甜玉米、笋玉米的起源与遗传

甜玉米是由籽粒鲜嫩、糖份含量高的一类胚乳突变体转育而成的。笋玉米是指幼穗柔软、食用纤维丰富的一类多穗（甜）玉米,也有几种基因型,近二十年来发展迅速,和甜玉米一样,也已成为一种玉米产业。１甜玉米、笋玉米的起源、遗传与基因型关于甜玉米的起源时间,可以追溯...     

利用嫩玉米穗饲养大螟的技术

[目的]提供一种新的饲养大螟的方法,为获得充足的、高质量虫源提供技术保障。[方法]使用籽粒未形成的嫩玉米穗、鲜茭白和市场上出售的成熟甜玉米3种天然饲料分别饲养大螟,对比3种天然饲料饲养下大螟幼虫发育历期、存活率、化蛹率、羽化率、蛹重和单雌产卵量等适合度参数。[结果]大螟在嫩玉米穗上的平均幼虫存活率为85.3%,化蛹率为77.1%,羽化率为66.3%,显著优于茭白和甜玉米的饲养效果。在嫩玉米穗上,大螟世代发育历期为36.2 d,幼虫发育历期为16.6 d,显著短于在茭白和甜玉米上的发育时间。取食嫩玉米穗的大螟单雌产卵量为81.1粒,与野生型大螟的产卵量没有显著差异。[结论]嫩玉米穗可为大螟的生长发育和繁殖提供足够的营养物质,提高了初孵幼虫的存活率,加快了其世代发育速率,可做为一种适宜的饲料用于大螟的大规模饲养。     

甜玉米EMS突变体资源共享库的构建及初步鉴定

优异的种质资源是培育丰产、优质农作物新品种的基础和首要条件,创制甜玉米突变体材料对优良甜玉米新品种选育和玉米分子育种研究具有重要的意义。本研究中,采用甲基磺酸乙酯(EMS)诱变剂对甜玉米自交系华甜选H-16-2-2-3的花粉进行诱变及人工授粉,构建甜玉米EMS诱变突变体资源库。通过田间筛选与表型考察,共获得影响生育期、散粉抽丝间隔期、植株叶夹角、叶片大小、雄穗姿态、雄性育性、植株高、穗位高、穗行数、子粒顶端颜色、子粒大小、子粒皱缩程度等重要农艺性状的M_2代突变体材料24363份。对其中2000份M_2代突变体进行田间初步表型筛选,并借助高通量测序分析对部分单隐性核基因突变引起的突变体进行基因定位分析。在上述工作基础上,提出构建国内甜玉米种质资源共享库,为甜玉米育种及基因功能研究提供宝贵的试验材料和基因资源,促进甜玉米育种相关资源的共享。     

马蔺全身是宝

甜玉米是玉米的一个亚种,起源于美国。早在哥伦布发现新大陆之前,印第安人就已经种植甜玉米了,并用甜玉米制糖、制点心和酿造原始的啤酒。超甜玉米是甜玉米的一种类型,原产美国弗罗里达州,果穗很小,很甜很好吃。1950年在弗罗里达州召开了种子大会,参加会议的玉米专家,带回去这种玉米进行研究,1959年培育出第一个超甜玉米杂交种,60年代初进入商业化生产。     

罐头玉米笋的氨基酸分析

<正> 近年来,在国际上除甜玉米罐头外,又流行玉米笋罐头(cut young corn)、玉米笋又称珍珠笋、这种新产品是刚长出的玉米雌穗,经过盐水煮熟后经高压灭菌制成罐头,可以整条作西餐的配莱,也可以切片作中餐的炒菜,其味可口,有玉兰片或竹笋片的味道,颇受中外人士的欢迎。随业我国玉米的大丰收,过剩玉米的出     

模拟酸雨对不同类型玉米种子萌发和幼苗生长的影响

以普通玉米、糯玉米、爆裂玉米和甜玉米为材料,研究了不同模拟酸雨(pH 6.0、5.0、4.0、3.0、2.0、1.0)对玉米种子萌发和幼苗生长的影响.结果表明:pH 2.0 ～5.0模拟酸雨对玉米种子萌发和幼苗生长没有显著影响;pH l.0处理的普通玉米、糯玉米、爆裂玉米和甜玉米的种子发芽率分别为91.3％、68.7％、27.5％和11.7％.与pH 6.0处理(CK)相比,pH l.0模拟酸雨显著降低了玉米种子的发芽率、发芽指数、活力指数、发芽速度、苗高、根长、苗和根干物质、贮藏物质运转效率,延长了平均发芽时间.pH l.0模拟酸雨对玉米幼苗生长阶段的影响大于发芽阶段,对幼苗地下部分的影响大于地上部分;受基因型的影响,普通玉米和糯玉米的抗酸雨能力最强,其次为爆裂玉米,甜玉米最差.玉米属于抗酸雨作物,酸雨抑制阈值介于pH1.0～2.0之间.酸雨地区可优先选择种植普通玉米和糯玉米.     

玉米穗腐病抗性鉴定、遗传分析与分子机制*

玉米是我国主要农作物之一,其产量占全国谷物总产量三分之一左右,在国民生活中发挥了重要作用。玉米生长过程中受多种病害侵扰,其中穗腐病是一种由真菌导致的常见病害,目前已鉴定出40余种可诱发玉米穗腐病的病原菌。穗腐病不仅可造成玉米产量损失也导致籽粒品质严重下降,病原微生物所产生次生毒素更是危及人畜安全。目前穗腐病防治以化学方法为主,但是因此所造成的种植成本增加和环境污染问题日益突出,选育抗性品种成为防控玉米穗腐病最经济和安全有效的方法。玉米穗腐病抗性属于典型数量性状,国内外已有多个研究组通过建立玉米穗腐病抗性研究体系,开展玉米群体大规模穗腐病抗性鉴定工作,并筛选出一批抗病材料,这为玉米穗腐病抗性遗传改良奠定了材料基础。利用数量性状位点(quantitative trait locus, QTL)定位和全基因组关联分析(genome-wide association study, GWAS)等方法在玉米 1~10号染色体均检测到显著相关位点。尽管如此,玉米穗腐病抗性研究成果应用于生产的实例较少,生产上仍然缺乏综合性状优良且高抗穗腐病的玉米品种。这一方面是由于玉米穗腐病抗性遗传机制十分复杂、抗性基因克隆工作进展缓慢;另一方面为缺乏对玉米穗腐病抗性遗传研究进展进行系统总结,未有效开发分子标记用于分子育种所致。通过综述玉米穗腐病抗性遗传研究进展,汇总已定位QTL位点和显著关联SNP,构建一致性图谱和鉴定出定位热点区间,并进一步对比分析定位区间候选基因特征和转录组、代谢组研究进展,对促进玉米穗腐病抗性机制研究和玉米抗性育种均具有重要意义。     

玉米螟

王米螟(Pyrausta nubilalis Hubner)也叫玉米钻心虫,它是螟蛾科(Pyralid(?)e)的一种大害虫。它以幼虫期蛀食玉米的茎和穗部,同时也为害叶、雄花、穗丝、苞壳、种粒等部分。第一代的幼虫孵出后有集中食害心叶的习性,能吃透几层     

不同类型玉米籽粒的营养品质及其与籽粒质地的关系

测定普通玉米、爆裂玉米、糯玉米和甜玉米4种类型玉米籽粒不同发育时期的直链淀粉、支链淀粉、总淀粉、可溶性糖和蛋白的含量,分析这些营养物质与角质率的关系。结果表明：灌浆期间4种类型玉米的直链淀粉、支链淀粉和总淀粉含量呈上升趋势,总蛋白含量呈下降趋势,可溶性糖含量变化规律不明显。爆裂玉米的直链淀粉含量始终最高（4．7％-23．1％）,甜玉米（1．4％-4．6％）和糯玉米（2．3％-4．9％）的始终较低;甜玉米的支链淀粉含量一直最低（15．7％-35．5％）,除授粉10d以外,糯玉米的支链淀粉含量一直最高（65．5％-69．8％）;甜玉米总淀粉含量始终最低（17．1％36.1％）、总蛋白含量（15．2％-26．9％）和授粉30d后的可溶性糖含量最高（14．2％-17．6％）。高蛋白含量可能是爆裂玉米和甜玉米角质率高的原因,糯玉米的角质率低可能与支链淀粉含量高和蛋白积累少有关。     

玉米千粒重的结构方程模型分析与研究

本文以中国作物网提供的黄淮海玉米种植区的880条玉米数据为研究对象,利用结构方程模型对影响玉米千粒重的内在因素进行分析.研究结果表明穗粗和株高性状对千粒重的影响最大,路径系数分别达到0.42、0.41;生育日数通过株高性状对千粒重的间接影响大于生育日数对千粒重的直接影响;另外,穗粗对穗长、穗行数也有直接影响,路径系数均为0.34,且均达到显著水平.本研究可以表明结构方程模型在探究作物产量构成因素以及各因素间相互关系,尤其是因果关系方面有重要的应用前景,可以为玉米品种的选育提供指导依据.     

Corn Residue Supply in the Irrigated Corn Belt

The present study quantifies the profit-maximizing supply of corn stover per unit of land under alternative crop rotations in irrigated cropland with and without limits to irrigation. The model is parameterized based on growing conditions in Nebraska, USA. Our analysis quantifies a trilemma between stover supply, groundwater consumption, and food/feed supply per unit of land. In the absence of water conservation policies, higher stover prices are associated with higher supply and increased irrigation application. If an upper limit is imposed on irrigation at the baseline level (for groundwater conservation purposes), an increase in net revenue from stover sale from $15 to $25/metric ton is associated with an increase in stover supply of 5 metric tons/ha and a 2-metric ton reduction in corn yield under continuous corn. Under corn/soybean rotation, such an increase in net revenue is associated with an increase in stover supply of 10 metric tons/ha, and reductions of 0.5 metric tons in corn yield and 0.7 metric tons in soybean yield.     

Modeling Corn Ethanol and Climate

New fuel regulations based on life cycle greenhouse gas (GHG) emissions have focused renewed attention on life cycle models of biofuels. The BESS model estimates 25% lower life cycle GHG emissions for corn ethanol than does the well-known GREET model, which raises questions about which model is more accurate. I develop a life cycle metamodel to compare the GREET and BESS models in detail and to explain why the results from these models diverge. I find two main reasons for the divergence: (1) BESS models a more efficient biorefinery than is modeled in the cases to which its results have been compared, and (2) in several instances BESS fails to properly count upstream emissions. Adjustments to BESS to account for these differences raise the estimated global warming intensity (not including land use change) of the corn ethanol pathway considered in that model from 45 to 61 g CO₂e MJ⁻¹. Adjusting GREET to use BESS's biorefinery performance and coproduct credit assumptions reduces the GREET estimate from 64 to 61 g CO₂e MJ⁻¹. Although this analysis explains the gap between the two models, both models would be improved with better data on corn production practices and by better treatment of agricultural inputs.     

Sterol Composition of the Corn Cyst Nematode,Heterodera zeae,and Corn Roots

Sterols from free sterol and steryl ester fractions from Heterodera zeae and from total lipids of Zea mays roots were analyzed by gas-liquid chromatography (GLC) and by GLC-mass spectrometry. The major free sterols of H. zeae were 24-ethylcholesterol (54.4% of total free sterol), 24-ethylcholesta-5,22-dien-3β-ol (13.3%), 24-methylcholesterol (12.5%), and cholesterol (7.2%). The same four sterols comprised 34.6%, 7.2%, 30.3%, and 18.6%, respectively, of the esterified sterols of H. zeae. Corn root sterols included 46.6% 24-ethylcholesta-5,22-dien-3β-ol, 16.7% methylcholesterol, 16.4% cycloartenol, 12.7% 24-ethylcholesterol, and 0.5% cholesterol. The sterol 24-composition of H. zeae differed greatly from that of the only other cyst nematode previously investigated, Globodera solanacearum.     

Actinomycetales from Corn

Mesophilic Actinomycetales were isolated from whole corn, brewer's grits, and break flour received from three different mills. In addition, strains were isolated from high-moisture (27%) field corn; high-moisture, silo-stored corn (untreated); and high-moisture corn treated with ammonia, ammonium isobutyrate, or propionic-acetic acid. According to standard techniques, 139 strains were extensively characterized and 207 additional strains were partially characterized. On the basis of these characterizations, the streptomycete strains were identified by both the systems of Pridham et al. and Hütter because these systems are rapid and accurate. In general, only Streptomyces griseus (Krainsky) Waksman and Henrici was isolated from high-moisture whole corn (treated or untreated) except from grain exposed to ammonium isobutyrate. Strains isolated from high-moisture corn subjected to that treatment represented both S. griseus and S. albus (Rossi Doria) Waksman and Henrici. The strains isolated from corn and corn products from the three mills were identified with a number of streptomycete species. Of all Actinomycetales isolated, only three were not streptomycetes—two from brewer's grits and one from break flour.     

Plant Nucleases. II. Properties of Corn Ribonucleases I and II and Corn Nuclease I

Three enzymes with ribonuclease activity, one of which also had deoxyribonuclease activity, have been isolated and partially purified from corn seeds and seedlings. The purification of Ribonuclease I from mature seed was previously reported. This enzyme has a pH optimum near 5.0, is loosely adsorbed to carboxymethyl-cellulose, and has a molecular weight of 23,000, determined by gel filtration.

Ribonuclease II was isolated from the microsomes of corn roots, and was partially purified by gel filtration. It has a pH optimum plateau from 5.4 to 7.0, and molecular weight of 17,000.

Nuclease I hydrolyzes both RNA and DNA. It was isolated from the large particles of a corn root homogenate and was partially purified on a carboxymethyl-cellulose column. It has a pH optimum at 6.2 and a molecular weight of 31,000.

The relative activities of the 3 enzymes for deoxyribonuclease and at pH 5 and pH 6.2 for ribonuclease may be used to characterize them during purification operations. Assays on homogenates of corn roots, and especially of the root tips, suggested that a fourth enzyme, which possesses deoxyribonuclease activity, is also present.