Mapping Quantitative Trait Loci Associated with Photoperiod Sensitivity in Maize(Zea mays L.)

Photoperiod sensitivity in maize plays an essential role in utilizing tropic and sub-tropic germplasm to temperate areas. This study aims to identify and map the QTLs responsible for the characteristics measuring photoperiod sensitivity, days from planting to silking （SD）, photoperiod response coefficient of silking （PRC）, and anthesis-silking interval （ASI）. Using the population derived from Zheng 58, photoperiod-insensitive parent, and Ya 8701, photoperiod-sensitive parent, a linkage map was constructed with 93 single sequence repeat （SSR） markers. Phenotyping of 296 F2-3 families of the population in replicated-field test was conducted in both long-day （Beijing, China） and short-day （Sichuan, China） conditions. Ten QTLs were identified to be associated with the SD and ASI on chromosomes 3, 4, 6, 8, and 10 in the longday conditions, and 11 QTLs were detected to be related to the SD and ASI on chromosomes 2, 3, 4, 5, 6, 8, and 10 in the short-day conditions, respectively. A QTL associated with the PRC as a major effect in the long-day conditions located in the same position as the QTL related to the SD and ASI in the map, and was on chromosome 10 linked with marker bnlg1655. Using these QTLs in the marker-assisted selection, the photoperiod sensibility could be reduced by selection of the alleles responsible for the SD, PRC, and ASI in breeding programs.

Identification of quantitative trait loci and epistasis for root characteristics and root exudations in maize (Zea mays L.) under deficient phosphorus

The phosphorus uptake (PU) in above-ground parts of plant,root characteristics and root exudations as well as the quantitative trait loci (QTLs) associated with these characteristics were determined for a F2:3 population derived from the cross of two contrasting maize (Zea mays L.) genotypes,082 and Ye107.A total of 241 F2:3 families were evaluated in replicated trials under deficient phosphorus conditions in 2007 at two sites (Kaixian County and Southwest University,Chongqing,P.R.China).The results show pleiotropy and close linkage among QTLs.Four common regions in different environments were in bnlg100bnlg1268b (bins 1.02) for QTL of H+,bnlg1268a-umc1290a (bins 1.09) for QTL of AP (acid phosphatase activity),dupssr15-P1M7/a (bins 6.06) for QTLs of PU (phosphorus uptake) and RW (root weight),and P1M3/d-P1M3/g (bins9.04) for QTLs of PU and AP.These QTLs are non-environment or minor QTLs × environment.By epistatic analysis,three main QTLs and eighteen QTLs × QTLs interactions were detected for the seven measured characteristics.These QTLs may affect trait expression by epistatic interaction with the other loci,and make a substantial contribution to phosphorus utilization efficiency,which should be considered when breeding maize varieties with high P efficiency.Two regions were detected in dupssr15-P1M7/a (bins 6.06) for QTL of RW and P1M3/d-P1M3/g (bins 9.04) for QTL of PU and AP.They were detected in two different environments and by two methods of QTL analysis,which were useful for marker-assisted selection.

QTL analysis of ear leaf traits in maize(Zea mays L.)under different planting densities

Modem maize varieties have become more productive than ever, owing largely to increased tolerance of high plant density. However, the genetics of ear leaf traits under different densities remains poorly understood. In this study, Zhongdan 909 recombinant inbred lines(RILs) derived from a cross between Z58 and HD568 were genotyped for 3072 single-nucleotide polymorphisms(SNPs), and phenotyped for leaf length(LL), leaf width(LW), and leaf angle(LA) of the uppermost ear leaf under three planting densities(52,500,67,500, and 82,500 plants ha-1, respectively). A genetic map was then constructed using1358 high-quality SNPs. The total length of the linkage map was 1985.2 cM and the average interval between adjacent markers 1.46 cM. With increasing density, LL and LW decreased from 63.68 to 63.02 cm and from 8.56 to 8.21 cm, respectively, while LA increased from19.42° to 19.66°. All three traits had high heritabilities, of 0.75, 0.78, and 0.84, respectively.Using inclusive composite interval mapping, 23, 25, and 17 quantitative trait loci(QTL) were detected for LL, LW, and LA, respectively. Of these, 35 were simultaneously detected under two or three plant densities, while 30 were detected under only one. Sixty-five individual QTL explained 2.41% to 16.53% of phenotypic variation, while eight accounted for >10%.These findings will help us understand the genetic basis of leaf traits in maize as well as the response of maize to increased plant density.

QTL Mapping for Stalk Related Traits in Maize (Zea mays L.) Under Different Densities

Stalk related traits, comprising plant height （PH）, ear height （EH）, internode number （IN）, average internode length （ALL）, stalk diameter （SD）, and ear height coefficient （EHC）, are significantly correlated with yield, density tolerance, and lodging resistance in maize. To investigate the genetic basis for stalk related traits, a doubled haploid （DH） population derived from a cross between NX531 and NX110 were evauluated under two densities over 2 yr. The additive quantitative trait loci （QTLs）, epistatic QTLs were detected using inclusive composite interval mapping and QTL-by-environment interaction were detected using mixed linear model. Differences between the two densities were significant for the six traits in the DH population. A linkage map that covered 1 721.19 cM with an average interval of 10.50 cM was constructed with 164 simple sequence repeat （SSR）. Two, two, seven, six, two, and eight additive QTLs for PH, IN, AIL, EH, SD, and EHC, respectively. The extend of their contribution to penotypic variation ranged from 10.10 to 31.93%. Seven QTLs were indentified simultaneously under both densities. One pair, two pairs and one pair of epistatic effects were detected for AIL, SD and EHC, respectively. No epistatic effects were detected for PH, EH, and IN. Nineteen QTLs with environment interactions were detected and their contribution to phenotypic variation ranged from 0.43 to 1.89%. Some QTLs were stably detected under different environments or genetic backgrounds comparing with previous studies. These QTLs could be useful for genetic improvement of stalk related traits in maize breeding.

QTL mapping and transcriptome analysis identify candidate genes influencing water–nitrogen interaction in maize

Water and nitrogen fertilization are the key factors limiting maize productivity.The genetic basis of interactions between maize genotype,water,and nitrogen is unclear.A recombinant inbred line(RIL)maize population was evaluated for seven yield and five agronomic traits under four water and nitrogen conditions:water stress and low nitrogen,water stress and high nitrogen,well-watered and low nitrogen,and well-watered and high nitrogen.Respectively eight,six,and six traits varied in response to genotype–water interactions,genotype–nitrogen interactions,and genotype–water–nitrogen interactions.Using a linkage map consisting of 896 single-nucleotide polymorphism markers and multipleenvironmental quantitative-trait locus(QTL)mapping,we identified 31 QTL,including 12 for genotype–water–nitrogen interaction,across the four treatments.A set of 8060 genes were differentially expressed among treatments.Integrating genetic analysis,gene co-expression,and functional annotation revealed two candidate genes controlling genotype–water–nitrogen interactions,affecting both leaf width and grain yield.Genes involved in abscisic acid biosynthesis and bZIP,NAC,and WRKY transcription factors participated in maize response to water and nitrogen conditions.These results represent a step toward understanding the genetic regulatory network of maize that responds to water and nitrogen stress and provide a theoretical basis for the genetic improvement of both water-and nitrogen-use efficiency.

Quantitative Trait Loci Mapping of Maize Yield and Its Components Under Different Water Treatments at Flowering Time

Drought or water stress is a serious agronomic problem resulting in maize （Zea mays L.） yield loss throughout the world. Breeding hybrids with drought tolerance is one important approach for solving this problem. However, lower efficiency and a longer period of breeding hybrids are disadvantages of traditional breeding programs. It is generally recognized that applying molecular marker techniques to traditional breeding programs could improve the efficiency of the breeding of drought-tolerant maize. To provide useful information for use in studies of maize drought tolerance, the mapping and tagging of quantitative trait loci （QTL） for yield and its components were performed in the present study on the basis of the principle of a mixed linear model. Two hundred and twenty-one recombinant inbred lines （RIL） of Yuyu 22 were grown under both well-watered and water-stressed conditions. In the former treatment group, plants were well irrigated, whereas those in the latter treatment group were stressed at flowering time. Ten plants of each genotype were grown in a row that was 3.00 m × 0.67 m （length × width）. The results show that a few of the QTL were the same （one additive QTL for ear length, two additive QTL and one pair of epistatic QTL for kernel number per row, one additive QTL for kernel weight per plant）, whereas most of other QTL were different between the two different water treatment groups. It may be that genetic expression differs under the two different water conditions. Furthermore, differences in the additive and epistatic QTL among the traits under water-stressed conditions indicate that genetic expression also differs from trait to trait. Major and minor QTL were detected for the traits, except for kernel number per row, under water-stressed conditions. Thus, the genetic mechanism of drought tolerance in maize is complex because the additive and epistatic QTL exist at the same time and the major and minor QTL all contribute to phenotype under water-stressed conditions. In particular, epidemic QTL under water-stressed conditions suggest that it is important to investigate the drought tolerance of maize from a genetic viewpoint.

Comparative QTL Mapping of Resistance to Gray Leaf Spot in Maize Based on Bioinformatics

The integration QTL map for gray leaf spot resistance in maize was constructed by compiling a total of 57 QTLs available with genetic map IBM2 2005 neighbors as reference. Twenty-six ＂real QTLs＂ and seven consensus QTLs were identified by refining these 57 QTLs using overview and meta-analysis approaches. Seven consensus QTLs were found on chromosomes 1.06, 2.06, 3.04, 4.06, 4.08, 5.03, and 8.06, and the map coordinates were 552.53,425.72, 279.20, 368.97, 583.21, 308.68 and 446.14 cM, respectively. Using a synteny conservation approach based on comparative mapping between the maize genetic map and rice physical map, a total of 69 rice and maize resistance genes collected from websites Gramene and MaizeGDB were projected onto the maize genetic map IBM2 2005 neighbors, and 2 （Rgene32, htl）, 4 （RgeneS, rp3, scmv2, wsm2）, and 4 （ht2, Rgene6, Rgene8 and Rgene7） positional candidate genes were found in three consensus QTLs on chromosomes 2.06, 3.04, and 8.06, respectively. The results suggested that the combination of meta-analysis of gray leaf spot in maize and sequence homologous comparison between maize and rice could be an efficient strategy for identifying major QTLs and corresponding candidate genes for the gray leaf spot.

Mapping of QTL Associated with Drought Tolerance in a Semi-Automobile Rain Shelter in Maize (Zea mays L.)

Drought is a major constraint in maize production worldwide. We studied quantitative trait loci （QTL） underlying drought tolerance for maize plants grown in two different environments. Traits investigated included ASI, plant height, grain yield, ear height, and ear setting. A genetic linkage map was constructed with 120 simple sequence repeat （SSR） markers based on an F2 population derived from a cross between D5 （resistant parent） and 7924 （susceptible parent）. Correlation and heritability were calculated. QTLs of these traits were identified by composite interval mapping combined with a linkage map covering 1 790.3 cM. The markers were arranged in ten linkage groups. QTL mapping was made of the mean trait performance of the 180 F2：3 population. The results showed five, five, six, four, and five QTLs for ASI, plant height, grain yield, ear height, and ear setting under full irrigation condition, respectively, and four, seven, six, four, and four QTLs for ASI, plant height, grain yield, ear height, and ear setting under severe late stress conditions, respectively. Especially the four QTLs detected for five traits in 2008 and 2009. The universal QTLs information generated in this study will aid in undertaking an integrated breeding strategy for further genetic studies in drought tolerance improvement in maize.

QTL analysis of the developmental changes in cell wall components and forage digestibility in maize(Zea mays L.)

Cell wall architecture plays a key role in stalk strength and forage digestibility.Lignin,cellulose,and hemicellulose are the three main components of plant cell walls,and they can impact stalk quality by affecting the structure and strength of the cell wall.To explore cell wall development during secondary cell wall lignification in maize stalks,conventional and conditional genetic mapping were used to identify the dynamic quantitative trait loci(QTLs)of the cell wall components and digestibility traits during five growth stages after silking.Acid detergent lignin(ADL),cellulose(CEL),acid detergent fiber(ADF),neutral detergent fiber(NDF),and in vitro dry matter digestibility(IVDMD)were evaluated in a maize recombinant inbred line(RIL)population.ADL,CEL,ADF,and NDF gradually increased from 10 to 40 days after silking(DAS),and then they decreased.IVDMD initially decreased until 40 DAS,and then it increased slightly.Seventytwo QTLs were identified for the five traits,and each accounted for 3.48–24.04%of the phenotypic variation.Six QTL hotspots were found,and they were localized in the 1.08,2.04,2.07,7.03,8.05,and 9.03 bins of the maize genome.Within the interval of the pleiotropic QTL identified in bin 1.08 of the maize genome,six genes associated with cell wall component biosynthesis were identified as potential candidate genes for stalk strength as well as cell wall-related traits.In addition,26 conditional QTLs were detected in the five stages for all of the investigated traits.Twenty-two of the 26 conditional QTLs were found at 30 DAS conditioned using the values of 20 DAS,and at 50 DAS conditioned using the values of 40 DAS.These results indicated that cell wall-related traits are regulated by many genes,which are specifically expressed at different stages after silking.Simultaneous improvements in both forage digestibility and lodging resistance could be achieved by pyramiding multiple beneficial QTL alleles identified in this study.

Integrated linkage mapping and genome-wide association study to dissect the genetic basis of zinc deficiency tolerance in maize at seedling stage

Zinc(Zn)deficiency is the most widespread micronutrient deficiency,affecting yield and quality of crops worldwide.Identifying genes associated with Zn-deficiency tolerance in maize is a basis for elucidating its genetic mechanism.A K22×CI7 recombinant inbred population consisting of 210 lines and an association panel of 508 lines were used to identify genetic loci influencing Zn-deficiency tolerance.Under-Zn and-Zn/CK conditions,15 quantitative trait loci(QTL)were detected,each explaining 5.7%-12.6%of phenotypic variation.Sixty-one significant single-nucleotide polymorphisms(SNPs)were identified at P<10^(-5)by genome-wide association study(GWAS),accounting for 5%-14%of phenotypic variation.Among respectively 198 and 183 candidate genes identified within the QTL regions and the 100-kb regions flanking these significant SNPs,12 were associated with Zn-deficiency tolerance.Among these candidate genes,four genes associated with hormone signaling in response to Zn-deficiency stress were co-localized with QTL or SNPs,including the genes involved in the auxin(ZmARF7),and ethylene(ZmETR5,ZmESR14,and ZmEIN2)signaling pathways.Three candidate genes were identified as being responsible for Zn transport,including ZmNAS3 detected by GWAS,ZmVIT and ZmYSL11 detected by QTL mapping.Expression of ZmYSL11 was up-regulated in Zn-deficient shoots.Four candidate genes that displayed different expression patterns in response to Zn deficiency were detected in the regions overlapping peak GWAS signals,and the haplotypes for each candidate gene were further analyzed.

The Genetic Architecture of Flowering Time and Photoperiod Sensitivity in Maize as Revealed by QTL Review and Meta Analysis

The control of flowering is not only important for reproduction, but also plays a key role in the processes of domestication and adaptation. To reveal the genetic architecture for flowering time and photoperiod sensitivity, a comprehensive evaluation of the relevant literature was performed and followed by meta analysis. A total of 25 synthetic con- sensus quantitative trait loci （QTL） and four hot-spot genomic regions were identified for photoperiod sensitivity including 11 genes related to photoperiod response or flower morphogenesis and development. Besides, a comparative analysis of the QTL for flowering time and photoperiod sensitivity highlighted the regions containing shared and unique QTL for the two traits. Candidate genes associated with maize flowering were identified through integrated analysis of the homologous genes for flowering time in plants and the consensus QTL regions for photoperiod sensitivity in maize （Zea mays L.）. Our results suggest that the combination of literature review, meta-analysis and homologous blast is an efficient approach to identify new candidate genes and create a global view of the genetic architecture for maize photoperiodic flowering. Sequences of candidate genes can be used to develop molecular markers for various models of marker-assisted selection, such as marker-assisted recurrent selection and genomic selection that can contribute significantly to crop environmental adaptation.

Quantitative genetic analysis of chlorophyll a fluorescence parameters in maize in the field environments

Chlorophyl fluorescence transient from initial to maximum fluorescence （“P”step） throughout two intermedi-ate steps （“J”and“I”） （JIP-test） is considered a reliable early quantitative indicator of stress in plants. The JIP-test is particularly useful for crop plants when applied in variable field environments. The aim of the present study was to conduct a quantitative trait loci （QTL） analysis for nine JIP-test parameters in maize during flowering in four field environ-ments differing in weather conditions. QTL analysis and identification of putative candidate genes might help to explain the genetic relationship between photosynthesis and different field scenarios in maize plants. The JIP-test param-eters were analyzed in the intermated B73 ？ Mo17 （IBM） maize population of 205 recombinant inbred lines. A set of 2,178 molecular markers across the whole maize genome was used for QTL analysis revealing 10 significant QTLs for seven JIP-test parameters, of which five were co-localized when combined＆amp;nbsp;over the four environments indicating polygenic inheritance and pleiotropy. Our results demonstrate that QTL analysis of chlorophyl fluorescence parameters was capable of detecting one pleiotropic locus on chromosome 7, coinciding with the gene gst23 that may be associated with efficient photosynthe-sis under different field scenarios.

Genome-wide Analysis of Transcriptional Variability in a Large Maize-Teosinte Population

Gene expression regulation plays an important role in controlling plant phenotypes and adaptation. Here, we report a comprehensive assessment of gene expression variation through the transcriptome analyses of a large maize-teosinte experimental population. Genome-wide mapping identified 25 660 expression quantitative trait loci （eQTL） for 17 311 genes, capturing an unprecedented range of expression variation. We found that local eQTL were more frequently mapped to adjacent genes, displaying a mode of expression piggybacking, which consequently created co-regulated gene clusters. Genes within the co-regulated gene clusters tend to have relevant functions and shared chromatin modifications. Distant eQTL formed 125 significant distant eQTL hotspots with their targets significantly enriched in specific functional cate- gories. By integrating different sources of information, we identified putative trans- regulators for a variety of metabolic pathways. We demonstrated that the bHLH transcription factor R1 and hexokinase HEX9 might act as crucial regulators for flavonoid biosynthesis and glycolysis, respectively. Moreover, we showed that domestication or improvement has significantly affected global gene expression, with many genes targeted by selection. Of particular interest, the Bx genes for benzoxazinoid biosynthesis may have undergone coordinated cis-regulatory divergence between maize and teosinte, and a transposon insertion that inactivates Bx12 was under strong selection as maize spread into temperate environments with a distinct herbivore community.

Transcriptome analysis of near-isogenic lines provides molecular insights into starch biosynthesis in maize kernel

Starch is the major component in maize kernels,providing a stable carbohydrate source for humans and livestock as well as raw material for the biofuel industry.Increasing maize kernel starch content will help meet industry demands and has the potential to increase overall yields.We developed a pair of maize near-isogenic lines（NILs） with different alleles for a starch quantitative trait locus on chromosome 3（q HS3）, resulting in different kernel starch content. To investigate the candidate genes for q HS3 and elucidate their effects on starch metabolism, RNA-Seq was performed for the developing kernels of the NILs at 14 and 21 d after pollination（DAP）. Analysis of genomic and transcriptomic data identified 76 genes with nonsynonymous single nucleotide polymorphisms and 384 differentially expressed genes（DEGs） in the in trogressed fragment, including a hexokinase gene, Zm HXK3 a, which catalyzes the conversion of glucose to glucose-6-phosphate and may play a key role instarch metabolism. The expression pattern of all DEGs in starch metabolism shows that altered expression of the candidate genes for q HS3 promoted starch synthesis,with positive consequences for kernel starch content. These results expand the current understanding of starch biosynthesis and accumulation in maize kernels and provide potential candidate genes to increase starch content.

Enhancing phosphorus uptake efficiency through QTL-based selection for root system architecture in maize

Root system architecture （RSA） plays an important role in phosphorus （P） acquisition, but enhancing P use efficiency （PUE） in maize via genetic manipulation of RSA has not yet been reported. Here, using a maize recombinant inbred line （RIL） population, we investigated the genetic relationships between PUE and RSA, and developed P-efficient lines by selection of quantitative trait loci （QTLs） that coincide for both traits. In low-P （LP） fields, P uptake efficiency （PupE） was more closely correlated with PUE （r = 0.48 -0.54）, and RSA in hydroponics was significantly related to PupE （r=0.25-0.30） but not to P utilization efficiency （PutE）. QTL analysis detected a chromosome region where two QTLs for PUE, three for PupE and three for RSA were assigned into two QTL clusters, Cl-bin3.04a and Cl-bin3.04b. These QTLs had favorable effects from alleles derived from the large-rooted and high-PupE parent. Marker-assisted selection （MAS） identified nine advanced backcross-derived lines carrying Cl-bin3.04a or Cl-bin3.04b that displayed mean increases of 22%-26% in PUE in LP fields. Furthermore, a line L224 pyramiding Cl- binB.04a and Cl-bin3.04b showed enhanced PupE, relying mainly on changes in root morphology, rather than root physiology, under both hydroponic and field conditions. These results highlight the physiological and genetic contributions of RSA to maize PupE, and provide a successful study case of developing P-efficient crops through QTL-based selection.

Genetic study and molecular breeding for high phosphorus use efficiency in maize

Phosphorus is the second most important macronutrient after nitrogen and it has many vital functions in the life of plants.Most soils have a low available P content,which has become a key limiting factor for increasing crop production.Also,low P use efficiency(PUE)of crops in conjunction with excessive application of P fertilizers has resulted in serious environmental problems.Thus,dissecting the genetic architecture of crop PUE,mining related quantitative trait loci(QTL)and using molecular breeding methods to improve high PUE germplasm are of great significance and serve as an efficient approach for the development of sustainable agriculture.In this review,molecular and phenotypic characteristics of maize inbred lines with high PUE,related QTL and genes as well as low-P responses are summarized.Based on this,a breeding strategy applying genomic selection as the core,and integrating the existing genetic information and molecular breeding techniques is proposed for breeding high PUE maize inbred lines and hybrids.

玉米5个农艺性状的QTL定位

利用“豫玉 2 2”构建的 2 6 6个玉米F2∶3家系为材料 ,通过一年两点的随机区组田间试验和分子标记分析 ,研究了玉米穗位高、雄穗分支数、茎粗、抽雄期、吐丝期 5个重要农艺性状。相关分析表明 ,穗位高、雄穗分支数、茎粗与单株产量显著正相关 ,抽雄期与吐丝期高度正相关 ,雄穗分支数与茎粗显著正相关。采用复合区间作图法 ,通过5 0 0次排列测验分别确定各性状的LOD阈值 ,在武汉和襄樊两地共定位了 7个穗位高QTL、9个雄穗分支数QTL、8个茎粗QTL、9个抽雄期QTL和 7个吐丝期QTL ;这些QTL在染色体上分布不均匀 ,具有集中分布的特点。研究表明 。

玉米数量性状基因定位

以 4 8 2× 5 0 0 3的 16 6个F2 :3家系作为定位群体 ,采用 13× 13α 简单格子方设计 ,在成都、雅安分别调查了株高、穗位高、穗长、秃尖长、穗行数、行粒数、穗粗、轴粗、粒深、30 0粒重、出籽率、小区产量等 12个经济性状 ,采用区间作图法对其进行QTL定位分析 ,共检测出 5 9个QTL ,每个性状检测出 3～ 8个QTL ,单个QTL的作用可解释表型变异的 8 4 %～4 2 2 % ,每一性状的QTL可解释表型变异的 19 5 %～ 70 9%。 5 9个QTL分布于 10个连锁群的 33个标记区域 ,其中第 1、3连锁群较多 ,分别占 2 4 2 %、15 2 % ;33个标记区域中 19个区域作用单一性状 ,6个区域分别作用两个性状 ,4个标记区域 (bnlg10 83、bnlg10 35、bnl8 4 5a、csu16 )分别作用于 3个性状 ,3个标记区域 (csu9、phi0 5 3、phi0 2 2 )分别作用于 4个性状 ,nc0 12区域同时作用于 5个性状。

氮胁迫和正常条件下玉米穗部性状的QTL分析

【目的】分析氮胁迫和正常条件下玉米穗部性状的QTL。【方法】以优良玉米杂交种"农大108"的一套203个F2:3家系为材料,构建了包含189个SSR标记的遗传连锁图谱,在施氮(N+)和不施氮(N-)条件下,通过一年两点的田间试验,利用复合区间作图法对玉米穗长、穗粗、穗行数、行粒数、穗粒重和百粒重等6个穗部性状进行了QTL分析。【结果】亲本许178对N胁迫的敏感程度远小于黄C;F2:3群体的穗长、穗粗、穗行数和行粒数与单株产量大多呈显著或极显著正相关。在郑州和新郑两地,2种氮处理水平下定位了玉米穗部性状的53个QTL,其中郑州点检测到28个QTL,主要集中在第2、8和9染色体上(占57.14%);新郑点检测到25个QTL,主要分布在第1、2、6、7和8染色体上(占60%);在所检测到的53个QTL中,表现加性、部分显性、显性和超显性效应的QTL依次为13(24.5%)、20(37.7%)、6(11.3%)和14(26.4%)个,单个QTL解释表型变异介于7.1%～23.3%之间。N+条件下6个性状在两个地间检测到的QTL数量明显高于N-条件下检测到的QTL数量,同时在郑州点2种氮处理水平下检测到3个相同的QTL(qED2a,qKW8a,qKW10a),新郑点检测到1个相同的QTL(qEL1a),推断在缺氮条件下检测到的各性状特异表达的QTL可能与玉米的氮高效利用有关。【结论】在两地、2种供氮水平下所定位的53个穗部性状QTL,主要集中在第1、2、8和9染色体上,部分显性和超显性效应的QTL占60%以上。

在干旱和正常水分条件下玉米穗部性状QTL分析

穗部性状与产量密切相关,因此对其进行遗传剖析可为玉米高产育种提供理论基础,尤其是对干旱胁迫下的稳产有重要意义。本研究以玉米骨干亲本黄早四分别与自交系掖478和齐319进行杂交,构建了两套F2：3群体（分别记为Y/H和Q/H）。在正常水分灌溉和干旱胁迫下对穗长、穗粗、轴粗、穗行数、行粒数、穗粒重和穗重等7个穗部性状进行了表型鉴定,采用基于混合线性模型的单环境分析和相同处理水平的联合分析方法进行了QTL分析。结果表明,在干旱胁迫下,2个群体的亲本及F2：3家系的各性状值均低于正常水分条件,且穗粒重与穗长、穗重、穗粗呈正相关。在干旱胁迫下和正常水分条件下,通过两种检测方法共定位到75个玉米穗部性状QTL,其中Y/H群体共定位了20个QTL,分布在第1、第2、第5、第6、第7、第10染色体上;Q/H群体共定位了55个QTL,分布在第2、第3、第4、第5、第6、第7、第9、第10染色体上;但是在干旱条件下两群体分别只检测到4个和19个QTL,明显低于正常水分条件下检测到的QTL数目。通过联合分析只检测到3个QTL与环境发生显著互作和6对QTL存在上位性互作效应,说明玉米穗部性状的遗传基础较为复杂。同时还发现,Y/H群体在正常灌溉与干旱条件下检测到2个一致性的QTL,分别是qKRE1-5-1和qKRE1-7-1,对表型变异解释的变化范围是6.15%19.48%;Q/H群体检测到3个一致性QTL,分别是qKRE2-5-1、qGW2-10-1和qKRE2-3-1,对表型变异解释的变化范围是7.14%16.65%,说明这些QTL受环境影响较小,能够稳定遗传,可以作为分子标记辅助选择的候选区间应用于玉米穗部性状抗旱性改良。