Evaluation of yield performance in rice near-isogenic lines with increased spikelet number

Rice yield potential is determined by the balance between sink size and source capacity. To clarify the factors that limit yield in temperate japonica cultivars, we compared the yield performance of Sasanishiki, a temperate japonica cultivar, with those of three near-isogenic lines (NILs) of Sasanishiki with introgression of quantitative trait loci (QTL) derived from a high-yielding indica cultivar, Habataki: qSBN1, which increases the number of secondary rachis branches; qPBN6, which increases the number of primary rachis branches; and a pyramid line that combines these two QTLs. NIL (SBN1), NIL (PBN6), and NIL (SBN1 + PBN6) produced 28–37%, 9–16%, and 62–65% more spikelets per panicle than Sasanishiki, respectively. However, the NILs with increased spikelet number per panicle did not increase grain yield significantly, because compensation is taken place among different yield components. The pyramid line nevertheless had 4–12% higher yield than Sasanishiki due to greater translocation of carbohydrates from stem to panicle. There was no difference in carbohydrate accumulation before heading or in biomass production among Sasanishiki and the three NILs. The results indicate that increasing sink size does not substantially improve yield in Sasanishiki, which lacks sufficient substrate supply to fully satisfy the increased sink demand that results from the spikelet-number QTLs.     

Identification of Chromosomal Regions Controlling the Leaf Photosynthetic Rate in Rice by Using a Progeny from Japonica and High-yielding Indica Varieties

Abstract

The whole-leaf photosynthetic rate in rice plants is controlled by various physiological processes. In a high-yielding indica rice variety, Habataki, the leaf photosynthetic rate (LPR) of the uppermost fully expanded leaves was approximately 130 to 140% of that in a japonica variety, Sasanishiki, from booting to the early ripening stage. We characterized the difference in the LPR between Habataki and Sasanishiki. Leaves of Habataki contained higher levels of nitrogen and, as a consequence, of Rubisco, and had higher stomatal conductance that was associated with higher hydraulic conductance from roots to leaves than those of Sasanishiki. These features were responsible for the higher LPR of Habataki. An analysis of chromosome segment substitution lines (CSSLs) in which chromosome segments from Habataki were substituted into the genetic background of Sasanishiki showed that three genetic regions on chromosomes 4, 5 and 11 were responsible for the increase in the LPR. Each of these regions was estimated to increase the LPR by 15 to 30%, and we showed that they were associated with higher activity of mesophyll photosynthesis due to higher leaf nitrogen content and greater stomatal conductance. Leaf nitrogen content and stomatal conductance may be useful parameters for further quantitative trait locus analysis of efficient photosynthesis in leaves.     

Identification of QTLs for Improvement of Plant Type in Rice (Oryza sativa L.) Using Koshihikari / Kasalath Chromosome Segment Substitution Lines and Backcross Progeny F2 Population

Abstract

Thirty-nine chromosome segment substitution lines (CSSLs) population derived from a Koshihikari / Kasalath cross was used for quantitative trait locus (QTL) analysis of plant type in rice (Oryza sativa L.). Putative rough QTLs (26.2～60.3cM of Kasalath chromosomal segments) for culm length, plant height, panicle number, chlorophyll content of flag leaf blade at heading and specific leaf weight, were mapped on the several chromosomal segments based on the comparison of CSSLs with Koshihikari in the field experiment for 3 years. In order to verify and narrow QTLs detected in CSSLs, we conducted QTL analyses using F₂ populations derived from a cross between Koshihikari and target CSSL holding a putative rough QTL. The qPN-2, QTL for panicle number was mapped on chromosome 2. In traits of flag leaf, the qCHL-4-1 and qCHL-4-2 for chlorophyll content was mapped on chromosome 4, and the qSLW-7 for specific leaf weight on chromosome 7. All QTLs were detected in narrow marker intervals, compared with rough QTLs in CSSLs. The qPN-2, qCHL-4-1 and qCHL-4-2 had only additive effect. On the other hand, the qSLW-7 showed over-dominance. It could be emphasized that QTL analysis in the present study with the combination of CSSLs and backcross progeny F₂ population can not only verify the rough QTLs detected in CSSLs but also estimate allelic effects on the QTL.     

稻米淀粉RVA谱特征值与直链淀粉、蛋白含量的相关性及QTL定位分析

【目的】检测到新的控制稻米品质性状相关的QTL并分析各性状间的相关性,为了解控制水稻品质的遗传机理和培育优质水稻品种奠定基础。【方法】利用Sasanishiki×Habataki回交重组自交系(backcross inbred lines,BILs)群体在两个环境下种植的结果,检测与稻米直链淀粉含量、蛋白质含量及RVA谱特征值相关的加性QTL。【结果】表型分析结果显示,Habataki的蛋白含量明显高于Sasanishiki;而除消减值以外其余的稻米品质性状指标,Sasanishiki均高于Habataki。利用BIL群体共检测到加性QTL 42个,其中10个QTL位点在2个环境中均能被检测到,即q PC8、q AC4、q AC10、q PKV2、q PKV7、q HPV7、q CPV1、q BDV4、q BDV7、q SBV7,且q CPV1、q BDV4、q PKV7、q HPV7和q AC10等5个QTL尚未见报道。同时,我们还利用Sasanishiki×Habataki染色体片断置换系(Chromosome segment substitution lines,CSSLs)验证了10个稳定表达的QTL位点。【结论】稻米RVA谱特征值与直链淀粉含量、蛋白质含量之间呈现一定相关性,且控制不同品质性状的QTL之间具有共定位现象。     

Confirmation of Novel Quantitative Trait Loci for Seed Dormancy at Different Ripening Stages in Rice

Seed dormancy contributes resistance to pre-harvest sprouting.Effects on respective quantitative trait loci (QTLs) for dormancy should be assessed by using fresh seeds before germinability altered through storage.We investigated QTLs related to seed dormancy using backcross inbred lines derived from a cross between Nipponbare and Kasalath.Four putative QTLs for seed dormancy were detected immediately after harvest using composite interval mapping.These putative QTLs were mapped near C1488 on chromosome 3 (qSD-3.1),R2171 on chromosome 6 (qSD-6.1),R1245 on chromosome 7 (qSD-7.1) and C488 on chromosome 10 (qSD-10.1).Kasalath alleles promoted dormancy for qSD-3.1,qSD-6.1 and qSD-7.1,and the respective proportions of phenotypic variation explained by each QTL were 12.9%,9.3% and 8.1%.We evaluated the seed dormancy harvested at different ripening stages during seed development using chromosome segment substitution lines (CSSLs) to confirm gene effects.The germination rates of CSSL27 and CSSL28 substituted with the region including qSD-6.1 were significantly lower than those of Nipponbare and other CSSLs at the late ripening stage.Therefore,qSD-6.1 is considered the most effective novel QTL for pre-harvest sprouting resistance among the QTLs detected in this study.     

The QTL Analysis of RuBisCO in Flag Leaves and Non-Structural Carbohydrates in Leaf Sheaths of Rice Using Chromosome Segment Substitution Lines and Backcross Progeny F2 Populations

Abstract

In rice (Oryza sativa L.), the maintenance of high photosynthetic rate of flag leaves and the carbon remobilization from leaf sheaths after heading is a critical physiological component affecting the yield. To clarify the genetic basis of RuBisCO content of the flag leaf, a major determinant of photosynthetic rate, and non-structural carbohydrate (NSC) concentration in the third leaf sheath at heading, we carried out quantitative trait loci (QTL) analysis with 39 Koshihikari/Kasalath chromosome segment substitution lines (CSSLs) and backcross progeny F₂ population derived from target CSSL holding the QTL/Koshihikari in the field. QTLs for RuBisCO content and NSC concentration at heading were detected between R2447-C1286 and R2447-R716 on chromosome 10, respectively, by comparing Koshihikari with four CSSLs for chromosome 10 (SL-229, -230, -231 and -232). The progeny QTL for RuBisCO content and for NSC concentration at heading qRCH-10 and qNSCLSH-10-1, respectively, were detected at similar marker intervals between RM8201 and RM5708. In addition, QTLs for RuBisCO content at 14 d after heading, qRCAH-10-1 and qRCAH-10-2, were detected in regions different from that of qRCH-10. No QTL for NSC concentration at 14 d after heading was detected between RM8201 and R716, the region analyzed in this study. The QTLs qRCH-10 and qRCAH-10-1 for RuBisCO content would have additive effects. These QTLs for RuBisCO content and NSC concentration newly found using CSSLs and their backcross progeny F₂ population should be useful for better understanding the genetic basis of source and temporary-sink functions in rice and for genetic improvement of Koshihikari in terms of their functions.     

Growth and yield potential of Oryza sativa and O. glaberrima upland rice cultivars and their interspecific progenies

A recent breakthrough in generating fertile progeny from Oryza sativa×O. glaberrima crosses gives rice breeders access to a broader range of germplasm. Interspecific crosses might provide new solutions to the low productivity of upland rice systems prone to weed competition. Two field and one pot experiments conducted during 1995 and 1996 served to characterize growth and yield potential of CG14 (O. glaberrima), WAB56-104 (O. sativa) and their progeny. During the 1995 wet season and the 1996 dry and wet seasons, the lines were seeded in a well-drained upland field in Ivory Coast with supplemental sprinkler irrigation. A randomized complete-block design with three replications was used, with cultivar and nitrogen levels as sub-plots. Specific leaf area (SLA), leaf area index (LAI), leaf chlorophyll content (SPAD method) and tiller number were measured at 2-week intervals until flowering. Grain yield and yield components were measured at maturity. In all environments, CG14 produced two to three times the LAI and tiller numbers as WAB56-104. This was associated with a high SLA and low leaf chlorophyll content. Grain yields of CG14 did not respond to N inputs, although the sink potential did. The difference was mainly caused by grain shattering. The progenies had intermediate LAI, SLA and leaf chlorophyll content, but their grain yields, tiller numbers and resistance to lodging and grain shattering were similar to WAB56-104. Across lines, LAI and SLA were significantly correlated. A paddy field experiment confirmed the relationship between LAI and SLA for a wider range of rice cultivars and interspecific progenies. A pot experiment demonstrated that leaf net CO₂ assimilation rates (A_max) followed a common linear function of areal leaf chlorophyll content across cultivars. The main common cause of differential LAI and A_max appeared to have been genotypic patterns of SLA, which might be an important determinant of growth vigor and competitiveness with weeds. The possibility is discussed of combining, in a single line, high SLA during vegetative growth (for weed competitiveness) with low SLA during the reproductive growth phase (for high yield potential), to produce an efficient plant type for low-management conditions.     

Analysis of QTLs for Flag Leaf Shape and Its Response to Elevated CO2 in Rice （Oryza sativa）

To understand the responses of flag leaf shape in rice to elevated CO2 environment and their genetic characteristics,quantitative trait loci(QTLs)for flag leaf shape in rice were mapped onto the molecular marker linkage map of chromosome segment substitution lines(CSSLs)derived from a cross between a japonica variety Asominori and an indica variety IR24 under free air carbon dioxide enrichment(FACE,200μmol/mol above current levels)and current CO2 concentration(Ambient,about 370μmol/mol).Three flag-leaf traits,flag-leaf length(LL),width(LW)and the ratio of LL to LW (RLW),were estimated for each CSSL and their parental varieties.The differences in LL,LW and RLW between parents and in LL and LW within IR24 between FACE and Ambient were significant at 1%level.The continuous distributions and transgressive segregations of LL,LW and RLW were also observed in CSSL population,showing that the three traits were quantitatively inherited under both FACE and Ambient.A total of 16 QTLs for the three traits were detected on chromosomes 1,2,3,4,6,8 and 11 with LOD(Log10-likelihood ratio)scores ranging from 3.0 to 6.7.Among them,four QTLs (qLL-6*,qLL-8*,qLW-4*,and qRLW-6*)were commonly detected under both FACE and Ambient.Therefore,based on the different responses to elevated CO2 in comparison with current CO2 level,it can be suggested that the expressions of several QTLs associated with flag-leaf shape in rice could be induced by the high CO2 level.     

Chromosome Segment Substitution Lines: A Powerful Tool for the Introgression of Valuable Genes from Oryza Wild Species into Cultivated Rice (O. sativa)

Wild species of rice (genus Oryza) contain many useful genes but a vast majority of these genes remain untapped to date because it is often difficult to transfer these genes into cultivated rice (Oryza sativa L.). Chromosome segment substitution lines (CSSLs) and backcross inbred lines (BILs) are powerful tools for identifying these naturally occurring, favorable alleles in unadapted germplasm. In this paper, we present an overview of the research involving CSSLs and BILs in the introgression of quantitative trait loci (QTLs) associated with the improved performance of rice including resistance to various biotic and abiotic stresses, and even high yield from wild relatives of rice and other unadapted germplasm into the genetic background of adapted rice cultivars. The CSSLs can be used to dissect quantitative traits into the component genetic factors and evaluate gene action as single factors (monogenic loci). CSSLs have the potential to uncover new alleles from the unadapted, non-productive wild rice accessions, develop genome-wide genetic stocks, and clone genes identified in QTL studies for functional genomics research. Recent development of high-density single-nucleotide polymorphism (SNP) arrays in rice and availability of custom-designed medium- and low-density SNP arrays will enhance the CSSL development process with smaller marker-defined segment introgressions from unadapted germplasm.     

利用玉米叶片SPAD值预测子粒蛋白质含量分析

利用深松和深松结合秸秆还田技术,对玉米生长5个关键生育时期的叶片SPAD值进行测定分析,获得叶片SPAD值的变化规律;利用FOSS近红外谷物分析仪获得成熟期玉米子粒蛋白质含量,并建立叶片SPAD值与成熟期子粒蛋白质含量的相关关系.相关分析表明,叶片SPAD递减值与成熟期子粒蛋白质含量呈显著负相关,最佳相关模型为y=14.027-0.203x.叶片SPAD递减值可作为判定成熟期子粒蛋白质含量高低的指标,可利用叶片SPAD值递减值并结合相关模型快速预测玉米子粒蛋白质含量.     

应用SPAD值预测小麦叶片叶绿素和氮含量的初步研究

2003～2004年以中筋小麦品种扬麦11号、WH510和徐州26为试验材料,研究不同生育时期(拔节、孕穗、抽穗)不同叶位叶片SPAD值变化特征及其与叶片叶绿素含量、全氮含量及NO3--N含量的关系,旨在为小麦上应用SPAD快速诊断施肥提供理论依据。结果表明,不同品种及不同叶位小麦叶片SPAD值明显不同;小麦叶片SPAD值与叶绿素含量之间的关系因品种和生育时期的不同而有明显差异,同一品种小麦不同叶位叶片SPAD值与叶绿素含量呈极显著正相关。小麦叶片SPAD值与全氮含量呈正相关,SPAD值高,全氮含量也高,可以用SPAD值估算全氮含量进行小麦氮素营养状况诊断,但同一品种不同叶位SPAD值与全氮含量的关系表现不一致,即用SPAD值来诊断小麦叶片氮含量时应选择完全展开并已进入功能盛期的叶片。小麦叶片SPAD值与NO3-N含量相关性不显著。     

Genotypic variations in the plasticity of nodal root penetration through the hardpan during soil moisture fluctuations among four rice varieties

Rainfed lowland rice fields are characterized by soil moisture fluctuations (SMF) and the presence of hardpan that impedes deep rooting and thus limits water extraction from deep soil layer during the periods of drought. In this study, we used rootboxes with three layers; shallow layer, artificial hardpan, and deep and wet layer below the hardpan, to evaluate differences in the plasticity of nodal roots elongation through the hardpan and promote root branching below the hardpan in response to SMF among four rice varieties; Sasanishiki, Habataki, Nipponbare, and Kasalath. Experiments were conducted during the summer and autumn seasons. Plasticity was computed as the difference in root traits within each variety between the SMF and continuously well-watered treatments. In both experiments, Habataki consistently tended to exhibit higher root plasticity than the other three varieties by increasing number of nodal roots that penetrated the hardpan during rewatering period in SMF, when the soil moisture increased and penetration resistance decreased. This root plasticity then contributed to greater water use at the deeper soil during the subsequent drought period and overall shoot dry matter production. Habataki had significantly higher δ¹³C value in roots at deep layer than roots at the shallow and hardpan layers under SMF, which may indicate that these were relatively newly grown roots as a consequence of root plasticity. This study also indicates that CSSLs derived from Sasanishiki and Habataki varieties may be suitable for the analysis of QTLs associated with root plasticity expression in rainfed lowland with hardpan and experiencing SMF.     

Identification of Rice QTLs for Important Agronomic Traits with Long-Kernel CSSL-Z741 and Three SSSLs

Rice kernel shape affects kernel quality (appearance) and yield (1000-kernel weight) and therefore is an important agronomic trait, but its inheritance is complicated. We identified a long-kernel rice chromosome segment substitution line (CSSL), Z741, derived from Nipponbare as a recipient and Xihui 18 as a donor parent. Z741 has six substitution segments distributed on rice chromosomes 3, 6, 7, 8 and 12 with an average replacement length of 5.82 Mb. Analysis of a secondary F₂ population from a cross between Nipponbare and Z741 identified 20 QTLs for important agronomic traits. The kernel length of Z741 is controlled by a major QTL (qKL3) and a minor QTL (qKL7). Candidate gene prediction and sequencing indicated that qKL3 may be an allele of OsPPKL1, which encodes a protein phosphatase implicated in brassinosteroid signaling, and qKL7 is an unreported QTL. Finally, we validated eight QTLs (qKL3, qKL7, qRLW3-1, qRLW7, qPH3-1, qKWT3, qKWT7 and qNPB6) using three selected single- segment substitution lines (SSSLs), S1, S2 and S3. Also, we detected five QTLs (qKL6, qKW3, qKW7, qKW6 and qRLW6) in S1, S2 and S3, which were not found in the Nipponbare/Z741 F₂ population. However, qNPB3, qNPB7 and qPL3 QTLs were not validated by the three SSSLs in 2019, suggesting that minor QTLs are susceptible to environmental factors. These results lay the foundation for studying the biodiversity of kernal length and molecular breeding of different kernel types.     

水稻回交群体剑叶性状综合评价及QTL定位

【目的】通过对水稻剑叶性状的综合评价,明确剑叶相关性状间及与6个农艺性状的关系。检测剑叶相关性状的QTL,为优良株型品种选育,剑叶性状基因的精细定位和克隆奠定基础。【方法】以日本优质粳稻品种越光和葡萄牙粳稻地方种Bertone构建的回交群体两个世代为实验材料,利用BC₃F₁群体基因型构建遗传连锁图谱;测定亲本和BC₃F₂群体各株系剑叶SPAD、剑叶长、剑叶宽,计算剑叶长宽比、剑叶面积;利用隶属函数和标准差系数赋予权重法获得剑叶性状综合评价值(D值),分析其与6个农艺性状间的关系。分别利用单标记分析(SPA)和区间作图(IM)检测水稻剑叶相关性状QTL。【结果】在抽穗灌浆期,两亲本剑叶SPAD值呈现先升高后降低的动态变化。BC₃F₂群体的5个剑叶相关性状变异丰富,总体表现趋向轮回亲本越光。4个剑叶形态性状间相关性均达到极显著水平,与剑叶SPAD的相关性不显著。主成分和逐步线性回归分析表明剑叶宽、剑叶SPAD、剑叶长、剑叶面积是影响剑叶综合评价值(D值)的主要因子。高D值株系的株高、穗长、茎基粗和单株产量均极显著高于低D值株系,两者的分蘖数和有效穗数差异不显著。共检测到18个控制剑叶性状的QTL,分布在水稻第1、4、7和8染色体上,贡献率分布范围为4.00%~28.00%(SPA)和3.41%~27.00%(IM),除qFLSPAD1之外的17个QTL增效基因均来自Bertone。在第8染色体上的RM22720-RM404区间发现1个QTL簇,含6个主效QTL,分别为qFLL8.1、qFLL8.2、qFLA8.1、qFLA8.2、qD8.1和qD8.2。【结论】获得了剑叶宽、剑叶SPAD、剑叶长和剑叶面积4个评价剑叶性状的关键指标;明确了剑叶性状与单株产量之间的正相关关系;检测到18个剑叶相关性状QTL,位于第8染色体RM22720-RM404区间的QTL簇,是影响剑叶性状的1个重要染色体区域。     

Genetic relationship between grain chalkiness,protein content,and paste viscosity properties in a backcross inbred population of rice

A backcross inbred line population derived from a cross between Koshihikari and Kasalath was used to dissect the genetic relationship among chalkiness, protein content, and paste viscosity properties in rice in three environments. A total of 11 traits (or parameters) were analyzed, including percentage of grains with chalkiness (PGWC), protein content (PC) and protein index (PI), and eight parameters from the viscosity profile. PGWC, PC and PI were significantly correlated with the paste viscosity parameters. We identified 39 QTLs in three environments; ten QTL clusters emerged. Eight QTLs were consistently detected across the three environments and further confirmed using a set of chromosome segment substitution lines (CSSLs) where Kasalath was used as the donor parent and Koshihikari as the recurrent parent. One and two major clusters on chromosome 6 corresponded to the Wx and Alk loci, respectively. The former was responsible for PGWC and most of the viscosity parameters, and the latter for PI and some viscosity parameters. Particularly, QTL qPI-6.1 was linked with both the Wx and Alk loci. The co-locations of QTLs for PGWC and viscosity parameters and the linkage of qPI-6.1 and qBDV-6 at the Wx locus could be largely responsible for the phenotypic correlations between these traits.     

A novel Rice QTL <Emphasis Type="Italic">qOPW11</Emphasis> Associated with Panicle Weight Affects Panicle and Plant Architecture

Background

The improvement of rice yield is a crucial global issue, but evaluating yield requires substantial efforts. Rice yield comprises the following indices: panicle number (PN), grain number per panicle (GN), 1000-grain weight, and percentage of ripened grain. To simplify measurements, we analyzed one panicle weight (OPW) as a simplified yield index that integrates GN, grain weight, and percentage of ripened grain, and verified its suitability as a proxy for GN and grain weight in particular.

Results

Quantitative trait locus (QTL) analysis using 190 recombinant inbred lines derived from Koshihikari (large panicle and small grain) and Yamadanishiki (small panicle and large grain), japonica cultivars detected three QTLs on chromosomes 5 (qOPW5), 7 (qOPW7) and 11 (qOPW11). Of these, qOPW5 and qOPW11 were detected over two years. qOPW5 and qOPW7 increased OPW, and qOPW11 decreased it at Yamadanishiki alleles. A chromosome segment substitution line (CSSL) with a genomic segment from Yamadanishiki substituted in the Koshihikari genetic background harboring qOPW5 increased grain weight. qOPW11 had the largest genetic effect of QTLs, which was validated using a CSSL. Substitution mapping using four CSSLs revealed that qOPW11 was located in the range of 1.46 Mb on chromosome 11. The CSSL harboring qOPW11 decreased primary and secondary branch numbers, culm length, and panicle length, and increased PN.

Conclusions

In this study, three QTLs associated with OPW were detected. The CSSL with the novel and largest QTL, qOPW11, differed in some traits associated with both panicle and plant architecture, indicating different functions for the meristem in the vegetative versus the reproductive stages. qOPW5 coincided with an identified QTL for grain width and grain weight, suggesting that qOPW5 was affected by rice grain size. OPW can be considered a useful trait for efficient detection of QTLs associated with rice yield.

     

QTL mapping for crude protein and protein fraction contents in rice (Oryza sativa L.)

Improvement of rice storage proteins is important in rice breeding for high nutritional quality. Seventy-one recombinant inbred lines (RIL) derived from a cross between japonica variety Asominori and indica variety IR24 were used to study the inheritance of crude protein and protein fraction contents in rice. A total of 16 QTL were identified and mapped on eight chromosomes. Several QTL affecting contents of different protein fractions were mapped in the same chromosomal region. In particular, two QTL with a significant contribution were identified to simultaneously affect prolamin and glutelin contents. One QTL denoted as qCP-12 affecting crude protein content (CP) was located in the same region as QTL qGLT-12 affecting glutelin content, in agreement with the positive correlation between glutelin level and protein content. QTL with larger genetic effects were further confirmed using two sets of chromosome segment substitution lines (CSSL), where Asominori and IR24 were used as the recurrent parents. By QTL comparative analysis, two QTL for CP, three for globulin content and one for prolamin content were located in the vicinity of CP QTL previously identified in polished rice. Application of these results in rice breeding is discussed.     

Roles of Root Aerenchyma Development and Its Associated QTL in Dry Matter Production under Transient Moisture Stress in Rice

Abstract

Enhanced aerenchyma development in rice under transient drought-to-waterlogged (TD-W) stress promotes root system development by promoting lateral root production. This study analyzed the quantitative trait loci (QTLs) associated with the plasticity in aerenchyma development under TD-W stress. A mapping population of 60 F₂ genotypes of chromosome segment substituted lines (CSSL) derived from CSSL47 and Nipponbare crosses were grown in rootboxes and evaluated for shoot and root growth, and aerenchyma development (expressed as root porosity). The TD-W stress was imposed starting with water saturated soil condition at sowing and then to progressive drought from 0 to 21 days after sowing (DAS) prior to exposure to sudden waterlogging for another 17 days (21 to 38 DAS). We performed simple and composite interval mapping to identify QTLs for aerenchyma development. QTL associated with aerenchyma development was mapped on the short-arm of chromosome 12 and designated as qAER-12. The effect of qAER-12 on the plasticity in aerenchyma development under TD-W was significantly associated with the increase in lateral root elongation and branching. This resulted in greater root system development as expressed in total root length and consequently contributed to higher dry matter production. This qAER-12 is probably the first reported QTL associated with aerenchyma development in rice under TD-W and is a useful trait for the improvement of the adaptive capability under fluctuating soil moisture conditions.     

春小麦旗叶长度、宽度及叶绿素含量QTL分析

为了提高高产和理想株型小麦的选育效率,以普通小麦(Triticum aestivum L.)宁春4号和宁春27号杂交得到的128个F9代重组自交系(RILs)为试验材料,利用从1 001个SSR标记中筛选出的307个在亲本之间存在多态性的标记对该群体进行遗传分析和QTL检测.构建了覆盖小麦21对染色体的包含291个SSR标记的遗传连锁图谱,遗传距离总计2 576.09 cM,标记间平均遗传距离为8.85 cM.以复合区间作图法(ICIM)分别对旗叶长度、宽度和叶绿素含量进行加性QTL检测,分别检测到6、8和4个QTL.多数QTL只在单一生态环境下检测到,说明这些性状受一定环境因素的影响.     

QTL Mapping for Rice RVA Properties Using High-Throughput Re-sequenced Chromosome Segment Substitution Lines

The rapid visco analyser （RVA） profile is an important factor for evaluation of the cooking and eating quality of rice. To improve rice quality, the identification of new quantitative trait loci （QTLs） for RVA profiling is of great significance. We used a japonica rice cultivar Nipponbare as the recipient and indica rice 9311 as the donor to develop a population containing 38 chromosome segment substitution lines （CSSLs） genotyped by a high-throughput re-sequencing strategy. In this study, the population and the parent lines, which contained similar apparent amylose contents, were used to map the QTLs of RVA properties including peak paste viscosity （PKV）, hot paste viscosity （HPV）, cool paste viscosity （CPV）, breakdown viscosity （BKV）, setback viscosity （SBV）, consistency viscosity （CSV）, peak time （PET） and pasting temperature （PAT）. QTL analysis was carried out using one-way analysis of variance and Dunnett＇s test, and stable QTLs were identified over two years and under two environments. We identified 10 stable QTLs： qPKV2-1, qSBV2-1; qPKV5-1, qHPV5-1, qCPV5-1; qPKV7-1, qHPV7-1, qCPV7-1, qSBV7-1; and qPKV8-1 on chromosomes 2, 5, 7 and 8, respectively, with contributions ranging from -95.6% to 47.1%. Besides, there was pleiotropy in the QTLs on chromosomes 2, 5 and 7.