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.     

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     

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。     

鲜食玉米病虫害防治技术

在乳熟期采摘的玉米果穗我们通常把它称为鲜食玉米,这种类型的玉米可以直接食用,也可以用作加工。鲜食玉米可分为笋玉米、糯玉米、甜玉米等诸多品种。它既可以作为粮食也可以作为菜肴,并且具有较高的营养价值和良好的口感,风味独特,颇受广大消费者的喜爱。特别是作为黑色食品的黑玉米,在我国的各大城市中备受青睐。从种植成本、生长期以及适应性等方面来看,与其他玉米相比鲜食玉米都有较大的优势,具有较高的经济价值,其市场前景非常广阔。因此实现鲜食玉米产业化生产,对农民的增收、农业现代化的推进以及提升城市居民的消费水准都具有非常重要的现实意义。     

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。     

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。     

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.     

甜玉米种子活力测定及其田间成苗能力的评估

室内和田间条件下检测18种基因型甜玉米种子活力状况的结果表明:不同甜玉米种子基因型间的活力差异显著,但均以品种京科甜116较佳.用电导率、糖含量、脱氢酶活性、醛含量、穿纸和老化发芽率均可评估田间出苗率,且前三者还可评估出苗速度,尤以电导率最佳.建立回归方程可对田间成苗能力进行预测.     

弱光胁迫对不同基因型玉米生长发育和产量的影响

以不同基因型玉米为材料,在玉米生长发育的3个主要阶段(苗期、穗期、粒期)进行分期遮光试验,研究不同时期弱光胁迫对不同基因型玉米生长发育和产量的影响。结果表明,遮光延缓了玉米叶片的出生速度,使叶片变薄;遮光可以延缓叶片的衰老,但遮光解除后则加速叶片的衰老;遮光造成植株高度增加,但恢复正常光照后,其株高却逐渐低于对照;遮光使干物质积累下降,抽雄吐丝日期推迟,尤其是吐丝日期推迟更多,并使产量降低,但不同基因型玉米不同遮光处理下降程度不同。试验的4个品种中,掖单2 2和豫玉2号受遮光影响较小,而掖单36 38和丹玉13受影响较大,即不同基因型玉米对弱光胁迫的敏感性不同     

基于相对叶绿素含量的玉米自交系氮敏感性鉴定与评价

氮敏感性鉴定与评价是培育耐低氮与氮高效利用玉米品种的重要的研究内容。本研究采用前期建立的快速无损伤测定SPAD值分析相对叶绿素含量的模型,于低氮与正常供氮大田试验处理下,对我国玉米育种与生产上重要的 189 份玉米自交系开展了低氮与正常供氮条件下不同时期与不同部位叶片的相对叶绿素含量分析。方差分析结果表明,低氮与正常供氮条件下,叶绿素含量均存在极显著的基因型与环境差异,基因型差异是氮敏感性差异的重要原因之一。开花期和开花后10天玉米主要功能叶穗三叶(穗位上第1叶、穗位叶、穗位下第1叶)叶绿素含量之间具有极显著正相关;大喇叭口期玉米全展叶叶绿素含量与各时期各部位叶绿素含量之间呈现极显著中度相关。将正常供氮条件下的性状值与低氮胁迫下性状值的差值占正常供氮条件下性状值的百分比定义为氮敏感性。189份玉米自交系氮平均氮敏感指数变幅为23.86%- 36.00%,表现高度耐低氮的材料有合344和昌7-2等40份自交系,高度敏感的材料有CML206和CA375等40份自交系。本研究提供了一种快速高效的种质资源氮敏感性鉴定与评价方法,并为玉米耐低氮与氮高效育种的遗传育种提供了重要分析结果与基础数据。     

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.