大豆苗期耐盐性的遗传及QTL定位分析

利用重组自交系群体NJRIKY进行大豆苗期耐盐性的遗传及QTL定位分析。以每个家系的平均存活时间为耐盐指标,采用主基因+多基因混合遗传模型进行RIL遗传分析,结果表明,NJRIKY群体的耐盐性遗传符合F-3模型,即由3对主基因控制,没有多基因修饰,主基因遗传率是64.4%。利用Cartographer V.2.5进行QTL定位。结果显示,共检测到3个耐盐QTL,它们分别位于B1、G和K三个连锁群上,分别解释8.4%、17.9%和11.3%的表型变异。     

春小麦旗叶大小相关性状的QTL定位分析

为了发掘控制春小麦旗叶大小相关性状的QTL,以宁春4号/Drasdale构建的包含148个家系的RIL群体F8代为试验材料,在正常灌溉和不同干旱胁迫共3种处理下对小麦开花期旗叶长、宽、面积和周长进行了QTL定位。结果表明,共检测到相关加性QTL 22个,其中,控制旗叶面积的QTL有3个,控制旗叶长的QTL有5个,控制旗叶宽的QTL有9个,控制旗叶周长的QTL有5个,分布于1B、2D、3B、4B、7A、7B和7D染色体上,单个QTL的贡献率在6.58%~39.83%之间。其中,qFLW-2D-2.T1在T1和T3处理下均能够检测到,qFLW-7D.T1在T1和T2处理下也均能够检测到,说明这2个QTL表达不依赖于水分条件,属于稳定表达的QTL。其他QTL只在一种处理下能够检测到,说明其表达依赖于水分条件。同时,本研究也检测到了在不同处理下同时控制2种或3种性状的QTL,推测这些区域的QTL可能为一因多效QTL,但有待于进一步验证。     

Dough quality of bread wheat lacking α-gliadins with celiac disease epitopes and addition of celiac-safe avenins to improve dough quality

Celiac disease is a T-cell mediated immune response in the small intestine of genetically susceptible individuals caused by ingested gluten proteins from wheat, rye, and barley. In the allohexaploid bread wheat (Triticum aestivum), gluten proteins are encoded by multigene loci present on the homoeologous chromosomes 1 and 6 of the three homoeologous genomes A, B, and D. The effect of deleting individual gluten loci was analyzed in a set of deletion lines of T. aestivum cv. Chinese Spring with regard to the level of T-cell stimulatory epitopes (Glia-α9 and Glia-α20) and to technological properties of the dough including mixing, stress relaxation, and extensibility.     

QTL mapping rolling,stomatal conductance and dimension traits of excised leaves in the Bala × Azucena recombinant inbred population of rice

The identification of markers linked to genes contributing to drought resistance promises opportunities to breed high yielding rice varieties for drought prone areas. Several studies using different mapping populations have previously identified quantitative trait loci (QTLs) for traits theoretically related to drought resistance. A mapping population of 176 F₆ recombinant inbred lines (RILs) derived from two upland rice varieties with contrasting aboveground drought avoidance traits (Bala and Azucena) with a linkage map of 157 markers was used to map QTLs for aboveground leaf morphological and physiological traits related to drought avoidance. Plants were grown for 6 weeks under controlled environmental conditions with three replications. Leaves were excised and placed on a balance. The rate of leaf rolling and water loss was recorded, after which leaf area, dry weight and specific leaf area were characterized. A simple method of estimating time to stomatal closure was employed. A total of 13 QTLs were detected for leaf morphological traits, three for initial transpiration and four for the proportion of water loss required to reach a specific advanced state of leaf rolling. No QTLs were detected for time of stomatal closure or speed of leaf rolling, nor for either water loss or transpiration at stomatal closure despite clear parental differences and moderate heritabilities in most of these traits. The co-location of QTLs for traits measured here and for drought avoidance previously reported from field experiments on chromosome 1, 3 and 5 link the genetics of drought resistance to leaf dimensions and physiology. However, a physiological explanation for a QTL for drought avoidance on chromosome 7 remains elusive.     

Mapping quantitative trait loci associated with root growth in upland rice (Oryza sativa L.) exposed to soil water-deficit in fields with contrasting soil properties

A mapping population of 114 lines from Bala × Azucena was grown under drought stress at two field sites with contrasting soil physical properties. Drought was imposed between 35 and 65 days after sowing (DAS) and root density at 35 cm depth was measured 70 DAS. Leaf rolling, leaf drying and relative water content were recorded as indicators of drought avoidance. Root density correlated with indicators of drought avoidance. Two significant and two putative quantitative trait loci (QTLs) for root density and 28 QTLs for drought avoidance were identified. Most QTLs did not agree between sites. There was also reasonable agreement between leaf-drying QTLs and previously reported root-growth QTLs detected under controlled conditions (in contrast to a previous screen on soil with a higher penetration resistance). These data also reveal QTL × environment interaction, which will need to be understood more clearly if progress towards breeding for drought resistance via alterations of root morphology is to be achieved.     

QTLs for malting flavour component associated with pre-harvest sprouting susceptibility in barley (Hordeum vulgare L.)

Lipoxygenase (LOX) is a key factor affecting quality of beer in terms of foam stability and flavour. Low LOX content is a desirable trait for malting quality. A doubled haploid (DH) population was made from a cross of Australian malting barley Stirling and Canadian malting barley Harrington and mapped with 513 molecular markers. The 120 DH lines with their parents were planted in field trials and the harvested grains were micro-malted for analysis of LOX content in two consecutive years. LOX content was controlled by both genetic effects and environment conditions. Three QTLs were consistently detected. One QTL flanked by the markers E6216 and SCssr03907 at the telomere region of chromosome 5HL contributed 39% of genetic variation in LOX content. The second QTL close to the centromere region of chromosome 5H accounted for 17% of genetic variation. A minor QTL on chromosome 2H explained 6% of genetic variation but was significant in both years. The Australian variety Stirling contributed to higher LOX content for the three QTLs. The two QTLs mapped at chromosome 5H for LOX content coincided with the QTLs for seed dormancy/pre-harvest sprouting from the same population. The pre-harvest sprouting susceptible alleles were associated with low LOX content, which indicated that the low LOX QTL from the Canadian malting barleys are only useful in the barley growing areas where the pre-harvest sprouting risk is low. New genetic sources for low LOX should be exploited in different germplasm with different mechanisms.     

Molecular genetic mapping of quantitative trait loci associated with loaf volume in hexaploid wheat (Triticum aestivum)

Major efforts in wheat research are being made to improve the yield and quality of wheat. Loaf volume (Lv) is the main quality parameter deciding the bread making potential of wheat. To genetically dissect quantitative trait loci (QTLs) for Lv, a Recombinant Inbred Line (RIL) population (F₈) was developed from a cross between two Indian wheat varieties “HI 977” and “HD 2329”. A total of 914 SSR and 100 ISSR primers were used for molecular analysis and the genetic map comprising 19 chromosomes was constructed with 202 SSR markers and 2 HMW glutenin subunit loci: Glu-B1 and Glu-D1. The phenotypic data were collected from six environments including three different agro-climatic zones for 2 consecutive years. Dissection of Lv through AMMI model revealed significant G×E variance for the trait. QTL analysis was performed using composite interval mapping. A total of 30 QTLs for Lv were detected and significant QTLs were identified on 6B and 6D chromosomes; 1B, 1D, 2A, 3A, 5B and 5D also contributed genetically to Lv. Association between 6B and 6D QTLs and variable expression of gliadins on group 6 chromosomes were discussed. QTLs detected in this study were compared with other QTL analysis in wheat.     

QTL analysis of cold tolerance at seedling stage in rice (Oryza sativa L.) using recombination inbred lines

Cold tolerance at seedling stage of rice (Oryza sativa L.) is a favorable trait for the stable establishment in temperate and high-elevation areas. In the present study, 71 recombinant inbred lines (RIL) derived from the cross of Asominori (Japonica) and IR24 (Indica) were used to identify quantitative trait loci (QTL) affecting cold tolerance at seedling stage. The putative QTL was further confirmed using some chromosome segment substitution lines (CSSLs), in which IR24 was used as the donor parent and Asominori as the recurrent parent. The average seedling mortality was used as cold tolerance after cold treatment with 6 °C for 7 days and recovery culture with 25 °C for 4 days at three-leaf seedling stage. Three QTL affecting cold tolerance at seedling stage were detected on chromosomes 1, 5 and 6 with LOD scores ranging from 2.2 to 4.1 using composite interval mapping (CIM). Among them, qSCT-1 located in the region of XNpb87-2-C955 on chromosome 1 was a major QTL which explained 24.51% of total phenotypic variance and favorable allele came from japonica parent, Asominori. In addition, IR24 alleles at the other two loci (qSCT-5 and qSCT-6) increased cold tolerance. And these three QTL were confirmed by four lines from the IR24 CSSLs. Transferring favorable allele from japonica variety to indica background or pyramiding different QTL identified from indica is an effective way to improve cold tolerance of rice.     

水稻籼粳交DH群体幼苗中胚轴长度的QTLs定位和上位性分析

应用籼粳交IR64/Azucena的DH群体及其构建的分子标记遗传图谱,在遮光条件下,通过适温和低温逆境下发芽,测定中胚轴长度。采用QTL Mapper 基因定位软件检测控制中胚轴长度的加性效应QTLs和加性×加性上位性QTLs,在第1、3、6、7、8、12等6条染色体上定位了8个控制中胚轴长度的QTLs,其中在第1、3、7、8染色体上定位了4个具有加性效应的QTLs,位于第7染色体的1个加性效应QTL的增长等位基因来自于父本Azucena,它能使中胚轴伸长0.26 cm,其贡献率达17.5%,其余3个加性效应QTLs的增长等位基因来自于母本IR64,能使中胚轴伸长0.10～0.21 cm,在第3、7、12等3条染色体中共检测到2对加性×加性上位性效应,其贡献率分别为21.62%和2.27%,同时各检测到2对加性效应×环境的互作效应和上位性与环境的互作效应。对应用分子标记辅助育种选育中胚轴伸长的矮秆水稻的可能性进行了讨论。     

水稻籼粳交DH群体白叶枯病抗性的QTL定位

以中抗白叶枯病的粳稻品种春江06、感病品种TN1及其DH群体为材料,接种白叶枯病菌浙173后,考察了该DH群体的白叶枯病抗性,并进行了数量性状座位(QTL)分析。共检测到控制白叶枯病的3个QTL（qBBR1、qBBR3 1和qBBR7）,分别位于第1、3和第7染色体上,其中第3染色体上的qBBR3 1和第7染色体上的qBBR7加性效应为正值;而位于第1染色体上的qBBR1为负值,3个QTL的总效应达54.4%。春江06中不存在白叶枯病抗性主基因,它的抗性由微效多基因控制,其中在第3和第7染色体上分别有1个QTL。     

Characterization of two 1D-encoded ω-gliadin subunits closely related to dough strength and pan bread-making quality in common wheat (Triticum aestivum L.)

Gliadin proteins of 113 common or bread wheat (Triticum aestivum L.) cultivars and advanced lines from China and other countries, were analyzed by high performance capillary electrophoresis (HPCE) and reversed-phase high performance liquid chromatography (RP-HPLC). A major protein peak migrating at 3 min by HPCE and eluting at about 20 min by RP-HPLC was identified in the ω-gliadin region. It was present in cultivars with good pan bread-making quality, whereas most cultivars with poor bread-making quality lacked this protein peak. Quality testing and statistical analysis showed that this ω-gliadin peak was significantly related to dough strength, loaf volume and loaf score. It was separated into two apparent protein components by one-dimensional SDS-PAGE and two-dimensional electrophoresis (2-DE). According to their relative mobilities on the gels, the proteins were designated ω-15 and ω-16, and their accurate molecular masses (42590.5 Da for ω-15 and 41684.1 Da for ω-16) were determined by MALDI-TOF-MS. The ω-15 and ω-16 gliadins possessed the N-terminal amino acid sequences of ARELNPSNKELQQQQ and KELQSPQQQF, and therefore they belonged to 1D-encoded ω-2 type and ω-1 type gliadins, respectively. Both gliadin subunits were always present together among the 86 cultivars analyzed, suggesting that they were encoded by two closely linked genes at Gli-D1 locus. The accumulative characteristics of gliadins during grain development indicated possible additive quantitative effects of ω-15+16 on dough strength. The ω-15 and ω-16 gliadins could be used as valuable genetic markers for wheat quality improvement.     

Transgressive variants for red pericarp grain with high yield potential derived from Oryza rufipogon × Oryza sativa: Field evaluation, screening for blast disease, QTL validation and background marker analysis for agronomic traits

Five transgressive variants (advanced breeding lines from BC₂F₅ and BC₂F₆ generation) were derived from a cross between the wild relative, O. rufipogon Griff. and O. sativa L. subsp. indica cv. MR219, a popular high yielding Malaysian rice cultivar. The aim of the study was to evaluate the pericarp colour of the grains along with yield potential and to validate quantitative trait loci (QTLs) for agronomic traits. The variants were screened against blast disease. Background marker analysis was also done for the promising variants. The field trials were carried out at a single location (due to containment purposes) over two seasons using randomized complete block design (RCBD) with three replications. A trait-based marker analysis was used to identify QTLs for validation in BC₂F₅ generation. Analysis of variance (ANOVA) showed that the seasonal factors influenced different agronomic traits. Variant G33 produced significantly (p < 0.05) higher yield (5.20 t/ha) than the control, MR219 (4.53 t/ha). Eighteen QTLs for different agronomic traits were identified in BC₂F₂ population in a previous study. Among them 14 QTLs were found in BC₂F₅ population of the present study. The yield of variant G33 was influenced by several QTLs viz. qGPL-1, qSPL-1-2, qSPL-8 and qYLD-4, which were introgressed from the donor parent revealed by background marker analysis using BC₂F₇ generation. Percentage (99%) of red pericarp grain of G33 and G34 in BC₂F₅ and BC₂F₆ generations indicated the stability of pericarp colour which was transferred from the wild relative. Variant G33 showed resistance against two pathotype of blast disease (Magnaporthe oryzae). Among the evaluated variants, G33 could be considered for inclusion in the cultivar development program for red rice with high yield potential and resistance to blast disease. This study demonstrated that the alleles from wild relative could improve the yield and yield related traits through allelic interaction, even though the phenotypic traits were inferior to the recurrent parent.     

Genetic analysis and validation of quantitative trait loci associated with reproductive-growth traits and grain yield under drought stress in a doubled haploid line population of rice (Oryza sativa L.)

Drought is a major constraint for rice production and yield stability in rainfed ecosystems, especially when it occurs during the reproductive stage. Combined genetic and physiological analysis of reproductive-growth traits and their effects on yield and yield components under drought stress is important for dissecting the biological bases of drought resistance and for rice yield improvement in water-limited environments. A subset of a doubled haploid (DH) line population of CT9993-5-10-1-M/IR62266-42-6-2 was evaluated for variation in plant water status, phenology, reproductive-growth traits, yield and yield components under reproductive-stage drought stress and irrigated (non-stress) conditions in the field. Since this DH line population was previously used in extensive quantitative trait loci (QTLs) mapping of various drought resistance component traits, we aimed at identifying QTLs for specific reproductive-growth and yield traits and also to validate the consensus QTLs identified earlier in these DH lines using meta-analysis. DH lines showed significant variation for plant water status, reproductive-growth traits, yield and yield components under drought stress. Total dry matter, number of panicles per plant, harvest index, panicle harvest index, panicle fertility, pollen fertility, spikelet fertility and hundred grain weight had significant positive correlations with grain yield under drought stress. A total of 46 QTLs were identified for the various traits under stress and non-stress conditions with phenotypic effect ranging from 9.5 to 35.6% in this study. QTLs for panicle exsertion, peduncle length and pollen fertility, identified for the first time in this study, could be useful in marker-assisted breeding (MAB) for drought resistance in rice. A total of 97 QTLs linked to plant growth, phenology, reproductive-growth traits, yield and its components under non-stress and drought stress, identified in this study as well as from earlier published information, were subjected to meta-analysis. Meta-analysis identified 23 MQTLs linked to plant phenology and production traits under stress conditions. Among them, four MQTLs viz., 1.3 for plant height, 3.1 for days to flowering, 8.1 for days to flowering or delay in flowering and 9.1 for days to flowering are true QTLs. Consensus QTLs for reproductive-growth traits and grain yield under drought stress have been identified on chromosomes 1 and 9 using meta-QTL analysis in these DH lines. These MQTLs associated with reproductive-growth, grain yield and its component traits under drought stress could be useful targets for drought resistance improvement in rice through MAB and/or map-based positional analysis of candidate genes.