Graft-induced variants as a source of novel characteristics in the breeding of pepper (Capsicum annuum L.)

A line with genetic changes that was obtained from selfed seeds of the scion of an intraspecific pepper graft was used as a source of new characteristics in this breeding experiment. Five new variant lines and several sublines were bred by the use of this graft-induced variant strain and two other cultivars. Gradual introduction of the desired quantitative traits and selection resulted in combinations which significantly outperform the parental lines. Our breeding aim was to combine the two-lobed fruit shape that is characteristic for the graft-induced variants with thick pericarp, high sugar content, large fruit size, and significantly reduced or eliminated pungency in the new variants. A bushy plant type, typical for the graft-induced variants could be maintained in some selected sublines. The use of the three different genotypes resulted in many favorable combinations of quantitative traits, and lines were selected with the most valuable new characteristics. However, not all of these expressed the two-lobed fruit apex of the graft-induced variants. Our results reveal that the new characteristics which are induced by grafting are stable, new traits, and can be used as a novel genetic source in the breeding of pepper. This revised version was published online in July 2006 with corrections to the Cover Date.     

玉米自交系性状保持和纯化的分子依据

研究玉米自交系繁殖过程中保种圃建立的理论和株系性状的选择依据对自交系性状的保持、保纯以及杂交种特性保持具有重要意义。利用3个不同纯度水平玉米自交系连续自交3代,在SSR水平上和SNP水平上检测玉米纯合度,并在S₂和S₃调查田间性状。利用不同初始纯合度的自交系建立保种圃应自交的代数。不同株系在SSR分子检测具有一致性的前提下,在SNP水平上仍然存在较高的杂合度,随初始纯合度升高自交纯合的效率减低,选择初始纯度高的材料有利于后代遗传位点的快速纯合。在田间选择自交系时,根据性状稳定性并结合自交代数依次进行。首先依据较易稳定纯合的群体目测性状;其次,数量性状中,果穗长、果穗直径、雄穗一级侧枝数、穗行数等可作为第二类依据的性状;最后,在自交高代选择穗位高/株高、行粒数、叶长、叶宽等较难稳定的性状。     

水稻高世代回交导入系耐盐性的遗传研究

水稻是一种对盐敏感的作物，盐分是限制水稻产量的主要因子之一。本研究利用广泛推广种植的杂交籼稻的亲本珍汕97（ZS97）和测序粳稻品种日本晴（Nipponbare）杂交、回交构建的导入系，对水稻的耐盐性进行遗传研究。用88份导入系作苗期盐胁迫（0．3％氯化钠）处理试验，发现6份导入系的耐盐性同受体亲本ZS97有显著差异，其中5份导入系耐盐，1份对盐敏感。图示基因型分析表明5份导入系中含有少数外源导入片段及耐盐相关的基因。     

Cell selection as a possible reason for the specificity of somaclonal variation in pea

A study of regenerants obtained from long-term callus cultures of different pea (Pisum sativum L.) genotypes revealed specificity of in vitro mutagenesis. The specificity was displayed in the preferential generation of the somaclonal variations affecting quantitative and developmental characters. About 60% of regenerated lines obtained from the cultivar Ranny Zeleny carried mutations in the Lf and Sn loci, which control initiation of flowering. An in vitro study of isogenic lines differing at the Lf and Sn loci illustrates the growth advantages of mutant genotypes in tissue culture. These experiments suggest that mutations affecting developmental characters (e.g. mutations in loci which control flowering behaviour) may be expressed in tissue culture and may cause increased adaptation in mutant cells to the in vitro conditions. Rapid propagation of mutant cells during in vitro culture may lead to a higher proportion of quantitative mutations among the regenerated plants.     

基于形态特性的豌豆(Pisum sativum)F_1,F_2和F_3代遗传研究和高产抗白粉病品系的选育(英文)

本研究的目的是确定豌豆F1和F2代的6个相对性状的遗传和连锁关系,并在F3代中选择高产抗白粉病株系.选择两个近等基因系Falloner和11760-3ER进行杂交,得到的F2代的性状分离比均为3:1,这符合X2(p＞0.07)适合度检测,表明是单基因遗传.花色和种子颜色与花青素关联的似然比分别为44.31和34.91,每个叶片中小叶数目和卷须类型关联的似然比为33.21.这三个关联的质量性状在P＜0.00具有非常显著的相关性,但与白粉病性状均不相关联.选择F3代的4个与产量密切相关的数量性状进行研究,发现总荚重和种荚比分别具有49.77%和20.01%的最高变异系数.相关性研究发现,总荚重与籽粒重量、荚宽、荚长和种荚比呈显著正相关.荚长与种荚比呈显著正相关.根据数量性状值和白粉病抗性表现,选择GN070140-2,GN070143-1和GN070140-0三个株系作为以后的栽培品种.     

Quantitative trait loci mapping for flag leaf traits in rice using a chromosome segment substitution line population

To study the genetic basis of rice flag leaf morphology, quantitative genetic analysis was conducted in a population of 37 chromosome segment substitution lines (CSSLs) of indica elite variety ‘Habataki’ in the background of japonica cultivar ‘Sasanishiki’ across three different environments. The CSSLs showed normal distribution with transgressive segregation, indicating that these four traits are controlled by polygenes. Moreover, analyses of variance showed that these traits were highly influenced by the growing environment, which are typical for polygenic quantitative traits. Seven quantitative trait loci (QTLs) on four chromosomes were detected in total: four for flag leaf width, one for flag leaf area and two for flag leaf angle. Two key QTLs, qFLW4 and qFLAG5 controlling flag leaf width and angle, respectively, were identified in all three environments. These QTLs could provide useful information for marker‐assisted selection in improving the performance of plant architecture with regard to leaf angle and area. Moreover, developed CSSLs with these QTLs information are also useful research materials to reveal the importance of leaf morphology in relation to grain yield.     

Winter curing of <Emphasis Type="Italic">Prunus dulcis</Emphasis> cv ‘Butte,’ <Emphasis Type="Italic">P. webbii</Emphasis> and their interspecific hybrid in response to <Emphasis Type="Italic">Xylella fastidiosa</Emphasis> infections

In traditional quantitative genetics, additive effects of genes acting in a population of biparental homozygous lines are estimated on the basis of the phenotypic observations only, usually by taking a difference between mean values for extreme lines. Current molecular methods allow to estimate the additive effects by additionally taking into account the marker data. In this paper we compare these two methods of estimation of additive gene action effects analytically, by simulations and by analysis of real data sets for doubled haploid lines and recombinant inbred lines. The analytic comparison shows under which conditions an agreement of the two methods can be achieved. In most of the considered experimental data and in simulations we observe that the additive effect calculated on the basis of the marker observations is smaller than the total additive effect obtained from phenotypic observations only. This result is discussed, and a weighted regression approach is proposed as a method which can close the gap between the purely phenotypic and genotypic approaches.     

Genetic analysis of heterotic loci detected in a cross between indica and japonica rice (Oryza sativa L.)

The study on the genetic basis of heterosis has received significant attention in recent years. In this study, using a set of introgression lines (ILs) and corresponding testcross F₁ populations, we investigated heterotic loci (HL) associated with six yield-related traits in both Oryza sativa L. subsp. indica and japonica. A total of 41 HL were detected on the basis of mid-parent heterosis values with single-point analysis. The F₁ test-cross population showed superiority in most yield-related traits and was characterized by a high frequency of overdominant HL. Thirty-eight of the 41 HL were overdominant, and in the absence of epistasis, three HL were dominant, suggesting that heterotic effects at the single-locus level mainly appeared to be overdominant in rice. Twenty-four HL had a real positive effect, suggesting that they are viable candidates for the improvement of rice yield potential. Compared with the quantitative trait loci (QTLs) detected in the ILs, only six out of the 41 (14.6%) HL were detected in QTL analysis under the same statistical threshold, indicating that heterosis and trait performance may be conditioned by different sets of loci.     

Optimization of DH-line based recurrent selection procedures in maize under a restricted annual loss of genetic variance

Doubled haploid (DH) lines are increasingly being used in commercial hybrid maize (Zea mays L.) breeding. They allow for various quantitative genetic and logistic advantages provided that they are implemented in efficient and optimally allocated breeding procedures. In the present study, a new software was applied to optimize two recurrent selection (RS) schemes for hybrid maize breeding based on DH lines under a restricted annual budget and an upper limit for the relative annual loss of genetic variance. This software maximizes the expected gain from selection in general combining ability by means of quantitative genetic model calculations. Optimization results are compared for one, two, and three stages of testcross selection under different assumptions regarding the evaluation of lines per se and the annual budget. Results show that the optimum allocation of technical and budget resources to the individual steps of an RS program and the efficiency of alternative RS procedures are decisively determined by the number of selection stages. Under standard assumptions, one-stage selection was superior to two- and three-stage selection. Thus, shortening the length of an RS scheme considerably increases its efficiency. By intercrossing a reduced number of selected lines for starting a new RS cycle, the short-term response to selection may be increased, but the population size and, thus, the selection limits in the long run are diminished. Therefore, fair comparisons of alternative RS procedures require to define the intended time span for maximizing the genetic gain from RS and to restrict the relative annual loss of genetic variance accordingly.     

Mapping of quantitative trait loci for floral scent compounds in cowpea (Vigna unguiculata L.)

Floral scent is a very important trait in plant evolution. Currently, little is known about the inheritance of floral scent in cowpea (Vigna unguiculata L.) or changes that might have occurred during its domestication. Therefore, we analysed scent volatiles and molecular markers in a population of 159 F₇ recombinant inbred lines derived from a cross of a domesticated blackeye cowpea cultivar, ‘524B’ and a wild accession ‘219‐01’. Using gas chromatography‐mass spectrometry (GC–MS) 23 volatile compounds were identified that fall into five general functional categories. Twenty‐two of the compounds displayed quantitative variation in the progeny, and a total of 63 QTLs influencing the amounts of these volatiles were mapped onto the cowpea genetic marker map. Although QTLs for volatile compounds putatively involved in cowpea flower scent were found on 9 of the 11 cowpea chromosomes, they were not evenly distributed with QTLs mainly clustered on LGs 1, LGs 2 and LG 4. Our results serve as a starting point for both more detailed analyses of complex scent biosynthetic pathways and the development of markers for marker‐assisted breeding of scented rose varieties.     

利用染色体片段代换系定位水稻叶片形态性状QTL

水稻叶片形态是理想株型的重要组成部分,控制叶片形态基因的挖掘对于塑造水稻理想株型,实现水稻超高产目标具有重要意义。本研究利用广陆矮4号为受体亲本,日本晴为供体亲本构建的一套染色体片段代换系,对水稻上三叶(倒一叶、倒二叶和倒三叶)形态性状与单株籽粒产量进行了相关性分析,并开展了相关QTL定位。结果表明,除剑叶宽外,水稻上三叶的叶长、叶宽都与单株产量呈极显著正相关。同时,通过单因素方差分析和Dunnett’s多重比较,在两年间重复检测到20个控制叶形的QTL,其中叶长QTL 13个(8个表现正向效应,5个表现负向效应);叶宽QTL 7个(4个表现正向效应,3个表现负向效应)。这些QTL的鉴定为水稻叶形性状的分子改良提供了重要遗传信息。     

Genetic mapping of sedimentation volume across environments using recombinant inbred lines of durum wheat

SDS-sedimentation volume (SV) is a biochemical index widely used to evaluate flour quality in durum and bread wheats. Significant association between SV and endosperm proteins (gliadin, high-molecular-weight- and low-molecular-weight-glutenin subunits) have been reported. Protein loci, however, account for only a portion of the total genetic variability. The objective of this study was to identify and locate quantitative trait loci (QTLs) associated with SV in a set of recombinant inbred (RI) lines, derived from a cross between the cv.‘Messapia’ of durum wheat and the accession MG4343 of the var. dicoccoides, and characterized for 259 genetic and molecular (RFLP) markers. Significant differences were detected for the quality index in the six environments examined, while the pattern of variability was that of a quantitative trait. Regression analysis of marker loci and sedimentation volume indicated, as expected, that chromosome 1B, on which are located the Gli-B 1/Glu-B 3 loci for some gliadin and glutenin subunits, is important for wheat quality. Two additional regions located on chromosomes 6AL and 7BS, and four regions on 1AL, 3AS, 3BL and 5AL, were shown to have single-factor effects on sedimentation volume at P < 0.001 and P < 0.01, respectively. Positive effects were contributed by both parents. A multiple linear regression model consisting of seven significant loci on different chromosomes explained 62–91% of the genotypic variation of the trait. The availability of linked markers to QTLs may facilitate the genetic dissection of quantitative traits and the early selection in wheat breeding programmes.     

陆地棉重组自交系产量及产量构成因子性状的上位性QTL分析

棉花的产量及产量构成因子性状是以复杂的方式遗传,遗传力较低并易受环境条件影响。经典数量遗传学指出,上位性是复杂性状的遗传基础。本研究以湘杂棉2号F8和F9世代重组自交系为材料,调查了3个环境下的产量及产量构成因子性状,并构建了遗传连锁图。旨在定位产量及产量构成因子性状的上位性QTL并分析QTL与环境的互作效应。所有产量及产量构成因子性状均检测到上位性QTL,共检测到16对加性互作QTL（AA）,涉及的位点中仅4个有单位点效应,这反映了上位性的复杂性及其对产量和产量构成因子性状的重要贡献。共检测到17对QTL加性和环境互作（AE）,以及14对上位性QTL与环境的互作,表明环境因素对产量和产量构成因子性状起重要影响作用。研究结果还表明上位性效应作为湘杂棉2号的遗传基础起着重要作用。对各性状在不同环境的优良基因型进行了预测。综合优良家系（GSL）和特定环境下的优良家系（SL）的性状表现高于两亲本,表明湘杂棉2号重组自交系各性状都有提高的潜力。由于QTL加性和环境互作以及上位性QTL与环境互作的影响,预测的优良家系基因型会随着环境的改变而不同,表明应针对特定环境开展棉花育种。     

小麦种子根结构及胚芽鞘长度的QTL分析

为探讨小麦种子根结构及胚芽鞘长度的遗传基础,以小麦DH群体(旱选10号×鲁麦14)的150个株系为材料,利用凝胶室培养幼苗,测定种子根的数目和最大根长、胚芽鞘长度、根苗干重比等性状,并通过扫描仪测定幼苗种子根的总长度、根直径及角度。利用已经构建的DH群体遗传连锁图谱,采用基于混合线性模型的复合区间作图法分析上述性状的QTL。在1A、1B、2B、2D、3B、4A、4D、5A、5B、6A、7A和7B共12条染色体上检测到12个加性效应QTL和7对加性×加性互作效应QTL。QTL的加性效应值在0.02~8.45之间,对表型变异的贡献率为5.64%~12.37%。7对加性×加性互作效应QTL分布在1A–2B(2)、1A–6A、1B–2D、5B–6A、6A–7A和6A–7B等6对染色体之间,其互作效应值为0.20~7.45,对表型变异的贡献率为8.70%~15.90%。在染色体3B和7A上各检测到1个种子根结构相关性状的QTL簇。     

普×爆F3家系穗粒性状及其与膨化倍数的相关分析

在春播和夏播两种环境条件下,对一个普通与爆裂玉米自交系杂交组合的259个F3家系的穗粒性状及其与膨化倍数的相关分析结果表明：F3代分离出优于爆裂亲本穗粒性状的家系较多;穗粒性状是由微效多基因控制的数量性状;百粒重、穗粒重对膨化倍数直接或间接作用为较大负效应,行粒数、轴粗、穗长对膨化倍数的直接作用为正效应,其它性状通过行粒数和穗长对膨化倍数的间接作用多为正效应。因此,可以直接对穗长和行粒数进行正向选择,提高普×爆后代选系的产量。     

Genotypic variation for tolerance to phosphorus deficiency in rice and the potential for its exploitation in rice improvement

Deficiency in phosphorus (P) can severely limit rice yields. Developing cultivars with tolerance to P deficiency may represent a more sustainable solution than sole reliance on fertilizer application. To assess genotypic variation for tolerance to P deficiency the P uptake of 30 genotypes was measured on P‐deficient soil. Variation for P uptake was high, ranging from 0.6 to 12.9 mg P/plant. Traditional varieties were superior to modern varieties. A major quantitative trait locus for P uptake had previously been identified in a population developed by crossing the modern variety ‘Nipponbare’ with the P deficiency‐tolerant landrace ‘Kasalath’. This quantitative trait locus was transferred to ‘Nipponbare’ by three backcrosses. Under P deficiency this improved line surpassed ‘Nipponbare’ in P uptake by 170% and in grain yield by 250%. These results show that the genotypic variation for tolerance to P deficiency in rice can be used successfully in rice improvement. By combining high P uptake of the donor variety ‘Kasalath’ with a high harvest‐index characteristic of modern varieties it was possible to more than triple the grain yield of ‘Nipponbare’ under P deficiency.     

基于CSSSLs的水稻穗长QTL的定位

穗长是影响水稻产量的重要因子之一,是典型的数量性状,遗传基础复杂,且易受环境等因素的影响。染色体单片段代换系(Chromosome single segment substitution lines,CSSSLs)减少了个体间遗传背景的干扰,是鉴定复杂性状QTL的新型遗传材料。本研究以广陆矮4号为受体、日本晴为供体的85个染色体单片段代换系群体为试验材料,通过单因素方差分析和Dunnett’s多重比较测验单片段代换系与受体亲本广陆矮4号之间穗长的差异,对代换片段上穗长QTL进行了鉴定。以P<0.001为阈值,共检测到22个穗长QTLs,分布于除第10染色体以外的11条染色体上,其加性效应值的变化范围为-2.63～3.87,加性效应百分率变化范围为-11.47%～16.88%。这些QTLs的鉴定,为进一步克隆穗长QTL以及水稻穗长的分子改良提供了重要的依据。     

QTL Mapping of Boll Weight Trait Based on Recombinant Inbred Lines in Gossypium hirsutum L.

[Objective] The aim of this study was to explore the quantitative trait locus (QTL) related to the boll weight. [Method] A single seed descended population of 137 recombinant inbred lines (RILs) was developed from the cross of upland cotton (Gossypium hirsutum L.) CCRI 36 and G2005, an introgression inbred line introgressed from G. barbadense. Using restriction-site associated DNA sequencing (RAD-seq), a genetic linkage map composed of 6 434 makers, including 6 295 single nucleotide polymorphisms (SNP) and 139 simple sequence repeat (SSR) markers, was developed from the RILs population. [Result] This map spanned 4 071.98 cM with an average distance of 0.63 cM between adjacent markers. QTL mapping was performed by using boll weight data of five environments through WinQTLCart 2.5 software. Thirty-two QTL, with 4.46%-15.84% explained phenotypic variation related boll weight, were detected and found distributing on 15 chromosomes. qBW-A4-1, qBW-A4-2, qBW-A5-2, qBW-D9-1, and qBW-D9-2 were detected in two environments, which explained 5.07%-15.84% of the phenotypic variation. [Conclusion] Major QTLs detected in this study will provide an important reference for analysis of the genetic mechanism of boll weight.     

Fine mapping the QTL qFS‐chr.23, using a CSIL

In an earlier advanced‐backcross quantitative trait locus (QTL) analysis of an interspecific cross of Gossypium hirsutum cv. ‘Xinluzhong 36’(‘XLZH36’) and G. barbadense cv. ‘Xinhai 21’(‘XH21’), a QTL for fibre strength in the chromosome segment introgression line IL23‐09 was analysed. Single marker analysis revealed that the markers on chro.23 were associated with fibre strength. Using composite interval mapping with the F₂ population (1296 plants), a QTL for fibre strength was detected on chro. 23. The QTL explained 8.9% and 15.9% of phenotypic variances in the F₂ and F_2 : 3 generations, respectively. Substitution mapping suggested that the QTL was located at a physical distance of 23.4 kb between the markers BNL1414 and the single nucleotide polymorphism (SNP) locus D09_43776813 C‐G. We designated this QTL as qFS‐chr.23 (quantitative trait locus for fibre strength on chro.23). This work provides a valuable genetic resource for the breeding of high fibre quality in cotton and will facilitate future efforts for map‐based cloning.     

Associations between 23 Quantitative Traits and 10 Genetic Markers in a Barley Cross

Associations of 23 quantitative traits and 10 genetic marker characters were examined in 63 chromosome-doubled lines (DH-lines) derived from the F₁- generation of a cross between an old and a modern spring barley variety. One fourth of the marker × trait combinations showed significant associations. More than two thirds of these associations were to earliness (heading date). Earliness was found to be controlled by two loci: the previously known eak locus and a new locus designated Ea. It is concluded that the associations of quantitative traits with the earliness loci were caused by pleiotropy. Associations were found between two absolutely linked C-bands on chromosome 3 and QTLs (quantitative trait loci) for lodging, straw diameter, and length of top internode of the straw. The three loci on chromosome 5, eak and the two linked powdery mildew loci, Mla9 and Mlk, were associated with a possible QTL for magnesium concentration in grain. Association to the C-band on chromosome 6 suggests QTLs for TGW (thousand grain weight), straw diameter and magnesium concentration in grain. Locus Estl on chromosome 3 was not associated with any of the quantitative traits.