【作者】 万群；

【导师】 张正圣；

【作者基本信息】 西南大学 ， 作物遗传育种， 2007， 硕士

【摘要】 棉花是世界上最重要的天然纤维作物。棉纤维是重要的纺织工业原料，绝大多数商品棉由四倍体栽培种陆地棉和海岛棉生产，其中陆地棉占90％以上。然而，作为纺织工业原料，陆地棉纤维品质，包括长度、强度和细度等，均比海岛棉纤维差。我国年产皮棉600万吨左右，纺织工业年需原棉大约在650万吨左右。棉花生产在我国国民经济中起着重要的作用。随着纺织技术的不断改进以及人民生活水平的提高，对棉花纤维品质的要求也越来越高。如何在提高陆地棉品种产量的同时，迅速改良纤维品质、提高抗病性是棉花育种者集中关注的焦点。虽然传统的遗传改良方法在棉花品种改良中起着重要作用，但其效率受到以下因素限制：1)棉花产量、纤维品质等性状属数量性状，由多个基因控制，易受环境影响；2)棉花产量与纤维品质（长度、强度和细度等）间存在负相关：此外，棉花产量测定、纤维品质检测需在收花后集中进行。因此急需一种能够提高育种效率的遗传改良方法。现代DNA标记技术的发展，为育种者提供了一种快速、准确的选择方法。利用高密度的分子遗传图谱，定位控制数量性状的基因／QTL，并通过与数量性状基因紧密连锁的分子标记对控制数量性状的基因进行选择（marker assisted selection，MAS）。目前，已构建了密度比较高的异源四倍体棉花种间遗传图谱，利用这些种间遗传图谱，对棉花的进化、染色体的同源关系以及产量、纤维品质等数量性状的基因定位进行了研究，但这些种间图谱难以应用于陆地棉的遗传改良。因此，人们开始用陆地棉种内杂交群体构建连锁图，并定位产量、纤维品质等数量性状的基因。由于所构建的陆地棉种内遗传连锁图的基因组覆盖率低，定位的产量、纤维品质等性状QTL的数量偏少、准确性不高。因此，需要构建密度更高的遗传图谱，并对陆地棉产量、纤维品质等数量性状的基因进行准确定位。本研究利用SSR和形态标记对（渝棉1号×T586）F_2：7群体进行了遗传连锁图谱的构建，并利用（渝棉1号×T586）F_2：7重组近交系进行了衣分QTL的定位。其主要研究结果如下：1亲本及F_2：7群体的衣分表现2004-2006年重庆-重庆-海南-重庆，四个环境进行衣分鉴定，两亲本的衣分差异较大，渝棉1号44.00-45.89％，平均43.22％，T586 3.60-11.87％，平均8.08％，渝棉1号的衣分是T586的5.4倍。2004-2006年重庆-重庆-海南-重庆，四个环境下F_2：7群体的衣分大部分介于双亲之间，表现超双亲分离。四个环境下衣分均呈连续分布，表现主基因和微效多基因控制遗传特点。2004-2006年重庆-重庆-海南-重庆，四个环境衣分的基因型方差与环境方差均达极显著差异。表明衣分性状除受基因型影响外，同时还受环境的影响。2引物多态性分析利用4591对棉花SSR引物，对渝棉1号和T586进行多态性筛选，其中349对引物在两亲本间表现多态性，多态性引物占总引物数的7.0％。3重组近交系群体标记基因型检测349对SSR引物对重组近交系群体进行标记基因型检测，获得357个标记位点，其中8对SSR引物检测到两个标记位点。共显性标记位点336个，占91.6％；显性标记位点31个，占8.4％。365个标记（357个SSR、8个形态标记）中有112个偏离1：1的孟德尔分离比例，占30.7％。多数偏分离位点表现较小的偏离孟德尔分离比例（χ2＜10），只有31个标记表现出严重的偏离孟德尔分离比例（χ2＞10），占标记位点的8.5％。4陆地棉遗传连锁图谱的构建对365个标记位点进行连锁分析，构建了包含56个连锁群，346个标记位点的遗传连锁图谱，其中43个连锁群定位到24条染色体，13个连锁群暂未定位到染色体。标记间的平均距离为5.8cM，图谱覆盖2014cM，约占棉花基因组45.3％。5衣分QTL定位以四个环境的衣分的鉴定结果，利用MapQTL5.0软件的区间作图法，LOD=2.0，共检测到5个衣分QTLs位点，分别位于Ch6、Ch7、Ch12、Ch14、Ch21五个不同的染色体上。5个QTL解释衣分变异4.8-63.8％，其中3个QTLs在四个环境均能检测到。渝棉1号或T586的等位基因增加衣分2.9-7.61。更多还原

【Abstract】 Cotton is the leading natural fiber crop and fiber is the main resource of the textile manufacture. The world cotton production was supplied by two tetraploid species, G. hirsutum L. and G. barbadense L., and G. hirsutum L. account for 90% of the total production. However, as the basic raw materials of textile industry, upland cottons generally have lower quality fibers than sea-island cotton, i.e., short or coarse fibers of relatively low strength. Cotton has been playing an important role in the economy of China, one of the largest cotton producing and textile manufacturing countries in the world, with lint yield of 600 million kilograms per year, and the textile manufacturing needs raw cotton 650 million kilograms per year. With the advances in spinning technology and the needs of the people, the better fiber quality will be required. These requirements of fiber quality have attracted a lot of efforts of governments and scientists to improve cotton fiber quality, especially that of upland cotton.Conventional genetic strategies have been employed to enhance the fiber properties of upland cotton for over half a century. However, lint yield, fiber quality and disease resistance are quantitatively inherited, and usually affected by environments; （2） unfavorable correlations exist between lint yield and fiber quality traits, e.g., fiber length, fiber strength and fiber fineness; additionally, the yield and fiber quality must be measured after harvesting. These factors greatly limited the efficiency of conventional breeding efforts in cotton, and it is imperative to develop effective breeding approaches. Recent advances in DNA markers offer plant breeders a rapid and precise alternative approach to conventional selection schemes to improve quantitative traits. Using detailed molecular linkage maps, quantitative trait loci （QTL） affecting economically important traits could be mapped, genetically evaluated and selected through linked markers. At present, the maps developed from interspecific population have been employed to document chromosomal relationships and evolutions in allotetraploid cotton and to locate genes/QTL affecting yield and fiber quality. However, these interspecific maps currently have little use in conventional upland cotton improvement. The linkage maps developed from upland cotton covered only a relatively small part of cotton genome, so the QTLs identified for agronomic and fiber quality traits cannot satisfy the marker assisted selection. Therefor, the comprehensive linkage map covering a wide range of the genome is needed to map QTL precisely and completely. The present study constructed a genetic linkage map with SSR and morphological markers using 270 F_2:7 recombinant inbred lines （RILs） developed from a cross between upland cotton cultivar Yumianl and T586, and the genetic linkage map was used to identify and map the QTL affecting lint percentage. The mainly results were as following:Lint percentage performances of mapping parents and F_2:7 RILsThe lint percentage was tested on the RIL population across four environments （Chongqing-Chongqing-Hainan-Chongqing, 2004-2006）. The two mapping parents were markedly different in lint percentage. The lint percentage of high quality cultivar Yumian 1 ranged from 44.00 to 45.89%, with a mean of 43.22%. The lint percentage of multiple dominant gene cultivar T586 ranged from 3.60 to 11.87%, with a mean of 8.08%. The lint percentage of Yumian 1 was 5.4 times more than that of T586.The lint percentage of RILs population mostly ranged between two parents, but transgressive segregation was observed falling beyond both Yumianl and T586, across four environments. Lint percentage segregated continuously in four environments, and the result suggested that the lint percentage was controlled by major and minor multiple genes.The significant variances of genotype and environment tested in four environments indicated lint percentage was affected by both the genotype and environment.Primer pair polymorphism between mapping parentsA total of 349 polymorphic primer pairs were found among 4591 cotton SSR primer pairs between the two mapping parents, and the polymorphic primer pairs accounted for 7.0% of the total primer pairs.Genotyping recombinant inbred lines349 SSR primer pairs revealed a total of 357 polymorphismic loci in recombinant inbred lines, and 8 SSR primer pairs revealed 2 polymorphismic loci per primer pair. Out of these SSR loci, 336 loci segregated as dominant markers （91.6% of the total SSR loci） and 31 as co-dominant markers （8.4% of the total SSR loci）.Chi-square examination demonstrated that 112 out of 365 markers （30.7%） including 357 SSR and 8 morphological markers exhibited segregation deviation from the expected 1:1 ratio. The majority of those loci showed a mild deviation from Mendelian segregation （X²<10）, and only 31 locus （ 8.5% ） had extremely severe segregation distortion （x²>10）.Linkage mapA total of 365 loci, including 357 SSR and 8 morphological markers, were employed to perform linkage analysis, and 346 loci were distributed into 56 linkage groups. Out of these linkage groups, 43 linkage groups were assigned on 24 chomosomes, while 13 linkage groups were not assigned on any chromosome. The linkage map covered 2014 cM with the average distance about 5.8 cM between two markers, accouting for approximately 45.3% of the total recombination length of the cotton genome.QTL analysisBased on interval mapping, 5 QTLs affecting lint percentage were identified, and these QTLs distributed on 5 chromosomes （Chromosomes 6, 7, 12, 14 and 21）, explaining 4.8-63.8% of the lint percentage variance. 3 out of 5 QTLs were identified in four environments. The alleles originating from Yumian 1 or T586 increased lint percentage by 2.9 to 7.61 %.更多还原