【作者】 申国境；

【导师】 邢永忠；

【作者基本信息】 华中农业大学 ， 生物化学与分子生物学， 2014， 博士

【摘要】 水稻是我国目前第二大粮食作物,全世界有50%以上的人口吃饭问题需要它来满足。因此提高水稻产量是我国乃至全世界的粮食安全重要战略,而水稻高产是主要目标之一。杂种优势是指杂种F1代在性状表现上优于双亲。过去几十年来,人们利用杂种优势进行了多种作物的育种和遗传改良,在生产和实践中取得了巨大的成功。尽管人们针对杂种优势现象做了很多研究工作,但杂种优势形成的遗传机理仍有很多未知的地方。汕优63是一个非常优良的杂交稻,本研究以汕优63的两个原始亲本珍汕97和明恢63为亲本,通过连续回交策略,构建了一套以珍汕97为背景、明恢63为供体的染色体片段代换系,分析染色体片段代换系对产量及其相关性状的遗传效应。同时利用染色体代换系与轮回亲本珍汕97配置的杂交组合剖析了单片段代换系的杂种优势效应,通过杂种优势组装分析上位性对杂种优势的贡献。另外,我们构建了三套正反交材料,探索了生物钟调控途径在杂种优势形成中的作用。主要结果如下：1、通过珍汕97和明恢63连续回交,结合分子标记辅助选择,构建了一套202份染色体代换系。202份代换系背景回复率为95.2%,最高为99.0%,最低为91.8%。所有目标片段总长度为2367.5cM,相当于水稻基因组的1.5倍,而目标片段覆盖基因组的长度为1420.3cM,约为水稻基因组的93.2%；导入片段长度在1.2-30.7cM之间,平均长度为11.2cM,其中片段长度小于10cM代换系数目约占20%,介于10～20cM的代换系数目约占70%,而大于20cM的代换系数目约占10%。代换系基本覆盖了珍汕97为背景的全基因组。2、两年重复实验考察了染色体代换系群体抽穗期、株高、每穗颖花数、单株产量、单株有效分蘖数、穗长、千粒重和每穗实粒数,研究染色体代换系的遗传效应。结果显示,所有考察性状均有很大的变异范围,明恢63染色体片段的导入影响了珍汕97重要农艺性状的表型变异。3、在回交种和染色体代换系群体中,发现不同导入片段位点的遗传效应不同,分别表现为加性效应和显性效应,本研究中没有检测到超显性效应。通过互作分析结果发现,上位性互作对表型变异具有非常大的影响。说明导入片段位点的加性效应和显性效应以及位点与位点之间的互作对表型变异起到非常重要的作用。4、以202份染色体代换系为母本,珍汕97为父本,配置了CSSL/珍汕97杂交种,分别考察抽穗期、株高、单株产量等8项性状指标,研究导入明恢63染色体片段的杂种优势。针对所有考察性状,平均有17.8%的杂交组合与对照珍汕97呈现显著差异,所有杂种优势位点均表现出部分显性。2010年分别有4.5%、5.8%、5.9%和5.1%的杂交组合在单株产量、每穗颖花数、株高和每穗实粒数上与ZS97和染色体代换系之间具有显著差异。5、在染色体代换系中,我们共检测到12个抽穗期QTL,单个片段对抽穗期变异的贡献率从5.2%到83.5%。其中有5个QTL在F2和RIL群体中没有检测到。通过比较测序结果显示,抽穗期3个主效QTL QHD6, QHD7.2和QHD7.3分别是已经克隆的Hdl, Ghd7和Ghd7.1。其中QHD7.1和QHD2是新的QTL。另外,QHD2,QHD4和QHD8这3个QTL的加性效应大约为4.5天,非常有利于QTL的克隆。两位点互作分析结果显示,QHD7.2和QHD7.3通过遗传互作来调控水稻开花。6、本研究中,我们共检测到15个株高杂种优势位点。它们对杂种优势的贡献为显性效应,每个杂种优势位点的中亲优势(MPH)从-7.4%到14.4%。4位点互作分析显示,4位点主效QTL之间存在显著的上位性互作,它们的互作形式主要是加性效应与加性效应(AA),加性效应与显性效应(AD)。其中两个主效株高QTL qPH7.2和qPH7.3的加加互作效应为负值来增加水稻株高。7、202个染色体代换系中,我们检测到13个每穗颖花数杂种优势位点和9个单株产量杂种优势位点.其中9个产量杂种优势位点的CSSLs/珍汕97F1的单株产量处于回交亲本珍汕97和染色体代换系的产量之间,也就是说这9个产量杂种优势位点为显性效应杂种优势位点。我们将其中8个单株产量主效位点进行杂种优势组装,产生了2个4位点F1和一个8位点F1。其中8位点的产量杂种优势能够达到汕优63的75.4%。在4位点F2群体中,就每穗颖花数和单株产量而言,上位性互作效应对杂种优势的贡献非常显著,我们检测到加性效应与加性效应,加性效应与显性效应和显性效应与显性效应的互作形式,其中HYD7.1和HYD7.2两位点的加性效应与加性效应的遗传互作效应为负值而提高产量。8、我们构建三套正反交材料,分析了生物钟调控的基因网络与产量杂种优势形成的关系。通过表型考察,我们发现正反交之间的表型或杂种优势没有显著差异,也就是说母性遗传对杂种优势没有影响；籼稻亚种内和籼粳亚种间的杂种优势非常明显,生物钟基因及其调控的下游基因(叶绿素合成和淀粉合成基因)的相对表达量也具有非常显著的杂种优势。同时我们检测了叶绿素和淀粉含量,结果显示在正反交F1中含有较多的叶绿素和淀粉。相比较而言,粳稻亚种内的杂种优势不是很明显,生物钟调控网络的基因相对表达量杂种优势也比较低。更多还原

【Abstract】 Up to now, rice is the second largest food crop in china. Rice yield improvement guarantees the food security,which feeded the more than half world’s population. So the development of high-yield varieties is one of the most important objectives in rice breeding. Heterosis, or hybrid vigor, refers to the superior performance of the hybrids relative to the parents. Utilization of heterosis has contributed tremendously to the increased productivity in many crops for decades. Although there have been a range of studies on various aspects of heterosis, the key to understanding the biological mechanisms of heterotic performance in crop hybrids is the genetic basis, much of which is still uncharacterized. Shanyou63is an elite hybrid, in this study, we used original parent Zhenshan97and Minghui63of Shanyou63as the parents, a series of CSSLs were developed following the consecutive backcrossing strategy to study the genetic effects of Minghui63segments on yield and yield-related traits in the genetic background of Zhenshan97. In order to characterize the effects of Minghui63segments on heterosis, the population of CSSLs/Zhenshan97was used. In addition, we we generated three sets of reciprocal F1hybrids of indica and japonica subspecies to evaluate the relationship between yield heterosis and the circadian clock. The major results are as follows:1. A total of202CSSLs were constructed, each carrying one to three substitution segments. The average percent recovery of recurrent parent genome is95.2%. The total length of all substitution segments was2367.5cM, which was1.5times of the rice genome. The overlapped substitution segments covered1420.3cM (93.2%) of the entire rice genome. The estimated length of single introgression segments in CSSLs ranged from1.2to30.7cM with an average of11.2cM.2. Phenotypic evaluation of CSSLs was carried out in two environments. The traitscharacterized are heading date (HD), plant height (PH), panicles number per plant (PN), panicle length (PL), grains per panicle (GPP), spikelets per panicle (SPP), kilo-grain weight (KGW) and yield per plant (YD). Transgressive segregations observed in all these traits implied that the introgressed Minghui63segments had an effect on agronomic traits.3. The genetic effects of Minghui63segments composed of additive and dominant. Genetic effects differentiated among different introgression segments, epistasis interaction was significant contribution to phenotypic variation based on epistasis analysis. These results suggested that additive dominant and epistasis played an important role in trait performance.4. CSSLs/Zhenshan97was developed by selecting CSSLs as female and Zhenshan97as the male parents, to study the effects of Minghui63segments on heterosis. Eight traits were evaluated in two environments. Taken all these traits into consideration,17.8percent of hybrids significantly deviated from SY63, and all heterosis loci showed partial dominance. In2010, there were5.7,14.3and5.0percent of chromosome segment substitution lines for grain yield, Spikelet per panicle and grain per panicle, respectively.5. Twelve QTLs were identified for heading date. Single QTL individually explained5.2%to83.5%of heading date variation. Five QTLs were not detected in both F2and RIL populations from the same cross Zhenshan97/Minghui63. Parental comparative sequencing showed that the three major QTLs of QHD6, QHD7.2and QHD7.3are allelic with the cloned genes of Hdl, Ghd7and Ghd7.1, respectively. QHD7.1and QHD2are novel QTLs. The QTLs of QHD2, QHD4and QHD8with additive effects of about4.5d would be worthy to conduct QTL cloning. In addition, di-genic interaction between QHD7.2and QHD7.3significantly regulated heading date under long-day conditions. The diverse performance in agronomy and biology between the parents Zhenshan97and Minghui63indicated that the set of CSSLs would be idea materials for QTL mapping and cloning for other traits.6. In this study, Fifteen CSSLs had varied plant heights within lines. A total of15partial dominance QTLs for plant height were detected in these15CSSL-F2populations. All hybrids between the15CSSLs and the recurrent parent, Zhenshan97, were shorter than the corresponding CSSLs, but taller than Zhenshan97. These indicated that these15QTLs were also heterosis loci (HLs) contributed to heterosis acted in dominance. Each HL contributed from-7.4to14.4%of midparent heterosis. Additive by additive (AA) and additive by dominance (AD) interactions were detected in the Tetra-F2population segregating at the four major QTLs with the largest effects on plant height. Substantial negative AA effects were detected between two major QTLs qPH7.2and qPH7.3, which increased heterosis in the study.7. To understand the genetic basis of heterosis, we developed a set of202chromosome segment substitution lines (CSSLs) of an elite hybrid, Shanyou63.Thirteen and nine partial dominance QTLs for spikelets per panicle and yield were detected. Without exceptional, All hybrids between the9CSSLs and the recurrent parent, Zhenshan97, had less trait values than the corresponding CSSLs, but more than Zhenshan97. These indicated that these9QTLs acted in dominance and contributed to heterosis. Conversely, we generated two4-way F1s and one8-way F1with the genetic background of Zhenshan97. The heterosis of8-way F1reached up to75.4%that of Shanyou63for grain yield. Additive by additive (AA), additive by dominance (AD) and dominance by dominance (DD) interactions were detected in the both Tetra-F2populations each segregating at four major QTLs with the large effects on spikelets per panicle. Substantial negative AA effects were detected between two major QTLs HYD7.1and HYD7.2, which increased heterosis in the study.8. In this study, we generated three sets of reciprocal F1hybrids of indica and japonica subspecies to evaluate the relationship between yield heterosis and the circadian clock. There were no differences in trait performance or heterosis between the reciprocal hybrids, indicating no maternal effects on heterosis. The indica-indica and indica-japonica reciprocal F1hybrids exhibited pronounced heterosis for chlorophyll and starch content in leaves and for grain yield/biomass. In contrast the japonica-japonica F1hybrids showed low heterosis. In the hybrids that showed very strong better-parent heterosis (BPH) for grain yield, the investigated three circadian clock genes were expressed in an above-high-parent pattern during the vegetative period35days after sowing.更多还原