Genetic Analysis of Cotton Fiber Traits by Molecular Markers

1.Development of EST-SSRs derived from G.barbadense:One hundred and nineteen EST-SSRs were developed based on 98 unique ESTs from a cDNA library constructed in our laboratory using developing fibers from G.barbadense cv.3-79.Among the SSRs,trinucleotide AAG appeared

Analysis and identification of SCAR molecular markers associated with birch fiber length trait

The fiber length trait （FLT） of 538 individuals from nature birch population in Maorshan region, Heilongjang, China were measured, of which 100 individuals were selected as representative variety of correlated fragments screening with random amplified polymorphism DNA （RAPD） technique. In total of 20 RAPD primers were tested through multiple regression analysis between amplified strip and the character behaviors, and a correlative segment BFLR-16 was obtained. The correlation coefficient between BFLI-16 and FLT was 0.6144, with the significant level of 1%. BFLI-16 was then cloned, sequenced and transformed into SCAR marker. The percentage of identifying long fiber birches by this SCAR was more than 92. The result indicates that the SCAR markers has high specificity for the long fiber individuals and is highly linked with the gene controlling the character of fiber length, and its existence is significantly correlative with the increase in the fiber length.

Genetic variability for yield and fiber related traits in genetically modified cotton

Background:Cotton(Gossypium hirsutum L.)is grown for fiber and oil purposes in tropical and sub-tropical areas of the world.Pakistan is the 4th largest producer of cotton.It has a significant contribution in the GDP of Pakistan.Therefore,the present study was performed to assess the genetic variations and genetic diversity of yield and fiber quality traits in cotton and to analyze the associations present among them.Results:Analysis of variance exhibited significant variation for all studied traits except total number of nodes and the height to node ratio.The phenotypic coefficient of variation was higher than the genotypic coefficient of variation for all studied traits.Plant height,monopodial branches,total number of bolls,lint index,seed index,and seed cotton yield displayed high heritabilities in a broad sense with maximum genetic advanee.Correlation analysis revealed that seed cotton yield had a significant positive association with plant height,the nu mber of monopodial branches,the nu mber of sympodia I branches,ginning outturn(GOT),the number of bolls,seed per boll,seed index,uniformity index,the number of sympodial branches,reflectance,and seed index at the genotypic level while a significant positive relationship was observed with plant height,the number of sympodial branches,boll number,and GOT.Plant height,monopodial branches,GOT,boll weight,seeds per boll,and short fiber index exerted direct positive effects on seed cotton yield.The first 6 principal component analysis(PCs)out of the total fourteen PCs displayed eigenvalues(>1)and had maximum share to total variability(82.79%).The attributes that had maximum share to total divergence in eluded plant height,uniformity index,the nu mber of sympodial branches,seed per boll,GOT,seed cotton yield,and short fiber index.Conclusion:The genotype AA-802,IUB-13,FH-159,FH-458,and CIM-595 were genetically diverse for most of the yield and fiber quality traits and could be utilized for the selection of better performing genotypes for further improvement.

QTL and genetic analysis controlling fiber quality traits using paternal backcross population in upland cotton

Background:Genetic improvement in fiber quality is one of the main challenges for cotton breeders.Quantitative trait loci(QTL)mapping provides a powerful approach to dissect the molecular mechanism in fiber quality traits.In present study,F14 recombinant inbred line(RIL)population was backcrossed to paternal parent for a paternal backcross(BC/P)population,deriving from one upland cotton hybrid.Three repetitive BC/P field trials and one maternal backcross(BC/M)field trial were performed including both two BC populations and the original RIL population.Results:In total,24 novel QTLs are detected for fiber quality traits and among which 13 QTLs validated previous results.Thirty-five QTLs in BC/P populations explain 5.01%–22.09%of phenotype variation(PV).Among the 35 QTLs,23 QTLs are detected in BC/P population alone.Present study provides novel alleles of male parent for fiber quality traits with positive genetic effects.Particularly,qFS-Chr3–1 explains 22.09%of PV in BC/P population,which increaseds 0.48 cN·tex−1 for fiber strength.A total of 7,2,8,2 and 6 QTLs explain over 10.00%of PV for fiber length,fiber uniformity,fiber strength,fiber elongation and fiber micronaire,respectively.In RIL population,six common QTLs are detected in more than one environment:qFL-Chr1–2,qFS-Chr5–1,qFS-Chr9–1,qFS-Chr21–1,qFM-Chr9–1 and qFM-Chr9–2.Two common QTLs of qFE-Chr2–2(TMB2386-SWU12343)and qFM-Chr9–1(NAU2873-CGR6771)explain 22.42%and 21.91%of PV.The region between NAU4034 and TMB1296 harbor 30 genes(379 kb)in A05 and 42 genes(49 kb)in D05 for fiber length along the QTL qFL-Chr5–1 in BC/P population,respectively.In addition,a total of 142 and 46 epistatic QTLs and QTL×environments(E-QTLs and QQEs)are identified in recombinant inbred lines in paternal backcross(RIL-P)and paternal backcross(BC/P)populations,respectively.Conclusions:The present studies provide informative basis for improving cotton fiber quality in different populations.

QTL Mapping for Fiber Quality Traits Based on a Dense Genetic Linkage Map with SSR,TRAP,SRAP and AFLP Markers in Cultivated Tetraploid Cotton

Cotton is one of the most important economic crops in the world,and it provides natural fiber for the textile industry.With the advancement of the textile technology and increased consumption demands on cotton fiber,both cotton yield and quality should be enhanced.However,cotton yield

Identification of candidate genes controlling fiber quality traits in upland cotton through integration of meta-QTL,significant SNP and transcriptomic data

Background:Meta-analysis of quantitative trait locus(QTL)is a computational technique to identify consensus QTL and refine QTL positions on the consensus map from multiple mapping studies.The combination of meta-QTL intervals,significant SNPs and transcriptome analysis has been widely used to identify candidate genes in various plants.Results:In our study,884 QTLs associated with cotton fiber quality traits from 12 studies were used for meta-QTL analysis based on reference genome TM-1,as a result,74 meta-QTLs were identified,including 19 meta-QTLs for fiber length;18 meta-QTLs for fiber strength;11 meta-QTLs for fiber uniformity;11 meta-QTLs for fiber elongation;and 15 meta-QTLs for micronaire.Combined with 8589 significant single nucleotide polymorphisms associated with fiber quality traits collected from 15 studies,297 candidate genes were identified in the meta-QTL intervals,20 of which showed high expression levels specifically in the developing fibers.According to the function annotations,some of the 20 key candidate genes are associated with the fiber development.Conclusions:This study provides not only stable QTLs used for marker-assisted selection,but also candidate genes to uncover the molecular mechanisms for cotton fiber development.

Molecular Markers in Improvement of Fiber Quality Traits in Cotton

Cotton is the worlds leading natural fiber crop,and it is the cornerstone of textile industries worldwide.The cotton industry is confronted with problems in cost of production and

陆地棉抗虫与抗草甘膦基因的分子聚合及经济性状相关分析

培育抗棉铃虫兼抗草甘膦的棉花,可以同步提高品种的抗虫与抗除草剂能力,降低植棉的除虫、除草用工成本,提升植棉综合经济效益。本研究利用自育的高产优质陆地棉品系、国产转Bt基因抗虫棉品系以及转GR79+GAT基因的抗草甘膦陆地棉品系为杂交亲本,配置复交组合。在繁殖的复交分离群体后代,通过在苗床喷洒0.2%草甘膦,去除不抗草甘膦棉苗;并在大田不防治棉铃虫的条件下,筛选抗虫棉株。而后在实验室利用特异引物对抗虫基因与抗草甘膦基因进行分子跟踪检测,将同时具有Bt基因与GR79+GAT基因的单株繁殖成株系,经大田筛选获得9个抗虫兼抗草甘膦的优良品系。然后对育成品系进行产量比较试验,结果显示,其中品系BG-6不但实现了抗虫与抗草甘膦基因的聚合,而且该品系的皮棉产量水平较高、纤维品质表现良好:纤维长度达30.9 cm、比强度30.1 cN tex^(-1)、马克隆值4.9。对产量性状与纤维品质性状相关分析显示,只有衣分与棉纤维整齐度呈极显著负相关(r=-0.838**),其他产量性状与纤维品质性状均不存在显著相关性。文章最后得出结论:在复合杂交组合的分离后代,通过在苗床喷洒草甘膦筛选抗性棉苗,再结合大田不治虫筛选抗虫单株;而后在室内对2种抗性基因进行PCR分子跟踪检测,再在大田对产量性状与品质性状进行系统选育,可实现抗虫与抗草甘膦基因以及高产与优质性状的多元聚合。

5个工业大麻品种(系)产量品质性状分析

试验对‘Гресия’、‘Глесия’、‘B10-2020’、‘BGL-2019’和‘BLG-2019’ 5个工业大麻品种(系)的6个产量性状、4个品质性状以及7个农艺性状进行相关性和主成分分析,结果表明,通过产量、农艺性状相关性分析得出茎粗、工艺长度与鲜皮重、干皮重、鲜茎重等产量性状之间普遍呈显著正相关;同时,通过主成分分析从14个性状指标中提取出3个主成分,累积贡献率为90.20%,根据综合评分,得出不同品种(系)综合性状排名为‘B10-2020’>‘Гресия’>‘Глесия’>‘BLG-2019’>‘BGL-2019’,相关性分析显示综合得分与大部分农艺性状显著正相关,与品质性状显著负相关,表明综合得分可以较好地反映5个试验品种的综合表现情况,为培育、开发高产量及高品质工业大麻纤维提供参考。

宝天曼8种阔叶树木材密度的解剖学决定因素及其与叶性状的协同与权衡

【目的】探究影响木材密度的解剖学机制,揭示茎叶解剖和生理性状的协同与权衡关系,有助于阐明不同树种适应环境的生理生态机制。【方法】选择宝天曼天然林中常见的8种落叶阔叶树,测定木材密度、木质部导管及纤维等解剖性状、叶片压力-容积曲线参数等21个茎叶性状,探究决定木材密度的解剖学性状,分析茎叶性状的协同和权衡关系。【结果】1) 8个树种的木材密度与组成木质部的导管、薄壁组织和纤维组织这3大组织的比例都不相关,更多受到纤维细胞性状的影响。2)对木材密度影响最大的木质部性状是纤维细胞腔占横截面的比例,其次是纤维细胞壁占纤维细胞的比例、纤维细胞壁厚与腔直径比、纤维细胞壁厚度等性状。3)木材密度与叶片单叶面积、失膨压时相对含水量和弹性模量呈负相关。4)失膨压时相对含水量与导管水力直径、最大导管直径、平均导管直径、纤维细胞腔面积、纤维细胞腔直径呈正相关;与导管密度、纤维细胞壁厚与腔直径比、纤维细胞壁占横截面比例呈负相关。【结论】木材密度主要由纤维细胞性状决定,而非导管和薄壁组织性状;高的叶片忍耐失水能力耦合于致密的茎纤维细胞和木材密度。

不同种植密度对中棉113农艺性状及产量的影响

【目的】研究不同种植密度对棉花品种中棉113农艺性状、产量及纤维品质等影响,为确定机采模式下中棉113适宜的种植密度提供参考。【方法】以中棉113为供试品种,设置6种密度处理,分别为9×10^(4)株/hm^(2)(D_(1))、12×10^(4)株/hm^(2)(D_(2))、15×10^(4)株/hm^(2)(D_(3))、18×10^(4)株/hm^(2)(D_(4))、21×10^(4)株/hm^(2)(D_(5))和24×10^(4)株/hm^(2)(D_(6)),分析机采模式下不同种植密度对中棉113生长发育、棉铃空间分布、干物质积累及产量的影响。【结果】中棉113株高、茎粗随着种植密度的增大而降低;叶面积指数均在苗后88 d(8月1日左右)达到峰值,其中D_(5)处理最高,为4.1;随着种植密度的增加,棉铃脱落的果枝高度逐渐由第2果节和3果节向第1果节靠拢,同时棉株上部和下部的两个脱落高频区向中部果枝靠拢。棉铃着生趋向棉株内侧靠拢,吐絮铃主要着生在棉株下部。棉花营养器官干物质积累量随着密度的增加呈先增加后减小的趋势,而生殖器官干物质积累量则随着密度的增加而增加。籽棉产量上D_(5)处理最高,为5217.83 kg/hm^(2),与D_(4)处理差异不显著,较D_(1)、D_(2)、D_(3)、D_(6)处理均存在显著差异。【结论】合理密植有利于促进棉花生长发育,机采棉在1膜6行(66 cm+10 cm)机采模式、种植密度21×10^(4)株/hm^(2)(D_(5))时,有利于中棉113获取较高的产量。

饲粮粗纤维水平对猪生长性能、胴体性状及肉品质的影响

【目的】探讨饲粮粗纤维(CF)水平对育肥期马身猪和杜洛克猪×长白猪×大白猪(杜长大猪)生长性能、胴体性状及肉品质的影响,为猪精准营养需要量构建和优质猪肉的生产提供理论依据。【方法】选取体重为(49.67±5.85) kg的健康马身猪和杜长大猪各80头,品种内随机分为4组,每组5个重复,每个重复4头猪,各组猪分别饲喂粗纤维水平为2%、5%、8%和11%的饲粮,分别记为2%CF、5%CF、8%CF、11%CF组。预试期7 d,正试期30 d。试验结束后,每个处理挑选体重接近平均值的3头猪屠宰,测定胴体性状和肉品质指标。【结果】饲粮粗纤维水平显著影响猪的生长性能,其中11%CF组马身猪平均日增重显著低于其他3组(P<0.05),11%CF组杜长大猪料重比显著高于其他3组(P<0.05)。饲粮粗纤维水平对猪的背膘厚、眼肌面积和后腿比例等胴体性状有显著影响,其中2%CF组马身猪背膘厚显著高于其他3组(P<0.05),11%CF组杜长大猪背膘厚显著低于其他3组(P<0.05);随着粗纤维水平的提高,眼肌面积呈逐渐增大趋势,在马身猪和杜长大猪中均表现为11%CF组的眼肌面积极显著高于其他3组(P<0.01),8%CF组显著高于2%CF和5%CF组(P<0.05);5%CF和8%CF组马身猪后腿比例显著高于其他2组(P<0.05)。饲粮粗纤维水平对猪肉品质有显著影响,其中2%和5%CF组马身猪肌内脂肪含量极显著高于其他2组(P<0.01);5%CF组马身猪胱氨酸含量显著高于其他3组(P<0.05),2%CF组蛋氨酸含量显著低于其他3组(P<0.05);8%CF组马身猪棕榈酸、硬脂酸、油酸和亚油酸含量均为最高,而杜长大猪的变化趋势则相反。【结论】马身猪在饲喂8%粗纤维水平饲粮时,饲料转化率升高,背膘厚降低,眼肌面积增大,肉色得到改善;杜长大猪在饲喂5%粗纤维水平饲粮时,日增重增加,饲料转化率提高,眼肌面积增大,胴体性状和肌肉嫩度较好。

微生物菌剂对棉花生长及土壤理化性质的影响

【目的】研究施用“菌临天下”微生物菌剂对棉花生长发育、产量品质性状及土壤理化性质的影响。【方法】大田示范方法,菌剂示范133.33 hm^(2)(2000亩)、对照133.33 hm^(2)(2000亩),均为149团7连53.33 hm^(2)(800亩)、134团11连40 hm^(2)(600亩)、141团13连40 hm^(2)(600亩)。苗期、蕾期、花铃期对农艺性状调查,絮期对产量及品质性状测定。【结果】棉花吐絮比对照可以提前2 d;单株铃数增加0.11~0.3个、收获铃数增加12090~18708个/667m^(2)、单铃重增加0.03~0.3 g;测产籽棉产量微生物菌剂处理较对照增产76.0~100.46 kg/667m^(2),机采产量增产籽棉47.66~66 kg/667m^(2);衣分提高0.57~1.14个百分点、断裂比强度0.4~0.8个百分点、马克隆值降低0.2。同时使用微生物菌剂可以降低、改善土壤结构,活化土壤磷素、提高土壤有效磷含量。【结论】施用“菌临天下”微生物菌剂可以促进棉花生长发育,增加产量,提高品质,同时使用微生物菌剂可以降低、改善土壤结构,活化土壤磷素、提高土壤有效磷含量。

低升糖型马铃薯品种的筛选

【目的】筛选低升糖型马铃薯品种,是控制血糖、减少肥胖、保护口腔健康的需要,也是满足多元消费需求和增加马铃薯产出效率的重要途径,为实现低升糖指数马铃薯品种选育和生物育种改良提供依据。【方法】以8个国内外主栽马铃薯品种为试验材料,考证块茎农艺性状、分析蒸制加工前后块茎总淀粉、直链淀粉、快速消化淀粉、慢速消化淀粉、抗性淀粉、可溶性糖、不可溶性膳食纤维、可溶性膳食纤维、可溶性蛋白质的含量和保留程度,以及加工后块茎风味品质和体内外升糖指数。【结果】8个品种产量为21.50—49.90 t·hm^(-2),商品率为60.04%—90.21%,长宽比为1.21—2.90;品种风味感官评价得分为64—73;物性分析仪测定结果,硬度为9.78—19.97 N,粘附性为0.44—1.66 mJ,内聚性为0.052—0.070,弹性为0.51—1.02 mm,咀嚼性为0.28—1.38 mJ。蒸制前后,8个品种总淀粉含量范围分别为67.07%—76.72%和57.69%—67.40%DW(dry weight,DW);直链淀粉含量范围为5.36%—19.23%DW和5.43%—6.83%DW;快速消化淀粉含量范围为1.18%—8.23%DW和14.31%—28.56%DW;慢速消化淀粉含量范围为3.33%—7.69%DW和12.81%—27.65%DW;抗性淀粉含量范围为53.71%—70.36%DW和11.80%—25.80%DW;可溶性糖含量范围为25.98—56.86 mg·g^(-1)DW和11.38—50.24 mg·g^(-1)DW;总膳食纤维含量范围为29.62%—36.17%DW和43.67%—52.55%DW;不可溶性膳食纤维含量范围为17.69%—23.70%DW和30.31%—44.12%DW;可溶性膳食纤维含量范围为11.07%—18.48%DW和7.37%—14.09%DW;可溶性蛋白质含量范围为42.26—64.14 mg·g^(-1)DW和0.71—4.82 mg·g^(-1)DW。加工后8个品种总淀粉含量变化范围为-15.49%—-5.97%,直链淀粉含量变化范围为-12.39%—0.56%,快速消化淀粉、慢速消化淀粉和抗性淀粉的变化范围分别为10.44%—25.86%、5.12%—23.09%和-56.8%—-29.88%,可溶性糖含量变化范围为-27.07%—15.70%,不可溶性膳食纤维和可溶性膳食纤维变化范围分别为11.41%—25.19%和-4.73%—0.77%,可溶性蛋白质变化范围为-60.86%—-39.67%;相关性分析发现,升糖指数与块茎总淀粉、快速消化淀粉和慢速消化淀粉含量呈显著正相关,与抗性淀粉和不可溶性膳食纤维含量则呈显著负相关;8个品种体内升糖指数为58.08—100.64,体外升糖指数为57.80—92.47。【结论】体外升糖指数可作体内升糖指数的替代评价方式,块茎总淀粉、快速消化淀粉、慢速消化淀粉、抗性淀粉和不可溶膳食纤维含量是选育和筛选低升糖型马铃薯品种的关键指标,Lucinda是蒸煮加工后风味品质较好的低升糖指数型马铃薯品种。

动物骨骼肌结缔组织及其调控肉质性状的研究进展

结缔组织是一种广泛分布于动物机体的基本组织,主要由间质细胞及间质细胞分泌形成的胶原蛋白等细胞外基质(ECM)构成,发挥着连接、缓冲、支撑、修复和调控等多种生物学功能。在骨骼肌中,结缔组织不仅为肌纤维发育形成、损伤修复、收缩运动、物质代谢和脂肪沉积等提供了重要的空间环境,同时对畜禽宰后的肌肉嫩度等品质性状形成有着重要影响。本文综述了骨骼肌结缔组织的细胞分化起源、存在形式以及骨骼肌结缔组织ECM的合成表达调控与影响因素相关研究进展,探讨了骨骼肌结缔组织与畜禽肉质性状的关系,以期为畜禽肉质性状的遗传选择和营养调控研究提供科学依据。

六月龄滩羊不同部位羊毛性状的比较

通过测定6月龄滩羊的羊毛直径、断裂强力、卷曲数及羊毛长度等性状信息,探索6月龄滩羊不同部位(肩部、腹部、后腿、臀部)羊毛性状的差异及相关性。结果表明,6月龄滩羊各部位羊毛的伸直长度、自然长度、断裂强力、羊毛直径、卷曲数均无显著差异;各部位羊毛长度均匀度较好,羊毛的伸直长度与自然长度变化趋势基本趋于一致,说明二者有一定的相关性;两型毛、无髓毛直径的变异系数为6.21%~8.02%,表明羊毛直径较稳定;两型毛的断裂强力明显大于无髓毛,说明羊毛直径与断裂强力存在较强的相关性;腹部、后腿、肩部、臀部的无髓毛卷曲数均大于两型毛,说明羊毛直径小对卷曲有利;由6月龄滩羊腹部羊毛各性状的相关性分析可知,无髓毛性状间的相关系数大多较两型毛大,可能原因是两型毛较长,易受营养和外界因素影响。

Correlation Analysis on Single Nucleotide Polymorphism of CAPN1 Gene and Meat Quality and Carcass Traits in Chickens

The selection of meat quality has received considerable focus in chicken breeding. This study was aimed at investigating the effect of CAPN1 gene on meat quality traits in chicken populations. Primer pairs for 3 UTR in CAPN1 were designed from database of chicken genomic sequence. Polymorphisms were detected using PCR-SSCP and DNA sequencing. A mutation at position 9 950 nt （G/A, locus A） was found among individuals in each population. The allele and genotype frequencies significantly differed among eight lines with higher frequencies of allele A2 and genotype AIA2 （P〈0.01）. The least square analysis showed that there was significant difference （P 〈 0.05） in muscle fiber density and some carcass traits among genotypes and that the breast muscle fiber density （BFD） of birds ofAIA1 genotype was significantly higher （P〈0.05） than that of birds ofA2A2 genotype. It was concluded that the CAPN1 gene was the major gene affecting the muscle fiber traits of chicken or was linked with the major gene. These results were useful for studying the molecular mechanism that influences meat traits and were used as the base of molecular-assisted selection to meat quality traits. So, this site may be a potential marker affecting the muscle traits of chickens.

QTL mapping of agronomic and economic traits for four F_(2)populations of upland cotton

Background:Upland cotton(Gossypium hirsutum)accounts for more than 90%of the annual world cotton output because of its high yield potential.However,yield and fiber quality traits often show negative correlations.We constructed four F_(2)populations of upland cotton,using two normal lines(4133B and SGK9708)with high yield potential but moderate fiber quality and two introgression lines(Suyuan04–3 and J02–247)with superior fiber quality,and used them to investigate the genetic basis underlying complex traits such as yield and fiber quality in upland cotton.We also phenotyped eight agronomic and economic traits and mapped quantitative trait loci(QTLs).Results:Extensive phenotype variations and transgressive segregation were found across the segregation populations.We constructed four genetic maps of 585.97 centiMorgan(cM),752.45 cM,752.45 cM,and 1163.66 cM,one for each of the four F_(2)populations.Fifty QTLs were identified across the four populations(7 for plant height,27 for fiber quality and 16 for yield).The same QTLs were identified in different populations,including qBW4 and qBW2,which were linked to a common simple sequence repeat(SSR)marker,NAU1255.A QTL cluster containing eight QTLs for six different traits was characterized on linkage group 9 of the 4133B×Suyuan04–3 population.Conclusions:These findings will provide insights into the genetic basis of simultaneous improvement of yield and fiber quality in upland cotton breeding.

Genetic variations in plant architecture traits in cotton(Gossypium hirsutum) revealed by a genomewide association study

Plant architecture traits influence crop yield. An understanding of the genetic basis of cotton plant architecture traits is beneficial for identifying favorable alleles and functional genes and breeding elite cultivars. We collected 121 cotton accessions including 100 brownfiber and 21 white-fiber accessions, genotyped them by whole-genome resequencing, and phenotyped them in multiple environments. This genome-wide association study(GWAS)identified 11 quantitative trait loci(QTL) for two plant architecture traits: plant height and fruit spur branch number. Negative-effect alleles were enriched in the elite cultivars. Based on these QTL, gene annotation information, and published QTL, candidate genes and natural genetic variations in four QTL were identified. Ghir_D02 G017510 and Ghir_D02 G017600 were identified as candidate genes for qD02-FSBN-1, and a premature start codon gain variation was found in Ghir_D02 G017510. Ghir_A12 G026570, the candidate gene of qA12-FSBN-2, belongs to the pectin lyase-like superfamily, and a significantly associated SNP, A12_105366045(T/C), in this gene represents an amino acid change. The QTL, candidate genes, and associated natural variations in this study are expected to lay a foundation for studying functional genes and developing breeding programs for desirable architecture in brown-fiber cotton.

A targeted QTL analysis for fiber length using a genetic population between two introgressed backcrossed inbred lines in upland cotton(Gossypium hirsutum)

Cotton fiber is the most important natural raw material for the textile industry, and fiber length(FL) is one of the most important traits in cotton.Quantitative trait locus(QTL)mapping based on high-density genetic maps is an efficient approach to identify genetic regions for FL.In our study, two backcrossed inbred lines(BILs) were chosen as parents to construct a high-density genetic map in F2 which was used to fine map FL QTL in F2:3 population.The genetic map had a total size of 3462.8 cM, containing 9182 singlenucleotide polymorphisms(SNPs) based on genotyping-by-sequencing.Two FL related stable QTL were identified on two chromosomes(qFL-A08–1 on A08 and qFL-D03–1 on D03),and qFL-A08–1 was confirmed by a meta-analysis.Utilizing previously obtained RNA-seq data for the two BILs and qRT-PCR analysis, two candidate genes annotated as cytochrome b5(CB5, Gh_A08 G1729) and microtubule end-binding 1 C(EB1C, Gh_D03 G0232) that may regulate FL during the fiber elongation stage were identified.In addition, nine recombination hotspots in this population were found.The results of this study will provide an important foundation for further studies on the molecular and genetic regulation of fiber elongation.