Detection of quantitative trait loci (QTLs) for seedling traits and drought tolerance in wheat using three related recombinant inbred line (RIL) populations

In order to detect quantitative trait loci (QTLs) for drought tolerance in wheat during seed germination conditional and unconditional QTL analyses of eight seedling traits were conducted under two water regimes using three related F₉ recombinant inbred line populations with a common female parent. A total of 87 QTLs for the eight seedlings traits and 34 specific QTLs related to drought tolerance were detected. Seventy-one of these QTLs were major QTLs with contributions to phenotypic variance of >10 %. Of the 34 QTLs related to drought tolerance only eight were also detected by unconditional analysis of seedling traits under osmotic stress conditions indicating that most of the QTLs related to drought tolerance could not be detected by unconditional QTL analysis. Therefore, conditional QTL analysis of stress-tolerance traits such as drought tolerance was feasible and effective. Of 11 important QTL clusters located on chromosomes 1BL, 1D, 2A, 2B, 2D, 4A, 6B, and 7B, nine were detected in multiple populations and eight were detected by both unconditional and conditional analyses.     

用3种方法定位玉米萌发期和苗期的耐盐和耐碱相关性状QTL

以耐盐碱郑58和盐碱敏感昌7-2为亲本,构建包含151份F2:5重组自交系(RILs)群体。基于3K芯片对郑58、昌7-2及其F2:5家系进行基因型分析,构建了包含1407个SNP分子标记的高密度遗传连锁图谱。该图谱的各染色体标记数在84～191之间,标记间的平均距离为0.81 cM。胁迫液为200 mmol L–1 NaCl和100 mmol L–1 Na2CO3,对照液为蒸馏水或霍格兰营养液,对盐、碱胁迫和自然条件下玉米的发芽率(GP)、株高(PH)、植株干、鲜重(FW、DW)、幼苗组织含水量(TWS)、植株地上部分钠含量(SNC)、钾含量(SKC)、钠/钾含量比(NKR)、苗期耐盐率(STR)、耐碱率(ATR)10项指标,采用3种不同的作图方法同时定位研究,对加性QTL定位采用复合区间作图法(CIM)和完备区间作图法(ICIM),对加性QTL与环境互作联合分析采用混合线性模型的复合区间作图法(MCIM)。结果表明,(1)与对照条件下各性状表型值相比,耐碱相关性状的降低较耐盐相关性状明显,说明玉米对碱胁迫更加敏感和碱胁迫对玉米的伤害更严重。碱与盐胁迫下SKC相当而SNC差异较大,表明Na+、K+的吸收和运输是相互独立的两个过程,玉米盐、碱胁迫可能是两种性质不同的胁迫。(2)在自然、盐和碱胁迫条件下,运用CIM分别检测到27、28、40个加性QTL;运用ICIM分别检测到28、23、17个加性QTL;运用MCIM共检测到11个耐盐加性QTL、4个环境互作QTL以及11个耐碱加性QTL、3个环境互作QTL。(3)盐胁迫条件下的qPH-9、qSTR-8、qNKR-6、qNKR-7和碱胁迫条件下的qPH-9、qATR-3能被3种作图方法重复检测到。与前人结果比较, qPH-9、qSTR-8、qNKR-6、q-ATR-3定位在相同或邻近区域,qNKR-7尚未见报道。本研究结果为精细定位玉米耐盐碱主效基因、挖掘候选基因和开发用于标记辅助选择的实用功能标记奠定基础。     

Identification of quantitative trait loci for agronomic and physiological traits in maize (<Emphasis Type="Italic">Zea mays</Emphasis> L.) under high-nitrogen and low-nitrogen conditions

Low-nitrogen (LN) tolerance is a compound character with a complex genetic basis. Many agronomic traits have been shown to be closely related to LN tolerance in maize. In this study, 150 F₇ recombinant inbred lines derived from a cross between inbreds 178 and K12 were evaluated for agronomical and physiological traits under high-nitrogen (HN) and LN conditions in 2 years. Inclusive composite interval mapping (ICIM) was used to identify the quantitative trait loci (QTLs) for traits recorded under different treatments (LN and HN) in 2 years. In total, 86 QTLs were detected: 38 for HN and 35 for LN, while 13 QTLs were detected under both nitrogen levels, suggesting that LN-specific QTLs may play a role in improving LN tolerance in maize. Overlapping QTLs for different traits were located on all chromosomes except chromosome 4 and chromosome 9. Many of these regions overlapped with previously reported QTLs. Several consensus major QTLs and LN-specific major QTLs found in the study can be used in marker-assisted selection breeding for genetic improvement and LN tolerance in maize in the future.     

Identification of salt tolerance‐improving quantitative trait loci alleles from a salt‐susceptible rice breeding line by introgression breeding

To improve salt tolerance of two elite rice varieties, Ce258 and Zhongguangxiang1 (ZGX1), two sets of introgression lines (ILs) each comprising 200 BC₁F₁₀ lines derived from a common donor, IR75862, and two recipient parents, Ce258 and ZGX1, were used for mapping of QTLs for four salt tolerance‐related traits at the seedling stage. Although the three parents were susceptible to salt, the two IL populations showed transgressive segregations for salt tolerance with 12 and 8 salt tolerance ILs in the Ce258‐ILs and ZGX1‐ILs. Eighteen main‐effect QTLs were identified for the four traits in the two IL populations, and the IR75862 alleles at most loci showed increased and decreased salt tolerance in the ZGX1 and Ce258 backgrounds, suggesting overwhelming genetic background effects on QTL detection for salt tolerance. The qDSS11 simultaneously detected in the two backgrounds was validated in a F₂ population derived from a salt tolerance line and ZGX1. Our results indicated that salt tolerance‐enhancing allele could be identified in the elite susceptible breeding lines and that introgression of the favourable alleles could facilitate the development of superior lines with greater salt tolerance levels.     

Mapping QTLs for aluminum tolerance in maize

Aluminum toxicity is one of the major constraints for plant development in acid soils, limiting food production in many countries. Cultivars genetically adapted to acid soils may offer an environmental compatible solution, providing a sustainable agriculture system. The aim of this work was to identify genomic regions associated with Al tolerance in maize, and to quantify the genetic effects on the phenotypic variation. A population of 168F_3:4 families derived from a cross between two contrasting maize inbred lines for Al tolerance was evaluated using the NSRL and RSRL parameters in nutrient solution containing toxic level of aluminum. Variance analyses indicated that the NSRL was the most reliable phenotypicindex to measure Al tolerance in the population, being used for further QTL mapping analysis. RFLP and SSR markers were selected for bulked segregant analysis, and additional SSR markers, flanking the polymorphisms of interest, were chosen in order to saturate the putative target regions. Seven linkage groups were constructed using 17 RFLP and 34 SSR markers. Five QTLs were mapped on chromosomes 2, 6 and 8, explaining 60% of the phenotypic variation. QTL₄ and marker umc043 were located on chromosomes 8and 5, close to genes encoding for enzymes involved in the organic acids synthesis pathways, a widely proposed mechanism for Al tolerance in plants. QTL₂ was mapped in the same region as Alm2,also associated with Al tolerance in maize. In addition, dominant and additive effects were important in the control of this trait in maize. This revised version was published online in July 2006 with corrections to the Cover Date.     

Mapping of Quantitative Trait Loci Associated with Reproductive‐Stage Salt Tolerance in Rice

Salinity tolerance in rice varies with the state of growth, with the seedling and reproductive stages being the most sensitive. However, association between tolerances at the two stages is poor, suggesting that they are regulated by different processes and genes. Tolerance at the reproductive stage is the most crucial as it determines grain yield. An F₂ mapping population was developed from two rice genotypes contrasting in tolerance: Cheriviruppu and Pusa Basmati 1 (PB1). Cheriviruppu is highly tolerant at the reproductive stage, while PB1 is highly sensitive at both seedling and reproductive stages. One hundred and thirty‐one microsatellite markers polymorphic between the parents were used to construct a linkage map of 1458.5 cM (Kosambi), with a mean intermarker distance of 11.1 cM. Sixteen QTLs with LOD values ranging from 3.2 to 22.3 were identified on chromosomes 1, 7, 8 and 10, explaining 4–47 % of the phenotypic variation. The maximum number of QTL clusters for different component traits was colocalized on the long arm of chromosome 1 and chromosome 7. We identified several significant epistatic interactions, including three inter‐QTL interactions, using MapManager. The results suggest that pollen fertility, Na⁺ concentration and Na/K ratio in the flag leaf are the most important mechanisms controlling salt tolerance at the reproductive stage in rice. The study reports the construction of a genetic map for reproductive‐stage salt tolerance in rice and demonstrates its utility for molecular mapping of QTLs controlling salinity tolerance‐related traits, which will be useful in marker‐assisted selection in the future.     

Development of molecular markers for crown rot resistance in wheat: mapping of QTLs for seedling resistance in a '2-49' × 'Janz' population

Crown rot, caused by Fusarium pseudograminearum, is an important disease of wheat in Australia and elsewhere. In order to identify molecular markers associated with partial seedling resistance to this disease, bulked segregant analysis and quantitative trait loci (QTL) mapping approaches were undertaken using a population of 145 doubled haploid lines constructed from ‘2‐49’ (partially resistant) × ‘Janz’ (susceptible) parents. Phenotypic data indicated that the trait is quantitatively inherited. The largest QTLs were located on chromosomes 1D and 1A, and explained 21% and 9% of the phenotypic variance, respectively. Using the best markers associated with five QTLs identified by composite interval mapping, the combined effect of the QTLs explained 40.6% of the phenotypic variance. All resistance alleles were inherited from ‘2‐49’ with the exception of a QTL on 2B, which was inherited from ‘Janz’. A minor QTL on 4B was loosely linked (19.8 cM) to the Rht1 locus in repulsion. None of the QTLs identified in this study were located in the same region as resistance QTLs identified in other populations segregating for Fusarium head blight, caused by Fusarium graminearum.     

Identification of Quantitative Trait Loci Associated with Aluminum Tolerance in Rice (Oryza Sativa L.)

Summary Quantitative trait loci (QTL) analysis for Al tolerance was performed in rice using a mapping population of 98 BC₁F₁₀ lines (backcross inbred lines: BILs), derived from a cross of Al-tolerant cultivar of rice (Oryza sativa L. cv. Nipponbare) and Al-sensitive cultivar (cv. Kasalath). Three characters related to Al tolerance, including root elongation under non-stress conditions (CRE), root elongation under Al stress (SRE) and the relative root elongation (RRE) under Al stress versus non-stress conditions, were evaluated for the BILs and the parents at seedling stage. A total of seven QTLs for the three traits were identified. Among them, three putative QTLs for CRE (qCRE-6, qCRE-8 and qCRE-9) were mapped on chromosomes 6, 8 and 9, respectively. One QTL for SRE (qSRE-4) was identified on chromosome 4. Three QTLs (qRRE-5, qRRE-9 and qRRE-10) for RRE were detected on chromosomes 5, 9, 10 and accounted for 9.7–11.8% of total phenotypic variation. Interestingly, the QTL qRRE-5 appears to be syntenic with the genomic region carrying a major Al tolerance gene on chromosome 6 of maize. Another QTL, qRRE-9, appears to be similar among different rice populations, while qRRE-10 is unique in the BIL population. The common QTLs for CRE and RRE indicate that candidate genes conferring Al tolerance in the rice chromosome 9 may be associated with root growth rates. The existence of QTLs for Al tolerance was confirmed in substitution lines for corresponding chromosomal segments. These results also provide the possibilities of enhancing Al tolerance in rice through using marker-assisted selection (MAS) and pyramiding QTLs.     

碱胁迫下粳稻幼苗前期耐碱性的数量性状基因座检测

以粳粳交“高产106/长白9号”F_2:3代200个家系为作图群体, 在0.15% Na₂CO₃溶液的碱性胁迫下, 进行了水稻耐碱性鉴定, 并以SSR标记构建的分子连锁图谱为基础, 对水稻幼苗前期的根数、根长和苗高及其相对碱害率进行了数量性状基因座(QTLs)的检测。结果表明, 上述性状在F₃家系群中均表现为具有1~2个峰的连续分布, 认为由主效基因和微效基因共同控制的数量性状。共检测到与碱胁迫下幼苗前期根数、根长和苗高及其相对碱害率相关的QTL 26个, 分布于第1、5、6、7、8、9和11染色体上。其中, 碱胁迫下与根数相关的QTL 4个, qRN6-1和qRN11对表型变异的解释率较大, 分别为29.91%和13.42%;与根数相对碱害率相关的QTL 5个, qRRN11-2对表型变异的解释率较大, 为23.86%;与根长相关的QTL 6个, qRRL11-2对表型变异的解释率较大, 为21.06%;与根长相对碱害率相关的QTL 2个, 但对表型变异的解释率均较低;与苗高相关的QTL 5个, qSH1和qSH11-2对表型变异的解释率较大, 分别为15.81%和16.53%;与苗高相对碱害率相关的QTL 4个, qRSH5和qRSH6-2对表型变异的解释率分别为29.89%和34.63%。而这些解释率较大的QTL所处的标记区间距离, 除qRN6-1相对较小(19.0 cM)外, 其余QTL的标记区间距离均大于26.3 cM, 需作进一步的精细定位。在所检测到的QTL中, 13个QTL的增效等位基因均来自耐碱亲本长白9号, 而其余QTL的增效等位基因来自敏碱亲本高产106;基因的主要作用方式为超显性或部分显性。     

The genetic architecture of zinc and iron content in maize grains as revealed by QTL mapping and meta-analysis

Micronutrient malnutrition, especially zinc (Zn) and iron (Fe) deficiency in diets, has aroused worldwide attention. Biofortification of food crops has been considered as a promising approach for alleviating this deficiency. Quantitative trait locus (QTL) analysis was performed to dissect the genetic mechanism of Zn and Fe content in maize grains using a total of 218 F_2:3 families derived from a cross between inbred lines 178 and P53. Meta-analysis was used to integrate genetic maps and detect Meta-QTL (MQTL) across several independent QTL researches for traits related to Zn or Fe content. Five significant QTLs and 10 MQTLs were detected. Two informative genomic regions, bins 2.07 and 2.08, showed a great importance for Zn and Fe content QTLs. The correlation between Zn and Fe level in maize grains was proposed by MQTLs as 8 of the 10 involved both traits. The results of this study suggest that QTL mapping and meta-analysis is an effective approach to understand the genetic basis of Zn and Fe accumulation in maize grains.     

Mapping QTLs for salt tolerance in an introgression line population between Japonica cultivars in rice

QTL analysis of physiological traits related to salt tolerance was carried out using 117 BC₃F₅ lines derived from a cross between “Ilpumbyeo” as a recurrent parent and “Moroberekan” as a donor parent. The 117 introgression lines with the parents were evaluated for five traits; dry weight, fresh weight, leaf area, seedling height, and survival rate under control and salinity conditions (55 mM) at the seedling stage. To identify QTLs related to salt tolerance, 125 SSR markers showing polymorphisms between the parents were genotyped for the 117 BC₃F₅ lines. A total of eight QTLs were detected on chromosomes 1, 6, and 7. These include two QTLs on chromosomes 6 and 7 for reduction rate of dry weight (R² = 10.2∼13.6%), three QTLs on chromosomes 1, 6, and 7 for reduction rate of fresh weight (R² = 10.9∼13.9 %), two QTLs on chromosomes 1 and 7 for reduction rate of leaf area (R² = 12.1%), and one QTL on chromosome 7 for reduction rate of seedling height (R² = 10.5%). The Moroberekan alleles contributed the positive effect at these eight QTL loci. Although the parents, Ilpumbyeo and Moroberekan, were not salt tolerant as the salt tolerant check variety, Pokkali, some lines displayed a similar level of tolerance as Pokkali. The effect of the QTL on chromosome 7 was further confirmed by evaluating four lines containing the target QTL for fresh and dry weight, turgid weight, and relative water content (RWC). Significant differences between each line and Ilpumbyeo were detected for dry and fresh weight, and RWC values, and these results seem to indicate the beneficial effect of the Moroberekam alleles for salt tolerance. A set of introgression lines are being developed containing only few chromosomal segments from Moroberekan in the Ilpumbyeo background. These would be useful in developing salt tolerant lines in the breeding program.     

Quantitative trait loci controlling rice seed germination under salt stress

Salt tolerance of rice (Oryza sativa L.) at the seed germination stage is one of the major determinants for the stable stand establishment in salinity soil. One population of recombinant inbred lines (RILs, F_2:9), derived from a cross between a japonica rice landrace tolerant to salt stress and a sensitive indica rice variety, was used to determine the germination traits including imbibition rate and germination percentage under control (water) and salt stress (100 mM NaCl) for 10 days at 30 °C. The multiple interval mapping (MIM) were applied to conduct QTL for the traits. The results showed that seed germination was a quantitative trait controlled by several genes, and strongly affected by salt stress. A total of 16 QTLs were detected in this study, and each QTL could explain 4.6–43.7% of the total phenotypic variance. The expression of these QTLs might be developmentally regulated and growth stage-specific. In addition, only one digenic interaction was detected under salt stress, showing small effect on germination percentage with R² 2.7%. Among sixteen QTLs detected in this study, four were major QTLs with R² > 30%, and some novel alleles of salt tolerance genes in rice. The results demonstrated that the japonica rice Jiucaiqing is a good source of gene(s) for salt tolerance and the major or minor QTLs identified could be used to improve the salt tolerance by marker-assisted selection (MAS) in rice.     

QTL analysis for alkaline tolerance of rice and verification of a major QTL

Alkaline stress causes injuries to rice seedlings in many parts of the world and is therefore an important factor affecting rice production in such areas. In this study, we preliminarily located quantitative trait loci (QTLs) for survival days of seedlings (SDS) and the concentrations of Na⁺ and K⁺ in shoots (SNC and SKC) and roots (RNC and RKC) under alkaline stress using an F_2:3 population, which was derived from a cross between Caidao and WD20342 with 151 simple sequence repeat (SSR) markers. A total of seven QTLs were detected. Of these QTLs, qSNC3 had the largest effect, which explained 21.24% of the total phenotypic and is a major QTL. Next, a mapping population consisting of 190 BC₂F₂ plants was constructed using WD20342 as a donor parent to verify qSNC3. As a result, qSNC3 was delimited to an 81.7‐kb region between markers RM1221 and RM4404. In this region, LOC_Os03 g62500 and LOC_Os03 g62620 exhibited different expression between Caidao and WD20342 under alkaline stress. These results provide a basis for identifying genes related to alkaline tolerance in rice.     

Identification of QTL for acid phosphatase activity in root and rhizosphere soil of maize under low phosphorus stress

To provide theoretical and applied references for acid phosphatase (APase) activity of maize, this study was to identify quantitative trait locus (QTL) for APase activity in root and rhizosphere soil of maize under low phosphorus (p) stress. The correlation and the QTL of APase activity in root (APR) and APase activity in rhizosphere soil (APS) were studied for the F_2:3 population derived from the cross 082×Ye107 under low P stress in two sites. Analysis for each environment and joint analysis across two environments were used to identify QTL for the F_2:3 population. A significant difference in APR and APS was found between 082 (P efficient genotype) and Ye107 (P deficient genotype). A large genetic variation and transgressive segregation of the F_2:3 population were observed in Beibei and Hechuan. One stable QTL for APR was detected in different environments, which was located in the interval bnlg1350 to bnlg1449 on chromosome 3. Two stable QTLs for APS were detected, which were located in the interval umc2083 to umc1972 on chromosome 1 and in the interval umc2111 to dupssr10 on chromosome 5. The stable QTLs can be used in MAS breeding and theoretical study of maize.     

利用永久F2群体在不同光周期环境下定位玉米株高QTL

为了研究热带玉米株高的遗传机制, 利用温热组合黄早四×CML288衍生的重组自交系群体构建了一个包含278个组合的永久F₂群体, 分别在海南三亚、河南郑州和洛阳、北京昌平和顺义等5个地点3种光周期环境中进行株高鉴定。利用复合区间作图法在3种光周期环境下共定位到12个不同的玉米株高QTL。位于第1染色体上的qPH1-2和位于第4染色体上的QTL qPH4在3个环境中同时被检测到, 表明这2个QTL在不同日照环境下均能稳定表达。位于第3染色体上的qPH3在短日照环境下能解释株高遗传变异的32.13%, 而在2个长日照环境下并未被检测到, 表明此QTL是短日照环境下特异表达的主效QTL。第10染色体上QTL qPH10-1分别解释2个长日照环境中株高遗传变异的25.39%和39.58%, 是长日照环境下特异表达的主效株高QTL。     

小麦燕大1817×北农6号重组自交系群体在正常和盐胁迫水培条件下苗期性状的QTL定位

小麦苗期性状能够指示品种的耐盐性。本研究以小麦骨干亲本燕大1817与品系北农6号衍生的230个重组自交系为材料,利用2013年3个不同时间的水培试验数据和已经构建的SSR和SNP高密度遗传连锁图谱分别对正常和盐胁迫条件下根数和最长根长等7个苗期性状进行QTL定位。利用完备复合区间作图法(ICIM)共检测到69个加性效应QTL(LOD≥2.5),分布于除1A染色体外的所有20条染色体上,单个QTL解释的表型变异率为2.70%~19.00%。有46个QTL的增效效应来自于燕大1817,有23个QTL的增效效应来自于北农6号。有12个QTL能够在3个或3个以上的环境中被检测到,在燕大1817中定位到稳定的多分蘖主效QTL QTn.cau-7BS.1和盐胁迫条件下特异表达的根数QTL QRn.cau-2A,解析了小麦骨干亲本燕大1817的繁茂性和抗逆性遗传基础,为解析小麦品种耐盐遗传机制和耐盐性的分子标记辅助选择提供了重要信息。     

Fine mapping of grain weight QTLs using near isogenic lines from a Cross between <Emphasis Type="Italic">Oryza sativa</Emphasis> and <Emphasis Type="Italic">O. grandiglumis</Emphasis>

In a previous study, we reported the grain weight QTL, tgw2 in the 150 F2:3 lines derived from a cross between Oryza sativa subssp. Japonica cv. Hwaseongbyeo and HG101. This QTL was confirmed in F4 lines (CR1242) segregating for the target region. For fine mapping of tgw2, one F₅ plant homozygous for the O. grandiglumis DNA in the target region was selected from CR1242 and crossed with Hwaseongbyeo to produce the F₂ and F₃ populations. QTL analysis using 490 F₂ plants confirmed the existence of tgw2 with an R ² value of 28.0%. This QTL explained 61.3% of the phenotypic variance for 1,000-grain weight in 64 F₃ lines. Substitution mapping with 47 F₃ lines and 74 F₄ plants with informative recombination breakpoints in the target region was carried out to narrow down the position of the tgw2. The result indicated that tgw2 was located in the 384-kb interval between two SSR markers, RM12813 and RM12836. Annotation data of BACs in this 384-kb region revealed that forty-five putative genes exist in this interval including the GW2 gene responsible for grain weight and width. Considering the position of the QTL tgw2, it appears that tgw2 is functionally related to the gene GW2. However, the possibility that another unknown mechanism might be responsible for regulation of grain weight at tgw2 cannot be ruled out. Four QTLs for grain length, grain width, and grain thickness were also located in the same interval suggesting that a single gene is involved in controlling these four traits. Substitution mapping also indicated that two QTLs for grain weight and culm length, tgw2 and cl2, were tightly linked.     

Identification of QTLs for tolerance to hypoxia during germination in rice

Direct seeding of rice as a method of crop establishment is increasingly being adopted by farmers as a means of saving labor and reducing costs. However, the method often results in a poor environment for germination as excessive water levels after seeding can cause poor seedling establishment and a concomitant reduction in yield potential, especially in submergence-prone areas. In this study, we discovered QTLs associated with tolerance of anaerobic germination (AG) in new genetic accessions using genotypic data derived from the Illumina 6K SNP chip. The mapping population developed for QTL analysis comprised 285 F_2:3 plants derived from a cross between Tai Nguyen and Anda. In order to evaluate AG tolerance within the mapping population, phenotyping was carried out under anaerobic conditions for 21 days. Three QTLs associated with AG tolerance were identified in the population, qAG1a and qAG1b on chromosome 1 and qAG8 on chromosome 8 using composite interval mapping (CIM). The percentage of variance explained by these QTLs ranged from 5.49 to 14.14%. The lines with three QTLs (qAG1b?+?qAG1a?+?qAG8) demonstrated an approximate 50% survival rate under anaerobic conditions, while lines with two QTLs including qAG1b demonstrated survival rates of 36 and 32% after the treatment, respectively. The QTLs detected in this study may be used to improve AG tolerance during germination and may be combined with other QTLs for anaerobic germination to enhance adaptation to direct seeding and to broaden the understanding of the genetic control of tolerance of germination under anaerobic conditions.     

玉米抗纹枯病QTL定位

以玉米自交系R15（抗）×掖478（感）的229个F₂单株为作图群体,构建了包含146个SSR标记位点的遗传连锁图谱,全长1 666 cM,平均图距11.4 cM。通过麦粒嵌入法对F2:4群体进行人工接种纹枯病菌,并以相对病斑高为病级划分标准鉴定了玉米纹枯病的抗性。用复合区间作图法分析抗病QTL及遗传效应,共检测到9个抗性QTL,分布于第1、2、3、4、5、6和10条染色体上,单个QTL可解释表型方差的3.72%~7.19%,其中有2个QTL位于染色体6.01抗病基因簇附近。     

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.