The effects on grain endosperm structure of an introgression from <Emphasis Type="Italic">Aegilops speltoides</Emphasis> Tausch. into chromosome 5A of bread wheat

The endosperm structure of the wheat kernel determines its end-use quality. The known diversity in endosperm structure is related to the Pina-D1 and Pinb-D1 genes comprising the Ha locus on chromosome 5DS. We studied the effect of a gene introduced into bread wheat from the diploid relative, Aegilops speltoides, a putative donor of the B genome. Grain hardness and vitreousness were investigated in lines with homoeologous introgressions into chromosome 5A of spring wheat cultivar ‘Rodina’. One introgression changed the endosperm texture from hard to soft and had the same effect when transferred to other wheat genotypes. This indicated that its action was analogous to the dominant allele at the Ha locus. The temporary symbol Ha–Sp is given to the gene. Segregation for vitreousness in F₃ offspring from monosomic hybrids was also investigated. Genetic variability for endosperm structure in wheat may be extended by manipulating both hardness and vitreousness. Wheat germplasm with introgressions from wild relatives can increase the genetic variability of milling characteristics.     

高赖氨酸玉米主要品质性状的配合力分析

用4个软质胚乳和4个硬质（或半硬质）胚乳的高赖氨酸玉米自交系，进行8×8完全双列杂交试验，分析了后代籽粒品质性状的遗传表现和配合力。软质胚乳亲本和硬质胚乳亲本杂交时，当代F1籽粒的胚乳硬质度表现出显著的正反交差异，以硬质亲本作母本时F1籽粒硬质度较高，但F2籽粒的硬质度无显著的正反交差异。硬×硬类型杂交后代的     

Particle-Bombardment-Mediated Co-Transformation of Maize with a Lysine Rich Protein Gene (sb401) from potato

Summary Little work has been reported on genetic transformation with maize inbred lines, especially elite inbred lines used in breeding. In this work, 7 self-pollinated inbred lines and 4 hybrid lines have been screened. The results revealed that calli derived from immature embryos from two inbred lines X333 and X301 were compact, hyperhydric and unsuitable for transformation, but the calli induced from other inbred lines and all the hybrid lines were friable and yellow and could be used for genetic transformation. The sb401 gene isolated from potato (Solanum berthaultii) encodes a protein with a high lysine content. Maize calli from 5 self-pollinated inbred lines and 4 hybrid lines were transformed using particle-bombardment with different plasmids to simultaneously introduce the sb401 lysine rich gene and the selectable gene hpt respectively. Two hundred and sixty-eight regenerated plants were obtained from these genotypes. Co-insertion was confirmed in 29 regenerated plants by PCR and Southern blot analysis. Transgene segregation of the R1 plants was observed and one marker-free transgenic maize line was recovered. Analysis of the crude protein content in mature seeds of R1 transgenic plants also showed an increase from 36.8% to 48.2%. This study thus provides a workable system for generating transgenic maize free from selectable marker genes and generates valuable resources for obtaining marker free transgenic maize with a high-lysine protein content.     

Variation in sweet corn kernel characteristics associated with stand establishment and eating quality

Summary A better understanding of the relationships between kernel characteristics associated with eating quality and stand establishment could be helpful in selection of superior genotypes by the sweet corn industry. A set of sweet corn (Zea mays L.) inbred lines with different endosperm mutations (su1, su1 se1 and sh2) were evaluated for field emergence and seedling growth rate at two locations over two years. Kernel characteristics associated with eating quality (kernel moisture concentration, kernel tenderness, sugars, phytoglycogen and dimethyl sulfide (DMS) concentrations were determined for the same inbreds by laboratory analysis from ears harvested at 18 and 22 days after pollination (DAP). Amounts of sugars, phytoglycogen and starch were also measured in mature dry kernel samples of the same inbreds. Extensive genetic variability was found among endosperm mutations and among genetic backgrounds within the different endosperm groups for most of the characteristics under study. Most of the kernel attributes associated with eating quality were uncorrelated indicating that selection to improve specific eating quality characteristics can be conducted simultaneously. A negative correlation between field emergence and sugar concentrations in immature kernels suggests that in breeding programs designed to develop germplasm with improved germination and stand establishment, concurrent attention must be given to the fresh quality of the harvested product. This information is of value to breeders and commercial growers for selection of sh2 and su1 se1 lines with superior field emergence and eating quality.Abbreviations (DAP) days after pollination - (DMS) dimethyl sulfide     

Molecular characterization of endosperm and amino acids modifications among quality protein maize inbreds

Modifier loci in QPM play a vital role in achieving acceptable degree of kernel hardness and accumulation of lysine and tryptophan. This study was undertaken to characterize a set of diverse QPM inbreds using SSRs linked to endosperm and amino acids modifier loci for their effective utilization in the breeding programme. Significant variation was observed for endosperm modification (25–100% opaqueness), tryptophan (0.056–0.111%) and lysine (0.223–0.444%). Generally, inbreds with soft endosperm possessed more tryptophan and lysine than inbreds with higher vitreousness. SSRs generated 341 alleles with two to seven alleles per locus. The frequency of unique and rare alleles was more for amino acid modifications, compared to endosperm modifications. Phylogenetic analyses grouped the inbreds into three major clusters, and the study identified suitable crosses for accumulation of endosperm and amino acids modifiers. QPM inbreds with desirable modifications identified here would serve as suitable donor for both opaque2 and modifier loci in the marker‐assisted backcross breeding. Further, contrasting inbreds can be used for generating mapping populations to identify new modifier loci underlying both endosperm and amino acids modifications.     

Assessing the genetic diversity of Portuguese maize germplasm using microsatellite markers

A collection of Portuguese maize accessions representing a valuable source of genes for introduction into modern cultivars is stored at the Portuguese Plant Germplasm Bank (Banco Português de Germoplasma Vegetal—BPGV). To assess genetic diversity among inbreds, microsatellite analysis was carried out for 54 inbred lines representing the diversity of Portuguese dent and flint maize germplasm. Fifty American and other European elite inbreds were also analysed for comparison. Fifteen microsatellite loci distributed throughout the maize genome were chosen based on their repeat unit and base composition. A total of 80 alleles were detected with an average allele number of 5.33 per locus. Polymorphism information content (PIC) values and observed genetic distances showed the existence of large variability among inbreds. Cluster analysis indicated that almost all of the inbreds could be distinguished from each other and Portuguese inbreds were present in all clusters formed. These associations were consistent with the known pedigree records of the inbreds, confirming a mixed origin of Portuguese materials. Comparative analysis of microsatellite diversity among groups was established according to important traits for both breeding and line identification. This revealed that, although most of the genetic diversity (>95%) was attributable to differences among inbreds of different groups, the existence of phenotypic differentiation in endosperm colour, kernel type and cob colour could be suggested for grouping. These findings support the joint use of molecular and morphological traits in management of the germplasm collection. In this study, SSR markers proved to be effective to characterise and identify maize inbred lines, and demonstrate associations among them. This revised version was published online in July 2006 with corrections to the Cover Date.     

QTL mapping of improving forage maize starch degradability in European elite maize germplasm

Improving maize starch content is of great importance for both forage and grain yield. In this study, 13 starch degradability traits were analysed including percentage of the seedling area, floury endosperm, hard endosperm of total grain area, percentage of the floury endosperm surface and vitreousness ratio surface hard: floury endosperm surface, etc. We mapped quantitative trait loci (QTL) in a biparental population of 309 doubled haploid lines based on field phenotyping at two locations. A genetic linkage map was constructed using 168 SSR (simple sequence repeat) markers, which covered 1508 cM of the maize genome, with an average distance of 9.0 cM. Close phenotypic and genotypic correlations were found for all traits, and were all statistically significant (p = 0.01) at two locations. Major QTL for more than two traits were detected, especially in two regions in bins 4.05–4.06 and 7.04–7.05, associated with 13 and 9 traits, respectively. This study contributes to marker‐assisted breeding and also to fine mapping candidate genes associated with maize starch degradability.     

玉米淀粉含量的杂种优势与基因效应分析

以10个玉米自交系及按10×10完全双列杂交设计的90个F2杂交组合在两个地点的试验资料,研究玉米淀粉含量的杂种优势和基因效应。结果表明,淀粉含量表现正向的平均杂种优势,但变异幅度较小,最大值在10%左右,并在组合间、地点间存在极显著差异;淀粉含量的遗传符合加性-显性模型,不存在上位性效应。基因显性效应的作用远大     

普通玉米主要营养品质性状的遗传效应分析

用13个普通玉米自交系按NCⅡ设计（7×6）研究了普通玉米主要营养品质性状的遗传效应。结果表明，普通玉米主要营养品质性状的遗传受种子二倍体胚、三倍体胚乳、细胞质和二倍体母体植株4套遗传体系的控制；主要品质性状4套遗传体系的效应值之间无太大的差异，蛋白质、淀粉和赖氨酸含量的胚遗传效应全部体现为胚加性遗传效应，而4种品质性状的胚乳遗传效应则全部由胚乳显性遗传效应构成；母体遗传效应主要表现为母体加性效应；遗传效应预测值表明亲本9636、99S2041-1-1-1和478在普通玉米品质改良中可能有一定的应用潜力。结果还发现，不同品质性状间存在不同程度的遗传相关，因此对这些性状进行间接选择或杂种优势利用均可取得一定的效果。     

Molecular identification of Pm12-carrying introgression lines in wheat using genomic and EST-SSR markers

The traditional process of obtaining maize hybrids involves the generation of inbred lines through successive generations of selfing and subsequent testcrosses in order to identify the best combining ability by allelic complementation. A fast alternative to obtain inbred lines is to induce the formation of haploids followed by chromosome doubling. However, even with the aid of haploid-inducing genetic sources, this strategy has not been widely used in maize breeding programs, partly due to difficulties inherent to haploid generation and identification. In order to evaluate the possibility of using dihaploids to generate homozygous maize tropical lines, we used the androgenetic haploid inducer line W23 as a female parent in crosses with the tropical single-cross hybrid BRS1010. Within the progeny of these crosses, 462 seeds were phenotypically selected as putative haploids by the purple-colored endosperm and colorless embryo conditioned by the R1-nj gene. Among these, only four individuals were confirmed as being haploids using SSR markers, chromosome counting and flow cytometry, showing that the phenotypic marker was not efficient in detecting haploids in the tropical maize genotype used. All four haploids as well as some diploid plants presented reduced size, corroborating the difficulties for haploid identification by phenotypic evaluation. Genetic diversity analysis revealed by SSR markers divided the haploids in two groups represented by flint and dent maize inbred lines, which could be helpful in identifying complementary dihaploid lines. The present article demonstrates that a combination of haploid production and SSR fingerprinting is a feasible strategy for maize hybrid development in tropical germplasm.     

不同来源玉米自交系籽粒品质性状研究

为提供玉米育种品质改良的依据,研究了不同来源的211份玉米自交系籽粒品质性状间的差异及相关性。采用近红外光谱分析仪测定籽粒粗蛋白、粗脂肪、粗淀粉、赖氨酸含量4个籽粒品质性状,并在系统聚类分析的基础上进行了类群间各性状变异分析。结果表明,各性状不同自交系间、年份间、地点间、年份×自交系、自交系×年份×地点均存在显著或极显著差异;不同自交系间粗蛋白、粗脂肪和赖氨酸的含量存在明显差异,赖氨酸含量变异系数最大（22.77%）,粗淀粉含量变异系数相对较小（1.89%）;各品质间的相关性分析显示粗脂肪和粗蛋白、赖氨酸和粗蛋白、赖氨酸和粗脂肪含量间呈显著正相关,粗淀粉和粗蛋白、粗脂肪、赖氨酸含量间呈负相关;供试自交系可分为9类,其中类群G1~G5包含205个自交系,占97.16%,品质性状优良的自交系以类群G1、G2、G4和G5最多,与‘郑单958’和‘先玉335’两大杂交种的4个亲本自交系比较,本研究共选出32份籽粒品质优良自交系,为玉米自交系籽粒品质性状的改良提供参考。     

优质蛋白玉米籽粒性状的遗传效应

选用8个胚乳性状差异显著的优质蛋白玉米(QPM)自交系, 采用Griffing I交配设计组配, 通过对亲本、F₁和F₂的鉴定, 探讨主要籽粒性状的遗传效应和杂种优势, 为有效利用热带硬质QPM种质改良、扩增我国温带QPM种质以及QPM籽粒性状改良和硬质QPM品种选育提供依据。结果表明, 籽粒百粒重、百粒体积、胚乳修饰度和籽粒密度在F₁和F₂代都表现一定的正向杂种优势; 胚乳修饰度在F₁代存在正反交差异, 母体效应明显; 4个性状的F₂代表型值与中亲值的相关性最大; 百粒重和百粒体积主要受母体效应控制, 基因效应以显性效应为主; 胚乳修饰度主要受种子直接效应控制, 基因效应以加性效应为主; 籽粒密度主要受母体效应控制, 基因效应以加性效应和显性效应同等重要。这4个籽粒性状的细胞质效应均较小, 主要受核基因控制。     

Genetic improvement of cell-wall digestibility in forage maize (Zea mays L.). I. Performance of inbred lines and related hybrids

Summary The current study deals with genetic improvement of the nutritive value of forage maize. In separate field trials, maize inbred lines without the brown midrib trait and derived hybrids were evaluated for stalk quality as well as some other agronomic traits. The aim was to relate the performance of lines and hybrids. Quality traits studied were the contents of ash and cell walls expressed as percentage of dry matter and the digestibilities of organic matter and cell walls (stalk-dv% and stalk-dcw%, respectively). The performance of hybrids was established in a trial at two locations with three replicates per location and the performance of lines at one location in an unreplicated trial.The range for stalk-dcw% was about 10 percentage units between hybrids and 15 percentage units between inbred lines. Stalk-dcw% had of all quality traits of hybrids the highest broad-sense heritability (h ²=0.74), and determined about 80% of the variation in stalk-dv%. The only stalk quality trait where a significant correlation was found between the mean hybrid performance and the corresponding midparent value was stalk-dcw% (r=0.70, P<0.01).In conclusion, stalk-dcw% proved to be the only stalk quality trait worth evaluating at the inbred line level in a breeding programme aimed at producing commercial hybrid varieties of forage maize.     

Logistic model-based genetic analysis for kernel filling in a maize RIL population

Kernel filling is an important factor that directly affects kernel yield in maize. Based on a Logistic model, the process of kernel filling in maize can be effectively fitted, and the characteristic parameters with biological significance can be estimated. To clarify the genetic mechanism of characteristic parameters of kernel filling in maize, a recombinant inbred line (RIL) population including 208 lines derived from the maize inbred lines DH1M and T877 were evaluated in Nantong in 2015 and in Yangzhou in 2016, respectively. The kernel dry weights of recombinant inbred lines were measured 10, 15, 20, 25, 30, 35, 40, 43, 46, 49, 52, 55, 58 and 61 days after pollination (DAP). A total of 12 characteristic parameters related to kernel filling were estimated in different environments using the Logistic model. These parameters showed abundant phenotypic variation across two environments in the recombinant inbred line population. Some more ideal genotypes were selected through clustering based on BLUP values of characteristic parameters. Genetic analysis indicated that the 12 characteristic parameters conformed to the “major gene plus polygenes” model. The results of two environments were reproduced well. Most of the characteristic parameters related to kernel filling were controlled by two major genes, and a few characteristic parameters were controlled by three or four major genes. In addition, the genetic models of some characteristic parameters differed in the two environments due to interactions between the genes and environments. This study not only laid a foundation for further clarifying the genetic mechanism of maize kernel filling and mapping the related genes but also suggests a new paradigm for dynamic developing traits.     

普通玉米子粒性状四类效应的遗传分析

采用二倍体胚和三倍体胚乳种子遗传模型及其分析方法,以５个玉米自交系及其间配制的Ｆ１,Ｆ２,ＢＣ１,ＢＣ２为材料,研究了５个玉米种子性状的胚直接效应、胚乳直接效应、母体效应和细胞质效应。结果表明,除粒宽外,各性状的遗传同时由质效应和胚、胚乳、母体基因效应所控制,丰粒重主要受胚乳和母体效应的影响,粒长的遗传以母体效应为主,粒宽和粒厚以胚乳效应为主。各部位子粒百粒重的胚乳直接加性效应与母体加性效应的协方差达显著或极显著水平,其余性状的胚、胚乳直接效应与母体效应间的协方差均不显著,通过母体植株的遗传表现可对这些性状进行有效的选择。在提高丰粒重的玉米育种中,以任一部位子粒百粒重作为选择标准可起到相同的选择效果,直接选择粒宽的分离类型有利于获得大粒的遗传材料。Ｓ２２是改良百粒重的优良亲本。     

耐低磷玉米自交系根系性状的主基因+多基因遗传分析

目前对玉米自交系耐低磷能力评价缺乏统一的指标,为探明耐低磷玉米苗期根性状的遗传机制,为耐低磷玉米自交系的筛选及杂交种选育提供理论支撑,利用主基因+多基因遗传模型,研究了玉米自交系及其杂交和回交世代苗期根系性状的遗传机制.结果表明,总根长受加性-显性-上位多基因控制,在F2世代筛选效率最高,环境对其影响较大;根体积受2对加性-显性-上位性主基因+加性-显性多基因控制,主基因间存在互作效应,主基因显性效应为负效应,在B2世代筛选效率最高,受环境影响较小;根表面积的遗传受2对加性-显性-上位性主基因+多基因控制,主基因显性效应对根表面积起负向作用,主基因加性效应起正向作用,在F2代筛选效率最高,受环境影响较小.     

硬胚乳高赖氨酸玉米选育方法的研究

以O_2基因为遗传背景的高级氨酸玉米(简称O_2玉米)比普通玉米同型种一般产量低7—15%,这是粉质胚乳导致子粒容重降低的结果.育种上解决的途径是利用硬胚乳修饰基因选育子粒容重较高的硬胚乳或半硬胚乳O_2自交系.不同类型玉米携带的硬胚乳修饰基因贫富悬殊很大,只有筛选利用较丰富的亲本材料,通过自交或自交与姊妹交相结合的二环系选育方法,以早代子粒出现“角帽”和“角圈’为选择目标,才能有效地育成硬胚乳或半硬胚乳O_2玉米交系.     

QTL for maize grain yield identified by QTL mapping in six environments and consensus loci for grain weight detected by meta‐analysis

Grain yield is the most important and complicated trait in maize. In this study, a total of 498 recombinant inbred lines (RIL) derived from a biparental cross of two elite inbred lines, 178 and P53, were grown in six different environments. Quantitative trait locus (QTL) mapping was conducted for three grain yield component traits (100 grain weight, ear weight and kernel weight per plant). Subsequently, meta‐analysis was performed after a comprehensive review of the research on QTL mapping for grain weight (100, 300 and 1000) using BioMercator V4.2. In total, 62 QTLs were identified for 100 grain weight, ear weight and kernel weight per plant in six environments. Forty‐three meta‐QTLs (MQTLs) were detected by meta‐analysis. A total of 13 candidate genes homologous to eight functionally characterized rice genes were found, and four candidate genes were located in the two hot spot regions of MQTL1.5 and MQTL2.3. Our results suggest that the combination of literature collection, meta‐analysis and homologous blast searches can offer abundant information for further fine mapping, marker‐assisted selection (MAS) breeding and map‐based cloning for maize.     

Mapping QTLs for kernel oil content in a tropical maize population

Maize cultivars often have low kernel oil content. To increase the oil content, efficient maize breeding programs have to be developed, which require the knowledge of the inheritance of this trait. Thus, the objective of this research was to map quantitative trait locus (QTLs) and estimate their effects for kernel oil content in a tropical maize population. Two maize inbred lines, contrasting for kernel oil content, were used to develop an F₂ population. Four hundred and eight F₂ plants were self-pollinated, and their kernels (F_2:3 progenies) were used for kernel oil evaluation. A genetic map with 75 microsatellites was developed, and the QTLs were mapped using the composite interval map (CIM); also, estimates of genetic and phenotypic variances, and heritability coefficient were computed. The map presented 10 linkage groups, spanned 1,438.6 cM in length with an average interval of 19.18 cM between adjacent markers. The kernel oil content averaged 58.40 g kg^–1, and the broad-sense heritability was high (h²= 0.98). Thirteen QTLs were mapped, which were distributed into eight chromosomes, and explained 26.64% of the genetic variation. QTLs in chromosomes 1, 5, and 6 contributed the most for kernel oil content. Nine out of 13 QTLs with favorable alleles were from the parental inbred with the highest kernel oil content. The average level of dominance was partial, but gene action of the QTLs ranged from additive to overdominance. Eight out of 13 mapped QTLs were already reported for temperate maize populations.     

玉米拟轮枝镰孢菌穗腐病抗性基因的挖掘

玉米穗腐病是一种严重危害玉米生产的真菌性病害,而目前在世界范围内玉米育种上应用的大多数自交系缺少对穗腐病的抗性。玉米穗腐病抗性位点的挖掘和抗病基因的克隆,对玉米穗腐病的遗传改良至关重要。本研究旨在通过转录组测序和全基因组关联分析的方法进行玉米拟轮枝镰孢菌穗腐病抗性位点的挖掘并初步确定候选基因。抗病自交系法A和感病自交系掖81162的转录组测序结果表明,人工接种拟轮枝镰孢菌后7d两个自交系的差异表达基因有10,761个。通过全基因组关联分析共检测到5个与穗腐病抗性显著相关的SNP,这些SNP分布在1号和9号染色体上。通过比对B73 RefGen_v3并注释,发现SNP位点附近涉及的基因包括酰基激活酶1过氧化物酶体、蛋白磷酸酶2C 48、镁转运蛋白、受体蛋白激酶CRINKLY4和锌指CCCH域蛋白19。将在转录组测序中获得差异表达基因和全基因组选择中关联到的基因进行比对,发现全基因组关联分析中关联到的锌指CCCH域蛋白19同时也是转录组测序中获得的差异表达基因,表明锌指CCCH域蛋白19可能与玉米拟轮枝镰孢菌穗腐病的抗性相关。本研究结果不仅能为抗病基因的克隆和玉米的抗病分子育种提供一定的理论依据和重要的遗传资源,而且能为玉米和病原菌的相互作用机理的解析奠定基础。