玉米对黄曲霉菌抗性的遗传控制

用7个玉米自交系进行完全双列杂交, 对杂种F1进行自交, 获得P1、 P2、 F1、 F’1、 F2、 F’26个家系。 对6个家系的种子用黄曲霉菌 (Aspergillus f lavus Link)接种。 根据种子的感病程度, 对抗性进行遗传分析。 结果表明： 玉米对 黄曲霉菌的抗性遗传主要受2n核遗传体系控制, 细胞质对抗性的遗传也有影响, 但3n胚乳 对     

Genetic variation among European maize inbreds for resistance to the European corn borer and relation to agronomic traits

The univoltine European corn borer (ECB) has become a major limiting factor for maize (Zea mays L.) production in central Europe. The objective of this study was to survey the genetic variation for ECB resistance in European elite maize germplasm. Eighteen flint and 23 dent inbreds were screened under artificial ECB infestation at two locations in 1993 and 1994. Resistance was assessed by damage rating of broken plants, measurement of tunnel length in dissected stalks, and yield reduction in infested plots relative to insecticide-protected control plots. Flint lines showed significantly greater means for damage rating than dent lines with grain yield reduction of 35% and 24%, respectively. Significant genotypic variances among lines and high heritabilities were found for agronomic traits and damage rating. Heritabilities were intermediate for tunnel length and relative grain yield. Significant associations of days to silking, ear dry matter content, and dry matter yield of the whole plant with damage rating and tunnel length suggested a better resistance in late-maturing, high-yielding inbreds. Genotypic correlations of relative grain yield with tunnel length and damage rating ranged between ?0.46 and ?0.72. Partial correlations, eliminating the effect of flowering time, confirmed these associations. Damage rating of stalks is the most suitable trait for evaluation of ECB damage owing to its high heritability and easy recording. Tunnel length below the primary ear is a useful trait for assessing antibiosis because it is not correlated with days to silking. Inbreds with extreme resistance and susceptibility were identified which can be used as parents for establishing breeding and QTL mapping populations.     

杨树花发育相关基因及基因工程调控

杨树作为世界上重要的速生栽培树种和林木基因工程的模式树种,对其花发育分子机理的深入研究既是进行杨树开花调控的前提和基础,也为研究其它多年生木本植物花发育的研究提供借鉴.与其他开花植物相似,杨树的花发育也分为开花诱导、花的发端和花器官发育三个阶段,并且每个阶段都有多种基因的参与和调控.依据拟南芥等植物中花发育基因的信息,在杨树中也克隆了一大批与其花发育相关的基因,这些基因在表达方式、基因功能、调控等方面与其在拟南芥等植物中既有相似性,又具有杨树自身的特点.在杨树花发育相关基因的研究基础上,已经获得了提早开花及不育的转基因杨树.随着杨树花发育研究的不断深入以及实验技术的不断更新,杨树遗传改良必将发生历史性的变革.     

Genetic variation in testcrosses of European maize inbreds for resistance to the European corn borer and relations to line per se performance

The European com borer (ECB) Ostrinia nubilalis H. is a major pest in World maize Zea mays L. production. Objectives of this study were to (1) investigate the genotypic variance and covariance in testcrosses of European flint and dent inbreds for ECB resistance and agronomic traits, and (2) estimate the correlation between line per se and testcross performance for ECB resistance traits. A total of 16 flint and 24 dent inbreds and their testcrosses with two testers from the opposite germplasm pool were evaluated in four and three German environments, respectively. Using artificial infestation with ECB larvae, resistance was assessed by damage rating of stalks, tunnel length in dissected stalks, and relative yield of infested plots compared with protected plots. Yield losses due to ECB damage in testcross hybrids amounted to 40%. Significant genotypic variances between flint and dent lines and high heritabilities were found for damage rating of stalks for both line per se and testcross performance. Heritabilities were low or intermediate for tunnel length and relative grain yield. Correlations between line per se and testcross performance were tight for the damage rating of stalks and moderate for tunnel length and relative yield in both flint and dent germplasm. For damage rating of stalks, per se performance of lines tested in a few environments can be used to predict their testcross performance. In contrast, assessment of testcross performance for tunnel length and relative yield requires evaluating testcrosses with several testers in multi-environment trials.     

Genetics of resistance to kernel infection by Aspergillus flavus in maize *

Although kernel infection by Aspergillus flavus Link ex Fries and subsequent pre-harvest aflatoxin contamination of maize (Zea mays L.) grain are major production problems in the south-eastern United States and elsewhere in the world, limited progress has been made in developing and identifying sources for resistance. Genetics of kernel infection by A. flavus remains poorly understood. A 10-parent diallel experiment was conducted in 1992 and 1994 to study the genetic nature of percentage kernel infection (PKI) by A. flavus. General combining ability (GCA), specific combining ability (SCA), and reciprocal mean squares for PKI were significant. The GCA and SCA sums of squares were about equal. The GCA, SCA, and reciprocal effects varied across years, which implied that percentage kernel infection was greatly influenced by environments. The percentage kernel infection was always greater when Mo 17 was the male parent in a cross than when it was the female parent. The percentage kernel infection mean for female Mo 17 was 38.5% lower than that for male Mol7. Similarly, percentage kernel infection mean for female L668 was 23.7% lower than that for male L668. The use of inbred lines L729 and B73 as female parents should be avoided, as they showed significant, positive maternal reciprocal effects.     

Somatic Embryogenesis in Maize and Comparison of Genetic Variability Induced by Gamma Radiation and Tissue Culture Techniques

Sixteen inbred lines and one hybrid of manse were tested for their capability of somatic embryogenesis, and fully developed plants could be regenerated, from ten inbred, lines. The highest frequency of plant regeneration was expressed in the inbred line CHI 31, and when this line was crossed with a recalcitrant, non-regenerating line, the F₁ and BC hybrids were regenerable. The results of reciprocal crosses demonstrated that dominant nuclear genes and cytoplasmic factors are primarily responsible for the heritable determination of embryogenic callus proliferation and in vitro regeneration of maize plants. Somaclonal and radiation-induced variability was studied in maize to assess their nature and potential contribution to plant breeding., The inbred line CHI 31 possessing a high in vitro capacity of somatic embryo formation was used as experiments.] material. CHI 31 plants were selfed and twelve-day old zygotic embryos irradiated with ⁶⁰Co gamma radiation in situ. Mature caryopses were harvested and assigned as M₁ material. In another series, immature zygotic embryos (size 1.2—1.5 mm) were cultured in vitro on N-6 medium supplemented with 2,4-D (2.5 μM), and somatic embryos regenerated into plants; these were transplanted into soil and self-pollinated. Regenerants from non-irradiated cultures were grown as R₁ generation, while regenerants from irradiated explants were considered as M₁R₁ generation. The genetic variability was evaluated in the M₂, R₂ and M₂R₂ generations, respectively, and compared with a non-treated seed control. Irradiation induced a variety of chlorophyll and morphological variants segregating in the M; generation; however, the frequency of deviant types obtained in the R: generation (somaclonal variation) was significantly exceeding the one derived from the M₂ populations. The combination of expert irradiation and in vitro regeneration was most effective for the manifestation of chlorophyll and morphological o if types in the M₂R₂ generation, and increased drastically the frequency of early flowering variants. Differences in the segregation patterns of mutant phenotypes amonsister somaclones in the R₃ and M₃R₃ generations indicate a different genetic basis, of plants originating from the same explant. This phenomenon suggests a mutational sectoring of the callus during culture. Radiation induced and somaclonal variation exerted a similar spectrum of chlorophyll and morphological deviants.     

玉米株高主效QTL qPH3.2精细定位及遗传效应分析

株高是影响玉米产量的重要因子之一, 节间数目和节间长度是导致株高差异的主要因素。本研究发现2个高代回交重组自交系W₁和W₂株高差异显著(P<0.001), 二者穗上部和穗下部节间数目都相同, 细胞形态分析发现节间细胞长度是引起二者株高差异的主要原因; 外源GA试验结果表明控制株高差异的QTL/基因是GA途径之外的新基因。因此, 利用来源于W₁和W₂的F₂及F_2:3家系群体在2年3个环境中将控制株高的主效QTL qPH3.2共定位在第3染色体标记C42-P17之间20 Mb范围内, 最高可解释22.22%的表型变异。进一步利用目标区段重组交换单株及自交后代家系将qPH3.2分解为2个主效QTL qPH3.2.1和qPH3.2.2; 随后利用目标区段的跨叠系将qPH3.2.1和qPH3.2.2分别精细定位在YH305-Y72 (2 Mb)及YH112-Y150 (1.6 Mb)之间。本研究的结果为玉米株高的遗传改良提供了真实可靠的遗传位点, 也为后续株高QTL的克隆奠定了良好的工作基础。     

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.     

Relationship between European corn borer resistance and concentration of mycotoxins produced by Fusarium spp. in grains of transgenic Bt maize hybrids, their isogenic counterparts, and commercial varieties

The European corn borer (ECB), Ostrinia nubilalis Hb., is a major pest of maize in central Europe and promotes the infection of maize with Fusarium spp. In this study, transgenic Bt maize hybrids were compared with their isogenic counterparts, and with commercial hybrids from the recommended list with regard to their level of ECB resistance and their concentration of deoxynivalenol (DON), its 15‐acetyl (15‐A‐DON) and 3‐acetyl (3‐A‐DON) derivatives, nivalenol (NIV), fusarenon‐X (FUS‐X), fumonisins (FUM), and zearalenon (ZEN) in harvested grains. The field experiments were performed in Germany at four locations in 1999 and at five locations in 2000. Transgenic Bt hybrids showed significantly lower means than their corresponding isogenic counterparts and than commercial hybrids for all resistance traits: damage rating of stalks, number of larvae per plant, number of larvae per ear, and percentage of damaged plants or ears under infestation. Among all mycotoxins analysed, DON consistently showed the highest concentration across all year × location combinations. Mycotoxin concentrations varied significantly between locations, years and genotypes, whereas mycotoxin concentrations were not significantly different between infested and protected plots. Associations between ECB resistance traits and mycotoxin concentrations were not consistent across years. It is concluded that under central European conditions, the use of Bt maize hybrids will only slightly reduce the contamination of maize kernels with mycotoxins produced by Fusarium spp.     

Effect of maize streak virus disease on the growth and yield of maize as influenced by varietal resistance levels and plant stage at time of challenge

Field experiments were conducted from 1989 to 1991 at Ibadan, Nigeria, to assess effects of maize streak virus (MSV) disease on growth and yield of maize varieties having different levels of disease resistance. MSV disease reduced yield and growth in all years, but varieties differed significantly in amount of loss, disease severity and incidence. MSV disease was negatively correlated with plant height and dry weight, grain weight per plot, 1000-grain weight, ear length and diameter. In 1989 MSV disease decreased yield of resistant variety TZB-SR by 1.5%, of resistant hybrid 8321-21 by 10%, and of moderately resistant hybrid 8329-15 by 17%. Yield of susceptible variety TZB Gusao was reduced significantly more, by 71%. Plant age at time of virus challenge had significant effects on yield and growth characters, with earlier infection resulting in greater disease severity and yield reduction. A significant interaction between variety × age at challenge was also detected, indicating that varieties were differentially affected by MSV in relation to the growth stage when challenged. Disease incidence after challenge was lower for the most resistant varieties. This property of lower disease incidence under equal challenge opportunities (tolremicity) is an important aspect of resistance. The resistant varieties discussed here were bred for tolerance - good yield performance when diseased -, but TZB-SR and 8321-21 also exhibited tolremicity. Tolremicity combined with tolerance constitutes the overall disease resistance of a variety to a systemic pathogen such as MSV. This revised version was published online in July 2006 with corrections to the Cover Date.     

Grain Yields and Grain Nitrogen Concentration of Corn as Influenced by Fertilizer Nitrogen Rate

Knowledge of optimum fertilization for com production is required to increase crop yields while minimizing fertilizer costs. Field experiments were carried out from 1988 to 1993 to study the effects of fertilizer N rates on yield and N concentration of corn ( Zea mays L.) grain on a clay soil in Quebec. Grain yields and grain N concentrations generally followed a exponential relationship with increasing N fertilizer rates. The critical grain N concentration, defined as that associated with the highest grain yield, occurred at 285 kg N ha^-1 for all years except 1969 when it occurred at 170 kg N ha^-1. The critical grain N concentrations and grain yields over the years were found to be linearly related. The relationship between the critical grain N concentration and grain yield could serve as a diagnostic tool for N applications.     

Control of preharvest aflatoxin contamination in maize by pyramiding QTL involved in resistance to ear-feeding insects and invasion by Aspergillus spp.

Several resistance sources and resistance mechanisms to aflatoxin formation and corn earworm (Helicoverpa zea Boddie) damage to maize (Zea mays L.) have been identified. Based on this knowledge, experiments were initiated toward achievement of the following objectives: (1) to confirm earlier determinations on resistance traits of germplasm sources and to identify quantitative trait loci (QTL) associated with each of the traits, and (2) upon estimation of the degree of QTL effects on each trait, to generate a maize population, with chemical and physical resistance to Aspergillus spp. and ear-feeding insects, for inbred development. A 2-year field experiment to evaluate selected genotypes inoculated with A. flavus and infested with corn earworm revealed that significant variation exists among the genotypes for aflatoxin contamination and corn earworm damage. The protection of maize ears against aflatoxin contamination was primarily dependent on resistance to fungal infection and ear-feeding insects, and excellent husk coverage and tightness. A major QTL (p1) identified on chromosome 1S had effects of 54.0, 42.1, and 28.3% on the phenotypic variability for concentrations of silk maysin, 3′-methoxymaysin+apimaysin, and chlorogenic acid, respectively. Markers/QTLs for husk phenotypic traits and total aflatoxin concentrations have been determined, but more detailed mapping of these chromosomic regions will be necessary to locate precise markers/QTLs for husk traits and aflatoxin production. Realizing the complexity of the Aspergillus–aflatoxin-maize system and the factors affecting aflatoxin contamination, we are directing our program toward marker-assisted breeding to enhance or improve general genetic resistance to ear-feeding insects and invasion by Aspergillus spp.     

Inheritance of zeins: The catalogue of zein alleles of three multigenic loci and its potential for maize breeding

Inheritance of zein components in maize has been studied by a highresolution system of acidic continuous polyacrylamide gel electrophoresis. This method revealed extraordinarily high polymorphism of zeins. Previously, three multigenic loci, Zep1, Zep2 and Zep3, encoding most zein polypeptides were identified. Four other loci control the synthesis of some minor components. Single F₂ grains from 16 hybrid combinations involving 19 inbred lines were analysed. Correspondingly, 12 and 14 alleles of the Zep1 and the Zep2 loci were identified for 19 inbreds. Six alleles of the Zep3 locus were identified in five crosses. All 32 alleles of three multigenic loci were included in the catalogue of zein alleles. Genetic nomenclature for the alleles designation is proposed. Such nomenclature is in good agreement with ‘a standard for maize genetics nomenclature. The catalogue may serve for practical use and as basis for more detailed genetic studies of zeins. Practical application of the catalogue in maize breeding is discussed.     

我国不同年代玉米品种开花后叶片保护酶活性及膜脂过氧化作用的演进

通过比较研究我国50年代、70年代和90年代的几个主栽玉米((Zea mays L.)品种开花后叶片中抗氧化保护酶活性的变化得出：随品种更替叶片SOD、CAT和POD活性增加，膜脂过氧化产物MDA含量降低，在生育后期这种趋势愈加明显，不同叶位间以中下部叶片尤为显著。这些特征可能是近代玉米品种高产抗逆的有利因素之一。     

西南及四川区试玉米组合遗传多样性分析

采用表型性状分析、SSR标记和系谱分析对186个区试及引种试验玉米组合进行遗传多样性分析。结果表明,各组合间20个表型性状都变异在一个较小的范围内;利用筛选出的60对扩增条带清晰、具明显多态性的SSR引物,共检测到608个等位基因,每对引物检测到3~23个等位基因,平均为10.1个;SSR多态信息量（PIC）分布范围为0.5179~0.9256,平均值为0.7826;186个组合的遗传相似系数变幅在0.6067~0.9162之间,平均值为0.7722,相似系数在0.7000以上的组合有16 499对,占96.9%,供试材料分为10类,且88.2%的组合集中在第4、8、10类;51个系谱清楚的组合中有36个（占70.58%）与美国的PN种质有密切关系。以上结果均表明,供试组合相似程度较高,遗传差异较小,遗传基础相对单一,进一步拓展玉米种质遗传基础仍然显得十分必要。     

花期玉米(Zea mays)穗三叶叶形结构的遗传效应及配合力分析

为了剖析玉米叶形结构的遗传规律,进而拓宽优良株型自交系的遗传基础。本研究以12份不同叶形结构玉米自交系组配的32份F1杂交种为试材,在2个生态环境下,花期采用加性-显性-母体遗传模型(ADM)对其穗三叶叶长、叶宽、叶夹角、叶向值及叶面积进行遗传效应和配合力分析。结果表明:(1)玉米穗三叶叶长、叶宽及叶向值主要受基因的加性效应调控,其次是显性效应,同时还兼受加性×环境互作效应或母体×环境互作效应等遗传体系的调控,育种改良中宜在早代对其进行选择;叶夹角主要受基因的母体效应调控,其次是加性效应,另外还受加性×环境互作效应及母体×环境互作效应影响,育种中宜选择叶夹角较小的材料作为母本进行改良;叶面积只受基因的显性效应及显性×环境互作效应的调控,其应从较晚世代中进行遗传选择。(2)除父本叶长的一般配合力差异不显著外,父本其余性状的一般配合力和母本全部性状的一般配合力间差异均显著或极显著,且这5个叶形相关性状的全部特殊配合力间差异极显著。(3)从相应自交系各性状的一般配合力相对效应值分析发现,‘锋1999马’和‘锋1913硬’的综合性状表现优良,有利于组配出叶片大小适中及株型紧凑的优良耐密高产F1杂交组合。研究结果表明,玉米穗三叶5个叶形结构的遗传效应不尽相同,相应亲本5个叶形结构的一般配合和特殊配合力间存在明显差异,因此在玉米叶形结构遗传改良上应按照相应性状的遗传特征选择对应改良策略进行改良,并根据综合性状表现优良的亲本有目的地组配杂交组合,提高玉米理想株型育种效率。本研究为进一步剖析玉米叶形结构的遗传机理及玉米理想株型育种提供参考。     

抗双链RNA依赖性蛋白激酶PKR基因表达载体构建及在玉米中的遗传转化

玉米病毒性病害和杂草严重影响其产量和品质。以pCAMBIA5300为基础载体,应用In-Fusion克隆技术构建了双价植物表达载体pCAMBIA5300-Ubi-PKR-CaMV35S-EPSPS,其中含有抗双链RNA依赖性蛋白激酶PKR基因和磷酸烯醇式丙酮酸莽草酸-3-磷酸合酶EPSPS基因,分别由玉米泛素Ubi启动子和花椰菜花叶病毒35 S启动子启动。以玉米种子黄化苗的茎尖分生组织为受体,用农杆菌介导法进行遗传转化,将抗双链RNA依赖性蛋白激酶基因PKR和抗除草剂草甘膦基因EPSPS导入玉米自交系掖478中,获得转基因植株及其子代。     

Agronomic Performance and Nutrient Concentration of Maize (Zea mays L.) as Influenced by Nitrogen Fertilization and Plant Density

A field experiment was conducted at Samaru, Nigeria to study the influence of nitrogen fertilization and plant density on the agronomic performance and nutrient concentration of maize ( Zea mays L.). The treatments were factorial combinations of five nitrogen fertilization rates (0, 50, 100, 150 and 200 kg N/ha) and three plant density levels (25000, 50000 and 75000 plants/ha).
Nitrogen fertilization up to 150 kg N/ha enhanced grain and stover yields and increased kernel number and weight up to 100 kg N/ha. Nitrogen supply also increased maize ear length. Increased N fertilization rates increased concentrations of N, K and Mg but had no effect on P and Ca concentrations. Higher grain yield was closely associated with higher N concentration in ear leaf; with 0.1 % change in N concentration causing 177 kg/ha change in grain yield. Increased plant density increased stover yield up to 50 or 75 thousand plants/ha but depressed kernel number and weight and ear length.     

Influence of delayed emergence and canopy skips on the growth and development of maize plants: a plant scale approach with CERES-Maize

Our objective was to study by observation and simulation the effects of (1) three different dates of seedling emergence and (2) presence of short sequences of missing plants in rows of maize canopies which we refer to as skips. Trials were carried out in Belgium and France during two consecutive years. We had eight trials in total (i.e. two experimental designs in two locations for 2 years). In a field mechanically sown with a precision drill to give ‘normal plants’, ‘late 1 plants’ and ‘late 2 plants’ (respectively) were sown by hand when ‘normal plants’ had germinated or emerged. The radiation available at the top of the plants was measured for each cohort which allowed the calculation of a ‘coefficient of correction for light climate’ corresponding to the ratio of incident light at the top of each cohort relative to normal. Heterogeneity (skips) was created in maize canopies by removing three adjacent plants situated in the same row at 16 different locations across the field. The part of the canopy affected by the presence of these skips was considered to consist of the 12 plants bordering each skip. Radiation was measured near soil level on both sides of these plants: plants of the part of the canopy affected by skips received on average the same amount of radiation as a uniform stand with a population density equal to three quarters of the density of the parts of the stand without skips. To test if differences in radiation reaching the level of plants in each cohort could explain the effects on the plants the behaviour of each cohort of plants in each location x year was modelled separately with CERES-Maize after introducing into the model a ‘coefficient of correction for light climate’ corresponding to each cohort×location×year combination. Simulations generally reproduced correctly decreases in LAI, total biomass, grain number and total grain yield in the late 1 and late 2 cohorts, but not decrease in individual grain weight. The observed loss of grain yield per unit surface area in the parts of the canopy disturbed by skips was between 7 and 15%, whereas corresponding simulated values were between 6 and 11%. In the absence of compensation, values in the disturbed parts would have been 20%. Thus in our conditions amount of light reaching the different cohorts explained a large part of the treatments effects.