不同发育阶段水稻苗高的QTL分析

分析了不同发育阶段控制水稻苗高的QTL, 用5个阶段和4个净增长量的数据共检测到9个QTL,分别位于染色体1,4,6,7,8,11,和12号上。SH-4 是主基因,它在各个阶段都表达,对苗高的贡献率在20%以上。结果表明, 数量性状的发育或形态建成是由数量性状位点基因选择性表达的结果。 Abstract:QTLs conferring rice seedling height at different developmental stages were analyzed in this paper using a DH population with 122 lines deriving from a cross between indica variety Zai-Ye-Qing 8 and japonica variety Jing-Xi 17. A total of nine QTLs were identified with the data of five stages and four sets of net increase data between two successive stages. Of all the QTLs, Sh-4was a major gene, it expressed at all stages and accounted for more than 20% of the variance. The results revealed that the development of the quantitative trait was controlled by the selective expression of the genes at quantitative trait loci.     

数量性状基因座的动态定位策略

分子标记辅助数量性状基因（QTL）定位和效应分析技术为深入研究数量性状的遗传基础提供了一个有力手段．但目前的QTL定位策略是静态的,只估计各QTL在某观察时刻的累积效应,无法了解QTL的表达动态．本文提出一种新的QTL定位策略,称为“动态定位”,能够揭示QTI表达的动态过程,并能极大地提高QTL定位的统计功效.     

从QTL到QTG的路还有多远?

植物大多数重要的经济性状都是数量性状, 人们对许多植物进行了数量性状基因座(QTL)的研究, 并取得了长足的发展。文章详尽地分析了数量性状表型与基因型的复杂关系, 介绍了当前QTL研究领域里的几种精细作图策略。讨论了当前挖掘控制目标性状QTL基因的研究过程中存在的困难和问题, 提出几个有待发展的研究方向, 并展望了该领域的发展前景。因目前的QTL仍然是一个相当大的染色体区段, 往往含有多个候选基因。文章就怎样从QTL粗放位点研究进一步发展到数量性状基因(quantitative trait gene, QTG)水平上的变异, 再从QTG到相应于基因内多态性的数量性状核苷酸(quantitative trait nucleotides, QTN), 提出了一些见解。来迎接后基因组时代数量遗传领域的挑战。     

水稻QTL分析的研究进展

水稻许多重要的性状是由多基因控制的数量性状,经典的数量遗传学只能把数量性状作为一个整体进行研究。近年来．高密度分子标记连锁图的构建和有效的生物统计学方法的发展使人们对数量性状遗传基础的研究出现了革命性的变化。通过对不同群体内的个体或品系的分子标记基因型和表型数据的共分离分析,能对QTL进行检测和定位。本文对QTL定位的原理和方法进行了介绍,从QTL的数目和效应、上位性效应、QTL基因型与环境的互作、相关性状的QTL以及个体发育不同阶段的QTL等方面对水稻QTL分析的研究进展进行了综述。水稻基因组测序计划已经完成,本文还对基因组时代水稻QTL精细定位和克隆的方法进行了探讨,对QTL分析在水稻育种中的应用前景进行了展望。     

不同发育阶段大豆株高和茎粗QTL的动态分析

利用中豆29×中豆32的重组自交系,以复合区间作图法对不同发育阶段的大豆株高和茎粗同时进行非条件和条件QTL定位,在11个连锁群检测到18个株高QTL,在9个连锁群检测到19个茎粗QTL。不同发育时期影响大豆株高和茎粗QTL的数量、加性效应和贡献率均不相同,QTL表达具有时序性和选择性,有些QTL仅表达1次,有些可多次连续表达。有3个株高QTL和1个茎粗QTL在3个年度重复表达,有6个株高QTL和2个茎粗QTL在2个年度重复表达。F连锁群上株高和茎粗QTL存在共位性,R1～R4期均有株高和茎粗QTL同时表达,但株高和茎粗QTL的增效基因不同,株高QTL表达次数多而茎粗QTL表达次数较少,前期(V4～R3)QTL表达数量多而后期(R4～R5)表达数量较少。株高和茎粗QTL的动态变化与表型相关分析结果一致,对于适期选择粗秆抗倒的高产材料具有指导作用。     

植物数量性状变异的分子基础与QTL克隆研究进展

探讨数量性状变异规律以便对其进行遗传操纵一直是植物遗传学的一个重要领域。DNA分子标记和QTL作图技术的发展以及拟南芥和水稻全基因组测序的完成极大地促进了植物数量性状分子基础的研究。现已克隆了拟南芥ED1、水稻Hdl、玉米Tb1、番茄fw2．2和Brii9-2-5等控制目标数量性状的基因。数量性状表型变异不仅源于多个数量性状基因（QTL）的分离．而且还受到内外环境的修饰。QTL等位基因变异与孟德尔基因变异具有类似的分子基础,即基因表达或蛋白质功能发生改变。通过分析已克隆的植物QTL的变异特征及分子基础,讨论了植物QTL克隆技术策略,并对QTL研究所面临的挑战和应用前景进行了展望。     

利用回交导入系剖析水稻苗期和分蘖期耐盐性的遗传重叠

以籼稻品种IR64为受体,来自伊朗的粳稻农家品种Binam为供体培育的99个BC2F8回交导入系为材料,定位了水稻在2叶1心期和分蘖期控制耐盐相关性状的数量性状基因座（QTL）．共检测到影响苗期叶片盐害级别、幼苗存活天数和地上部钾、钠离子浓度的QTL 13个,影响分蘖期株高、分蘖数和地上部鲜重的QTL 22个．多数分蘖期QTL对盐胁迫表现出明显的表达差异,根据表达情况将这些QTL分成3组,第1组为在对照条件下表达的11个QTL;第2组为在对照和盐胁迫条件下共同表达的5个QTL,其中有3个（QPh5,QPh8,QTn9）在两种环境下的基因效应大小和方向一致,其表达受盐胁迫影响较小;第3组为受盐胁迫诱导表达的6个QTL．检测到13个影响胁迫与对照差值即性状稳定性的QTL,除QPh4,QTn2和QFw2a外,其余10个基因座增加性状稳定性或提高耐盐性的等位基因均来自Binam．上述受盐胁迫影响较小的3个QTL和影响性状稳定性的13个QTL对耐盐性有贡献,属耐盐QTL．比较苗期和分蘖期耐盐QTL的分布,发现多数（69％）影响苗期和分蘖期的耐盐QTL在遗传上相互独立,仅在第1,2,8和11染色体的4个相同或相邻区域定位到影响两个时期的耐盐QTL,表明苗期和分蘖期的耐盐性存在部分的遗传重叠．通过标记辅助选择将苗期和分蘖期的重要耐盐QTL进行累加,或针对苗期和分蘖期的重叠耐盐QTL进行选择,有可能培育出苗期和分蘖期均耐盐的水稻品种．     

大豆遗传图谱的构建和若干农艺性状的QTL定位分析

大豆许多重要农艺性状都是由微效多基因控制的数量性状,对这些数量性状进行QTL定位是大豆数量性状遗传研究领域的一个重要内容.本研究利用栽培大豆科新3号为父本、中黄20为母本杂交得到含192个单株的F2分离群体,构建了含122 个SSR标记、覆盖1719.6cM、由33个连锁群组成的连锁遗传图谱.利用复合区间作图法,对该群体的株高、主茎节数、单株粒重和蛋白质含量等农艺性状的调查数据进行QTL分析,共找到两个株高QTL,贡献率分别为9.15%和6.08%;两个主茎节数QTL,贡献率分别为10. 1%和8.6%;一个蛋白质含量QTL,贡献率为9.8%;一个单株粒重QTL,贡献率为11.4% .通过遗传作图共找到与所定位的4个农艺性状QTL连锁的6个SSR标记,这些标记可以应用于大豆种质资源的分子标记辅助选择,从而为大豆分子标记辅助育种提供理论依据.     

植物数量性状基因的定位与克隆

作物的许多重要农艺性状属于数量性状,鉴定和发掘控制数量性状的基因及其优异的等位变异,并使之快速应用于育种实践是新时期作物科学家和育种学家所面临的重大课题。本文从QTL作图、QTL的精细定位与图位克隆、QTL近等基因系和染色体片断代换系的建立以及基于LD的关联分析等方面对植物数量性状的研究进展进行了讨论,提出了以植物基因组学技术为平台,将QTL作图与关联分析方法相结合,是进行数量性状遗传机理研究同时服务于作物育种实践的有效途径。     

植物数量性状基因的定位与克隆

作物的许多重要农艺性状属于数量性状, 鉴定和发掘控制数量性状的基因及其优异的等位变异, 并使之快速应用于育种实践是新时期作物科学家和育种学家所面临的重大课题。本文从QTL作图、QTL的精细定位与图位克隆、QTL近等基因系和染色体片断代换系的建立以及基于LD的关联分析等方面对植物数量性状的研究进展进行了讨论, 提出了以植物基因组学技术为平台, 将QTL作图与关联分析方法相结合, 是进行数量性状遗传机理研究同时服务于作物育种实践的有效途径。     

Dissection of genetic overlap of salt tolerance QTLs at the seedling and tillering stages using backcross introgression lines in rice

QTLs for salt-tolerance(ST)related traits at the seedling and tillering stages were identified using 99 BC2F8 introgression lines(IL)derived from a cross between IR64(indica)as a recurrent parent and Binam(japonica)from Iran as the donor parent.Thirteen QTLs affecting survival days of seedlings(SDS), score of salt toxicity of leaves(SST),shoot K concentration(SKC)and shoot Na concentration(SNC) at the seedling stage and 22 QTLs underlying fresh weight of shoots(FW),tiller number per plant(TN) and plant height(PH)at the tillering stage were identified.Most QTLs detected at the tillering stage showed obvious differential expression to salt stress and were classified into three types based on their differential behaviors.Type I included 11 QTLs which were expressed only under the non-stress condition.Type II included five QTLs expressed in the control and the salt stress conditions,and three of them(QPh5,QPh8 and QTn9)had similar quantity and the same direction of gene effect,suggesting their expression was less influenced by salt stress.Type III included six QTLs which were detectable only under salt stress,suggesting that these QTLs were apparently induced by the stress.Thirteen QTLs affecting trait difference or trait stability of ILs between the stress and non-stress conditions were identified and the Binam alleles at all loci except QPh4,QTn2 and QFw2a decreased trait difference.The three QTLs less influenced by the stress and 13 QTLs affecting trait stability were considered as ST QTLs which contributed to ST.Comparing the distribution of QTLs detected at the seedling and tillering stages,most(69%)of them were genetically independent.Only four were the same or adjacent regions on chromosomes 1,2,8 and 11 harboring ST QTLs detected at the two stages,suggesting that partial genetic overlap of ST across the two stages occurs.It is likely,therefore,to develop ST rice variety for both stages by pyramiding of ST QTLs of different stages or selection against the overlapping QTLs between the two stages via marker-assisted selection(MAS).     

Association Mapping and Validation of QTLs for Flour Yield in the Soft Winter Wheat Variety Kitahonami

The winter wheat variety Kitahonami shows a superior flour yield in comparison to other Japanese soft wheat varieties. To map the quantitative trait loci (QTL) associated with this trait, association mapping was performed using a panel of lines from Kitahonami’s pedigree, along with leading Japanese varieties and advanced breeding lines. Using a mixed linear model corrected for kernel types and familial relatedness, 62 marker-trait associations for flour yield were identified and classified into 21 QTLs. In eighteen of these, Kitahonami alleles showed positive effects. Pedigree analysis demonstrated that a continuous pyramiding of QTLs had occurred throughout the breeding history of Kitahonami. Linkage analyses using three sets of doubled haploid populations from crosses in which Kitahonami was used as a parent were performed, leading to the validation of five of the eight QTLs tested. Among these, QTLs on chromosomes 3B and 7A showed highly significant and consistent effects across the three populations. This study shows that pedigree-based association mapping using breeding materials can be a useful method for QTL identification at the early stages of breeding programs.     

水稻叶绿素含量动态QTL分析

为剖析水稻不同生育时期叶绿素含量的变化动态及遗传机制,以‘Sasanishiki’（粳稻）、‘Habataki’（籼稻）及其杂交衍生的85个回交重组自交系（BILs）群体为材料,对控制水稻叶片叶绿素含量的数量性状基因位点（QTL）变化动态进行了分析。共检测到39个QTL,包括26个非条件QTL和13个条件QTL,分布在除第7和第11号染色体以外的10条染色体上,平均每个时期检测到3．25个非条件QTL。其中生育前期和生育中后期检测到的QTL位点较少,仅为1—3个;在生育中期（盛期）检测到的QTL位点相对较多,一般为4～5个。在生育期的中期和后期均能在第1和2号染色体上检测到控制叶绿素含量的QTL,并且这些QTL位点在1和2号染色体上呈现聚集现象。本研究同时发现了一些新的QTL位点,这些QTL将有助于我们更全面地了解叶绿素在不同发育时期的遗传基础。     

Detection of grain protein content QTLs across environments in tetraploid wheats

Grain protein content (GPC) is an important quality factor in both durum and bread wheats. GPC is considered to be a polygenic trait influenced by environmental factors and management practice. The objectives of this study were both to compare the quantitative trait loci (QTL) for GPC in a population of 65 recombinant inbred lines of tetraploid wheats evaluated in three locations for several years (eight data sets), and to investigate the genetic relationship among GPC and grain yield. QTLs were determined based on the Messapia × dicoccoides linkage map which covers 217 linked loci on the 14 chromosomes with 42 additional loci as yet unassigned to linkage groups. The map extends to 1352 cM; the average distance between adjacent markers was 6.3 cM. Seven QTLs for GPC, located on the chromosome arms 4BS, 5AL, 6AS (two loci), 6BS, 7AS and 7BS, were detected that were significant in at least one environment at P<0.001 or in at least two environments at P<0.01. One QTL was significant in all but one environment, two were significant in four or five environments, and four were significant in two out of eight environments. Six out of seven protein content QTLs had pleiotropic effects or were associated to QTLs for grain yield and explained the negative correlation among GPC and yield components. The present results support the concept that studies conducted in a single environment are likely to underestimate the number of QTLs that can influence a trait and that the phenotypic data for a quantitative trait should be collected over a range of locations to identify putative QTLs and determine their phenotypic effects.     

Mapping quantitative trait loci associated with days to flowering and photoperiod sensitivity in rice (Oryza sativa L.)

This study was undertaken to identify putative quantitative trait loci (QTLs) associated with days to flowering (DTF) and photoperiod response in rice. A population of 143 recombinant inbred lines derived from a cross between CO39 and Moroberekan was grown under greenhouse conditions and exposed to two different photoperiod regimes. DTF of individual plants was evaluated under 10 h and 14 h day lengths, and loci associated with photoperiod sensitivity were identified based on the delay in flowering under the 14 h photoperiod (DTF at 14 h minus DTF at 10 h). An RFLP data set consisting of 127 markers provided the basis for the QTL analysis. Both single marker and interval analysis were used and interactions between putative QTLs were estimated based on two-way ANOVA. Out of 15 QTLs associated with DTF, only 4 were identified as influencing the response to photoperiod. Interactions between flowering QTLs indicated the complex nature of the control of flowering in rice. The effectiveness of using a single recombinant inbred population to study a variety of complex phenotypes is discussed in relation to practical plant breeding.     

Quantitative trait loci for lodging resistance in a segregating wheat×spelt population

 Lodging can strongly affect both the grain yield and the quality of wheat. Lodging represents a quantitative trait and is difficult to assess on a phenotypic basis. Marker-assisted selection (MAS) could therefore become an important tool in breeding for lodging resistance. In this study, we mapped and characterised quantitative trait loci (QTLs) for lodging resistance, as well as morphological traits correlated with lodging, in a segregating population of 226 recombinant inbred lines derived from the cross of the lodging-resistant wheat variety Forno with the susceptible spelt variety Oberkulmer. Lodging, plant height, leaf width, leaf-growth habit, culm stiffness, culm swinging, culm thickness, days to ear emergence and days to flowering were assessed in field trials at two locations in 1996 and at one location in 1997. Additionally, at one location weight and length parameters were also assessed. Plant height and culm stiffness explained 77% of the phenotypic variance of lodging in a multiple regression model over all three environments. QTL analysis of lodging and morphological parameters was based on a genetic map containing 230 loci with 23 linkage groups (2469 cM). With the method of composite interval mapping nine QTLs for lodging resistance were detected, explaining 63% of the phenotypic variance in a simultaneous fit. Seven of these QTLs coincided with QTLs for morphological traits, reflecting the correlations between these traits and lodging. In our population the most efficient way to improve lodging resistance would be by a combination of indirect selection on plant height and culm stiffness together with MAS on the two QTLs for lodging resistance which did not coincide with QTLs for morphological traits. Received: 3 August 1998 / Accepted: 28 November 1998     

Dynamic expression of nine QTLs for tiller number detected with single segment substitution lines in rice

Nine single segment substitution lines (SSSLs) in rice, which contain quantitative trait loci (QTLs) for tiller number on substituted segments detected in previous studies, were selected as materials to analyse dynamic expression of the QTLs in this study. These SSSLs and their recipient parent, Hua-jing-xian 74 (HJX74), were grown in four different environments and were measured for tiller number at nine different growth stages. An indirect methodology was applied in QTL mapping through analyzing multi-environment phenotypic data. Dynamics of three types of effects (including total effect, main effect, and QE interaction effect) of QTLs was released. It was shown that nine QTLs exhibited statistically significant effects only at certain stages. Effects of a QTL, although insignificant at certain stages, displayed dynamic change with the growth of rice plants. Two common features of nine QTLs were detected, one is no expression within 7 days after transplanting, and the other is opposite expression existed during the whole growth period. Nine QTLs largely focused on expression in certain stages, and accordingly were suggested to partition into three types, expression in prophase, both in prophase and in anaphase, and evenly during the whole stage. It may be reasonable explanation that dynamics of main effects of QTLs are likely due to gene expression selectly at certain times, while dynamics of QE interaction effects of QTLs might attribute to the subrogation of environmental factors. Examination of the association between QE interaction effect and specified environmental factors across stages may provide useful information on how an environmental factor regulates QTL expression. G. Liu and R. Zeng contributed equally to this work.     

AFLP mapping of quantitative trait loci for yield-determining physiological characters in spring barley

 An amplified fragment length polymorphism (AFLP) map covering 965 cM was constructed using 94 recombinant inbred lines of a cross between the spring barley varieties Prisma and Apex. This map was employed to identify quantitative trait loci (QTLs) controlling plant height, yield and yield-determining physiological characters using an approximate multiple-QTL model, the MQM method. The seven physiological traits were parameters used in a process-based crop-growth model that predicts barley biomass production as affected by daily temperature and radiation. The traits were measured in experiments conducted over 2 years. Except for the relative growth rate of leaf area, all traits examined had at least one QTL in each year. QTLs and their effects were found to vary with developmental stages for one trait, the fraction of shoot biomass partitioned to leaves, that was measured at several stages. Most of the traits were associated, though to different extents, with the denso dwarfing gene (the height-reducing allele in Prisma) located on the long arm of chromosome 3. Some of the QTLs were mapped to similar positions in both years. The results in relation to effects of the dwarfing gene, the physiological basis for QTL×environment interaction, and the relative importance of the parameter traits with respect to yield, are discussed. Received: 17 September 1998 / Accepted: 28 December 1998     

Identification of QTL for increased fibrous roots in soybean

Drought stress adversely affects soybean at various developmental stages, which collectively results in yield reduction. Unpredictable rainfall has been reported to contribute about 36% to variation of yield difference between the rain-fed and irrigated fields. Among the drought resistance mechanisms, drought avoidance in genotypes with fibrous roots was recognized to be associated with drought resistance in soybean. Plant introduction PI416937 was shown to possess fibrous roots and has been used as a parent in breeding programs to improve soybean productivity. Little information is available on relative contribution and chromosomal location of quantitative trait loci (QTL) conditioning fibrous roots in soybean. To identify the genomic locations and genetic bases of this trait, a recombinant inbred line population was derived from a cross between PI416937 and ‘Benning’. To detect associated QTLs, phenotypic data were collected and analyzed for 2 years under rain-fed field conditions. The selective genotyping approach was used to reduce the costs and work associated with conducting the QTL analysis. A total of five QTLs were identified on chromosomes Gm01 (Satt383), Gm03 (Satt339), Gm04 (Sct_191), Gm08 (Satt429), and Gm20 (Sat_299), and together explained 51% of the variation in root score. Detected QTLs were co-localized with QTLs related to root morphology, suggesting that fibrous roots QTL may be associated with other morpho-physiological traits and seed yield in soybean. Genetic dissection of the fibrous roots trait at the individual marker loci will allow for marker-assisted selection to develop soybean genotypes with enhanced levels of fibrous roots.