RAPD分子标记与玉米杂种产量优势预测的研究

以２４个优良玉米自交系统ＮＣⅡ设计组配成１４３个单杂交种为材料，利用的ＲＡＰＤ分子标记技术研究玉米杂种优势群划分，遗传距离与特殊配合力，杂种产量，杂种产量优势的联系。结果表明：（１）ＲＡＰＤ技术可用于玉米杂种优势群划分。（２）亲本遗传距离杂种产量优势，杂种产量，特殊配合畋有一定相关关系，但决定系数很小，分别是１０％，１０％，１５％，利用ＲＡＰＤ技术预测杂种优势，杂种产量作用有限，应进一步研究与杂     

Development of Endopeptidase Activities in Maize (Zea mays L.) Endosperms

An activity stain was used after native polyacrylamide gel electrophoresis, and at least 17 different endopeptidase activities were detected in maize (Zea mays L.) endosperm extracts prepared during the first 6 d after imbibition. The enzymes detected were classified into four groups based on their time of appearance and on their mobility in polyacrylamide gels. The first group, which included two enzymes present in dry endosperms, disappeared soon after imbibition. The second group, comprising five activity bands, appeared during the first 2 to 3 d after imbibition and then disappeared. The third set of enzymes increased continuously throughout the experimental period. The fourth group appeared after d 3 and remained at a constant level after that time. The endopeptidase activities were characterized by the effect of specific inhibitors on their activities. The two enzymes of the first group are metalloendopeptidases based on their sensitivity to ethylenediaminetetracetate (EDTA). Enzymes of the second, third, and fourth groups are sulfhydryl-endopeptidases as judged by their sensitivity to antipain, chymostatin, leupeptin, and E-64 and by their requirement for 2-mercaptoethanol. Pepstatin, phenylmethylsulfonyl fluoride, or EDTA had no effect on these enzymes. Many of the second, third, and fourth group enzymes cleaved [alpha]-zein-rich proteins as well as such easily obtained proteins as gelatin (used in our standard assay) and hemoglobin. The second group had a high affinity for [gamma]-zein, whereas none of the bands in the fourth group of enzymes cleaved this type of zein. The two metalloenzymes of the first group cleaved neither [alpha]- nor [gamma]-zeins.     

Endopolyploidy in Diploid and Tetraploid Maize (Zea mays L.)

Nuclei from different tissues such as stem, mesocotyl, nodalroot and root tip of diploid and tetraploid maize were isolated,stained with propidium iodide and passed through an EPICS-751flow-cytometer cell sorter. Variations in flow histograms wereobserved in different tissues. Stem tissues of both the diploidand tetraploid had two peaks representing G1 and G2 somaticnuclei. The remaining tissues in both the diploids and tetraploidsexhibited three peaks. The first peak observed in these tissuesrepresents G1 somatic nuclei of the lowest ploidy level. Thesecond peak represent G2 somatic nuclei of the lowest ploidylevel+G1 somatic nuclei of the next ploidy level. The thirdpeak represents G2 of the higher ploidy level+G1 somatic nucleiof the next higher ploidy level. Statistically significant differenceswere observed between the diploid and tetraploid maize tissueswith respect to nuclei distribution in the higher ploidy levelpeaks implying variation in the degree of endopolyploidy inthe diploid and tetraploid maize. The results of this studysuggest that the amount of endopolyploid observed in maize genotypeshas an effect on their overall agronomic performance under thefield conditions.Copyright 1993, 1999 Academic Press Zea mays L., maize, endopolyploidy, diploid, tetraploid, flow cytometry     

玉米籽粒性状的遗传效应分析

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个玉米自交系及其配制的F1,F2,BC1,BC2世代为材料,研究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。分析结果表明,除粒宽外,各性状的遗传同时由细胞质效应和胚、胚乳、母体基因效应所控制,百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。各部位籽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到显著或极显著水平,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以对这些性状进行有效的选择。S22 是改良百粒重的优良亲本。 Abstract：The embryo,endosperm and cytoplasm effects of seven seed traits were studied by genetic model for diploid embryo and triploid endosperm plant seeds using five inbreds and their F1, F2, BC1 and BC2 generations. The estimates of genetic variance components indicated that the inheritance of all other kernel traits was controlled by the four effects except kernel width. The 100?kernel weight was mainly controlled by endosperm and maternal effects , and kernel length was controlled by the maternal effects,while endosperm conrrolled kernel width and kernel thickness. Except the significant or highly significant covariances between the endosperm direct additive and maternal additive effects for 100－kernel weight,all other traits between the embryo or endosperm direct effect and the maternal were not significant. So,maize inbreds could be developed by direct selection based on maternal plants for these traits. S22 was the best inbred of the improvement for kernel weight in this study.     

Fertility of Deep-frozen Maize (Zea mays L.) Pollen

On average, 50 per cent of maize pollen grains can be kept viableand almost 30 per cent remain fertile for up to a year whenthe water content on a fresh weight basis is reduced to about30 per cent of the original and the pollen is stored at –76or –196 °C. Over this period no significant differencewas found between storage at either temperature. Zea mays L., maize, pollen, fertility, viability     

Effects of Moniliformin on Mitosis in Maize (Zea mays L.)

Maize (Zea mays L. ‘Norfolk White’) roots were treatedwith solutions of moniliformin (a metabolite of Fusarium moniliformeSheldon) at 0.0001 M and 0.001 M for 8, 24, and 48 h. Only aslight inhibition of division was noted in root tips treatedwith the lower concentration. The higher concentration causeda disruption of the spindle apparatus and consequent C-mitosis,and metaphase accumulation. (Received February 14, 1984; Accepted May 18, 1984)     

The Growth and Development of Maize (Zea mays L.) at Five Temperatures

The objectives of this work were to measure growth and developmentrates over a range of temperatures and to identify processeswhich may limit vegetative yield of maize (Zea mays L.). Twosingle cross Corn Belt Dent maize hybrids were grown from sowingin a diurnal temperature regime of 16/6 °C day/night andin constant temperature environments of 16, 20, 24 and 28 °C.The 16/6 °C environment was close to the minimum for sustainedgrowth and 28 °C was near the optimum. Entire plants wereharvested at stages with 4, 6, 7 and 8 mature leaves in alltemperature treatments except 20 °C in which the final twoharvests were carried out at 9 and 10 mature leaves. Mean totalleaf number varied between 19.5 and 16.0 with the maximum occurringat 16/6 °C. Although harvests were carried out at comparableleaf numbers, and hence at similar developmental stages, thetime interval between sowing and harvest decreased considerablyas temperatures increased. The relative rates of dry weight and leaf area accumulationwith time increased with a Q₁₀ of 2.4 between 16 and 28 °C,while leaf appearance rate increased with a Q₁₀ of 2.9 overthe same range; both rates were highest at 28 °C. Althoughdry matter partitioning to the shoots increased with temperature,the area of individual leaves varied in a systematic patternwhich resulted in maximum leaf area, leaf area duration andconsequently dry weight being realized at 20 °C for anygiven stage of development. Zea mays, corn, low temperature stress, temperature response, growth, development     

Structural Analysis of Secreted Root Slime from Maize (Zea mays L.)

Secreted slime isolated from the incubation medium of Zea mays roots maintained axenically contains fucose, arabinose, xylose, galactose, and glucose as the major monosaccharides. The slime preparation contains low levels (3% weight/weight [w/w]) of uronic acids. Methylation analysis reveals an extraordinarily diverse range of glycosyl residues. The fucosyl residues are primarily terminal (60%) and 3-linked (33%) with a relatively small proportion being 2-linked (6%). The methylation data are consistent with, but not proof of, the presence of a range of polymers including arabinogalactan-proteins (AGPs), xyloglucans, arabinoxylans, and glucans in the slime. The specific binding of the β-glucosyl Yariv reagent, a dye which binds and precipitates AGPs, to the slime preparation and to the outer periclinal epidermal cell wall surface in root sections, is further evidence for the presence of AGPs. Low levels of phenolic acids (approximately 0.17% w/w), in particular trans-ferulic acid, and protein (approximately 6% w/w) were also detected.     

Further Studies on Mosaic Disease of Maize (Zea mays L.)

Schizaphis graminum (Rondani) is proved to be an additional vector of maize mosaic virus (MMV). The pH range for the infectivity of the virus in extracted juice is found to be from 4.4 to 9.0, the optimum being 5.6 to 7.2. Effect of certain chemicals on the virusin vitro has also been studied. Cross protection between MMV and Sugar-cane mosaic virus (SMV) indicated positive results. It has been concluded on the basis of similar physical properties, tolerance towards certain chemicals, host range, symptomatology, aphid vectors and positive immunological tests, that MMV and SMV are related viruses.     

Purification and Partial Characterization of Maize (Zea mays L.) beta-Glucosidase

Maize (Zea mays L.) β-glucosidase (β-d-glucoside glucohydrolase, EC 3.2.1.21) was extracted from the coleoptiles of 5- to 6-day-old maize seedlings with 50 millimolar sodium acetate, pH 5.0. The pH of the extract was adjusted to 4.6, and most of the contaminating proteins were cryoprecipitated at 0°C for 24 hours. The pH 4.6 supernatant from cryoprecipitation was further fractionated by chromatography on an Accell CM column using a 4.8 to 6.8 pH gradient of 50 millimolar sodium acetate, which yielded the enzyme in two homogeneous, chromatographically different fractions. Purified enzyme was characterized with respect to subunit molecular weight, isoelectric point, amino acid composition, NH₂-terminal amino acid sequence, pH and temperature optima, thermostability, and activity and stability in the presence of selected reducing agents, metal ions, and alkylating agents. The purified enzyme has an estimated subunit molecular mass of 60 kilodaltons, isoelectric point at pH 5.2, and pH and temperature optima at 5.8 and 50°C, respectively. The amino acid composition data indicate that the enzyme is rich in Glx and Asx, the sum of which approaches 25%. The sequence of the first 20 amino acids in the N-terminal region was H₂N-Ser-Ala-Arg-Val-Gly-Ser-Gln-Asn-Gly-Val-Gln-Met-Leu-Ser-Pro-(Ser?) -Glu-Ile-Pro-Gln, and it shows no significant similarity to other proteins with known sequence. The enzyme is extremely stable at 0 to 4°C up to 1 year but loses activity completely at and above 55°C in 10 minutes. Likewise, the enzyme is stable in the presence of or after treatment with 500 millimolar 2-mercaptoethanol, and it is totally inactivated at 2000 millimolar 2-mercaptoethanol. Such metal ions as Hg²⁺ and Ag⁺ reversibly inhibit the enzyme at micromolar concentrations, and inhibition could be completely overcome by adding 2-mercaptoethanol at molar excess of the inhibitory metal ion. The alkylating agents iodoacetic acid and iodoacetamide irreversibly inactivate the enzyme and such inactivation is accelerated in the presence of urea.     

Sugar Efflux from Maize (Zea mays L.) Pedicel Tissue

Sugar release from the pedicel tissue of maize (Zea mays L.) kernels was studied by removing the distal portion of the kernel and the lower endosperm, followed by replacement of the endosperm with an agar solute trap. Sugars were unloaded into the apoplast of the pedicel and accumulated in the agar trap while the ear remained attached to the maize plant. The kinetics of ¹⁴C-assimilate movement into treated versus intact kernels were comparable. The rate of unloading declined with time, but sugar efflux from the pedicel continued for at least 6 hours and in most experiments the unloading rates approximated those necessary to support normal kernel growth rates. The unloading process was challenged with a variety of buffers, inhibitors, and solutes in order to characterize sugar unloading from this tissue.

Unloading was not affected by apoplastic pH or a variety of metabolic inhibitors. Although p-chloromercuribenzene sulfonic acid (PCMBS), a nonpenetrating sulfhydryl group reagent, did not affect sugar unloading, it effectively inhibited extracellular acid invertase. When the pedicel cups were pretreated with PCMBS, at least 60% of sugars unloaded from the pedicel could be identified as sucrose. Unloading was inhibited up to 70% by 10 millimolar CaCl₂. Unloading was stimulated by 15 millimolar ethyleneglycol-bis(β-aminoethyl ether)-N,N,N′,N′-tetraacetic acid which partially reversed the inhibitory effects of Ca²⁺. Based on these results, we suggest that passive efflux of sucrose occurs from the maize pedicel symplast followed by extracellular hydrolysis to hexoses.

     

普通玉米籽粒性状的遗传效应分析

采用二倍体种子遗传模型及其分析方法,研究了５个玉米籽粒性状的直接效应、母体效应和细胞质效应．分析结果表明,各性状的遗传同时受种子直接效应和母体效应的影响,细胞质基因对百粒重和粒宽具有极显著影响．除粒长、粒厚的直接显性效应与母体显性效应间的协方差外,直接效应与母体效应间的协方差均不显著．因此,通过母体植株的表现可对这些性状进行有效的选择．Ｓ_２２和 ８７－１是改良粒重的优良亲本．选择粒较宽的自交系作母本有利于提高后代选系及Ｆ_１的百粒重．     

玉米中与DRE元件结合的转录因子的克隆和结构分析

DREB类的转录因子特异性地与DRE元件（脱水应答元件）结合,在植物感受干旱,高盐及低温等逆境条件时,激活一系列下游逆境应答基因的表达。进一步的研究发现,拟南芥DREB蛋白的DNA结合域（AP2区）中14位的缬氨酸和19位的谷氨酸对该转灵因子与DNA结合起着关键性的作用。利用酵母单杂交的方法,我们从玉米（Zea mays L.)的cDNA文库中分离到一个编码与DRE元件结合的蛋白的基因,命名为maDREB1。酵母体内的反式激活实验表明,该基因编码和蛋白能特异地与DRE元件结合并能激活下游报告基因的表达。对maDREB1蛋白14位和19位的氨基酸进行单位突变和双点突变实验,发现14位的缬氨酸突变为丙氨酸后maDREB1几乎丧了其转录激活能力,而19位的谷氨酸突变为天门冬氨酸后maDREB1的转录激活能力也受到较大影响。     

Acetolactate Synthase Activity in Developing Maize (Zea mays L.) Kernels

Acetolactate synthase (EC 4.1.3.18) activity was examined in maize (Zea mays L.) endosperm and embryos as a function of kernel development. When assayed using unpurified homogenates, embryo acetolactate synthase activity appeared less sensitive to inhibition by leucine + valine and by the imidazolinone herbicide imazapyr than endosperm acetolactate synthase activity. Evidence is presented to show that pyruvate decarboxylase contributes to apparent acetolactate synthase activity in crude embryo extracts and a modification of the acetolactate synthase assay is proposed to correct for the presence of pyruvate decarboxylase in unpurified plant homogenates. Endosperm acetolactate synthase activity increased rapidly during early kernel development, reaching a maximum of 3 micromoles acetoin per hour per endosperm at 25 days after pollination. In contrast, embryo activity was low in young kernels and steadily increased throughout development to a maximum activity of 0.24 micromole per hour per embryo by 45 days after pollination. The sensitivity of both endosperm and embryo acetolactate synthase activities to feedback inhibition by leucine + valine did not change during kernel development. The results are compared to those found for other enzymes of nitrogen metabolism and discussed with respect to the potential roles of the embryo and endosperm in providing amino acids for storage protein synthesis.     

玉米中与DRE元件结合的转录因子的克隆和结构分析

DREB类的转录因子特异性地与DRE 元件（脱水应答元件）结合,在植物感受干旱、高盐及低温等逆境条件时,激活一系列下游逆境应答基因的表达。进一步的研究发现,拟南芥DREB蛋白的DNA结合域（AP2区）中14位的缬氨酸和19位的谷氨酸对该类转录因子与DNA结合起着关键性的作用。利用酵母单杂交的方法,我们从玉米 (Zea mays L.) 的cDNA文库中分离到一个编码与DRE元件结合的蛋白的基因,命名为maDREB1。酵母体内的反式激活实验表明,该基因编码的蛋白能特异地与DRE元件结合并能激活下游报告基因的表达。对maDREB1蛋白14位和19位的氨基酸进行单点突变和双点突变实验,发现14位的缬氨酸突变为丙氨酸后maDREB1几乎丧失了其转录激活能力,而19位的谷氨酸突变为天门冬氨酸后maDREB1的转录激活能力也受到较大影响.     

玉米液泡膜焦磷酸酶基因ZmVPP1的克隆及逆境下的表达分析

采用同源克隆的方法在玉米中得到一个与拟南芥耐盐基因AVP1类似的基因.BLAST分析表明,该基因编码蛋白属于质子泵焦磷酸酶家族(H_PPase superfamily)中的Ⅰ型VPP,将其命名为ZmVPP1.ZmVPP1包舍一个2301bp的开放阅读框,编码766个氨基酸残基.蛋白比对结果表明,该蛋白在不同植物中相当保守.实时荧光定量PCR检测发现,ZmVPP1基因在成熟叶片中高丰度表达,在生殖器官中表达量较少.脱水、高盐、低温等逆境胁迫条件和ABA处理下的表达分析表明,ZmVPP1基因受逆境的诱导表达,属于不依赖于ABA的途径.由此推断,ZmVPP1可能参与玉米对Na+的隔离,从而起到耐盐的作用.     

不同基因型玉米间作的群体质量

采用大田试验,研究了不同基因型玉米间作的群体质量特征.结果表明,HF9‖XD20间作,植株中部叶片平均叶龄延长,而对下部和上部叶片影响不大;ZD958‖LD981间作,ZD958植株下部叶片平均叶龄延长,而中、上部叶片则缩短,LD981植株下、中、上部叶片平均叶龄均有所延长.吐丝前,群体叶面积指数(LAI)单间作无明显差异,吐丝后,HF9和LD981的LAI分别大于和显著大于单作群体,而ZD958和XD20则分别小于和显著小于单作群体.紧凑型品种和半紧凑型品种间作增加了群体透光率,吐丝后10d,4个品种棒三叶叶色值(SPADR)均有所增加,并且除ZD958外,其余3个品种棒三叶净光合速率均有所增加,其中LD981增加显著.间作对吐丝以前的群体干物质积累量影响不大,吐丝后,半紧凑型品种(HF9和LD981)的干物质积累量增加,其中LD981增加显著,而紧凑型品种(XD20和ZD958)的干物质积累量减少,其中ZD958显著减少;间作还提高了收获指数,并且两种间作群体的土地当量比(LER)均大于1.结果提示,紧凑型与半紧凑型玉米品种的间作可以提高群体质量,延长叶片功能期,提高光合效率,增加籽粒产量.     

Electrotropism of Maize (Zea mays L.) Roots (Facts and Artifacts)

Intact and decapped primary roots of maize (Zea mays L.) were exposed to DC electric fields of 0.5 to 8.0 V/cm in low-salinity media to resolve conflicting results about the direction of electrotropism. In DC fields of 0.5 V/cm or 1.0 V/cm, intact roots always curved toward the cathode. In a field of 8.0 V/cm, intact roots curved toward the anode and stopped growth. Decapped roots also curved toward the anode both in weak and strong fields. The results indicate that growth toward the cathode is the true response of healthy roots.     

Bacterial Streak Disease of Maize (Zea mays L.) in South Africa

Bacterial streak disease of maize is currently causing some concern among breeders in South Africa. The causal organism of this previously undescribed disease was successfully isolated and its pathogenicity established using KoCH's postulates. Standard physiological and biochemical tests used to identify phytopathogenic bacteria indicated that the bacterium is a Xanthomonas campestris pathovar. Comparisons between this organism and other recognized X. campestris pathovars of the Poaceae indicated that apart from some minor differences the maize streak pathogen is physiologically similar to X. campestris pv. holcicola. However, in repeated reciprocal inoculation experiments all attempts to induce disease symptoms in sorghum with the maize streak pathogen were unsuccessful. Conversely, X. campestris pv. holcicola did produce symptoms in maize leaves. In all the maize cultivars tested the symptoms produced by the maize streak pathogen were, however, always considerably more severe than those caused by X. campestris pv. holcicola. Notwithstanding its physiological similarity to X. campestris pv. holicola it would appear that on the grounds of host specificity the maize streak pathogen warrants new pathovar status. The name X. campestris pv. zeae is proposed.