【作者】 梁文科；

【导师】 徐尚忠；

【作者基本信息】 华中农业大学 ， 作物遗传育种学， 2008， 博士

【摘要】 玉米是我国第二大作物,常年播种面积达到2700万公顷;玉米属于粮、经、饲和工业原料农作物,不但在国民经济中占有重要地位,而且也是遗传学研究的模式作物之一,跳跃基因、杂种优势机理等重大发现都是在玉米的研究中完成的。玉米种质扩增是种质创新的重要途径之一,外来种质育种价值评估和利用是玉米品种改良的应用基础性研究;现代遗传学和统计学的发展推动了遗传育种学研究的不断进步,也为探讨玉米产量形成的遗传原因、杂种优势与遗传距离的关系、预测杂交后代杂种优势的表现和评估育种基础材料的育种价值提供了新的思路和技术方法。对来自玉米起源中心的地方品种（Landraces）、群体（populations）和自交系（inbred lines）等种质进行深入的评价、改良和利用,对发掘这些外来种质中有利和稀有等位基因具有重要的指导意义。本研究选用9个来自热带和温带的玉米群体、两个广泛利用的杂交种及其4个亲本自交系为研究材料,设计了两套遗传交配试验:（1）用9个群体按双列杂交方法Ⅱ,组配了36个杂交组合,采用完全随机区组设计进行了2年2点的田间鉴定试验,用混合线性（AD）模型对产量构成因素的遗传方差分量、遗传力、基因的加、显效应及其与环境互作效应进行了分析,探讨玉米产量形成的遗传原因;进一步分析9个群体之间的杂种优势表现,并且把杂种优势分解为杂种优势主效应和杂种优势与环境的互作效应,探讨了遗传距离和杂种优势的关系,还对杂交后代保持5%以上杂种优势的世代数进行了预测,以了解杂种后代自交衰退的程度,为育种材料的取舍提供科学依据。（2）利用9个群体和4个自交系,按NCⅡ遗传交配设计,组配了36个杂交组合,采用完全随机区组设计进行了2年2点的田间鉴定试验,采用Dudley的基因转移理论和方法,评估这9个群体的育种价值,对一系列评估参数的值进行了估计,提出了分别用来改良两个优良单交种的最佳供体,并指出了改良方向和改良方式。本研究还利用两个对光周期变化敏感性不同的自交系黄早四和HZ32为亲本,构建了一个光周期反应敏感性的F2:3分离群体,采用完全随机区组设计在两具有不同光周期的环境下对其进行鉴定,研究玉米光周期反应的最佳鉴定指标,为外来种质的适应性改良提供基础。本研究得到一下主要结果:1、玉米产量形成的主要遗传原因是显性和显性与环境互作,分别占总变异的35.16%和29.73%,二者之和达到64.89%,而加性和加性与环境互作分别为0.18%和4.33%,二者之和仅为4.51%;远远小于显性和显性与环境互作。在玉米产量构成因素中,狭义遗传力大小排列顺序是穗行数＞行粒数＞穗长＞千粒重＞小区产量,分别为26.38、16.44、11.36、9.13、0.18;其中穗行数最大,小区产量最小。2、就狭义遗传力而言,玉米产量构成因素在穗长、穗行数和行粒数上达到了极显著水平,而其它性状未达到显著水平;其排列顺序为穗行数＞行粒数＞穗长,分别为26.83、16.44和11.36。说明在育种的早代依据穗行数进行选择更为有效。3、玉米杂种优势表现与双亲的遗传距离之间不存在显著的线性关系;而F1的基因型与群体平均优势和群体超亲优势达到极显著的正相关,分别为0.86和0.80。4、Suwan 1×BSSS C₉和Stay green C₄×BSSS C₉是两对含有热带玉米种质的强优势组合,可能成为我国温带地区玉米杂种优势的替代模式,可以对改良瑞德×四平头,改良瑞德×旅大红骨两个主导杂种优势模式进行扩展。在黄淮海夏玉米主产区可以用Suwan 1改良四平头杂种优势群;在东北,包括西南一部分春玉米主产区,可以利用Stay green C₄来改良旅大红骨杂种优势群。5、通过对群体之间杂种优势和保持=5%超亲优势的世代数分析,认为Suwan 1和Stay green C₄还可以相互重组改良;重组改良之后与BSSS C₉形成杂种优势模式,并且Stay green C₄。保持＞5%超亲优势的世代数越多近交衰退越慢,说明组合含有较多的有利显性等位基因位点,在育种过程中要得到积累较多有利等位基因的家系应采用大群体和多世代的选择策略。6、杂种优势与环境之间存在显著互作效应,互作的强弱依组合的不同而有所不同,在地点和年份之间没有多少规律可循;组合1×2、1×3和3×6在主要性状上的杂种优势与环境的互作效应不显著,具有较好的适应性;而组合4×5和1×6两个组合的互作效应达到显著水平,其适应性较差,只在特殊的环境下有利用价值。7、利用Dudley基因转移理论,为温带玉米种质导入外来种质、评估其有利等位基因数目的多少,筛选出改良掖478×丹340的最佳供体是群体1＞群体5＞群体8,改良方向大多是掖478,改良方式是先回交一次,再自交选系较为有利。筛选出改良美22×HZ111的最佳供体是群体7＞群体8＞群体4,改良方向是美22,改良方式大多是直接自交选系较为有利;体现了直接自交或有限次回交育种方法的有效性。8、热带种质在温带利用的主要障碍是光周期反应的敏感性,本研究对231个F2:3家系进行鉴定,分析了散粉期、叶片数、ASI和吐丝期、穗位下叶片数、总叶片数和穗位下叶数与总叶数之比等性状对光周期变化的表现;认为吐丝期比散粉期对光周期变化更为敏感;穗位下叶数与总叶数之比能作为玉米光周期敏感性最简单的指标。9、提出玉米育种的两向分群育种策略:培育专门化的父本群和母本群,分别对父本群和母本群的有限性状进行改良和选择。根据杂种优势模式的原理,优先聚积和保持每个群的特征性优点,逐渐克服缺点,使双亲具有尽可能多的有利等位基因,避免拥有共同的不利的等位基因,充分利用父本群和母本群有利等位基因,达到优良性状互补,在杂交种中展现增产潜力。更多还原

【Abstract】 Maize is the second large crop in China.The planting area reaches 27 million hectares.Maize is the main feed,industrial materials,food and economic crop in China.It not only takes the important position in national economy,but also is a model crop in genetic research,the discovery of jumping gene and molecular mechanism of heterosis was just found in maize.Maize germplasm enhancement is one of the important ways to new germplasm creation.Evaluation and usage of exotic germplasm is the applicable basic research on maize variety improvement.The development of modern genetics and statistics promote the researches on genetics and breeding constantly to progress,and also provides new methods and technologies for finding the genetic reasons of maize yield formation,Understanding the relationship between heterosis and genetic distance, predicting heterosis of crosses,and evaluating breeding potential of basic materials. Detailed evaluation,improvement and usage of landraces,populations and inbred lines from the original center of maize are significant for discovering favorable and rare allele in exotic germplasm.In this research,9 populations from tropics and temperate zone,two widely used hybrids and its 4 parents inbred lines were used as the research materials.Two mating designs were performed:（1） Using the 9 populations,the 36 crosses were formed based on the design of diallel cross,then field tests were performed using the method of completely random design in two locations in two years.For understanding the genetic reasons of yield formation,genetic variance components,heritability,additive and dominance effects and G×E interaction effects of yield component factors were analyzed using mixed linear models.For investigate the relationship between heterosis and genetic distance,the heterosis performance among 9 populations were further analyzed,the heterosis performances were divided into major effects and G×E interaction effects.In order to understand the inbreeding depression,generations of crossed offspring which could maintain＞5%heterosis were predicted,and this provided scientific evidence for choosing basic breeding materials.（2） Using 9 populations and 4 inbred lines,36 crosses were produced according to the design of NCⅡ,and field tests were also made using the completely random design in two locations in two years.The breeding potential of 9 populations were evaluated using Dudley’s gene transfer theory,Some genetic parameters were estimated,and obtain some useful information on choosing best donors for improving the two superior single crosses and pointing out the direction of improvement and forms of improvement.In order to find out the indices of photoperiod sensitivity,two parents,Huangzao4 and HZ32,with different sensitivity of photoperiod were used to construct a F_2:3 segregation population about photoperiod sensitive,and F_2:3 segregation population was evaluated in two different photoperiod conditions using the completely random design, and this offers a basis for adaptability improvement of exotic germplasm. Here are the main conclusions of our research:1.The major genetic reason for maize yield formation is dominant effects and effects of dominance×environment interaction,and scored 35.16%,29.73%,respectively,the total is 64.89%.While the additive effect and effects of additive×environment interaction only scored 0.18%,4.33%,respectively,the total is 4.51%.2.Based on the narrow heritability,yield component factors could be sorted like this RPE＞KPR＞EL＞1000KW＞PKW,and scored 26.38,16.44,11.36,9.13 and 0.18 respectively;Among them,RPE possessed the first rank of narrow heritability,and PKW possessed the last rank of smallest narrow heritability.So,in early selected generations of a breeding program,selection based on RPE must be more effective than PKW.3.There was not significant linear correlation between heterosis and genetic distance.It must be a complex non- linear correlation.There is significant linear correlation between Pre（F₁）（G） and HPM（F₁）（G）,HPB（F₁）（G）,the value is 0.86,0.80, respectively.4.Suwan 1×BSSS C₉ and Stay green C₄×BSSS C₉ are two heterotic patterns containing tropical germplasm.They probably can be used as substitute pattern in temperate zone of our country for maize breeding utilization,and further more,They could be extending the two major heterotic patterns,Reid×Sipingtou and Reid×Lvda Honggu.In Huanghuaihai summer maize growing region,Suwan 1 can be used to improve Singpingtou heterotic groups,and in northern,northeast and a part of southwest of China’s spring maize growing region,Stay green C₄ can be used to improve Lvda Honggu heterotic groups.5.By analyzed the generations of crossed offspring which could maintain＞5% heterosis and heterosis performance,we found that Suwanl and Stay green C₄ could be recombined and improved mutually,after several cycle selections,it must be to form an elite heterotic group,and to unite with Sipingtou heterotic group,and then to form a extended heterotic pattern;The more generations（＞5%） are maintenance,the less inbred depressions are made.the meaning is the cross must contain more favored gene;In order to get elite lines that contain more favored genes,the breeding must be based on the large populations and long selection period.6.There are significant interaction effect between heterosis and environment.Heterosis performances could be divided into major heterotic effects and effects of G×E interaction.The degree of interaction effects depend on difference crosses;There are no any disciplinarian among locations and years;1×2、1×3 and 3×6 crosses have good adaptions,but 4×5 and 1×6 crosses.7.Based on Dudley’s gene transfer theory,for improving elite single hybrids Ye478×Dan340 and HZ111×Mei22,The rank of best donors populations is:for Ye478×Dan340,population 1＞population 5＞population 8＞population,the improvement direction is Ye478 and the improvement form is backcross first;for HZ111×Mei22, population7＞population 8＞population 4,.the improvement direction is Mei22 and the improvement form selfcross directly.8.The main problem for using tropical germplasm in temperate zone is sensitive to photoperiod.In this research,231 families of F_2:3 were used as material,then the traits related to photoperiod reaction,such as PSD,SD,ASI,LN1,LN2 and LN1/LN2,were analyzed in two different conditions.It demonstrated that SD was more sensitive to photoperiod than that of DPS;LN1/LN2 can be used as the simplest indices for photoperiod.9.Bi-dierectional Group was pointed out for maize breeding:breed specific male group and female group,then limited traits of them were improved and selected.According to the heterosis model,firstly,accumulates and maintains the characteristic advantages of each group,then overcomes their disadvantage.Through this way,two parents will possess as much useful alleles as possible,and avoid having common disadvantage alleles.By full utilization of the useful alleles in male group and female group to reach the aim of mutually complementary in superior character,and finally exhibit the yield potential of hybrids.更多还原