Breeding for drought tolerance in wheat (Triticum aestivum L.): constraints and future prospects

This review article is based on different aspects of wheat breeding for drought tolerance. Drought is regarded as one of the most serious threats to agriculture in Pakistan. Therefore, breeding for drought tolerance must be given top priority. Here, we try to study various options available to wheat breeders exploring the underlying mechanisms of drought tolerance. The progress made in conventional and non-conventional (molecular) based approaches with potential findings and constraints are reviewed in this article. Equipped with such information, it will be possible for breeders to further explore the mysteries of drought tolerance and to select genotypes with an improved yield under water-deficit conditions.     

Conditional and unconditional QTLs mapping of gluten strength in common wheat(Triticum aestivum L.)

Dissecting the genetic relationships among gluten-related traits is important for high quality wheat breeding. Quantitative trait loci(QTLs) analysis for gluten strength,as measured by sedimentation volume(SV) and gluten index(GI),was performed using the QTLNetwork 2.0 software. Recombinant inbred lines(RILs) derived from the winter wheat varieties Shannong 01-35×Gaocheng 9411 were used for the study. A total of seven additive QTLs for gluten strength were identified using an unconditional analysis. QGi1 D-13 and QSv1 D-14 were detected through unconditional and conditional QTLs mapping,which explained 9.15–45.08% of the phenotypic variation. QTLs only identified under conditional QTL mapping were located in three marker intervals:WPT-3743–GLU-D1(1 D),WPT-7001–WMC258(1 B),and WPT-8682–WPT-5562(1 B). Six pairs of epistatic QTLs distributed nine chromosomes were identified. Of these,two main effect QTLs(QGi1 D-13 and QSv1 D-14) and 12 pairs of epistatic QTLs were involved in interactions with the environment. The results indicated that chromosomes 1 B and 1 D are important for the improvement of gluten strength in common wheat. The combination of conditional and unconditional QTLs mapping could be useful for a better understanding of the interdependence of different traits at the QTL molecular level.     

小麦戊聚糖研究进展

戊聚糖是小麦籽粒中非淀粉多糖的主要成分.戊聚糖在小麦籽粒中的含量较低,但它对小麦的营养品质和加工品质都有重要的影响.本文综述了近年来国内外关于小麦戊聚糖的最新研究进展,包括小麦品种间戊聚糖含量的变异、戊聚糖的影响因素和遗传特性、戊聚糖与农艺性状关系及戊聚糖对小麦品质的影响等,旨在为中国小麦品质改良提供依据.     

QTL for grain yield and yield parameters in winter wheat(Triticum aestivum L.)

Field trials with a set of 108 doubled haploid lines(DHs) derived from a cross between the Chinese winter wheat cvs.CA9613 and H1488 were run at Beijing(China).Phenotypic data were recorded for major agronomic yield traits,i.e.grain weight per ear,grain number per ear and thousand grain weight(Tgw) in two field trials at Beijing.Based on the phenotypic data and a genetic map comprising 168 SSR markers,an analysis of quantitative trait loci(QTL) was carried out for yield and yield parameters using the composite interval mapping(CIM) approach.A total of 14 QTL were detected for these traits across two environments.Four of these QTL located on chromosomes 1A and 2B,respectively,exhibited pleiotropic effects.Loci showing pleiotropic effects will be very useful for understanding the homeologous relationships of QTL and designing an appropriate marker-assisted selection programme by multi-trait selection in order to accumulate("pyramide") favorable alleles at different loci.     

小麦雌性育性QTL的高效定位策略

为了高效地定位小麦雌性育性QTL,以选择表型及连锁不平衡结合策略筛选候选标记.对选取的SSR 标记在实验群体中以隐性极端不育亚群体估算其重组频率( c 值) ,确定染色体2AS、2DS 上可能存在QTL.再对候选染色体上18个标记分别计算c 值,并用育成品种与小麦雌性不育系XND 126组成的品种(系)群体计算标记与可能位点间的连锁不平衡值( LD 值) .结合c 值和LD 值提供的位点信息构建部分连锁群,通过实验群体F２ 的连锁分析定位了小麦雌性育性位点taf1.结果发现与taf1 位点连锁较紧密的标记,其c 值较小而LD 值较大.分析认为结合连锁分析和关联分析优势,同时选择c 值较小而LD 值较大的多态性标记有利于快速确定与位点紧密连锁的标记,从而达到高效定位QTL 的目的,并有助于揭示小麦雌性育性的遗传机制.     

小麦产量构成因素的基因效应和杂种优势分析

为提高对小麦产量构成因素的选择效率,以7个半冬性小麦品种及按7×7双列杂交设计的21个F1杂交组合在2个地点的试验资料,研究了小麦2个产量构成因素—每穗粒数和千粒质量的基因效应和杂种优势。结果表明,每穗粒数和千粒质量的遗传符合加性-显性模型,基因显性效应的作用远大于其加性效应,显性程度为超显性。增效基因为显性,减效基因为隐性。每穗粒数和千粒质量在2个试点的平均狭义遗传力分别为54.00%和63.17%。每穗粒数和千粒质量表现正向的平均杂种优势和超亲优势,变异幅度较大,并在基因型、地点及基因型与地点互作间存在极显著差异。     

盐胁迫对小麦叶片电阻抗图谱参数的影响

    为了解能够表征盐胁迫下小麦叶片细胞膜变化的一些电参数特性,应用电阻抗图谱方法研究小麦叶片对不同盐浓度溶液胁迫的反应,拟合叶片的胞外电阻、胞内电阻、弛豫时间及弛豫时间分布系数,分析盐浓度和胁迫时间对各个电阻抗图谱参数的影响以及这些参数彼此之间的相关性.结果表明:随着盐浓度和胁迫时间的增加,胞外电阻和弛豫时间表现为先增加后减小或者逐渐减小的变化趋势;在胁迫时间小于12 h或者盐浓度小于100 mmol·L-1时叶片的胞外电阻变化较剧烈,胞内电阻和弛豫时间分布系数先减小后增大;4个电阻抗图谱参数在时间上的差异极显著,在浓度上的差异只有胞内电阻不显著,其他参数均为极显著;胞外电阻和弛豫时间呈极显著正相关,与弛豫时间分布系数呈极显著负相关,弛豫时间与弛豫时间分布系数呈显著负相关.     

小麦粒长和粒宽的QTL定位分析

【目的】粒长、粒宽是小麦种子重要的形态性状,该性状对籽粒的外观商品品质、产量及磨粉品质均至关重要,研究不同环境条件下小麦粒长、粒宽的单个标记和复合区间作图的QTL定位,对小麦粒长、粒宽的分子标记辅助选择具有重要参考作用。【方法】应用一个由115个系组成的W7984/Opata 85重组自交系(RIL)群体,建立了由394个DNA分子标记组成的遗传连锁图,在2种不同环境条件下对小麦粒长、粒宽进行了单个标记的回归分析和复合区间作图的QTL定位。【结果】在单个标记的回归分析中检测到5个粒长的QTLs、3个粒宽的QTLs;复合区间作图分析结果表明,控制粒长的QTLs分别位于5BL和7DS上,在5BL上的贡献率为20.20%~20.81%,LOD值为4.50~4.55;在7DS上的贡献率为13.54%~13.91%,LOD值为2.94~3.20。控制粒宽的QTL位于2B上,贡献率为13.71%~19.30%,LOD值为2.98~4.18。【结论】位于5B和7D上的控制粒长的QTL和位于2B上的控制粒宽的QTL在2种条件下均能检测到。     

水稻和小麦根际的联合固氮作用

本文阐述了水稻和小麦根际的联合固氮作用的测定方法和联合固氮量。通常认为,     

Genome-wide association analysis for stripe rust resistance in spring wheat(Triticum aestivum L.) germplasm

Stripe rust is a continuous threat to wheat crop all over the world. It causes considerable yield losses in wheat crop every year. Continuous deployment of adult plant resistance(APR) genes in newly developing wheat cultivars is the most judicious strategy to combat this disease. Herein, we dissected the genetics underpinning stripe rust resistance in Pakistani wheat germplasm. An association panel of 94 spring wheat genotypes was phenotyped for two years to score the infestation of stripe rust on each accession and was scanned with 203 polymorphic SSRs. Based on D' measure, linkage disequilibrium(LD) exhibited between loci distant up to 45 c M. Marker-trait associations(MTAs) were determined using mixed linear model(MLM). Total 31 quantitative trait loci(QTLs) were observed on all 21 wheat chromosomes. Twelve QTLs were newly discovered as well as 19 QTLs and 35 previously reported Yr genes were validated in Pakistani wheat germplasm. The major QTLs were QYr.uaf.2 AL and QYr.uaf.3 BS(PVE, 11.9%). Dissection of genes from the newly observed QTLs can provide new APR genes to improve genetic resources for APR resistance in wheat crop.     

利用基因枪法进行小麦遗传转化影响因素研究

以生产上大面积推广的4个小麦品种为材料,对基因枪法转化小麦过程中的影响因素进行了研究。结果表明,在基因枪轰击时采用预培养10～15d的幼胚且在轰击前6h和轰击后18h经0 4mol L甘露醇处理,可明显提高植株再生率;轰击用金粉-DNA量以42-0 21μg 枪为宜;不同品种对筛选剂Bialaphos敏感性有差异,表现为豫麦18>豫麦34>豫麦70>温麦6号,最终确定适宜的筛选剂浓度为2～3mg L。利用上述的优化条件,通过愈伤组织培养、筛选和植株再生,4个品种共获得71株再生植株,其中豫麦18分化率最高达到34 7%,温麦6号分化率最低,未获得再生植株。对长势良好的39株再生苗进行PCR检测,全部呈阳性反应,表明上述优化条件不仅适用而且可行,具有一定的应用价值。     

基于小麦品种‘洛夫林10’的VIGS体系研究

为将病毒介导的基因沉默(Virus induced gene silencing,VIGS)技术应用于小麦-叶锈菌互作体系及小麦基因功能研究,本试验在优化适宜BSMV繁殖并引起发病的环境条件基础上,将病毒载体转染小麦品种‘洛夫林10’(简称L10)叶片并接种叶锈菌生理小种,发现接种病毒对叶锈菌侵染反应型没有影响,通过构建TaCAMTA4与TaATG8的BSMV-VIGS载体,将体外转录病毒转染小麦,以感染BSMV:PDS的L10作指示,在指示叶片变白后,经半定量RT-PCR检测,发现目的基因的表达量明显降低,表明用VIGS技术能够成功沉默L10中的目的基因,这一结果为进一步研究小麦与叶锈菌互作过程中小麦基因的功能及分子机制奠定了基础。     

普通小麦-华山新麦草异附加系的SSR分析

为了建立一套完整的小麦-华山新麦草异附加系,从筛选出的46对在华山新麦草与小麦间具有多态性的SSR引物中选出7对扩增条带清晰的引物,对20个小麦-华山新麦草二体附加系进行归类分析。结果发现:出现了11个小麦-华山新麦草异附加系类型,说明在这20个附加系中包括了华山新麦草7个同源群的附加系,并探讨了小麦与华山新麦草杂交及其后代衍生过程中发生华山新麦草染色体间重排的可能。     

铝胁迫下钙对小麦根液泡膜功能和膜脂组成的影响

用不连续蔗糖密度梯度离心法分离小麦根尖液泡膜微囊 ,比较了铝胁迫下钙对耐铝小麦品种Altas 6 6和铝敏感品种Scout 6 6的根长、根系液泡膜ATP酶和焦磷酸酶活性、膜脂组成的影响。铝胁迫下增加营养液中的钙浓度 ,可明显缓解铝对两品种根伸长的抑制作用 ,提高根系液泡膜H ATP酶、焦磷酸酶和Ca2 ATP酶活性 ;增加磷脂含量 ,部分抑制了铝胁迫所引起的半乳糖脂含量上升。     

QTL mapping of seedling biomass and root traits under different nitrogen conditions in bread wheat(Triticum aestivum L.)

Plant nitrogen assimilation and use efficiency in the seedling's root system are beneficial for adult plants in field condition for yield enhancement. Identification of the genetic basis between root traits and N uptake plays a crucial role in wheat breeding. In the present study, 198 doubled haploid lines from the cross of Yangmai 16/Zhongmai 895 were used to identify quantitative trait loci(QTLs) underpinning four seedling biomass traits and five root system architecture(RSA) related traits. The plants were grown under hydroponic conditions with control, low and high N treatments(Ca(NO_3)_2·4H_2 O at 0, 0.05 and 2.0 mmol L~(-1), respectively). Significant variations among the treatments and genotypes, and positive correlations between seedling biomass and RSA traits(r=0.20 to 0.98) were observed. Inclusive composite interval mapping based on a high-density map from the Wheat 660 K single nucleotide polymorphisms(SNP) array identified 51 QTLs from the three N treatments. Twelve new QTLs detected on chromosomes 1 AL(1) in the control, 1 DS(2) in high N treatment, 4 BL(5) in low and high N treatments, and 7 DS(3) and 7 DL(1) in low N treatments, are first reported in influencing the root and biomass related traits for N uptake. The most stable QTLs(RRS.caas-4 DS) on chromosome 4 DS, which were related to ratio of root to shoot dry weight trait, was in close proximity of the Rht-D1 gene, and it showed high phenotypic effects, explaining 13.1% of the phenotypic variance. Twenty-eight QTLs were clustered in 12 genetic regions. SNP markers tightly linked to two important QTLs clusters C10 and C11 on chromosomes 6 BL and 7 BL were converted to kompetitive allele-specific PCR(KASP) assays that underpin important traits in root development, including root dry weight, root surface area and shoot dry weight. These QTLs, clusters and KASP assays can greatly improve the efficiency of selection for root traits in wheat breeding programmes.     

小麦矮秆突变体矮秆基因的遗传分析

目前在小麦中虽然已经命名了20余个矮秆基因,但小麦矮秆基因资源应用单一化的现状仍然存在,因此对小麦新矮源的筛选与研究显得十分必要。本研究以1个小麦矮秆突变体‘矮128’为材料,通过赤霉酸处理、遗传分析、基因等位性测验和DNA分子标记等手段分析了该矮秆突变体矮秆基因的性质及可能来源。结果表明:‘矮128’属赤霉酸不敏感型矮秆突变体,其矮秆性状受1对隐性基因控制,该基因与Rht8、Rht9、Rht13、RhtB1b(Rht1)、RhtD1b(Rht2)、RhtD1c(Rht10)和Rht16等矮秆基因不是等位基因,也不同于Rht4、Rht5、Rht8、Rht9、Rht12、Rht13等6个已知矮秆基因。尽管如此,‘矮128’中的矮秆基因是否为新的矮秆基因仍然需进一步的遗传分析加以明确。     

小麦赤霉酸不敏感基因Gai3的遗传研究

以小麦Ｒｈｔ３的两个株高等基因系及其ＢＣ２３Ｆ２分离群体为材料,分析了与Ｒｈｔ３矮秆基因连锁的赤霉酸不敏感基因Ｇａｉ３的遗传规律及其与Ｒｈｔ３的遗传关系。结果表明：赤霉酸不敏感性由单个显性基因控制,Ｆ２分离比率为３∶１（不敏感∶敏感）,非常符合χ２测验。Ｇａｉ３基因与Ｒｈｔ３基因连锁紧密,交换值为０．０６０±０．０１２和０．０５５±０．０１３。     

Growth traits and nitrogen assimilation-associated physiological parameters of wheat(Triticum aestivum L.) under low and high N conditions

In this study, 14 wheat cultivars with contrasting yield and N use efficiency(NUE) were used to investigate the agronomic and NUE-related traits, and the N assimilation-associated enzyme activities under low and high N conditions. Under deficient-N, the cultivars with high N uptake efficiency(UpE) and high N utilization efficiency(UtE) exhibited higher plant biomass, yields, and N contents than those with medium and low NUEs. The high Up E cultivars accumulated more N than other NUE type cultivars. Under sufficient-N, the tested cultivars showed similar patterns in biomass, yield, and N content to those under deficient-N, but the varietal variations in above traits were smaller. In addition, the high Up E cultivars displayed much more of root biomass and larger of root length, surface area, and volume than other NUE type cultivars, indicating that the root morphological traits under N deprivation are closely associated with the plant biomass through its improvement of the N acquisition. The high Ut E cultivars showed higher activities of nitrate reductase(NR), nitrite reductase(NIR), and glutamine synthetase(GS) at stages of seediling, heading and filling than other NUE type cultivars under both low and high N conditions. Moreover, the high Up E and Ut E cultivars also displayed higher photosynthetic rate under deficient-N than the medium and low NUE cultivars. Together, our results indicated that the tested wheat cultivars possess dramatically genetic variations in biomass, yield, and NUE. The root morphological traits and the N assimilation enzymatic acitivities play critical roles in regulating N accumulation and internal N translocation under the N-starvation stress, respectively. They can be used as morphological and biochemical references for evaluation of Up E and Ut E in wheat.     

普通小麦农艺及品质性状的杂种优势和性状相关研究

本文利用5×3NCⅡ设计,对普通小麦的8个农艺性状和4个品质性状进行了杂种优势及性状相关分析,结果表明:(1)以千粒重和单株粒重的杂种优势为最大,分别为17.10%和9.62%;蛋白质含量和沉淀值的优势最小,分别为-6.57%和-7.34%,温面筋含量和干面筋含量的优势居中,分别为3.31%和1.56%。(2)性状相关分析表明:除穗长和千粒重外,其它农艺性状与4个品质性状间均有不同程度的负相关;而4个品质性状间均为显著正相关。