcrossing,index selection,and best linear unbiased prediction (BLUP) in animal and plant breeding.Theoretical and simulation studies show that marker-assisted selection can substantially increase the efficiency of selection in comparison to phenotypic selection,but is not yet a proven technology.Problems and prospects in MAS are also discussed.
Inheritance of Important Economic Traits in Chickens under Short Term Selection  [cached]
Ardeshir Bahmanimehr
International Journal of Animal and Veterinary Advances , 2012,
Abstract: The aim of this study is study the inheritance of economic traits in an Iranian Native chickens population by estimating genetic parameters (heritability, genetic, phenotypic and environment correlations) under short-term selection in breeding programs. Identification of genes determining the expression of economically important traits of plants and animals is a main research focus in agricultural genomics. Most of these traits are characterized by a wide variability of the expression of genes at certain loci called Quantitative Trait Loci (QTL). Characterization of the chromosomal regions carrying QTL can be applied in marker-assisted Selection (MAS) to improve breeding efficiency. Molecular linkage maps in combination with Powerful statistical methods facilitate the genetic dissection of complex traits, and the chicken is ideally suited for this task due to a relatively short life cycle and large number of progeny. Native chickens are important in some rural areas. They usually produce meat and eggs without extra feed, only picking food. Improving their economical traits, such production efficiency would save these genetic resources. The genetic parameters for various traits of economic importance were studied in an Iranian Native chickens population under short term selection for egg production and body weight for over 2 years. The parameters studied were body weight at day old (BW1) , 8 weeks (BW8) and body weight at 12 weeks (BW12), the weight of first egg (EGGW1) and egg weight at 30 weeks of age (EGGW30) also the average number of stock eggs per day (EGG/DAY). They showed mostly moderate to high heritability estimates. All these values were 0.56 to 0.44, 0.51 0.2, 0.56 and 0.15, respectively. Higher heritability estimate were obtained for body weight traits. There were positive genetic correlation between weight traits and egg weight traits. Higher estimate was obtained for BW1 and EGGW30 (0.64). However, negative genetic correlation between body weight traits and number of eggs are estimated. In the result, selection for body weight traits before mature ages will cause gain in egg weight traits and it will be useful in breeding plans.
Marker Assisted Selection for Leaf Blast Disease resistance and other yield traits in rice (Oryza sativa L.) using RAPD Markers
Immanuel Selvaraj. C, , Pothiraj Nagarajan, K. Thiyagarajan, M Bharathi, and R Rabindran
Electronic Journal of Plant Breeding , 2011,
Abstract: A segregating population of 220 F2 individuals was developed by raising the selfed F1 seeds of a single hybrid plant, White Ponnix Moroberekan. Two hundred and twenty F3 families were phenotyped for blast resistance under artificial condition. Bulksegregantanalysis resulted in the identification of 12 leaf blast resistant phenotype specific RAPD markers. Mapping survey wasdone with seven RAPD primers which co-segregated in BSA. Twelve RAPD markers were scored in the F2 mapping population.Out of 12 marker loci, 11 marker loci (91.97 per cent) fitted into the expected segregation ratio of 3:1 based on χ2- test at 0.05per cent probability value. One way ANOVA was performed to identify the marker phenotype association and this resulted in theidentification of seven RAPD markers linked to three traits viz., leaf blast resistance (OPBB 5258, OPBB 5194, OPAL 16940 andOPBD 12680), five markers for GPT and one marker for grain yield per plant.
Non-genetic inheritance and the patterns of antagonistic coevolution
Rafal Mostowy, Jan Engelst?dter, Marcel Salathé
BMC Evolutionary Biology , 2012, DOI: 10.1186/1471-2148-12-93
Abstract: Here, we show that another factor – non-genetic inheritance, mediated for example by epigenetic mechanisms – can completely eliminate oscillations in the presence of such negative frequency dependence, even if only a small fraction of offspring are affected. We analytically derive the threshold value of this fraction at which the dynamics change from oscillatory to stable, and investigate how selection, mutation and generation times differences between the two species affect the threshold value. These results strongly suggest that the lack of phenotype frequency oscillations should not be attributed to the lack of strong interactions between antagonistic species.Given increasing evidence of non-genetic effects on the outcomes of antagonistic species interactions, we suggest that these effects should be incorporated into ecological and evolutionary models of interacting species.
Discovery of novel genetic networks associated with 19 economically important traits in beef cattle
Zhihua Jiang, Jennifer J. Michal, Jie Chen, Tyler F. Daniels, Tanja Kunej, Matthew D. Garcia, Charles T. Gaskins, Jan R. Busboom, Leeson J. Alexander, Raymond W. Wright Jr., Michael D. MacNeil
International Journal of Biological Sciences , 2009,
Abstract: Quantitative or complex traits are determined by the combined effects of many loci, and are affected by genetic networks or molecular pathways. In the present study, we genotyped a total of 138 mutations, mainly single nucleotide polymorphisms derived from 71 functional genes on a Wagyu x Limousin reference population. Two hundred forty six F2 animals were measured for 5 carcass, 6 eating quality and 8 fatty acid composition traits. A total of 2,280 single marker-trait association runs with 120 tagged mutations selected based on the HAPLOVIEW analysis revealed 144 significant associations (P < 0.05), but 50 of them were removed from the analysis due to the small number of animals (≤ 9) in one genotype group or absence of one genotype among three genotypes. The remaining 94 single-trait associations were then placed into three groups of quantitative trait modes (QTMs) with additive, dominant and overdominant effects. All significant markers and their QTMs associated with each of these 19 traits were involved in a linear regression model analysis, which confirmed single-gene associations for 4 traits, but revealed two-gene networks for 8 traits and three-gene networks for 5 traits. Such genetic networks involving both genotypes and QTMs resulted in high correlations between predicted and actual values of performance, thus providing evidence that the classical Mendelian principles of inheritance can be applied in understanding genetic complexity of complex phenotypes. Our present study also indicated that carcass, eating quality and fatty acid composition traits rarely share genetic networks. Therefore, marker-assisted selection for improvement of one category of these traits would not interfere with improvement of another.
The genetic dissection of quantitative traits in crops
Semagn,Kassa; Bj?rnstad,?smund; Xu,Yunbi;
Electronic Journal of Biotechnology , 2010,
Abstract: most traits of interest in plant breeding show quantitative inheritance, which complicate the breeding process since phenotypic performances only partially reflects the genetic values of individuals. the genetic variation of a quantitative trait is assumed to be controlled by the collective effects of quantitative trait loci (qtls), epistasis (interaction between qtls), the environment, and interaction between qtl and environment. exploiting molecular markers in breeding involve finding a subset of markers associated with one or more qtls that regulate the expression of complex traits. many qtl mapping studies conducted in the last two decades identified qtls that generally explained a significant proportion of the phenotypic variance, and therefore, gave rise to an optimistic assessment of the prospects of markers assisted selection. linkage analysis and association mapping are the two most commonly used methods for qtl mapping. this review provides an overview of the two qtl mapping methods, including mapping population type and size, phenotypic evaluation of the population, molecular profiling of either the entire or a subset of the population, marker-trait association analysis using different statistical methods and software as well as the future prospects of using markers in crop improvement.
山羊经济性状标记辅助选择的遗传效应分析 Genetic Effect of the Marker Assisted Selection on Economic Traits of Goats
沈 伟,潘庆杰,李 兰,秦国庆,耿社民 SHEN Wei,PAN Qing-jie,LI Lan,QIN Guo-qing,GENG She-min
遗传 , 2004,
Abstract: 本研究以辽宁绒山羊、柴达木绒山羊和柴达木山羊3个群体共147只山羊为研究对象,运用PAGE和RAPD技术对山羊的体重、绒产量和绒细度3个性状进行了与标记基因关系的遗传分析,结果表明:EsD2-2型、LAPBB型和PA-32-2型分别为体重、绒产量和绒细度性状的优势标记基因型;可利用标记辅助预测的方法充分利用多基因座标记基因间的互作效应;在体重上,寻找到有显著选择效应的RAPD条带11个,在绒产量和绒细度上分别为9和6个;在多目标性状选择中,CY0818/A0型和OPW19/C1型为体重和绒产量的双重优势RAPD标记,CY0818/G1型为体重和绒细度的双重优势RAPD标记。Abstract: The genetic relationships between economic traits and genetic markers were studied in 147 goats including Chaidamu goat (CS), Chaidamu Cashmere goat (CRS) and Liaoning Cashmere goat (LRS) in Qinghai province, China. CRS was the population of CS×LRS crossbred. The results showed as follows: the selection reaction of these blood protein polymorphisic loci were great, such as EsD, LAP and PA-3; and EsD2-2, LAPBB and PA-32-2 were the superior marker genotypes on body weight ,Cashmere yield and Cashmere fineness respectively by Least Square method. The interaction between marker genotypes at double loci was found frequently, and their ratio between interaction variance component and genetic varia
Inheritance of Resistance to Turcicum Leaf Blight in Sorghum
MM Beshir, AM Ali, P Okori
African Crop Science Journal , 2012,
Abstract: Sorghum (Sorghum bicolor) has global socio-economic importance and is as model plant species for many tropical grasses with complex genomes. It is frequently devastated by Turcicum leaf blight, caused by Exserohilum turcicum, leading to considerable grain and fodder yield losses. Developing varieties with resistance against E. turcicum is the most cost-effective way to manage the disease. However, inheritance of resistance to E. turcicum in sorghum is poorly understood. Studies were carried out in Uganda to investigate the mode of inheritance of resistance to E. turcicum in sorghum under greenhouse and field conditions. Segregating families derived from a cross of MUC007/009 (a local resistant accession) and Epuripuri (susceptible, an elite sorghum variety) were used along with the two parents in the study. Evaluations of families also included four checks, namely GAO6/106 (moderately resistant), Lulud (susceptible), MUC007/010 (resistant) and GAO6/18 (moderately susceptible). Disease severity of F2 plants in the greenhouse were skewed toward resistance. In the field, the resistant parent had much lower disease severity than the susceptible parent. However, there was no difference between both parents under greenhouse conditions. Under field conditions, F2:3 progeny disease scores were skewed towards resistance, suggesting quantitative inheritance of resistance. In maize resistance to Turcicum leaf blight is both qualitative and quantitative. This study shows that resistance in sorghum to Turcicum leaf blight is quantitative suggesting that quantitative resistance in both maize and sorghum, close relatives, predates speciation. Breeding for such complex traits is often compounded by genotype by environment interactions and as such, marker assisted selection could hasten the process. Further characterisation of resistance loci and mapping of quantitative trait loci will support effective more resistance breeding.
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