应用RAPD分子标记技术对我国骨干玉米自交系进行类群划分

利用ＲＡＰＤ标记技术,对我国目前２５个主要玉米自交系进行亲缘关系类群划分,本项研究建立了从玉米种子、幼芽以及叶片组织提取微量ＤＮＡ的方法。从ＲＡＰＤ引物试验Ａ至Ｏ共计３００个引物中,筛选出对玉米扩增产的具有多态性的引物４０个,其中具有特别明显多态民生的引物１０个。它们是Ｆ３、Ｏ２０、Ａ１９、Ｍ２、Ｍ６、Ｎ１１、Ｎ１９、Ｃ２和Ｇ１４等。依据１０个引物扩增谱带建立０,１型数据,计算２５个自交系间遗传距     

AFLP分子标记在玉米优良自交系优势群划分中的应用

本文利用AFLP分子标记技术研究了17个玉米优良自交系的遗传多样性, 4个AFLP引物组合分别扩增出30、 30、 44、 41条多态性带, 平均每个引物组合扩出36.25条带, 4个引物组合共扩增出145条带, 每一个引物组合都可将17个自交系完全分开。 利用AFLP数据、 进行聚类分析, 将17个优良自交系聚为6群, 结果表明, 用AFLP标记进     

基于产量及主要品质性状的玉米自交系类群划分

用产量及主要品质性状对目前玉米生产上常用的7份自交系和本课题组选育的7份新自交系进行主成分和聚类分析,结果表明：入选的5个主成分因子对总变异的贡献达83.191%,自交系698-3和109可以作为较好的品质育种亲本;而48-2和226则是较好的高产育种亲本.自交系间的遗传距离变异范围为0.342～21.910,根据遗传距离可将14份自交系分为7类,其分类结果与育种实践相吻合.     

利用SNP标记划分玉米自交系杂种优势类群

利用4550个SNP位点对80份玉米自交系进行遗传分析,质控后剩余79份自交系用于后续分析;多态性信息含量(PIC)平均值为0.39;79 份自交系间的遗传相似度变化范围为 24.9%～99.9%,平均遗传相似度为51.2%。根据遗传距离信息,利用NJ聚类法将79份玉米自交系划分为两大类、7个亚群。一类包含瑞德、黄改、P群和Lancaster;一类包含Iodent、迪卡选系和先锋改良群。其中系谱来源不清晰的玉米自交系均被划分至不同类群中,明确了其优势类群。     

分子标记技术在玉米育种中的应用

简述分子标记的种类、方法及特点。分子标记技术主要用于玉米基因标记、基因图谱的绘制、指纹分析、遗传距离测定、预测杂种优势及鉴定等方面,极大地提高玉米育种效率。     

AFLP在水稻类群划分研究中的应用

利用AFLP分子标记技术研究了22个水稻品种的遗传多样性，从49对AFLP引物中筛选出了4对多态性高，分辨能力强的引物，4个AFLP引物组合分别扩增出43、37、49、33条多态性带，平均每个引物组合扩出40．5条多态性带，4个引物组合共扩增出246条带。利用AFLP数据进行聚类分析，将22个品种聚为8群，结果表明，AFLP在水稻类群划分的应用是可行的。     

玉米杂种优势类群的划分方法

玉米育种主要利用的是杂种优势,所以杂种优势类群的划分是玉米育种的重要内容。准确合理的划分玉米杂种优势群,探索最优的杂种优势模式,是选育优良组合的前提。在对玉米种质改良、扩增及创新时也必须遵循杂种优势群间优势模式的原理,这样才能避免事倍功半、浪费资源、提高育种效率。我国育种者对杂种优势类群和优势模式进行系统研究较晚,     

几个骨干自交系在玉米配合力育种中的应用潜力分析

几个骨干自交系在玉米配合力育种中的应用潜力分析王守才,杜鸣銮(沈阳农业大学农学系110161)本文对辽宁省内几个骨干系的产量及部分株形性状的配合力遗传动态进行分析,评价了它们做为骨干系的应用潜力。1材料与方法本研究的试材共有25个自交系。骨干系组包括……     

利用分子标记技术对玉米自交系子粒油分的改良研究

高油玉米是指子粒油分含量高于6%的玉米,是一种优良的粮油饲兼用型作物。高油玉米自交系By804含有qHO1和qHO6两个提高子粒油分的主效QTL。以By804为供体,利用分子辅助选择技术,结合田间农艺性状鉴定及核磁共振油分检测,将2个主效QTL分别回交转育至普通玉米自交系lx9801、lx03-2及lx00-1中。结果表明：来自By804的2个QTL均表现为随着回交次数的增加,子粒含油量较轮回亲本提高幅度逐步降低;不同遗传背景对QTL效应有较大影响：2个QTL在不同自交系的效应均以lx9801最佳,转育目标QTL后自交系绝对含油量较轮回亲本平均增加0.72%;2个位点效应相比,qHO6对子粒含油量的改良效果较优,3个自交系的改良系平均绝对含油量增加0.58%。     

采用RAPD分子标记,表型和杂种优势聚类分析法对玉米自交系类群的划分

以１５个我国生产上常用的玉米自交系为试验材料,采用裂型性状、杂种优势和ＲＡＰＤ分子标记三种聚类分析方法对玉米自交系的组群划分进行了比较研究。结果表明,表型聚类因以麦型性状为依据,受环境影响较大,其聚类结果与实际系谱来源出入较大。与表型性状聚类相比,杂种优势聚类与已知系谱来源更接近。ＲＡＰＤ分子标记,具有标记性状数量较多,不受生长发育时期限制和环境影响,无功能性表型效应,无上位及多效作用等诸多优点,     

Genetic diversity in tropical maize inbred lines: heterotic group assignment and hybrid performance determined by RFLP markers

Tropical maize inbred lines, eight derived from a Thai synthetic population (BR‐105) and 10 from a Brazilian composite population (BR‐106), were assayed for restriction fragment length polymorphisms with 185 clone‐enzyme combinations. The aim of this study was to investigate genetic distances among tropical maize material and their relationship to heterotic group allocation and hybrid performance. Genetic distances (GDs) were on average greater for BR‐105×BR‐106 lines (0.77) than for BR‐106×BR‐106 (0.71) and for BR‐105×BR‐105 (0.69) lines. Cluster analysis resulted in a clear separation of BR‐105 and BR‐106 populations and was according to pedigree information. Correlations of parental GDs with single crosses and their heterosis for grain yield were high for line crosses from the same heterotic group and low for line combinations from different heterotic groups. Our results suggest that RFLP‐based GDs are efficient and reliable to assess and allocate genotypes from tropical maize populations into heterotic groups. However, RFLP‐based GDs are not suitable for predicting the performance of line crosses from genetically different heterotic groups.     

Genetic diversity of Tainan-white maize inbred lines and prediction of single cross hybrid performance using RAPD markers

To evaluate the genetic diversity of 13 maize inbred lines, and to determine the correlation between genetic distance and single cross hybrid performance, we employed the randomly amplified polymorphic DNA(RAPD)- a PCR-based technique. Six of these lines came from the Taichung population, and others derived from seven different sites. Forty different primers were used to give a total of 646 reproducible amplification products, 547 (84.7%) of them being polymorphic. Genetic divergence was determined using Jaccard's similarity coefficient, and a final dendrogram was constructed by UPGMA (unweighted pair-group method with arithmetical averages) cluster analysis in the CLUSTER procedure of the SAS system. The RAPD analysis was a useful tool in determining the extent of genetic diversity among Tainan-white maize inbred lines in the present case. Cluster analysis showed that the 13 inbred lines could be classified into distinct heterotic groups. There was no significant linear regression of grain dry weight heterosis value and mean performance of hybrids on genetic distance. And their coefficients of determination(R²) are small, so that predictive value is limited. The present results showed that the Jaccard's similarity coefficients based on RAPD data cannot be used to precisely predict the F₁ hybrids yield performance and heterosis value. This revised version was published online in August 2006 with corrections to the Cover Date.     

Genetic diversity of maize inbred lines in relation to downy mildew

A major emphasis in maize breeding in Asian countries has been the improvement for resistance to downy mildew, a serious disease that causes significant yield losses. A total of 102 inbred lines, including lines from Asian breeding programs, Mexico, USA and Germany, were analyzed with 76 SSR markers to measure diversity and investigate the effect of selection for downy mildew resistance. A mean polymorphism information content of 0.59, with a range of 0.14 to 0.83, was observed. Diversity at the gene level showed an average of 5.4 alleles per locus and a range of two to 16 alleles per locus, with a total of 409 alleles. About half of the alleles in the Asian lines had frequencies of 0.10 or less, and only 2% had frequencies > 0.80, indicating the presence of many alleles, and thus a high level of diversity. Some of the high-frequency alleles were in chromosomal regions associated with disease resistance. However, the frequencies of alleles in three SSR loci that are linked to a QTL for resistance to downy mildews in Asia were not significantly different in the subtropical/tropical Asian lines as compared to all the lines in the study. Lines from the US, Germany, and China, comprised three clusters of temperate maize(GS = 0.31), while those from India, Indonesia, Philippines, Thailand, Vietnam and CIMMYT comprised seven indistinct clusters of subtropical and subtropical maize (GS = 0.29). We conclude that maize breeding activity in Asia has not caused a decline in the overall amount of diversity in the region. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genetic diversity of oilseed Brassica napus inbred lines based on sequence-related amplified polymorphism and its relation to hybrid performance

Significant heterosis for seed yield in oilseed rape has created interest in the development of hybrid cultivars. The DNA‐based marker protocol, sequence‐related amplified polymorphism (SRAP) was used to determine genetic diversity among oilseed rape maintainer and restorer lines. This measure was used in an attempt to establish an association between genetic distance and heterosis in hybrids for various agronomic traits. A total of 118 polymorphic loci were generated by 18 SRAP primer combinations. Based on the polymorphism generated by the markers, calculated similarity index values ranged from 0.46 to 0.97. Cluster analysis grouped 10 maintainer and 12 restorer lines into three groups, with the exception of two maintainer lines, PM5 and PM9, which fell outside these groups. The grouping of the lines was largely in agreement with the available pedigree data on their origin and agronomic performance. Analysis of variance among inbred lines and their resulting F₁ hybrids over two locations revealed significant differences for plant height, days to maturity and seed yield, but not for oil content. Substantial mid‐parent heterosis was observed only for seed yield, and ranged from 26% to 169%. All hybrids surpassed their respective inbred lines for this trait, except for a single cross combination of related lines. In general, crosses of lines located in different clusters yielded more than those from the same clusters. Regression analysis revealed a statistically significant relationship between the genetic distance of the parents and seed yield in their hybrid, and their derived mid‐parent and high‐parent heterosis. The correlation coefficient between genetic distance and yield (0.64) indicated a moderately strong relationship, so it is possible that some of the SRAP markers might be linked to quantitative trait loci for seed yield.     

Genetic characterization of 218 elite CIMMYT maize inbred lines using RFLP markers

Characterization of genetic diversity among maize inbred lines can facilitate organization of germplasm and improve efficiency of breeding programs. A set of 218 phenotypically diverse inbred maize lines developed at CIMMYT for hybrid production was characterized using 32 RFLP markers to: (1) analyze the genetic diversity present; (2) define potential heterotic groups based on clusters formed with marker data; and (3) identify the most representative testers for each potential heterotic group. Lines were clustered using five different genetic distance measurements to find consensus non-hierarchical clusters. Dendrograms were produced to study hierarchical classification within smaller groups of lines. A very high average allelic diversity was seen in this germplasm. Lines did not cluster based on phenotype, environmental adaptation, grain color or type, maturity, or heterotic response (as determined based on hybrid performance with testers), but lines related by pedigree usually did cluster together. Previously defined testers from opposite heterotic groups were not genetically differentiated, and did not represent well their heterotic group. Discrete clusters were difficult to find; thus, potential heterotic groups will be difficult to suggest using RFLP markers alone. However, suggestions on how to use molecular markers and cross performance information to refine heterotic groups and select representative testers are presented.     

Variation and inheritance of response to acetochlor among maize inbred lines and hybrids

Summary The variation of response to acetochlor was studied in a two-year experiment carried out by subjecting 18 maize (Zea mays L.) inbred lines to three herbicide rates (0, 2.5 and 5 l a.i./ha). In both years some inbred lines consistently exhibited an evident susceptibility, with symptoms consisting of the seedling curling up below the soil surface and causing impaired field emergence. The results were poor plant density and lower grain yield in comparison to control. In contrast, other lines showed a satisfactory level of tolerance.Then, to gather data on the inheritance of response to acetochlor, four tolerant inbreds (T) and four susceptible inbreds (S) were crossed to obtain four T×T, four S×S, four S×T and the corresponding four T×S two-way hybrids. These hybrids were studied together with parental lines by applying the same herbicide rates used in the previous trial. The S×S hybrids showed susceptibility to the herbicide and the T×T were tolerant, whereas the S×T and the T× S hybrids showed a tolerance very close to that of the T×T hybrids. No difference was found between S×T and the corresponding T×S hybrids as to herbicide response. On average, the 16 hybrids exhibited greater tolerance than the eight parental lines, with each hybrid group being more tolerant than its parental line group. These results indicate that tolerance to acetochlor is prevailingly dominant, that action of extranuclear genes should be ruled out, and that the level of plant vigour can affect herbicide reactiveness.     

黑龙江省部分审定玉米品种亲本自交系的遗传多样性分析

黑龙江省气候条件特殊,血缘关系有些混杂,系谱关系已不太清楚,种质资源匮乏问题尤为突出。利用SSR分子标记技术,分析黑龙江省近年来审定玉米品种亲本自交系的遗传多样性,从79对SSR核心引物目录中,选出43对引物对18份玉米自交系和5个标准测验种进行遗传多样性研究,共检测到174个等位基因位点,每对引物检测到2～8个等位基因,平均每个位点的等位基因变异数4.35个,平均多态性信息量为0.586。UPGMA聚类分析结果表明,23份自交系划分为4个类群。结果表明黑龙江省玉米生产上推广品种的亲本自交系仍然集中在兰卡斯特群和瑞德群两大杂种优势群。     

糯玉米自交系SSR标记遗传多样性及群体遗传结构分析

为了解糯玉米种质的遗传基础,利用29对SSR标记对87份糯玉米自交系进行遗传多样性分析,共检测出180个等位变异,平均每个位点6个等位变异,多态性信息含量变幅为0.308～0.915,平均为0.572。材料间遗传相似系数为0.49～0.93,平均为0.66。通过聚类分析UPGMA (unweighted pair-group method with arithmetic means)方法在遗传相似系数0.64处将87份糯玉米自交系划分为4个类群,分别包含9、66、10和2份材料。此外,利用Structure群体遗传结构分析也将87份糯玉米自交系分为4个类群,分别包含24、25、19和19份材料;进一步分析表明,供试群体中大部分糯玉米自交系的遗传变异较单一。本研究为糯玉米新品种选育和遗传进化分析提供了种质基础和理论依据。     

Genetic diversity of tropical maize inbred lines combining resistance to Striga hermonthica with drought tolerance using SNP markers

Striga hermonthica and drought are the major stresses limiting maize yields in sub‐Saharan Africa. The search for diverse maize lines’ tolerance to drought and resistance to S. hermonthica (DTSTHR) is very crucial for yield improvement in areas affected by the two stresses. Understanding the genetic diversity among the lines is important to develop cultivars resistant to S. hermonthica and tolerant to drought. The lines were developed from biparental crosses of drought‐tolerant and Striga‐resistant lines. A total of 128 DTSTHR maize lines were characterized using single‐nucleotide polymorphism (SNP) markers. Results of the cluster analysis based on 3297 SNP markers showed four distinct groups consistent with the pedigrees of the lines. Furthermore, model‐based analysis also formed the same groups of the DTSTHR lines. Integrating the pedigree information with combining ability and the SNP analyses may provide defined heterotic groups for maize improvement work in West and Central Africa. These results also help breeders to utilize DTSTHR lines present at IITA for developing biparental crosses without disrupting the heterotic groups they have established in their breeding programmes.     

Relationship between genetic markers and morphological traits in a maize inbred lines collection

Summary Genetic markers (isozymes), in addition to the traits recommended by the UPOV convention, have been used in France since 1989 to characterize the maize inbred lines submitted to registration. In the years 1989. 1990 and 1991, a total of 974 inbreds has been described according to this procedure. Relationships between genetic markers were investigated and underlined the occurrence of linkage disequilibria within the tested germplasm. These disequilibria appeared to depend strongly on the breeding history of the germplasm. In some cases, these disequilibria could be related to a major progenitor (foundation effect). Relationships between genetic markers and quantitative traits were also pointed out. High coefficients of determination (up to 60%) were in some cases observed at the within group level, and also appeared to be very dependent on the major progenitors of the group of interest. The consequences of these results for breeding and distinctiveness studies are discussed.