Low Level of Linkage Disequilibrium at the COMT (Caffeic Acid O-methyl Transferase) Locus in European Maize (<Emphasis Type="Italic">Zea mays</Emphasis> L.)

During recent decades, the whole plant yield of European maize (Zea mays L.) has increased substantially. However, during the same period of time cell wall digestibility, and consequently fodder quality, has decreased. Alleles for digestible cell walls have thus been lost, either during breeding for stalk standability or by genetic drift during breeding for grain yield. The brown-midrib 3 mutant (bm3) in maize (Z. mays L.), controlled by the caffeic acid O-methyl transferase (COMT) locus, has a positive influence on maize fodder quality. In this study, 42 European maize lines were used to evaluate the nucleotide diversity and linkage disequilibrium (LD) pattern across 2.3 kb of this locus. In agreement with what has been found for other maize loci, we found high diversity values (π = 0.00834), rapid LD decay even in an elite line sample, and indication of selection as well as of recombination events for seven site combinations. The diversity values differed slightly between inbreds of the Flint and Dent pools and most haplotypes were specific for one of the two heterotic groups. The polymorphisms identified at this single locus enable the construction of single nucleotide polymorphisms (SNP) and indel markers for haplotype identification and a rough discrimination of inbreds into Flint and Dent heterotic groups. The results reported here document the degree of allelic diversity in breeding materials and allow for targeted search of novel alleles in genetic resources.     

Purification and properties of a neutral peroxidase isozyme from turnip (Brassica napus L. Var. Purple Top White Globe) roots

A neutral peroxidase isozyme (pI 7.2) from turnip roots (TNP) was purified to homogeneity and partially characterized. TNP is a monomeric glycoprotein with 9.1% carbohydrate content and a molecular weight of 36 kDa. Optimum pH values for activity using 2,2'-azinobis(3-ethylbenzthiazoline-6-sulfonic acid (ABTS) and guaiacol as H donors were 4.5 and 5.5, whereas the K(m) values were 0.7 and 3.7 mM, respectively. The ABTS K(m) was approximately 7 times higher than that reported for basic commercial horseradish peroxidase (HRP-C). TNP retained approximately 70% activity after 11 min of heating at 65 degrees C, whereas the activation energy for inactivation (132 kJ/mol) was higher than or comparable to that of other peroxidases. The low ABTS K(m) and high specific activity (1930 units/mg) gave a high catalytic efficiency (500 M(-1) s(-1)). These properties make TNP an enzyme with a high potential as an alternative to HRP in various applications.     

Variability Among Maize (Zea mays L.) Inbred Lines for Seed Longevity

Genotypes conserved in active collections may suffer genetic erosion and modifications. The objective of this work was to investigate changes in germination and vigour in maize (Zea mays L.) inbred lines during cold storage in an active collection. Seeds of 16 maize inbreds produced along 16 years were evaluated for emergence and seedling vigour in a growth chamber. Linear and quadratic regressions of vigour and viability-related traits over seed age were calculated and tested for homogeneity. The seed of five production years of five inbreds that behaved differently in the regression analysis was multiplied in 1998, and original and renewed seed were evaluated in a growth chamber in 1999. Viability and vigour decreased linearly with age for most inbreds, particularly for B84 and EP10, varied at random for a few inbreds, and remained high for EP56 and A295. Aging caused reduction of vigour and loss of viability in most inbreds. There was variability for seed longevity among inbred lines; longevity was highest for inbred EP56. During storage, some seeds of each inbred died, while enduring seeds, when multiplied, produced new seed with enhanced viability and vigour compared to the average seed of the inbred, suggesting natural selection for viability and vigour during storage within inbred lines.     

辐射选育小麦易位系的研究

辐射处理六倍体小黑麦黑杂266×普通小麦克79F3-392的F0种子,通过一定的选育程序,选出了龙辐麦4号,龙辐10946和龙辐10877 3个易位系,经Giemsa-C带技术鉴定,其易位形式分别为6BS/6RL,2AS/2RL和7RL/7AL。酯酶同工酶和过氧化物同工酶的分析表明,3个易位系和黑杂266具有共同的特征酶带。试验证明,3个易位系具备双亲的优良特征特性,其中龙辐麦4号已由黑龙江省品种审定委员会审定推广种植。     

Comparison of isozyme and random amplified polymorphic DNA data for determining intraspecific variation in Cucumis

Variation at isozyme and random amplified polymorphic DNA (RAPD) loci in eight cucumber and seven melon cultivars, breeding lines, and plant introductions were used to determine the utility of these markers for assessing genetic variation among populations of each species. Although dendrograms derived from cluster analyses using species' variation at marker loci were dissimilar, these disparities were consistent with differences in the pedigrees and/or other information (e.g., morphological) known about each accession and species. Empirical estimations of variances associated with each marker type in the cucumber and melon accessions examined indicate that, per band, lower coefficients of variation can be attained in the estimation of genetic difference when using RAPDs compared to isozymes. The disparity between the marker analyses made may be related to the amount of genome coverage characteristic of a particular marker system in a species and its efficiency in sampling variation in a population.     

Relative activity of a tobacco hybrid expressing high levels of a tobacco anionic peroxidase and maize ribosome-inactivating protein against Helicoverpa zea and Lasioderma serricorne

Tobacco (Nicotiana tabacum) plants grown from seed obtained by crossing a tobacco line that expressed an activated maize ribosome-inactivating protein (RIP) with a line that overexpressed tobacco anionic peroxidase were tested for their effects on corn earworm Helicoverpa zea and cigarette beetle Lasioderma serricorne larvae as compared to the wild-type plant cross. Significant feeding reductions were noted for transgenic plants expressing both resistance proteins as compared to wild-type plants for both H. zea and L. serricorne. Significant increases in mortality were also noted for those insects fed on the transgenic cross as compared to wild-type plants in some cases. Levels of both peroxidase and maize RIP were significantly higher in transgenic as compared to wild-type plants (which did not produce maize RIP). The degree of feeding was significantly negatively correlated with the level of RIP or peroxidase individually.     

Reliable detection and identification of genetically modified maize, soybean, and canola by multiplex PCR analysis

Multiplex PCR procedures were developed for simultaneously detecting multiple target sequences in genetically modified (GM) soybean (Roundup Ready), maize (event 176, Bt11, Mon810, T14/25), and canola (GT73, HCN92/28, MS8/RF3, Oxy 235). Internal control targets (invertase gene in corn, lectin and beta-actin genes in soybean, and cruciferin gene in canola) were included as appropriate to assess the efficiency of all reactions, thereby eliminating any false negatives. Primer combinations that allowed the identification of specific lines were used. In one system of identification, simultaneous amplification profiling (SAP), rather than target specific detection, was used for the identification of four GM maize lines. SAP is simple and has the potential to identify both approved and nonapproved GM lines. The template concentration was identified as a critical factor affecting efficient multiplex PCRs. In canola, 75 ng of DNA template was more effective than 50 ng of DNA for the simultaneous amplification of all targets in a reaction volume of 25 microL. Reliable identification of GM canola was achieved at a DNA concentration of 3 ng/microL, and at 0.1% for GM soybean, indicating high levels of sensitivity. Nonspecific amplification was utilized in this study as a tool for specific and reliable identification of one line of GM maize. The primer cry1A 4-3' (antisense primer) recognizes two sites on the DNA template extracted from GM transgenic maize containing event 176 (European corn borer resistant), resulting in the amplification of products of 152 bp (expected) and 485 bp (unexpected). The latter fragment was sequenced and confirmed to be Cry1A specific. The systems described herein represent simple, accurate, and sensitive GMO detection methods in which only one reaction is necessary to detect multiple GM target sequences that can be reliably used for the identification of specific lines of GMOs.     

Purification and characterization of a peroxidase from corn steep water

Three cationic peroxidases have been detected in early, middle, and late corn steep water, with pI values of approximately 8.9, approximately 9.5, and >10.0. The major cationic corn steep water peroxidase (CSWP), with a pI >10, was purified 36400-fold with a 12% recovery from late steep water by a combination of acetone and ammonium sulfate precipitation and sequential chromatography on CM-cellulose, phenyl-Sepharose, and Sephadex G-75. The UV-vis spectrum of purified CSWP is typical of other plant class III peroxidases. The RZ (A(403)/A(280)) of CSWP was between 2.6 and 2.9. It is not glycosylated and exhibited an M(r) of 30662 +/- 7 by MALDI-TOF MS. The pH optimum of CSWP depends on the substrate, and it is active on 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid), guaiacol, ferulic acid, o-dianisidine, o-phenylenediamine, and pyrogallol but is not active on either syringaldazine or ascorbate. At 75 degrees C and pH 4.5, the enzyme has half-lives of 22.7 min (0 mM Ca(2+)) and 248 min (1 mM Ca(2+)). The enzyme is stable at room temperature (22-25 degrees C), losing <3% of the activity at pH 4.5 and <10% at pH 6.2 over 400 h in the presence of 1 mM Ca(2+).     

辐照诱导的新雄性不育系过氧化物酶和脂酶同工酶分析

采用聚丙烯酰胺凝胶垂直板电泳法,对甘蓝型油菜细胞质雄性不育系Polima、Shan2A、Ogu和辐照处理的新雄性不育系Xin1和Xin2及其保持系Shan2B的种子进行了脂酶和过氧化物酶分析,结果表明:5个细胞质雄性不育系比保持系Shan2B多1条迁移率为0.45的脂酶(EST)谱带;Xin1、Shan2A和Polima各有4条过氧化物酶(POD)谱带,保持系缺少1条迁移率为0.61的POD谱带,推测这一同工酶的表达可能与雄性不育相关。     

Physical,Compositional, and Wet Milling Characteristics of Grain from Crosses of Corn Inbreds with Exotic and Nonexotic Background

Corn breeders have developed hybrids with enhanced compositional characteristics, but exotic germplasm represents little of the germplasm base used to produce these hybrids. Effects of the exotic germplasm on physical, compositional, and wet‐milling properties as well as the proximate composition of recovered fractions need to be determined before these materials are of value to the corn processing industry. Ten lines from the Germplasm Enhancement of Maize (GEM) project with exotic germplasm introgressed from Argentina, Chile, Uruguay, Cuba, and Florida were crossed to three adapted inbred lines (testers) and grain from the resulting 30 hybrids were evaluated for physical, compositional, and wet‐milling characteristics and the expression of heterosis in these variables. The B73xMo17 adapted public hybrid was used as control. Grain obtained by self‐pollination of the hybrid plants was analyzed using near‐infrared transmittance (NIT) technology and a 100‐g wet‐milling procedure. There was great variation among physical, compositional, and wet‐milling characteristics, and some of the experimental hybrids with exotic origin had better starch yield and starch recovery than B73xMo17, which suggests that wet‐milling characteristics of U.S. hybrids can be improved by breeding with exotic germplasm. In particular, GEM breeding crosses AR16035:S19, CH05015:N15, CUBA117:S1520, and FS8B(T):N1802 could be valuable germplasm sources to produce inbreds with good milling properties. Testers varied in ability to produce hybrids with good milling properties, indicating that choice of tester is an important factor when evaluating this end use. Although general trait trends for mid‐ and high‐parent heterosis were revealed, individual variation among hybrids and testers was large for most traits. This demonstrates the importance of analyzing individual hybrids that are intended for the wet‐milling industry when breeding with exotic introgressed lines.     

Near-infrared reflectance spectroscopy (NIRS) for protein, tryptophan, and lysine evaluation in quality protein maize (QPM) breeding programs

Quality protein maize (QPM) has approximately twice the tryptophan (Trp) and lysine (Lys) concentrations in protein compared to normal maize. Because several genetic systems control the protein quality of QPM, it is essential to regularly monitor Trp and/or Lys in breeding programs. Our objective was to examine the potential of near-infrared reflectance spectroscopy (NIRS) to enhance the efficiency of QPM research efforts by partially replacing more expensive and time-consuming wet chemistry analysis. More than 276 maize samples were used to develop NIRS models for protein content (PC), Trp, and Lys. The standard error of prediction (SEP) for the calibration and the coefficient of determination for validation (R(2)(v)) were 0.26 and 0.96 for PC, 0.005 and 0.85 for Trp, and 0.02 and 0.75 for Lys. When the NIRS models were used to evaluate 266 S2 lines from five QPM breeding populations, the coefficients of determination between NIRS and the chemical data were 0.94, 0.76, and 0.80 for PC, Trp, and Lys, respectively. Therefore, the NIRS models can be used to support the QPM breeding efforts.     

Azo dye-mediated regulation of total phenolics and peroxidase activity in thyme (Thymus vulgaris L.) and rosemary (Rosmarinus officinalis L.) clonal lines

Thyme (Thymus vulgaris L.) and rosemary (Rosmarinus officinalis L.) clonal lines, which were previously isolated from a heterogeneous seed population by plant tissue culture techniques, have been targeted as potential plants for phytoremediation of organic pollutants such as azo dyes and related aromatic compounds. Three thyme clonal lines and three rosemary clonal lines were tested for the ability to grow on hormone-free medium containing 0.01% of azo dye Poly S-119. The results showed that dye tolerance was associated with reduced phenolics and enhanced peroxidase activity in these clonal lines. There was a clear inverse correlation between total phenolics and peroxidase activity in these plants in response to Poly S-119. The tolerance of these clonal lines showed variations at different growing stages. These observations suggested that the peroxidase activity was inducible. Because peroxidases are involved in lignification, wound healing, aromatic compound degradation, pathogen defense, and stiffening, the results suggest that azo dye stimulated the defense response of thyme and rosemary clonal plants by increasing the peroxidase activity. Stereomicroscopic observations revealed that the azo dye was sequestered within the growing axis of the plant roots, which may also enhance the polymerization of azo dye onto the cell wall with the help of enhanced peroxidase activity.     

缺磷对不同耐低磷玉米基因型酸性磷酸酶活性的影响

【目的】酸性磷酸酶活性与土壤及植株体内有机磷的分解和再利用有着密切的关系。本研究以不同耐低磷玉米自交系为材料,研究低磷胁迫下玉米叶片、根组织内以及根系分泌酸性磷酸酶活性的变化及基因型差异,探讨酸性磷酸酶与玉米耐低磷之间的关系,以期更深入地了解玉米耐低磷的生理机制。【方法】以5个典型耐低磷自交系99180T、99239T、99186T、99327T、99184T和2个磷敏感自交系99152S、99270S为试验材料,采用营养液培养方法,设正常磷和低磷两种处理,分别于缺磷处理3、8和12 d时调查取样,测定地上部干重、根干重、叶片中无机磷(Pi)含量、根和地上部磷累积量、根系分泌APase活性以及叶片中APase活性,并于缺磷处理12 d测定根系内APase活性。【结果】1)缺磷使玉米地上部干重下降,根干重、根冠比增加,随着缺磷处理(3 d→8 d→12 d)时间的延长,根干重、根冠比增加幅度增大,且耐低磷自交系根干重增加幅度普遍大于敏感自交系。2)低磷条件下,玉米自交系磷吸收、利用效率存在基因型差异,耐低磷自交系99239T、99180T和99327T磷吸收效率较高,99186T和99184T磷利用效率高,敏感自交系99152S、99270S磷吸收和利用效率均较低。3)低磷处理使玉米自交系叶片无机磷(Pi)含量显著下降,耐低磷自交系99184T、99327T和99239T下降幅度较小,相对叶片无机磷含量较高。4)缺磷诱导玉米根系分泌的APase活性升高。耐低磷自交系99184T和99186T根系分泌APase活性升高幅度较大,其余3个耐低磷自交系未表现出明显优势。缺磷处理3 d、8 d,玉米根系分泌APase活性与磷累积量显著正相关,而12 d时相关性不显著;根系分泌APase活性与磷利用效率在缺磷处理12d时达显著正相关。说明玉米根系分泌APase活性与磷吸收、利用效率相关关系不稳定。5)缺磷处理12 d,各玉米自交系根组织内APase活性与根系分泌APase活性变化情况较一致,两者相关系数r=0.755(P0.05)。6)缺磷条件下各玉米自交系叶片组织内APase活性均有升高趋势,并表现出明显的基因型差异。缺磷处理8 d,耐低磷自交系99184T和99239T叶片组织内APase活性升高幅度最大,其次是99327T和99186T,99180T、99270S和99152S升高幅度较小;缺磷处理12 d,各玉米自交系叶片APase活性仍继续增加,99239T、99184T、99327T和99186T的相对APase活性均较高,99270S和99152S的相对APase活性较低。相关性分析表明,缺磷条件下玉米自交系叶片中相对APase活性与叶片中相对无机磷(Pi)含量显著正相关,与磷吸收、利用效率不显著相关。【结论】低磷诱导玉米叶片、根组织和根系分泌APase活性升高,根组织和根系分泌APase活性的大小与玉米耐低磷能力不完全相关,叶片APase活性与玉米耐低磷能力有较好的一致性。     

普通玉米和特用玉米的SSR标记聚类

利用SSR标记研究了64份玉米自交系（包括普通玉米和特用玉米自交系）的亲缘关系。用30对扩增带型稳定的SSR引物,从供试材料中检测出116个等位基因变异,每对引物检测出等位基因2~10个,平均3.87个。SSR引物的PIC介于0.306~0.893之间,平均多态性信息量为0.717。按UPGMA方法对供试自交系进行聚类,以遗传距离0.586为基准,可将材料划分为11类。64份自交系的SSR标记聚类分析表明,普通玉米与特用玉米糯玉米、甜玉米、爆裂玉米等并不能严格地各自划为一类,只有亲缘关系较近的特用玉米自交系聚在一起,有些特用玉米与普通玉米聚在一起,部分特用玉米具有丰富的普通玉米种质资源遗传背景。特用玉米自交系间的遗传距离与普通玉米自交系间的遗传距离差异达到0.01的极显著水平。此外,不同类型特用玉米间、特用玉米与普通玉米间的遗传差异较大,特用玉米在进化和选育过程中积累并保存了丰富的遗传变异。     

Near-Infrared Reflectance Spectroscopy (NIRS) assessment of δ(18)O and nitrogen and ash contents for improved yield potential and drought adaptation in maize

The oxygen isotope composition (δ(18)O), accumulation of minerals (ash content), and nitrogen (N) content in plant tissues have been recently proposed as useful integrative physiological criteria associated with yield potential and drought resistance in maize. This study tested the ability of near-infrared reflectance spectroscopy (NIRS) to predict δ(18)O and ash and N contents in leaves and mature kernels of maize. The δ(18)O and ash and N contents were determined in leaf and kernel samples from a set of 15 inbreds and 18 hybrids grown in Mexico under full irrigation and two levels of drought stress. Calibration models between NIRS spectra and the measured variables were developed using modified partial least-squares regressions. Global models (which included inbred lines and hybrids) accurately predicted ash and N contents, whereas prediction of δ(18)O showed lower results. Moreover, in hybrids, NIRS clearly reflected genotypic differences in leaf and kernel ash and N contents within each water treatment. It was concluded that NIRS can be used as a rapid, cost-effective, and accurate method for predicting ash and N contents and as a method for screening δ(18)O in maize with promising applications in crop management and maize breeding programs for improved water and nitrogen use efficiency and grain quality.     

玉米自交系及F_2分离群体花药培养中的过氧化物同工酶分析

利用聚丙烯酰胺凝胶电泳分析了两个花粉诱导率不同的自交系 (A3和A46)及其杂种F2 代分离群体在花药培养过程中过氧化物同工酶的变化。结果表明 ,花药培养 7d以后 ,高诱导率自交系A3及高诱导率F2 单株均出现Rf0 50和Rf 0 52 2条过氧化物同工酶谱带 ,而难诱导自交系A46和难诱导F2 单株无此特征。据此认为 ,过氧化物同工酶可以作为花培能力选择的一项较为可靠的生化指标。     

植物防御酶与桉树对焦枯病抗性的关系

为筛选鉴定桉树对焦枯病(CylindrocladiumqulnqueSeptatumMorgan)抗性的生化指标,对福建省11个桉树主栽种系接种焦枯病菌前后关键防御酶系中的过氧化物酶(POD)和超氧岐化酶(SOD)活性及其同工酶变化进行了研究.结果表明:无论是桉树健叶还是接种后的病叶,体内POD、SOD活性均表现为抗病种系>中抗种系>中感种系>感病种系,呈规律性变化;接种前后POD同工酶谱带数与桉树对焦枯病的抗性间不呈规律性变化,而SOD谱带数与抗病性成正比.从抗病育种角度出发可将接种前后桉树POD、SOD活性和接种后SOD同工酶谱带作为桉树对焦枯病抗性早期鉴定的生化指标.     

Comparison of nutritional traits variability in selected eighty-seven inbreds from Chinese maize (Zea mays L.) germplasm

Among cereals, only maize has not only a high amount of carotenoids, tocopherols, and oil content but also is rich in starch and protein content compared with other major food crops, such as rice and wheat. The present investigation was made primarily to assess the genetic variability for nutritionally important traits in 87 elite maize inbreds representing major heterotic groups in China. Carotenoid and tocopherol fractions were measured by high-performance liquid chromatography (HPLC), whereas oil, starch, and protein contents were detected by a VECTER22/N near-infrared analyzer. Significant interactions between genotypes and years were observed for all the traits. The pooled mean values of beta-carotene, beta-cryptoxanthin, alpha-carotene, lutein, zeaxanthin, and total carotenoids were 0.449, 0.876, 0.121, 5.803, 3.048, and 10.298 microg g (-1), respectively, whereas the combined mean performance of alpha-tocopherol, gamma-tocopherol, delta-tocopherol, and total tocopherols were 23.98, 32.90, 2.189, and 59.55 microg g (-1), respectively. The average protein, starch, and oil contents were observed to be 12.28, 64.51, and 3.55%, respectively. High level of heritability estimates were observed for all the traits and ranged from 65.6% (protein content) to 92.5% (alpha/gamma-tocopherol ratio). Most of the traits studied in this experiment were either significantly positive correlated or independent. The present finding exhibits substantial opportunities to the breeders for improvement of these traits in maize cultivars and also suggests further exploration of a new source of elite breeding stocks containing a high level of these nutritionally important compounds. Finally, these findings may also help in biofortification of maize.     

华北热资源限制区实现夏玉米高产高效和机械粒收的适宜种植密度和施氮量

【目的】华北平原夏玉米高效生产不仅取决于产量和肥料利用率,也依赖于高效的机械粒收。本研究探讨了密度与氮肥用量对夏玉米产量形成和收获期籽粒水分含量的影响。【方法】以玉米‘京农科728’为材料,采用裂区试验设计,主区设置2个密度：7.5×10⁴株/hm² (D_7.5)和9.0×10⁴株/hm² (D_9.0),副区设置5个施氮(N)水平：0、180、240、300和360 kg/hm² (分别表示为N₀、N₁₈₀、N₂₄₀、N₃₀₀和N₃₆₀)。测定了不同密度和氮肥用量下玉米叶片SPAD值、叶面积指数(LAI)、干物质积累(DM)、籽粒灌浆、产量及其构成因素、氮肥偏生产力(PFP_N)和农学利用效率(AE_N)。【结果】与D_7.5相比,D_9.0处理V...     

玉米自交系48-2和R08辐照后代M_3株系遗传变异的SSR分析

为研究玉米自交系辐射诱变后代的性状遗传变异规律,促进突变体的高效选择和利用,本研究用3种剂量梯度的60Coγ射线对玉米自交系48-2和R08的种子进行辐射诱变处理,用32个多态性SSR分子标记对48-2和R08及其辐射诱变后代M3株系等103份材料进行了遗传变异分析。结果表明：48-2和R08 M3株系位点多态信息量（...