作物数量性状基因研究进展

分子生物技术的发展对作物数量性状基因(QTL)研究提供了条件,不同的定位群体各有其特点,相继出现的QTL定位方法也逐步完善.大量的研究揭示了QTL的基本特征,剖析了重要农艺性状的遗传基础,给作物遗传改良带来了新的策略,不断深入的研究已经完成了特定QTL的精细定位和克隆.本文从QTL的定位群体,定位方法,研究现状,精细定位与克隆,以及QTL利用等方面对作物数量性状基因的研究进行了综述。 Abstract:With the rapid development of molecular biotechnology,QTL analyses were executed for a lot of important agronomic traits in many crops.Different experimental populations and mapping methods had their own advantages in QTL analysis.Amounts of studies paid attention to locate the QTLs for important traits,and others tried to disect the genetic bases using molecular markers.Near isogenic lines were the best populations for QTL fine mapping and positional cloning,A few studies had been reported their results on materials with improvement traits using marker-assisted selection.This paper summarizes the recent progress on QTL mapping populations and methods,the status of QTL locating,QTL fine mapping and positional cloning,and QTL.application in breeding.     

单核苷酸多态性及其在鸡QTL定位上的应用

单核苷酸多态性是指DNA序列上的单个碱基变异,它具有分布广、多态信息含量大、易于检测和统计分析等优点,能较好用于基因图谱构建和数量性状QTL定位研究,被称为继RFLP和微卫星标记之后的第3代基因遗传标记。本文综述了单核苷酸多态性的性质及检测技术、利用候选基因SNP进行鸡QTL定位研究的现状,并对未来SNP的应用前景进行了展望。Abstract:Single nucleotide polymorphism (SNP) refers to the change of single nucleotide in DNA sequence.Because of its high density in genomes and easy in detection and analysis statistically,SNP can be used in genetic linkage map construction and QTL mapping.Here,the characters and detecting technology of SNP,as well as the status and foreground of the use of candidate gene SNP in chicken QTL mapping are introduced.     

猪主要经济性状候选基因的研究进展

随着人类基因组计划的完成和动物基因组计划的进行,许多控制动物经济性状的主基因逐渐被发现,并显示出巨大的应用前景。本文概述了影响猪繁殖、肉质、生长发育等主要经济性状的主基因的基因大小、基因定位和基因效应等,对主基因的研究在动物遗传育种科学发展中的意义也作了一些阐述。 Abstract:With the accomplishment of human genome project and the development of animal genome project,many major genes affecting animal economic traits were gradually detected,and they show great application prospect.Major genes affecting reproductive traits,meat quality traits,growing and developing traits of pig are summarized from their size,location and effect.In addition,the meaning of major gene in the improvement of animal breeding and genetics is also discussed.     

影响动物肉质性状主要候选基因的研究进展

随着分子生物学在动物遗传育种中的应用,对数量性状主效基因的研究成为必然。本文对影响肉质的脂肪酸结合蛋白基因、肥胖基因、leptin 基因、黑素皮质受体基因、脂蛋白脂酶基因、激素敏感脂酶基因的国内外研究状况加以综述。 Progress in Candidate Genes Influencing Meat Quality Traits in Chickens QIU Xue-mei1,3,LI Ning1,DEND Xue-mei2,WU Chang-xin2 1.The National Laboratories for Agrobiotechnology,China Agricultural University,Beijing 100094,China; 2.College of Animal Science and Technology,China Agricultural University,Beijing 100094,China; 3.College of Animal Science and Technology,Heilongjiang August First Land Reclamation University,Mishan 158308,China Abstract:As the molecular biology has been applied in animal genetics and breeding,it is important that we research major genes on quantitative traits for animal breeding by transgenic technology.In this paper,the research advance of FABP genes,obese gene,leptin gene,MCRs genes,LPL gene,HSL gene affecting meat quality in animals are reviewed. Key words：animal; meat quality; candidate gene     

绵羊基因组研究进展

过去几年中,家畜基因组计划取得了巨大进展。已经构建了猪、鸡、牛、绵羊、马、鹿的遗传图谱,其遗传标记间距在5～20cM。这些图谱对于家畜中与重要经济性状相关的基因或遗传标记的鉴定非常重要。该文从绵羊的基因图谱、比较图谱、重要经济性状基因及QTL定位方面对绵羊基因组的研究进展作了简要阐述。 Abstract:During the last few years,advances in livestock genome projects have been remarkable.Species-specific genetic maps exist for pig,chicken,cattle,sheep,horse,and deer with marker intervals of 5 to 20 cM.These maps have been essential for the identification of genes and genetic markers associated with importantly economic traits in livestock.In this paper,advances of gene map,comparative map,the genes for importantly economic traits and quantitative trait loci (QTL) mapping were briefly introduced in sheep.     

林木遗传连锁图谱构建研究进展与发展方向

本文就目前国内外林木连锁遗传图谱领域的研究进展进行了综述,指出了该领域研究中存在的主要问题,即一方面是作图个体的数量有限,另一方面是采用的标记以随机标记为主,导致了建成的图谱以及利用图谱获得的数量性状基因位点（QTLs）信息具有杂交组合特异性,造成了QTLs的可信度和在林木遗传改良以及标记辅助选择中的实用性降低等现象。针对存在的问题,讨论了根据林木生物学特点选择合适遗传标记的意义,指出进行林木比较作图研究的重要性和必要性。文中接着较为详尽地介绍了国外重要林木表达序列标签（EST）测序项目的研究进展,论述了功能已知和种间高度保守的表达序列标签多态性（ESTP）标记的由来,阐述了获得ESTP标记的主要方法,并指出应当利用ESTP标记进行林木遗传图谱构建、QTL定位和比较作图的研究。文中最后讨论了未来林木遗传图谱构建和QTL定位研究的发展方向,并探讨了我国在该领域取得重大进展的突破口,指出我国应首先进行杨树尤其是中国乡土杨树树种该方面的研究。 Abstract:The research progress in genetic linkage map construction of forest tree species both at home and abroad were reviewed in the paper.Two main problems involved in the field were discussed.One was the limitation of the number of individuals of mapping populations and the other was the random markers mostly employed by the majority of studies.These problems have resulted in crossing combination specificity in the constructed maps and the QTLs located on the basis of the maps.As a result,the QTLs discovered up to now have low credibility and poor practicability in marker-assisted selection.Therefore considering the biological characteristics of forest tree species,the selection of the most suitable genetic markers is crucial to obtain a high quality genetic linkage map,and it is both important and necessary to carry out comparative genetic mapping.Progress in the ongoing expressed sequence tag (EST) sequencing projects were summarized and EST polymorphism (ESTP),the most informative and highly conservative marker with known function,as well as the main ESTP detection techniques were elaborated.It was pointed out that ESTP markers should be integrated into the present studies of genetic linkage map construction,QTL mapping and genome comparative mapping.Finally the future prospects in the fields of genetic linkage map and QTL mapping were discussed.In China,Such studies around Populus,especially in the local Populus species should make a breakthrough in the related fields.     

Attractin(mahogany/ATRN)基因的研究进展

Attractin（mahogany/mg）是常染色体隐性基因,在近几十年里受到很大关注。已经发现attractin在黑色素沉着、调节运动行为和基础代谢、中枢神经的形成及功能、协调T细胞与巨噬细胞之间的反应等方面都起着十分重要的作用。ATTRACTIN蛋白可以抑制因多食而引起的肥胖,其在大脑中的表达水平与抑制肥胖症成正相关,这将预示它可能用来干扰哺乳动物的肥胖症,而且鼠类attractin基因位于包涵几个体重和肥胖QTL区域内。本文回顾了mg基因的研究历程,介绍其相关性基因及该基因的定位情况,并详细归纳了关于该基因产物在生理过程中的调节机理。在此基础上,提出了进一步研究的思路。 Abstract:Attractin is an autosomal recessive gene and received great attention within the last few decades.Attractin in different lines has been identified attractin to have multiple roles in regulating physiological process.It affects the balance between agonist and antagonist at receptors on melanocytes,modifies behaviour and basal metabolic rate,intervenes developing the central nervous system and its function,and modulates an interaction between activated T cell and macrophages.The attractin gene encodes a protein that is involved in the suppression of diet-induced obesity,its expression level in the brain has a significant relationship with obesity,the role indicates the therapeutic potential of attractin in the treatment of obesity.Furthermore,the murine attractin locus is located in a region harboring several QTL for body weight and fatness.In this paper,we review the research development of mahogany,introduce the related gene and gene mapping,and summarize its regulating mechanism in the physiological process.Additionally,the further research on the gene is also suggested.     

小麦基因组研究进展

本文从小麦遗传图谱、物理图谱、比较基因组、基因组测序和EST 5个方面,介绍国内外小麦基因组的研究进展。我们利用W7984×Opata重组近交系的RFLP作图群体,对33个与小麦水分利用效率有关的性状进行了QTL遗传图谱比较分析,结果显明：在第一部分同源群染色体（1A,1B）上的着丝粒周围,分布有控制光合作用和根系特性的基因簇。在第二部分同源染色体上,有控制单株水分利用效率、根冠形态和生长发育的基因簇存在。在第六部分同源染色体上,6A和6B上都分别有由控制根系多个QTL组成的基因簇,6D染色体着丝粒周围有一个大的基因簇,由7个控制叶片和单株水分利用效率的QTL组成,说明第六部分同源染色体在小麦水分利用效率遗传方面起重要作用。 Abstract:Research development of genetic mapping,physics mapping,genome sequencing and expressed sequence tags in wheat have been reviewed in this paper.RFLP genetic linkage map of wheat recombinant inbred lines derived from W7984×Opata,was used to study QTL of 33 traits associated with water use efficiency.Compared with QTL map of 7 group homeologues chromosomes,the results were showed as follows:nearby the centromeric region of 1A and 1B chromosome,the gene cluster of controlling photosynthetic and root traits were located.The gene clusters of controlling water use efficiency per plant,root and plant height and growth rate were located on the 2 group chromosomes.The gene clusters of controlling root traits were located on the 6A an 6B chromosome,there was a big gene cluster mad up by 7 QTLs controlling water use efficiency of wheat leaf and per plant nearby the centromeric region of 6D chromosome.It showed that 6th homeologous chromosomes play an important role in controlling water use efficiency in wheat.     

水产动物遗传连锁图谱的研究现状及应用展望

综述了近年来遗传连锁图谱在水产生物中的研究现状,包括作图群体、作图方法等,并对连锁图谱的应用前景作了展望,指出其在分子标记辅助育种、基因定位与克隆及比较基因组学等方面的应用潜力。 Abstract:Constructing genetic linkage map is an essential tool to acknowledge genome in aquaculture species.This paper has reviewed the current status of genetic linkage map research,including mapping population,mapping method and molecular markers used to construct linkage map.Linkage map has great potential in marker assisted selection (MAS),gene locating and cloning,and comparative genome mapping.Genetic linkage map with high density and wide coverage of genome will allow cloning the genes which contribute to economically important traits.The ultimate aim of the constructing linkage map is the development of fast-growing,disease-resistant strains of the major aquaculture species.     

玉米大斑病抗性遗传的研究进展

由于大斑病生理小种的变异,致使原来抗大斑病的玉米品种丧失抗性,对玉米生产造成严重危害,至今已经发现大斑病菌生理小种5个。玉米对大斑病的抗性可分为多基因控制的数量性状和显性单基因控制的质量性状,前者涉及玉米的10条染色体;后者包括t1、Ht2、Ht3、HtN等基因。本文对大斑病生理小种变化,玉米大斑病抗性单基因（Ht）的来源、遗传特点、染色体定位以及数量抗性基因的QTL分析等研究进展作了综述。 Abstract:As the rapid variation and mutation of the races of Exserohilum turcicum (Helminthosporium turcicum),maize varieties lost their resistance to northern corn leaf blight (NCLB) disease caused by new races of E.Turcicum.This brought the disaster in maize production.Up to now 5 races have been found.The maize resistance to E.turcicum can be divided into quantitative and qualitative resistance,the former is associated with 10 chromosomes in maize,and the later includes genes of t1、Ht2、Ht3 and HtN.The race variation of E.turcicum,the original gene resources and genetic characteristics of each Ht monogenic resistance,the chromosome location of t1、Ht2、HtN genes,and the QTL analysis of quantitative resistant genes for E.turcicum in maize were reviewed in this paper.     

A two‐step approach to map quantitative trait loci for meat quality in connected porcine F2 crosses considering main and epistatic effects

The aim of this study was to map QTL for meat quality traits in three connected porcine F₂ crosses comprising around 1000 individuals. The three crosses were derived from the founder breeds Chinese Meishan, European Wild Boar and Pietrain. The animals were genotyped genomewide for approximately 250 genetic markers, mostly microsatellites. They were phenotyped for seven meat quality traits (pH at 45 min and 24 h after slaughter, conductivity at 45 min and 24 h after slaughter, meat colour, drip loss and rigour). QTL mapping was conducted using a two‐step procedure. In the first step, the QTL were mapped using a multi‐QTL multi‐allele model that was tailored to analyse multiple connected F₂ crosses. It considered additive, dominance and imprinting effects. The major gene RYR1:g.1843C>T affecting the meat quality on SSC6 was included as a cofactor in the model. The mapped QTL were tested for pairwise epistatic effects in the second step. All possible epistatic effects between additive, dominant and imprinting effects were considered, leading to nine orthogonal forms of epistasis. Numerous QTL were found. The most interesting chromosome was SSC6. Not all genetic variance of meat quality was explained by RYR1:g.1843C>T. A small confidence interval was obtained, which facilitated the identification of candidate genes underlying the QTL. Epistasis was significant for the pairwise QTL on SSC12 and SSC14 for pH24 and for the QTL on SSC2 and SSC5 for rigour. Some evidence for additional pairwise epistatic effects was found, although not significant. Imprinting was involved in epistasis.     

Functional dissection of the Drosophila Kallmann's syndrome protein DmKal-1

Background

The proportion of muscle fibre types and their size affect muscularity as well as functional properties of the musculature and meat quality. We aimed to identify QTL for microstructural muscle properties including muscle fibre size, their numbers and fibre type proportions as well as biophysical parameters of meat quality and traits related to body composition, i.e. pH, conductivity, area of M. longissimus dorsi and lean meat content. A QTL scan was conducted in a porcine experimental population that is based on Duroc and Berlin Miniature Pig.

Results

Least square regression interval mapping revealed five significant and 42 suggestive QTL for traits related to muscle fibre composition under the line-cross model as well as eight significant and 40 suggestive QTL under the half-sib model. For traits related to body composition and biophysical parameters of meat quality five and twelve significant plus nine and 22 suggestive QTL were found under the line-cross and half-sib model, respectively. Regions with either significant QTL for muscle fibre traits or significant QTL for meat quality and muscularity or both were detected on SSC1, 2, 3, 4, 5, 13, 14, 15, and 16. QTL for microstructural properties explained a larger proportion of variance than did QTL for meat quality and body composition.

Conclusion

Microstructural properties of pig muscle and meat quality are governed by genetic variation at many loci distributed throughout the genome. QTL analysis under both, the line-cross and half-sib model, allows detecting QTL in case of fixation or segregation of the QTL alleles among the founder populations and thus provide comprehensive insight into the genetic variation of the traits under investigation. Genomic regions affecting complex traits of muscularity and meat quality as well as microstructural properties might point to QTL that in first instance affect muscle fibre traits and by this in second instance meat quality. Disentangling complex traits in their constituent phenotypes might facilitate the identification of QTL and the elucidation of the pleiotropic nature of QTL effects.     

Microsatellite mapping of quantitative trait loci affecting meat quality, stress hormones and production traits in Duroc × Large White F2 pigs

An F2 cross between Duroc and Large White pigs was carried out in order to detect quantitative trait loci (QTL) for 11 meat quality traits (L*, a* and b* Minolta coordinates and water-holding capacity (WHC) of two ham muscles, ultimate pH of two ham and one loin muscles), 13 production traits (birth weight, average daily gain during post-weaning and fattening periods, carcass fat depths at three locations, estimated lean meat content, carcass length and weights of five carcass cuts) and three stress hormone-level traits (cortisol, adrenaline and noradrenaline). Animals from the three generations of the experimental design (including 456 F2 pigs) were genotyped for 91 microsatellite markers covering all the autosomes. A total of 56 QTL were detected: 49 reached the chromosome-wide level (suggestive QTL with a maximal probability of 0.05) and seven were significant at the genome-wide level (with a probability varying from 6 × 10(-4) to 3 × 10(-3)). Twenty suggestive QTL were identified for ultimate pH, colour measurements and WHC on chromosome (SSC) 5, 6, 7, 8, 9, 11, 13, 14, 15 and 17. For production traits, 33 QTL were detected on all autosomes except SSC6, 8 and 9. Seven of these QTL, located on SSC2, 3, 10, 13, 16 and 17, exceeded the genome-wide significance threshold. Finally, three QTL were identified for levels of stress hormones: a QTL for cortisol level on SSC7 in the cortisol-binding globulin gene region, a QTL for adrenaline level on SSC10 and a QTL for noradrenaline level on SSC13. Among all the detected QTL, seven are described for the first time: a QTL for ultimate pH measurement on SSC5, two QTL affecting birth weight on SSC2 and 10, two QTL for growth rate on SSC15 (during fattening) and 17 (during post-weaning) and two QTL affecting the adrenaline and noradrenaline levels. For each QTL, only one to five of the six F1 sires were found to be heterozygous. It means that all QTL are segregating in at least one of the founder populations used in this study. These results suggest that both meat quality and production traits can be improved in purebred Duroc and Large White pigs through marker-assisted selection. It is of particular interest for meat quality traits, which are difficult to include in classical selection programmes.     

A Bayesian method for simultaneously detecting Mendelian and imprinted quantitative trait loci in experimental crosses of outbred species

Genomic imprinting is interpreted as a phenomenon, in which some genes inherited from one parent are not completely expressed due to modification of the genome caused during gametogenesis. Subsequently, the expression level of an allele at the imprinted gene is changed dependent on the parental origin, which is referred to as the parent-of-origin effect. In livestock, some QTL for reproductive performance and meat productivity have been reported to be imprinted. So far, methods detecting imprinted QTL have been proposed on the basis of interval mapping, where only a single QTL was tested at a time. In this study, we developed a Bayesian method for simultaneously mapping multiple QTL, allowing the inference about expression modes of QTL in an outbred F2 family. The inference about whether a QTL is Mendelian or imprinted was made using Markov chain Monte Carlo estimation by comparing the goodness-of-fits between models, assuming the presence and the absence of parent-of-origin effect at a QTL. We showed by the analyses of simulated data sets that the Bayesian method can effectively detect both Mendelian QTL and imprinted QTL.     

Fine mapping and single nucleotide polymorphism effects estimation on pig chromosomes 1, 4, 7, 8, 17 and X

Fine mapping of quantitative trait loci (QTL) from previous linkage studies was performed on pig chromosomes 1, 4, 7, 8, 17, and X which were known to harbor QTL. Traits were divided into: growth performance, carcass, internal organs, cut yields, and meat quality. Fifty families were used of a F2 population produced by crossing local Brazilian Piau boars with commercial sows. The linkage map consisted of 237 SNP and 37 microsatellite markers covering 866 centimorgans. QTL were identified by regression interval mapping using GridQTL. Individual marker effects were estimated by Bayesian LASSO regression using R. In total, 32 QTL affecting the evaluated traits were detected along the chromosomes studied. Seven of the QTL were known from previous studies using our F2 population, and 25 novel QTL resulted from the increased marker coverage. Six of the seven QTL that were significant at the 5% genome-wide level had SNPs within their confidence interval whose effects were among the 5% largest effects. The combined use of microsatellites along with SNP markers increased the saturation of the genome map and led to smaller confidence intervals of the QTL. The results showed that the tested models yield similar improvements in QTL mapping accuracy.     

Mapping carcass and meat quality QTL on Sus Scrofa chromosome 2 in commercial finishing pigs

Quantitative trait loci (QTL) affecting carcass and meat quality located on SSC2 were identified using variance component methods. A large number of traits involved in meat and carcass quality was detected in a commercial crossbred population: 1855 pigs sired by 17 boars from a synthetic line, which where homozygous (A/A) for IGF2. Using combined linkage and linkage disequilibrium mapping (LDLA), several QTL significantly affecting loin muscle mass, ham weight and ham muscles (outer ham and knuckle ham) and meat quality traits, such as Minolta-L* and -b*, ultimate pH and Japanese colour score were detected. These results agreed well with previous QTL-studies involving SSC2. Since our study is carried out on crossbreds, different QTL may be segregating in the parental lines. To address this question, we compared models with a single QTL-variance component with models allowing for separate sire and dam QTL-variance components. The same QTL were identified using a single QTL variance component model compared to a model allowing for separate variances with minor differences with respect to QTL location. However, the variance component method made it possible to detect QTL segregating in the paternal line (e.g. HAMB), the maternal lines (e.g. Ham) or in both (e.g. pHu). Combining association and linkage information among haplotypes improved slightly the significance of the QTL compared to an analysis using linkage information only.     

Genetic mapping of quantitative trait loci for meat quality and muscle metabolic traits in cattle

A whole‐genome scan was carried out in New Zealand and Australia to detect quantitative trait loci (QTL) for live animal and carcass composition traits and meat quality attributes in cattle. Backcross calves (385 heifers and 398 steers) were generated, with Jersey and Limousin backgrounds. The New Zealand cattle were reared and finished on pasture, whilst Australian cattle were reared on grass and finished on grain for at least 180 days. This paper reports on meat quality traits (tenderness measured as shear force at 4–5 ages on two muscles as well as associated traits of meat colour, pH and cooking loss) and a number of metabolic traits. For meat quality traits, 18 significant QTL (P < 0.05), located in nine linkage groups, were detected on a genome‐wise basis, in combined‐sire (seven QTL) or within‐sire analyses (11 QTL). For metabolic traits, 11 significant QTL (P < 0.05), located in eight linkage groups, were detected on a genome‐wise basis, in combined‐sire (five QTL) or within‐sire analyses (six QTL). BTA2 and BTA3 had QTL for both metabolic traits and meat quality traits. Six significant QTL for meat quality and metabolic traits were found at the proximal end of chromosome 2. BTA2 and BTA29 were the most common chromosomes harbouring QTL for meat quality traits; QTL for improved tenderness were associated with Limousin‐derived and Jersey‐derived alleles on these two chromosomes, respectively.     

Detection of a Cis [corrected] eQTL controlling BCMO1 gene expression leads to the identification of a QTG for chicken breast meat color

Classical quantitative trait loci (QTL) analysis and gene expression QTL (eQTL) were combined to identify the causal gene (or QTG) underlying a highly significant QTL controlling the variation of breast meat color in a F2 cross between divergent high-growth (HG) and low-growth (LG) chicken lines. Within this meat quality QTL, BCMO1 (Accession number GenBank: AJ271386), encoding the β-carotene 15, 15'-monooxygenase, a key enzyme in the conversion of β-carotene into colorless retinal, was a good functional candidate. Analysis of the abundance of BCMO1 mRNA in breast muscle of the HG x LG F2 population allowed for the identification of a strong cis eQTL. Moreover, reevaluation of the color QTL taking BCMO1 mRNA levels as a covariate indicated that BCMO1 mRNA levels entirely explained the variations in meat color. Two fully-linked single nucleotide polymorphisms (SNP) located within the proximal promoter of BCMO1 gene were identified. Haplotype substitution resulted in a marked difference in BCMO1 promoter activity in vitro. The association study in the F2 population revealed a three-fold difference in BCMO1 expression leading to a difference of 1 standard deviation in yellow color between the homozygous birds at this haplotype. This difference in meat yellow color was fully consistent with the difference in carotenoid content (i.e. lutein and zeaxanthin) evidenced between the two alternative haplotypes. A significant association between the haplotype, the level of BCMO1 expression and the yellow color of the meat was also recovered in an unrelated commercial broiler population. The mutation could be of economic importance for poultry production by making possible a gene-assisted selection for color, a determining aspect of meat quality. Moreover, this natural genetic diversity constitutes a new model for the study of β-carotene metabolism which may act upon diverse biological processes as precursor of the vitamin A.     

A genome scan reveals QTL for growth, fatness, leanness and meat quality in a Duroc-Pietrain resource population

We performed a genome-wide QTL scan for production traits in a line cross between Duroc and Pietrain breeds of pigs, which included 585 F(2) progeny produced from 31 full-sib families genotyped with 106 informative microsatellites. A linkage map covering all 18 autosomes and spanning 1987 Kosambi cM was constructed. Thirty-five phenotypic traits including body weight, growth, carcass composition and meat quality traits were analysed using least square regression interval mapping. Twenty-four QTL exceeded the genome-wide significance threshold, while 47 QTL reached the suggestive threshold. These QTL were located at 28 genomic regions on 16 autosomal chromosomes and QTL in 11 regions were significant at the genome-wide level. A QTL affecting pH value in loin was detected on SSC1 between marker-interval S0312-S0113 with strong statistical support (P < 3.0 x 10(-14)); this QTL was also associated with meat colour and conductivity. QTL for carcass composition and average daily gain was also found on SSC1, suggesting multiple QTL. Seventeen genomic segments had only a single QTL that reached at least suggestive significance. Forty QTL exhibited additive inheritance whereas 31 QTL showed (over-) dominance effects. Two QTL for trait backfat thickness were detected on SSC2; a significant paternal effect was found for a QTL in the IGF2 region while another QTL in the middle of SSC2 showed Mendelian expression.     

A molecular genome scan analysis to identify chromosomal regions influencing economic traits in the pig. II. Meat and muscle composition

Molecular genetic markers can be used to identify chromosomal regions that contain quantitative trait loci (QTL) that control meat quality and muscle composition traits in farm animals. To study this in pigs, a resource family was generated from a cross between two Berkshire grand sires and nine Yorkshire grand dams. A total of 525 F₂ progeny from 65 matings of F₁ parents were produced. Phenotypic data on 28 meat quality traits (drip loss, water holding capacity, firmness, color, marbling, percentage cholesterol, ultimate pH, fiber type, and several sensory panel and cooking traits) were collected on the F₂ animals. Animals were genotyped for 125 microsatellite markers covering the entire genome. Least squares regression interval mapping was used for QTL detection. Significance thresholds were determined by permutation tests. A total of 60 QTL were detected at the 5% chromosome level for meat quality traits, on Chrs 1, 2, 4, 5, 6, 7, 8, 10, 11, 12, 13, 14, 15, 17, 18, and X, of which 9 and 1 QTL were significant at the 5% and 1% genome-wise levels (on Chrs 1, 5, 12, 15, and 17), respectively. Received: 29 November 2000 / Accepted: 27 March 2001